# Adding a blend to a Promethium (HM-2)



## Danbieranowski

Hey all,

I've tried a few different things with this, and all have failed for one reason or another.

I just want to add a blend to a Promethium.

If I use the Promethium board alone (no blend mod), it sounds and works great.

I've tried the GuitarPCB Buff n' Blend, but it oscillates. No oscillation if I don't run it through the send and return of the Buff N Blend, so it's definitely the BNB causing the issue.

I've tried a Mini-Mixer (little parallel mixer), with the idea of giving him one volume knob that's his clean signal, and one volume knob that's the HM-2 so he can mix to taste. The problem that I have with this is:
A) I get a little bit of volume or tone loss with the Mini-Mixer (found here: http://www.generalguitargadgets.com/effects-projects/boosters/mini-mixer/). 
B) I can't think of a way to wire it up where, when switched off, the pedal is just standard true-bypass, but when on, I can feed the clean input signal to one pot of the Mini-Mixer, and feed the output signal of the circuit to another pot of the Mini-Mixer. 

I'm not sure what else I'm not thinking of here, but I feel like there's a glaringly obvious way to do this, and I just need a sanity check from the PedalPCB folks. Any help would be appreciated!


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## Dan M

I keep checking here to see if one of the resident circuit wizards has the answer...

I was curious about this too, mainly after watching the Fuzzlord HM-6 release video.  I found this:  http://peperspedals.blogspot.com/2017/08/boss-hm-2-moddingthis-time-blend-control.html?m=1

In the hm-6 video, Jason mentions he boosted the clean path to get the volume closer to the distorted path. So maybe the mod in the above link with a clean boost added?


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## Danbieranowski

Dan M said:


> I keep checking here to see if one of the resident circuit wizards has the answer...
> 
> I was curious about this too, mainly after watching the Fuzzlord HM-6 release video.  I found this:  http://peperspedals.blogspot.com/2017/08/boss-hm-2-moddingthis-time-blend-control.html?m=1
> 
> In the hm-6 video, Jason mentions he boosted the clean path to get the volume closer to the distorted path. So maybe the mod in the above link with a clean boost added?


This is great info, fellow Dan. Thank you for sharing. I'm trying to work out where the blend would actually go in the path, and how this would be wired to a 3PDT. Same with this one: http://tagboardeffects.blogspot.com/2012/02/split-n-blend.html

Just don't totally understand how you wire them to a 3PDT so that when the effect is off it's True Bypass, but when it's on, then the blend knob and HM2 circuit take effect.


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## daeg

Is the goal to use the HM-2 on Bass?


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## Danbieranowski

daeg said:


> Is the goal to use the HM-2 on Bass?


No, just guitar.


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## Chuck D. Bones

Try this:
1. get a B100K pot.  I think that will provide enough isolation.  If you get squealing, then use a buffer in place of the 1uF cap in step 2.
2. Connect a 1uF film cap from pin 1 of the pot to Q1-S.
3. Remove the wire that goes from the OUT pad on the board to the stomp switch.
4. Connect pin 3 of the pot to the OUT pad on the board.
5. Connect pin 2 of the pot to the stomp switch.  

Using a blend pot on a distortion pedal does not always yield the desired results.  The tone controls introduce phase-shift, which can lead to cancelling at some frequencies.  When the note decays, the dirty/clean blend changes because the dirty signal is compressed and the clean signal isn't.

Good luck!


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## Dan M

I don’t need another project in the queue, I don’t need another project in the queue, I don’t need another project in the queue, ...

Well I guess I’ll go order the pcb and build a mouser bom.


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## Chuck D. Bones

Remember, this mod is untested.  It might work right from the git-go, and it might need a little tweaking...


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## Danbieranowski

Chuck D. Bones said:


> Remember, this mod is untested.  It might work right from the git-go, and it might need a little tweaking...


Thanks Chuck. Gonna give it a shot!


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## Danbieranowski

Chuck D. Bones said:


> Remember, this mod is untested.  It might work right from the git-go, and it might need a little tweaking...


Hey Chuck, Tried both the 1uF Film cap as well as a Tillman buffer/preamp (I read that was a good basic buffer), and I still get the oscillation at the highest volume setting with both. If I roll back the volume like 10% the issue goes away. Again, this isn't an issue if I don't try to do a blend. It works just fine without the mod. Now I'm starting to think a better solution would be to somehow limit the volume pot to a lower level somehow. Is this possible?


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## Mir9

I tried the Peperspedals mod ( on real HM-2) yesterday , so I'm still experimenting, but it's working really well.  No distortion bleeds in when mixed clean, which remains at bypass volume level.  It should be great for bass

Like you, I mostly play guitar, and would want the clean to be as loud as the cranked pedal sometimes. The HM-2 has it's own "rules".


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## Danbieranowski

Mir9 said:


> I tried the Peperspedals mod ( on real HM-2) yesterday , so I'm still experimenting, but it's working really well.  No distortion bleeds in when mixed clean, which remains at bypass volume level.  It should be great for bass
> 
> Like you, I mostly play guitar, and would want the clean to be as loud as the cranked pedal sometimes. The HM-2 has it's own "rules".


Rad! Did you do the mod on the Promethium board? And if so, where did you dip into and out of the circuit?


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## giovanni

I find it weird that the blender would oscillate. Are you sure you’re not accidentally wiring so that the output is fed back into the input (like a feedbacker)? Also I was wondering what you meant when you mentioned wiring it with a 3PDT board?


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## Danbieranowski

giovanni said:


> I find it weird that the blender would oscillate. Are you sure you’re not accidentally wiring so that the output is fed back into the input (like a feedbacker)? Also I was wondering what you meant when you mentioned wiring it with a 3PDT board?


The current version I have is wired exactly as Chuck mentioned above. So with a 3PDT board it works as follows: 
Input Jack to Input Jack pad on 3PDT board. 
In on 3PDT board to In on Promethium PCB. 
Out on Promethium PCB to leg 3 on blend pot. 
Leg 2 on blend pot to Out on 3PDT board. 
Output Jack pad on 3PDT board to output Jack.

3PDT board in question is the standard PedalPCB 3PDT board.

Ive also tried using the GuitarPCB Buff N Blend and get the same issue.

If I don’t try to utilize a blend circuit, I do not encounter the issue.

I have no other wiring that would feed the output into the input.

The issue only occurs at the last bit of volume, which is louder than the clean signal regardless, so if I could find some way to limit the volume pot’s output I’d be set I think. I imagine I could do this with additional or less resistance somewhere. I’m just not sure where.


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## giovanni

Well, the output is wired to the input via some resistor, but I can’t tell if that would explain the positive feedback and thus oscillation. 
One thing to try could be a blender pedal like the Wetter Box or the Parallel Mixer to see if it’s just the distortion in question that’s causing the problem or something about the wiring. How did you wire the BuffNBlend?


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## Danbieranowski

giovanni said:


> Well, the output is wired to the input via some resistor, but I can’t tell if that would explain the positive feedback and thus oscillation.
> One thing to try could be a blender pedal like the Wetter Box or the Parallel Mixer to see if it’s just the distortion in question that’s causing the problem or something about the wiring. How did you wire the BuffNBlend?


Could the “resistor” in question be the blend knob itself? That’s wired between input and output to pass the clean signal directly to the output.
The Buff N Blend was wired:
Input Jack to Input on BNB. 
Send on BNB to input of Promethium. 
Out on Promethium to Return on BNB. 
BNB out to output Jack.


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## giovanni

Yeah that’s what I meant. But if you get the same effect with the BNB my guess is that it’s something to do with the distortion circuit itself. But I don’t know what that could be.


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## Danbieranowski

giovanni said:


> Yeah that’s what I meant. But if you get the same effect with the BNB my guess is that it’s something to do with the distortion circuit itself. But I don’t know what that could be.


All good. Thank you for trying to help! @Mir9 has a potential solution for me if he did his with the Promethium.


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## bifurcation

Danbieranowski said:


> @Mir9 has a potential solution for me if he did his with the Promethium.


Share! Share! Share!


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## Danbieranowski

Another positive note is that this forced me to do my first ever stripboard/perfboard build of that Tillman preamp and it worked! So that's cool.


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## Mir9

I modded my real HM-2. The schematic at the Peperspedals link shows it wired right in between the flip flop switching (Q4 & Q10).  The Promethium also has the in and out buffers, so it should work the same. 
	

	
	
		
		



		
			







You can see where "send", "return" and "output" are wired, when using the Tagboard layout he recommends.
http://tagboardeffects.blogspot.com/2012/01/mini-blend-jfet.html 
Attached is a schematic of the blending circuit, though Peppers used different values.


On the Promethium:
"send"     between Q1 and C2 to the blend board, which then goes to blend pot #1
"return"   from volume #2 to blend pot #3 (notice " disconnect here")
"output"  from blend pot #2.  I'm not sure if YOU need that 1uf (C32 on the Boss schem) as you're using true bypass.


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## Danbieranowski

Mir9 said:


> I modded my real HM-2. The schematic at the Peperspedals link shows it wired right in between the flip flop switching (Q4 & Q10).  The Promethium also has the in and out buffers, so it should work the same.
> 
> 
> 
> 
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> 
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> 
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> 
> You can see where "send", "return" and "output" are wired, when using the Tagboard layout he recommends.
> http://tagboardeffects.blogspot.com/2012/01/mini-blend-jfet.html   (he made the 10nf, 100nf on his)
> 
> On the Promethium:
> "send" would be between Q1 and C2
> "return"  would be from volume #2 to the blend circuit (notice " disconnect here"
> "output"  would connect back.  I'm not sure if YOU need that 1uf (C32 on the Boss schem) as you're using true bypass.


You're a golden god! I'll try this out.


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## Mir9

I hope it helps. I edited my post to describe the pot connections. 
An interesting use I'm finding for the blend is to place the HM-2  after another distortion pedal and blend in a little bit of "chainsaw" for all new tones.


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## Danbieranowski

Mir9 said:


> I hope it helps. I edited my post to describe the pot connections.
> An interesting use I'm finding for the blend is to place the HM-2  after another distortion pedal and blend in a little bit of "chainsaw" for all new tones.


Thank you for doing that for us!


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## Danbieranowski

Mir9 said:


> On the Promethium:
> "send"     between Q1 and C2 to the blend board, which then goes to blend pot #1
> "return"   from volume #2 to blend pot #3 (notice " disconnect here")
> "output"  from blend pot #2.  I'm not sure if YOU need that 1uf (C32 on the Boss schem) as you're using true bypass.


Do I need to do anything where it says "disconnect here". I saw in his original post that he actually cut through the PCB trace there.


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## Mir9

Danbieranowski said:


> Do I need to do anything where it says "disconnect here". I saw in his original post that he actually cut through the PCB trace there.


On the Promethium, it would splice between  the connection of Vol#2 and C21.   With this mod,  Vol#2 now goes to Blend#3 and Blend#2 goes to where Vol#2 used to be.

Here's a clip of me strumming a chord while I move the blend pot from clean to full.

__
		https://soundcloud.com/user-562468024%2Fhm2-blend-20210227


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## ANGRY_SWEDE

Danbieranowski said:


> Hey all,
> 
> I've tried a few different things with this, and all have failed for one reason or another.
> 
> I just want to add a blend to a Promethium.
> 
> If I use the Promethium board alone (no blend mod), it sounds and works great.
> 
> I've tried the GuitarPCB Buff n' Blend, but it oscillates. No oscillation if I don't run it through the send and return of the Buff N Blend, so it's definitely the BNB causing the issue.
> 
> I've tried a Mini-Mixer (little parallel mixer), with the idea of giving him one volume knob that's his clean signal, and one volume knob that's the HM-2 so he can mix to taste. The problem that I have with this is:
> A) I get a little bit of volume or tone loss with the Mini-Mixer (found here: http://www.generalguitargadgets.com/effects-projects/boosters/mini-mixer/).
> B) I can't think of a way to wire it up where, when switched off, the pedal is just standard true-bypass, but when on, I can feed the clean input signal to one pot of the Mini-Mixer, and feed the output signal of the circuit to another pot of the Mini-Mixer.
> 
> I'm not sure what else I'm not thinking of here, but I feel like there's a glaringly obvious way to do this, and I just need a sanity check from the PedalPCB folks. Any help would be appreciated!


GuitarPCB BnB is bad for high gain applications, especially if you are running the Promethium into a dirty channel. Mask Audio make a blender that may work. I do know from experience the Pepers Pedals blender works perfect for such an application.


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## Feral Feline

Check out JMK's Paralyzer as another option.


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## Danbieranowski

Feral Feline said:


> Check out JMK's Paralyzer as another option.


I was hoping for the JMK Panner or Paralyzer but both are sold out and he told me he doesn’t know when he will get them in stock unfortunately.


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## Feral Feline

Danbieranowski said:


> I was hoping for the JMK Panner or Paralyzer but both are sold out and he told me he doesn’t know when he will get them in stock unfortunately.


I'll have a snoop for vero/perf layout of it then.


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## Danbieranowski

Feral Feline said:


> I'll have a snoop for vero/perf layout of it then.


I made one of these today. Haven’t finished it or tested it but I’m hopeful.






						Splitter Blend Simpler by Flo | Online stripboard layout editor!
					






					diy-layout.com


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## mdc

ANGRY_SWEDE said:


> GuitarPCB BnB is bad for high gain applications, especially if you are running the Promethium into a dirty channel. Mask Audio make a blender that may work. I do know from experience the Pepers Pedals blender works perfect for such an application.


Trust this human their name is Angry Swede.


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## mdc

Danbieranowski said:


> I made one of these today. Haven’t finished it or tested it but I’m hopeful.
> 
> 
> 
> 
> 
> 
> Splitter Blend Simpler by Flo | Online stripboard layout editor!
> 
> 
> 
> 
> 
> 
> 
> diy-layout.com



If you're still having issues it might be worth trying a blender with a phase inversion option?


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## Danbieranowski

mdc said:


> If you're still having issues it might be worth trying a blender with a phase inversion option?
> 
> View attachment 13168


This is one of the ones I'm looking at. Waiting to test something else, but this is a definite option as well. Thanks for dropping it in here, as I think it's good for anyone interested.


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## Feral Feline

Hmm guessing there isn't such a JMK layout as it hasn't popped up in a search.
Given that the schematic is in JMK's build doc, I'm surprised it hasn't been done yet.


So I made 3 perf layouts, none verified, with two options for the Panner orienting the pot either on the back of the board or off to the side.

If anybody verifies any of the three, please let me know... Critiques of the layouts welcomed as well.


[DELETED due to error]


If anyone wants the schematic numbering instead of the values, I can upload that as well.


FIXed:


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## Danbieranowski

Feral Feline said:


> Hmm guessing there isn't such a JMK layout as it hasn't popped up in a search.
> Given that the schematic is in JMK's build doc, I'm surprised it hasn't been done yet.
> 
> 
> So I made 3 perf layouts, none verified, with two options for the Panner orienting the pot either on the back of the board or off to the side.
> 
> If anybody verifies any of the three, please let me know... Critiques of the layouts welcomed as well.
> 
> 
> View attachment 13186
> 
> 
> If anyone wants the schematic numbering instead of the values, I can upload that as well.


If I have the time and can find my perf I’ll build one tomorrow and test.


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## Danbieranowski

Feral Feline said:


> Hmm guessing there isn't such a JMK layout as it hasn't popped up in a search.
> Given that the schematic is in JMK's build doc, I'm surprised it hasn't been done yet.
> 
> 
> So I made 3 perf layouts, none verified, with two options for the Panner orienting the pot either on the back of the board or off to the side.
> 
> If anybody verifies any of the three, please let me know... Critiques of the layouts welcomed as well.
> 
> 
> View attachment 13186
> 
> 
> If anyone wants the schematic numbering instead of the values, I can upload that as well.


For the record I’ve never built anything on perf before so it’ll be an adventure. I’ll build the top left Panner. It seems like the best way to do this is print this and then print the reverse image to take care of the soldered traces on the bottom. Is that normal SOP for perf builds?


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## Feral Feline

Danbieranowski said:


> For the record I’ve never built anything on perf before so it’ll be an adventure. I’ll build the top left Panner. It seems like the best way to do this is print this and then print the reverse image to take care of the soldered traces on the bottom. Is that normal SOP for perf builds?


There's no right or wrong way, only the way that works for you.

I'll sometimes NOT cut leads off components and use the lead to continue the "trace", then go over it with solder as well — depending on the space constraints, whether or not I'm shifting something over for a larger component than indicated on the layout etc.





Upper left layout, just flip the above image in your graphics program.


@Danbieranowski — Hang on a tick, I found an error in the layout, pin 3 isn't connected... fixing it now.

PS: Schematic numbering so you can cross-check more easily.


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## Bobbyd67

Maybe you can look how Dunwich did it on their version of the HM-2






						OSH Park ~   Shared Projects by dunwichamps
					






					oshpark.com
				




There's a schematic in the project document... Or you could just order the oshpark board xD

It uses a extra tl072, my guess is everything connected to ic3 is the blend circuit


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## Danbieranowski

Bobbyd67 said:


> Maybe you can look how Dunwich did it on their version of the HM-2
> 
> 
> 
> 
> 
> 
> OSH Park ~   Shared Projects by dunwichamps
> 
> 
> 
> 
> 
> 
> 
> oshpark.com
> 
> 
> 
> 
> 
> There's a schematic in the project document... Or you could just order the oshpark board xD
> 
> It uses a extra tl072, my guess is everything connected to ic3 is the blend circuit


I have a few of those sitting on my desk just gotta get to it.


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## Mir9

I built one of the new Dunwich boards. Like the Pepper's blend, the clean is split off at the beginning and remains unity volume.  Since normal use of the HM-2 is maxing out those tone controls, you won't get an even clean blend. The distorted half will overpower the clean, but it works just fine for me.
 I use it as a boost  into an already distorted amp and blending some clean in with the Dunwich added some much needed clarity.


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## Danbieranowski

Mir9 said:


> I built one of the new Dunwich boards. Like the Pepper's blend, the clean is split off at the beginning and remains unity volume.  Since normal use of the HM-2 is maxing out those tone controls, you won't get an even clean blend. The distorted half will overpower the clean, but it works just fine for me.
> I use it as a boost  into an already distorted amp and blending some clean in with the Dunwich added some much needed clarity.


Just out of weirdo curiosity, would it be possible to insert a clean boost somewhere in that clean circuit? Maybe that's something someone can do to create a unique version of this.


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## Feral Feline

Danbieranowski said:


> Just out of weirdo curiosity, would it be possible to insert a clean boost somewhere in that clean circuit? Maybe that's something someone can do to create a unique version of this.


In the schematic floating around the net of the Dunwich HM-2, IC3A is the clean blend op-amp if I'm not mistaken. It's right below the blend pot.

R32 is the feedback resistor for that op-amp, it's 10k, if you stuck a 50k or 100k pot in series with it, that would give you a "clean-signal" gain boost. At least, that's where I'd start experimenting.


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## Danbieranowski

Feral Feline said:


> In the schematic floating around the net of the Dunwich HM-2, IC3A is the clean blend op-amp if I'm not mistaken. It's right below the blend pot.
> 
> R32 is the feedback resistor for that op-amp, it's 10k, if you stuck a 50k or 100k pot in series with it, that would give you a "clean-signal" gain boost. At least, that's where I'd start experimenting.


Maybe I’ll just throw a trimmer in there!


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## ANGRY_SWEDE

Danbieranowski said:


> This is one of the ones I'm looking at. Waiting to test something else, but this is a definite option as well. Thanks for dropping it in here, as I think it's good for anyone interested.


I built a stand-alone Mask Audio Electronics MAE blender, and it works 100% with an HM-2 into a dirty channel. Zero high freq squealing. That was my test before dedicating it to a pedal.


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## Danbieranowski

ANGRY_SWEDE said:


> I built a stand-alone Mask Audio Electronics MAE blender, and it works 100% with an HM-2 into a dirty channel. Zero high freq squealing. That was my test before dedicating it to a pedal.


I just bought a handful of those and I'm waiting for them to arrive. Thank you tons!


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## ANGRY_SWEDE

Danbieranowski said:


> I just bought a handful of those and I'm waiting for them to arrive. Thank you tons!


It has a dual footprint for the Q's [2n5457] so you can use either SMD or through-hole.


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## Kroars

Great thread!


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## Slurp

Danbieranowski said:


> I just bought a handful of those and I'm waiting for them to arrive. Thank you tons!


Hi there, did you ever end up getting one of these methods to work?

I did some mods to an HM2 and increased the overall output volume by a little bit, but my mask audio blend is whistling 

I just encapsulated the fx in and fx out with the send / return, no luck so far


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## Danbieranowski

Slurp said:


> Hi there, did you ever end up getting one of these methods to work?
> 
> I did some mods to an HM2 and increased the overall output volume by a little bit, but my mask audio blend is whistling
> 
> I just encapsulated the fx in and fx out with the send / return, no luck so far


I have not built one that didn’t whistle with a blend yet. Without a blend, yes. But not with. Gonna try the Dunwich next.


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## Slurp

Danbieranowski said:


> I have not built one that didn’t whistle with a blend yet. Without a blend, yes. But not with. Gonna try the Dunwich next


Ahhhh not the answer I was hoping to hear haha. I just finished building an FZ2 and couldn't get a blend to work with it either. Was hoping the HM2 might be more manageable since I've seen so many clones pull it off. I'll also give the dunwich opamp version a go and report back

One thing that is throwing me off though is the difference in the output section... So basically I will need to bypass everything after IC 1.1 in the promethium and implement a little custom board using an extra TL072 for the blend, output buffer, and new 100k Volume pot. Going to be a mess 

*

*


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## Feral Feline

Looking forward to seeing the Dunwich ones built by you guys... 🤞


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## Slurp

Danbieranowski said:


> I have not built one that didn’t whistle with a blend yet. Without a blend, yes. But not with. Gonna try the Dunwich next.





Feral Feline said:


> Looking forward to seeing the Dunwich ones built by you guys... 🤞


Ugh, it worked perfect with single coils, then when I switched to a guitar with humbuckers it was just as bad as anything else with the feedback at 50% volume. This is crazy, my build is actually really similar to the dunwich mods so I am very surprised that this one isn't working.

Plus this one seems to have a ton of bleed compared to the other blends? I kinda want to look into the actual circuit design considerations at this point, because this is honestly my 5th blend knob that I've attempted with a high gain pedal that has failed

I etched a little 805 smd PCB with the following schematic, and made these connections using the PedalPCB suggested 3PDT true bypass wiring:
- IN to center node of 3PDT
- 4V5 to left side of R21 (the side closer to IC2)
- TO_IC1.1_OUT to the (+) node of C20 (I removed C20)
- OUT to top right node of 3PDT (left Promethium PCB FX output floating)
- 9V and GND to power supply / gnd of course


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## Danbieranowski

Slurp said:


> Ugh, it worked perfect with single coils, then when I switched to a guitar with humbuckers it was just as bad as anything else with the feedback at 50% volume. This is crazy, my build is actually really similar to the dunwich mods so I am very surprised that this one isn't working.
> 
> Plus this one seems to have a ton of bleed compared to the other blends? I kinda want to look into the actual circuit design considerations at this point, because this is honestly my 5th blend knob that I've attempted with a high gain pedal that has failed
> 
> I etched a little 805 smd PCB with the following schematic, and made these connections using the PedalPCB suggested 3PDT true bypass wiring:
> - IN to center node of 3PDT
> - 4V5 to left side of R21 (the side closer to IC2)
> - TO_IC1.1_OUT to the (+) node of C20 (I removed C20)
> - OUT to top right node of 3PDT (left Promethium PCB FX output floating)
> - 9V and GND to power supply / gnd of course
> 
> View attachment 14851


Yeah it’s incredibly frustrating!!!


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## fractal33

Sorry for reviving a somewhat old thread, but I thought I'd put my 2 cents in here since I've been lurking for a while and I've also been trying to figure out how to add a blend control to a Promethium.

I built a Split 'n Blend(which is identical to the mask audio blend schematic) on perfboard using two 2N5457's for the buffers. I had zero bleed or phase issues and it seems to work very well overall. The intense noise and feedback that seems to turn into oscillation at dimed settings is present, but it is actually far worse on my original unmodified made-in-Japan HM-2.

I wish I had a better point of reference for what the Promethium sounded like dimed _without_ the blend control, but I don't usually run the distortion on max to begin with, as the chainsaw tone most people seek lies mainly in the maxed EQ. Unless I'm missing something here, the blend is functioning exactly as it should, and overall the Promethium even with the Split n' Blend is far less noisy on dimed settings than its original Boss counterpart - sans blend control. 

I believe this was posted here earlier, but this is the layout I used:
http://effectslayouts.blogspot.com/2015/12/split-n-blend.html 

I wired the Split 'n Blend to the Promethium and 3PDT as follows:

SNB IN to 3PDT board IN
SNB Send to promethium PCB IN
Promethium PCB OUT(return) to Blend lug 3
SNB blend 1(or OUT on mask audio's blend) to Blend lug 1
3PDT board OUT to Blend lug 2


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## fractal33

Small update... I realized after toying around with it for a while there was actually some bleed going on, so after playing operation for a while and disconnecting the ins and outs from the Promethium PCB to the blend control and 3PDT entirely, I noticed on dimed settings there was STILL a small amount of signal coming from the pedal output into the amp that was being processed by the engaged pedal! How is this possible?

Just to recap, I had no input or output connected to the Promethium board or the blend board. The only connections on the 3PDT breakout board were from input and output jack tips, 3PDT ground->promethium ground, 3PDT switch->promethium switch. I'm thoroughly baffled how that is even possible. I checked for bridged connections with a multimeter and couldn't find anything abnormal. Could this be some type of crossover from the 3PDT ground or switch out? Or is this some electrical phenomenon that I'm completely unaware of?(definitely possible)


----------



## Feral Feline

Another case of a possessed PCB.

You must call a high priest of your preferred denomination, but must be one that does exorcisms, because failing the exorcism ... you will have to put a hot soldering iron tip through the main IC right through the board to the other side. That will make it bleed out completely once and for all.

After it's pierced through its "heart", build a funeral pyre and burn the whole thing, lest it resurrect itself. The capacitors can sometimes give off a flare when they pop from the heat while releasing the demons, so stand well back. The colours of the flames are pretty, though, so it's well worth watching and besides, you need to watch to ensure all is burnt completely.


----------



## Danbieranowski

fractal33 said:


> Small update... I realized after toying around with it for a while there was actually some bleed going on, so after playing operation for a while and disconnecting the ins and outs from the Promethium PCB to the blend control and 3PDT entirely, I noticed on dimed settings there was STILL a small amount of signal coming from the pedal output into the amp that was being processed by the engaged pedal! How is this possible?
> 
> Just to recap, I had no input or output connected to the Promethium board or the blend board. The only connections on the 3PDT breakout board were from input and output jack tips, 3PDT ground->promethium ground, 3PDT switch->promethium switch. I'm thoroughly baffled how that is even possible. I checked for bridged connections with a multimeter and couldn't find anything abnormal. Could this be some type of crossover from the 3PDT ground or switch out? Or is this some electrical phenomenon that I'm completely unaware of?(definitely possible)


It's because we live in a hell of our own making, my friend.


----------



## fractal33

Yeah I'm at a loss here... Good news is it gave me a chance to A/B with and without the Split 'n Blend, and there was no difference in feedback or added oscillation. In fact, the SNB is working exactly how it should and this "bleed" is apparently not bleed from the blend at all. It goes away if I dial the settings back a little, but somewhere there is some input signal getting through to the mainboard even with the IN and OUT from the promethium PCB disconnected. Gonna go listen to Bleed by Meshuggah for a while and get that soldering iron nice and hot to prepare for the exorcism.


----------



## benny_profane

fractal33 said:


> Small update... I realized after toying around with it for a while there was actually some bleed going on, so after playing operation for a while and disconnecting the ins and outs from the Promethium PCB to the blend control and 3PDT entirely, I noticed on dimed settings there was STILL a small amount of signal coming from the pedal output into the amp that was being processed by the engaged pedal! How is this possible?
> 
> Just to recap, I had no input or output connected to the Promethium board or the blend board. The only connections on the 3PDT breakout board were from input and output jack tips, 3PDT ground->promethium ground, 3PDT switch->promethium switch. I'm thoroughly baffled how that is even possible. I checked for bridged connections with a multimeter and couldn't find anything abnormal. Could this be some type of crossover from the 3PDT ground or switch out? Or is this some electrical phenomenon that I'm completely unaware of?(definitely possible)


How do you have power connected to each circuit and what are you doing with the grounding of each circuit?


----------



## fractal33

@benny_profane
Promethium is wired directly to DC jack and so is the blend board.

Did some more experimenting today and I isolated the clean signal from the blend and sent it directly to the tip of a separate output which was grounded to the pedal jacks, and there was no distortion bleed over so that's good. When I hooked the clean signal back up to lug 1 of a potentiometer with the distortion on lug 3 and output of 3PDT on 2, the bleed was back.
Even when I disconnected the promethium from lug three there was still some bleed which was boggling my mind. However, if I shunted the return from promethium to ground, no more bleed.

I realized that the way I was testing this might have been conflating some of these issues because I was using a breadboard to make some of these connections and I also left some wires hang. I accidentally stumbled upon something cool when I was moving the output tip connection around on my breadboard... It was picking up the signal from the disconnected distortion return when I moved the end of the jumper close to the hanging promethium return wires. I guess I made myself an antenna. I'm thinking something like this must have been going on yesterday when I disconnected the send and return from the promethium and was still picking up some signal.

Gonna probably try the JMK panner or paralyzer soon since shunting the other signal to ground seemed to make this problem disappear in my testing. Honestly, at this point it is really the perfectionist in me because the amount of bleed when the pot is on fully clean isn't horrible and I don't see why I would want to run it fully clean anyway, but that is beside the point.


----------



## fractal33

Update:

Built the JMK Paralyzer on stripboard.

I hardwired send tip 1 to promethium IN and return tip 1 to promethium out. I connected send tip 2 to the tip of a mono switch jack, send jack's switch to return jack's switch, and the return jack's tip to return tip 2 on Paralyzer. (also connected the two jack's grounds together then to the regular output jack ground)

When nothing is plugged into the send and return jacks I added, it just blends a clean signal. When something is plugged into to loop, you can blend a separate distortion pedal or effect parallel to the promethium. No bleed. It works!!!

The only problem is the promethium signal tends to overpower the parallel clean/fx loop until the pot is turned almost all the way to the blend side. I'm sure it could be remedied by adding a boost for the loop somewhere. It could probably also benifit from a phase switch since some pedals are going to invert.

Regardless, it works!!!

I used this stripboard layout of the Paralyzer:








						JMK Paralyzer
					






					dirtboxlayouts.blogspot.com


----------



## delackattack

Mir9 said:


> I modded my real HM-2. The schematic at the Peperspedals link shows it wired right in between the flip flop switching (Q4 & Q10).  The Promethium also has the in and out buffers, so it should work the same.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> You can see where "send", "return" and "output" are wired, when using the Tagboard layout he recommends.
> http://tagboardeffects.blogspot.com/2012/01/mini-blend-jfet.html
> Attached is a schematic of the blending circuit, though Peppers used different values.
> 
> 
> On the Promethium:
> "send"     between Q1 and C2 to the blend board, which then goes to blend pot #1
> "return"   from volume #2 to blend pot #3 (notice " disconnect here")
> "output"  from blend pot #2.  I'm not sure if YOU need that 1uf (C32 on the Boss schem) as you're using true bypass.


----------



## delackattack

Mir9 said:


> I modded my real HM-2. The schematic at the Peperspedals link shows it wired right in between the flip flop switching (Q4 & Q10).  The Promethium also has the in and out buffers, so it should work the same.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> You can see where "send", "return" and "output" are wired, when using the Tagboard layout he recommends.
> http://tagboardeffects.blogspot.com/2012/01/mini-blend-jfet.html
> Attached is a schematic of the blending circuit, though Peppers used different values.
> 
> 
> On the Promethium:
> "send"     between Q1 and C2 to the blend board, which then goes to blend pot #1
> "return"   from volume #2 to blend pot #3 (notice " disconnect here")
> "output"  from blend pot #2.  I'm not sure if YOU need that 1uf (C32 on the Boss schem) as you're using true bypass.


I ended up making a Simple FET Blend on a trial and error run but I’m still VERY CONFUSED as to how to wire this thing lol.
Anyone have some pointers?


----------



## fractal33

delackattack said:


> I ended up making a Simple FET Blend on a trial and error run but I’m still VERY CONFUSED as to how to wire this thing lol.
> Anyone have some pointers?


What layout did you use for the blend? Maybe this will help you. I know you don't have the breakout board for your 3PDT which adds to the confusion. 


fractal33 said:


> I wired the Split 'n Blend to the Promethium and 3PDT as follows:
> 
> SNB IN to 3PDT board IN
> SNB Send to promethium PCB IN
> Promethium PCB OUT(return) to Blend lug 3
> SNB blend 1(or OUT on mask audio's blend) to Blend lug 1
> 3PDT board OUT to Blend lug 2


----------



## fractal33

@delackattack

If it is this one then:

Connect 9v and ground from SB(simple blend) to appropriate DC jack lugs.
Desolder the wires from Prom(ethium) IN and Prom OUT, but keep them attached to the 3PDT
Connect the wire from 3PDT that you desoldered from Prom IN and connect to SB IN
Connect the wire from 3PDT that you desoldered from Prom OUT and connect to SB OUT
Connect Prom IN to SB SEND
Connect Prom OUT to SB RETURN

Pretty sure that is right. It's confusing.


----------



## delackattack

fractal33 said:


> @delackattack
> 
> If it is this one then:
> 
> Connect 9v and ground from SB(simple blend) to appropriate DC jack lugs.
> Desolder the wires from Prom(ethium) IN and Prom OUT, but keep them attached to the 3PDT
> Connect the wire from 3PDT that you desoldered from Prom IN and connect to SB IN
> Connect the wire from 3PDT that you desoldered from Prom OUT and connect to SB OUT
> Connect Prom IN to SB SEND
> Connect Prom OUT to SB RETURN
> 
> Pretty sure that is right. It's confusing.


This is the exact one! Im gonna wire it up after work


----------



## Mike52

fractal33 said:


> @delackattack
> 
> If it is this one then:
> 
> Connect 9v and ground from SB(simple blend) to appropriate DC jack lugs.
> Desolder the wires from Prom(ethium) IN and Prom OUT, but keep them attached to the 3PDT
> Connect the wire from 3PDT that you desoldered from Prom IN and connect to SB IN
> Connect the wire from 3PDT that you desoldered from Prom OUT and connect to SB OUT
> Connect Prom IN to SB SEND
> Connect Prom OUT to SB RETURN
> 
> Pretty sure that is right. It's confusing.


I'm totally out of my depth here, but wouldn't you want to get your 9v for the buffer from the power filter section of the circuit rather than direct from the DC jack?


----------



## giovanni

If the blender circuit doesn't have power filter/protection, I'd say yes.


----------



## delackattack

So where would the power filter be on the Promethium?


----------



## delackattack

fractal33 said:


> @delackattack
> 
> If it is this one then:
> 
> Connect 9v and ground from SB(simple blend) to appropriate DC jack lugs.
> Desolder the wires from Prom(ethium) IN and Prom OUT, but keep them attached to the 3PDT
> Connect the wire from 3PDT that you desoldered from Prom IN and connect to SB IN
> Connect the wire from 3PDT that you desoldered from Prom OUT and connect to SB OUT
> Connect Prom IN to SB SEND
> Connect Prom OUT to SB RETURN
> 
> Pretty sure that is right. It's confusing.


I just got done wiring this up like such and it works like a charm.


----------



## fractal33

Mike52 said:


> I'm totally out of my depth here, but wouldn't you want to get your 9v for the buffer from the power filter section of the circuit rather than direct from the DC jack?


Good catch, I just assumed the blend did because most of the layouts on that website include power protection.


----------



## fractal33

delackattack said:


> I just got done wiring this up like such and it works like a charm.


Mike is right. You should probably get 9v from the promethium board instead because there is no power protection or filtering on that board.

I can try to walk you through this, but this might be a good learning experience for you if you don't know how to read a schematic yet. Where to tap the +9V from might depend on the location of this board in your enclosure. Any connection on the promethium schematic that says VCC (in this case, this doesn't apply to every schematic) is diode protected and filtered +9V power. Directly off the pad of where the cathode(stripe) of D8 is connected might be the closest place if you already have a wire going to the DC jack positive. There are a few ways you can do this, but a quick and dirty way would just be to solder a wire to this pad under the board but be careful not to have any exposed wire that could short out something under there. You could actually solder it to the top of the board if you wanted but it is ugly and you might scorch some components in the process.


----------



## delackattack

Well as far as functionality, it seems to works seem less.
No extra noise or any of that unwanted jazz


----------



## Mike52

delackattack said:


> So where would the power filter be on the Promethium?


It's this guy right here. You can see the 9v (VCC) supply rail and the 4.5v. (VREF).  This is a circuit block that is common, for the most part, to lots of these pedals. It's just the power plant for effects supplying whatever a particular circuit block or element needs, (9v+, 18v+, 9v-, 4.5v+ or -, etc). You can figure out what kind of power supply is being fed into a circuit block by paying attention to those little flags (VCC, VREF, etc). 

I suspect you want to tap the 9v rail, but again, out of my depth.




@fractal33, his offboard buffer will probably have a 9v+ and a ground coming off of it. Wouldn't he want to take power off the 9+ rail and elevate the ground by attaching it to the negative rail? Have I got that right?

The buffer he's describing probably works a lot like PedalPCB's simple JFET buffer:


----------



## Diynot

So I’m coming way late to the party, but I’ve built a couple standalone clean blend pedals as well as added one to an OCD build and by far, the best one that I have used was one called the “Schooner” designed by a familiar face in these parts @jubal81. The other one that I have used was from nucleonfx based on the schooner, but it oscillated terribly unless both pedals were powered on isolated sources. I think the difference was that jubal81s design used a rail splitter, I believe for a virtual ground. I have the schematic if he is ok with me posting it? @jubal81 is that ok?


----------



## jubal81

Diynot said:


> So I’m coming way late to the party, but I’ve built a couple standalone clean blend pedals as well as added one to an OCD build and by far, the best one that I have used was one called the “Schooner” designed by a familiar face in these parts @jubal81. The other one that I have used was from nucleonfx based on the schooner, but it oscillated terribly unless both pedals were powered on isolated sources. I think the difference was that jubal81s design used a rail splitter, I believe for a virtual ground. I have the schematic if he is ok with me posting it? @jubal81 is that ok?


That's fine.  If I were to do it over again, I would use a very different circuit, though.
Adding a clean blend needs to be considered on a pedal-by-pedal basis because a lot of circuits flip the phase.


----------



## Diynot

I think the analogman site may have a listing of pedals and circuit topology that are known phase flippers.


----------



## jeffwhitfield

Have to admit, I gave in and got a HM Demon. Gnarly version of an HM-2. Complete with a Clean/Blend knob. 









						HM Demon
					

Specifications: - Power: 9-12V center-negative power supply - Input Impedance: 1MΩ - Output Impedance: 100Ω - Soft-touch True Bypass Switching -...




					www.bardicaudiodevices.com


----------



## fractal33

Mike52 said:


> It's this guy right here. You can see the 9v (VCC) supply rail and the 4.5v. (VREF).  This is a circuit block that is common, for the most part, to lots of these pedals. It's just the power plant for effects supplying whatever a particular circuit block or element needs, (9v+, 18v+, 9v-, 4.5v+ or -, etc). You can figure out what kind of power supply is being fed into a circuit block by paying attention to those little flags (VCC, VREF, etc).
> 
> I suspect you want to tap the 9v rail, but again, out of my depth.
> View attachment 19986
> 
> @fractal33, his offboard buffer will probably have a 9v+ and a ground coming off of it. Wouldn't he want to take power off the 9+ rail and elevate the ground by attaching it to the negative rail? Have I got that right?
> 
> The buffer he's describing probably works a lot like PedalPCB's simple JFET buffer:
> View attachment 19988


Man my head has been all over the place but I'm pretty sure It doesn't matter where the ground is connected in terms of jack vs promethium as long as he is tapping the +9 after the protection diode on the promethium.


----------



## fractal33

jubal81 said:


> That's fine.  If I were to do it over again, I would use a very different circuit, though.
> Adding a clean blend needs to be considered on a pedal-by-pedal basis because a lot of circuits flip the phase.


I made my own clean blend on perf that includes a phase switch. This is ideal then you can use it with any pedal. It is similar to the Paramix. I have a monster multipedal in the works that is an hm-2 style pedal, 8 way clipping diode switch, clean blend with send/return insterts, and a muzzle. It's a beast. I started working on adding a boost to the clean signal but then I got side tracked fixing my amp and causing drama with tube amp corksniffers on another forum. Finally fixed it today so back to the pedal I suppose.
Muzzle -> Blend->Hm-2(murdock plus) Aint much to look at yet but it is a WIP.


----------



## Mike52

fractal33 said:


> Man my head has been all over the place but I'm pretty sure It doesn't matter where the ground is connected in terms of jack vs promethium as long as he is tapping the +9 after the protection diode on the promethium.


And the filter cap. Don't forget that.


----------



## fractal33

Mike52 said:


> And the filter cap. Don't forget that.


Yep, the cathode of the protection diode should be at a node with the cap though so anything apart of that net is good.



delackattack said:


> Well as far as functionality, it seems to works seem less.
> No extra noise or any of that unwanted jazz


It might work fine but if you accidentally plug the wrong plug into the pedal you could have a blown power supply or worse. You might be telling yourself "Nah I would never do that." That's how I felt too but let me tell you it happens and will probably happen to you at some point.


----------



## fractal33

Diynot said:


> I think the analogman site may have a listing of pedals and circuit topology that are known phase flippers.


@jubal81 Would you mind explaining why you went this route over just making a resistor-based voltage divider? I'm interested as I have no experience using the TLE2426.


----------



## delackattack

Mike52 said:


> It's this guy right here. You can see the 9v (VCC) supply rail and the 4.5v. (VREF).  This is a circuit block that is common, for the most part, to lots of these pedals. It's just the power plant for effects supplying whatever a particular circuit block or element needs, (9v+, 18v+, 9v-, 4.5v+ or -, etc). You can figure out what kind of power supply is being fed into a circuit block by paying attention to those little flags (VCC, VREF, etc).
> 
> I suspect you want to tap the 9v rail, but again, out of my depth.
> View attachment 19986
> 
> @fractal33, his offboard buffer will probably have a 9v+ and a ground coming off of it. Wouldn't he want to take power off the 9+ rail and elevate the ground by attaching it to the negative rail? Have I got that right?
> 
> The buffer he's describing probably works a lot like PedalPCB's simple JFET buffer:
> View attachment 19988


So if I was to wire it appropriately in this fashion, where on this circuit am I hitting?
Just the VCC and VREF points?


----------



## delackattack

fractal33 said:


> Yep, the cathode of the protection diode should be at a node with the cap though so anything apart of that net is good.
> 
> 
> It might work fine but if you accidentally plug the wrong plug into the pedal you could have a blown power supply or worse. You might be telling yourself "Nah I would never do that." That's how I felt too but let me tell you it happens and will probably happen to you at some point.


And blown power supply for the circuit or for my actual isolated power supply? (Walrus Phoenix)


----------



## Mike52

@delackattack  If I were dropping a simple Jfet buffer into the board, I'd probably solder the + and gnd to each side of either C23 or I'd tap the appropriate legs of the ICs (pins 4 and 8). But I'd defer to more experienced builders. The VCC and VREF locations aren't actually a place. They are a reference for reading the schematic.


----------



## Danbieranowski

I'm glad this thread made it so deep into nerd-town. Nice to know I'm not alone!


----------



## delackattack

Before I wire this up to C23, what filter cap should I use???


----------



## delackattack

So, this the second Promethium that I have added this SFB circuit to and now the pot acts as it’s reversed and there is NO blend only acting as a level.
Maybe I goofed on the circuit but I’ve checked my connections with a multimeter and everything seem okay but lug one and two on the pot are getting a matching signal.


----------



## delackattack

Update: Plugged pedal up with the circuit connected to probe and smoke started to come from the circuit.
I’ve wired it up back without the blend circuit and it sounds as usual so I’m going to build a new SFB and try again.
😢


----------



## Mike52

delackattack said:


> Update: Plugged pedal up with the circuit connected to probe and smoke started to come from the circuit.
> I’ve wired it up back without the blend circuit and it sounds as usual so I’m going to build a new SFB and try again.
> 😢


Hope you didn't let the magic smoke out. That's a bummer. Was a component in backwards? Were you using the audio probe on the signal path or was it touching source voltage. What component was smoking, btw? 

Maybe post a drawing of what precise modifications you were attempting to the circuit. With a thing like this, it would be really valuable for you and others to know exactly why the magic smoke showed up.

And if you decide to attempt another experiment here then this seems like one of those projects that you could easily fly in your modification ideas from a breadboard. As I think about it, it might even be cool for you to experiment with panning vs blending.


----------



## delackattack

Mike52 said:


> Hope you didn't let the magic smoke out. That's a bummer. Was a component in backwards? Were you using the audio probe on the signal path or was it touching source voltage. What component was smoking, btw?
> 
> Maybe post a drawing of what precise modifications you were attempting to the circuit. With a thing like this, it would be really valuable for you and others to know exactly why the magic smoke showed up.
> 
> And if you decide to attempt another experiment here then this seems like one of those projects that you could easily fly in your modification ideas from a breadboard. As I think about it, it might even be cool for you to experiment with panning vs blending.


I’m not sure as to what exact component was smoking but I just unplugged it as quickly as I saw it.


----------



## Mike52

Mike52 said:


> Hope you didn't let the magic smoke out. That's a bummer. Was a component in backwards?





delackattack said:


> I’m not sure as to what exact component was smoking but I just unplugged it as quickly as I saw it.


Sorry, I can't sort all that out. So the buffer circuit was the thing that was smoking? Where on the schematic did you fly in the wires of the buffer. I am having a hard time tracking the 9 wires coming off of it, which seems excessive. It's a simple Jfet buffer circuit, I'd think it would have a input, output, 9v and ground. What do the other wires do?


----------



## Mike52

delackattack said:


> I’m not sure as to what exact component was smoking but I just unplugged it as quickly as I saw it.


My mistake. You aren't adding a simple Jfet buffer, you are adding a blend circuit. And it's EffectsLayouts board so of course there's no schematic (I hate those guys for that. Schematics tell the story).

They recommend using a J201 Jfet and their wiring scheme assumes a D-S-G pinout. What did you actually use? (And J201s are pretty unobtanium right now, if that's what you used, how confident are you that it is authentic? How did you measure it?)  It also appears that there is a 10uf cap after the Jfet and their drawing makes it appear to be an electrolytic.

I don't really understand their layout (why are they linking the "in" and the "Send." That seems weird. And the way the pot is wired, it appears to be panning and not blending, but the confusing thing is that nothing is being dumped to ground. And the biasing on the drain looks sketchy. If you hook this circuit up to a breadboard and put 9 volts to it, what voltage do you get at the drain vs. the gate.  I guess I don't really understand how your EffectsLayout tagboard actually works. Here's a PCB that actually blends two signals. Not so say that one is better than the other, its just that I can look at the schematic and see that it makes sense to me. Without a schematic, the EffectsLayout board just looks like gibberish to me. 



			https://guitarpcb.com/wp-content/uploads/2018/06/Buff-N-Blend-v2-2021.pdf


----------



## delackattack

I actually used a 2n5457 instead on both circuits I’ve made.
The first is still completely operational and the second one has been a dud so far.
This is the one I just made with a Fairchild J201


----------



## Mike52

delackattack said:


> I actually used a 2n5457 instead on both circuits I’ve made.
> The first is still completely operational and the second one has been a dud so far.
> This is the one I just made with a Fairchild J201


That thing looks like it would be easy to connect to a breadboard. When you put 9v to it, what readings do you get on the drain and the gate?
And as a practical matter, maybe check continuity everywhere and make sure some solder hasn't dripped somewhere where it isn't supposed to be.

And a best practices thing that I'm sure you already know, but I would socket sensitive components (Jfets, ICs, etc). I just wouldn't ever put heat to them (though I'm sure they can mostly take it). And in your specific case, I'd socket the 4.7k resistor as well. That's a bias resistor and the value may have to change. 









						2 Pin 2.54mm DIP SIP IC Sockets Adaptor Solder Type
					

GTK - Get It Fast - Same Day Shipping




					www.taydaelectronics.com


----------



## delackattack

Also I had just noticed the side with Return/ out/ 9+ was in the wrong slots


----------



## Mike52

delackattack said:


> Also I had just noticed the side with Return/ out/ 9+ was in the wrong slots


I would work one problem at a time. You need to find out why you got smoke and, more importantly, did the smoke damage something. I'd isolate it on a breadboard and check voltages first. When you are sure in your mind that the Jfet is ok, then I'd start worrying about how to fly it into the existing circuit.

(So does that mean you were running 9v to one of the pot lugs?)

PS: Your particular blend circuit is explained in Post #21. Here's a schematic to it: 




And here's some discussion about it where the author says use only Linear pots:  








						Mini JFET Blend
					

Collection of vero (stripboard) & tagboard layouts for 100s of popular guitar effects, with over 500 verified designs. DIY your own boutique effects!




					tagboardeffects.blogspot.com


----------



## delackattack

I am pretty sure I was running it to a pot lug.
I wired a new one into the pedal but now I’m coming across the same issue.
Volume all the way with the blend is at zero, kind of a mix at 50 percent and dead silent when I max the blend.
I’ve also wired it both to the C23 cap and the DC jack.
I’m having my guitarist bring my first one back so I can re examine what I did or didn’t do to get to work on my first try.


----------



## delackattack

Mike52 said:


> I would work one problem at a time. You need to find out why you got smoke and, more importantly, did the smoke damage something. I'd isolate it on a breadboard and check voltages first. When you are sure in your mind that the Jfet is ok, then I'd start worrying about how to fly it into the existing circuit.
> 
> (So does that mean you were running 9v to one of the pot lugs?)
> 
> PS: Your particular blend circuit is explained in Post #21. Here's a schematic to it:
> View attachment 20152
> 
> And here's some discussion about it where the author says use only Linear pots:
> 
> 
> 
> 
> 
> 
> 
> 
> Mini JFET Blend
> 
> 
> Collection of vero (stripboard) & tagboard layouts for 100s of popular guitar effects, with over 500 verified designs. DIY your own boutique effects!
> 
> 
> 
> 
> tagboardeffects.blogspot.com


Can I check the voltages with a Multimeter?


----------



## delackattack

I do have a couple Buff N Blend pcbs laying around that I could try as well but I feel like a fella earlier had mentioned oscillation issues with it?
Probably worth a shot


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## Mike52

delackattack said:


> I am pretty sure I was running it to a pot lug.
> I wired a new one into the pedal but now I’m coming across the same issue.
> Volume all the way with the blend is at zero, kind of a mix at 50 percent and dead silent when I max the blend.
> I’ve also wired it both to the C23 cap and the DC jack.
> I’m having my guitarist bring my first one back so I can re examine what I did or didn’t do to get to work on my first try.


This is a perfect opportunity to use a breadboard. If you ran 9 volts to one of the pot lugs then the schematic is a clue to what you are possibly facing. The schematic tells the story.



I barely know what I'm talking about, (*and I keep hoping that more experienced builders will weigh in!!! Hello, [tap, tap] is this thing on?*) but my suspicion is that the negative side of that 10uf capacitor saw +9v DC, or some part of it. If that is the case then it is possible that that is the source of the savory aroma of "Oops" that you experienced. You can Google "what happens when electrolytic capacitors are installed backwards" to learn a little about the issue. But I'm not positive, just suspicious.

In any case, this is a simple circuit to run and test. You plug the 9v node into the breadboard power rail and you plug the ground into the negative rail and then hook those rails to the respective ends of a fresh 9v battery. Then you just read voltages at the drain and the gate (referenced to ground, of course). If you don't understand why that is important, definitely read up on Jfet transistors and how they work.

As you can see by the schematic, the drain should get 9 volts and the entrance to the gate is a voltage divider so that should get exactly half of the voltage that the drain is receiving. Make sense?

Now I just want to play guitar and build pedals that I want to play and then play them. Debugging circuits sucks and I don't want to waste time doing all that crap. But the fact is, when I spend the time studying circuits and debugging problems my knowledge base grows and at the same time it expands the opportunities for me to modify pedals to my particular liking, or construct something exactly the way I want it constructed. I'd strongly encourage you to chase down this problem and fix it now, rather than shift gears and go on to something that looks easier (especially when two other people in this thread have mentioned known problems with it). You will be happy that you did. Just sayin ....


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## delackattack

Mike52 said:


> This is a perfect opportunity to use a breadboard. If you ran 9 volts to one of the pot lugs then the schematic is a clue to what you are possibly facing. The schematic tells the story.
> View attachment 20181
> I barely know what I'm talking about, (*and I keep hoping that more experienced builders will weigh in!!! Hello, [tap, tap] is this thing on?*) but my suspicion is that the negative side of that 10uf capacitor saw +9v DC, or some part of it. If that is the case then it is possible that that is the source of the savory aroma of "Oops" that you experienced. You can Google "what happens when electrolytic capacitors are installed backwards" to learn a little about the issue. But I'm not positive, just suspicious.
> 
> In any case, this is a simple circuit to run and test. You plug the 9v node into the breadboard power rail and you plug the ground into the negative rail and then hook those rails to the respective ends of a fresh 9v battery. Then you just read voltages at the drain and the gate (referenced to ground, of course). If you don't understand why that is important, definitely read up on Jfet transistors and how they work.
> 
> As you can see by the schematic, the drain should get 9 volts and the entrance to the gate is a voltage divider so that should get exactly half of the voltage that the drain is receiving. Make sense?
> 
> Now I just want to play guitar and build pedals that I want to play and then play them. Debugging circuits sucks and I don't want to waste time doing all that crap. But the fact is, when I spend the time studying circuits and debugging problems my knowledge base grows and at the same time it expands the opportunities for me to modify pedals to my particular liking, or construct something exactly the way I want it constructed. I'd strongly encourage you to chase down this problem and fix it now, rather than shift gears and go on to something that looks easier (especially when two other people in this thread have mentioned known problems with it). You will be happy that you did. Just sayin ....


Okay, im gonna put it on a breadboard. But, would a breakoutboard make a difference as to how i should be wiring this up? I only ask cause the first one I did used a 3pdt and wired it "the ole fashion way" and its the one that worked on the first try


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## Mike52

delackattack said:


> Okay, im gonna put it on a breadboard. But, would a breakoutboard make a difference as to how i should be wiring this up? I only ask cause the first one I did used a 3pdt and wired it "the ole fashion way" and its the one that worked on the first try


The point of breadboarding is to see if your blender still works as it should. Does it have 9v where it's supposed to, does it have half voltage where its supposed to, is the electrolytic still functioning. That is a separate issue from how to fly this circuit into the host pedal. And I think how you could most effectively wire it is covered in this thread by someone else who is using the exact same blender circuit that you are using (Post #21 and on).

You could actually use the breadboard to test this as well. Just clip in wires to the suggested locations in the host pedal and see what happens. You can fly +9 volts and ground from the host pedal to the breadboard power rail. And then start the experiment.

Your 3pdt is just a switch that drops the blender circuit in and out of the host pedal on command, right? The 3pdt had to be connected to the host circuit somehow. But it sounds like what you are trying to do is make the blender circuit always on while the pedal is on, so adding an additional 3pdt may not be the right solution for you.

But now that I think about it, it seems like you could get filtered 9v and ground from a 3pdt PCB pad if you are using them, since they are getting their 9v from the circuit's power rail. This guy, as just one handy example, has additional grounding points and 9v power takeoff. (I'd be curious as to whether you could grab 9v from the LED circuit somehow so that when the host pedal is turned off, the blender circuit is also turned off. That circuit takes a signal from the "LED_BLK across a dropping resistor to the anode and cathode pads. Wouldn't that mean that there's 9 volts on the LED_BLK solder pad when the pedal is on? Hmm.)



Anyone else want to weigh in here?

I know we are late in the game here, but this also might be a good project to take the the Troubleshooting forum. Might get more experienced eyes on the problem.

(also, the thing that's been nagging at me is your wires. You have too many of them. That's why it looked so odd.




Your input and send are the same thing. You are scavenging a guitar signal from the host pedal so that the blender can process it. Only one wire comes into the circuit, not two. Then when you've got the signal and the circuit has done its magic, you send it back. Wiring pots always confuses me, but this thread will explain all that.)


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## delackattack

Mike52 said:


> The point of breadboarding is to see if your blender still works as it should. Does it have 9v where it's supposed to, does it have half voltage where its supposed to, is the electrolytic still functioning. That is a separate issue from how to fly this circuit into the host pedal. And I think how you could most effectively wire it is covered in this thread by someone else who is using the exact same blender circuit that you are using (Post #21 and on).
> 
> You could actually use the breadboard to test this as well. Just clip in wires to the suggested locations in the host pedal and see what happens. You can fly +9 volts and ground from the host pedal to the breadboard power rail. And then start the experiment.
> 
> Your 3pdt is just a switch that drops the blender circuit in and out of the host pedal on command, right? The 3pdt had to be connected to the host circuit somehow. But it sounds like what you are trying to do is make the blender circuit always on while the pedal is on, so adding an additional 3pdt may not be the right solution for you.
> 
> But now that I think about it, it seems like you could get filtered 9v and ground from a 3pdt PCB pad if you are using them, since they are getting their 9v from the circuit's power rail. This guy, as just one handy example, has additional grounding points and 9v power takeoff. (I'd be curious as to whether you could grab 9v from the LED circuit somehow so that when the host pedal is turned off, the blender circuit is also turned off. That circuit takes a signal from the "LED_BLK across a dropping resistor to the anode and cathode pads. Wouldn't that mean that there's 9 volts on the LED_BLK solder pad when the pedal is on? Hmm.)
> View attachment 20185
> Anyone else want to weigh in here?
> 
> I know we are late in the game here, but this also might be a good project to take the the Troubleshooting forum. Might get more experienced eyes on the problem.
> 
> (also, the thing that's been nagging at me is your wires. You have too many of them. That's why it looked so odd.
> 
> View attachment 20187
> Your input and send are the same thing. You are scavenging a guitar signal from the host pedal so that the blender can process it. Only one wire comes into the circuit, not two. Then when you've got the signal and the circuit has done its magic, you send it back. Wiring pots always confuses me, but this thread will explain all that.)


So I wouldn’t need the IN and OUT on the SFB or vice versa?
🧐


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## Mike52

delackattack said:


> So I wouldn’t need the IN and OUT on the SFB or vice versa?
> 🧐


I don't understand the question. Have you read this post and his followup posts? He used your circuit and made it work on the real pedal.






						Adding a blend to a Promethium (HM-2)
					

I modded my real HM-2. The schematic at the Peperspedals link shows it wired right in between the flip flop switching (Q4 & Q10).  The Promethium also has the in and out buffers, so it should work the same.     You can see where "send", "return" and "output" are wired, when using the Tagboard...




					forum.pedalpcb.com
				




He may be wrong, or he may be right. But you can figure it out by linking the two circuits to your breadboard as I described above.

As to your wires. Your picture shows that you have 9 wires coming off the circuit. As I look at the schematic, I can only see seven wires at most (and one is redundant in this specific case). There should be a (1) +9v, (2) a ground, an (3) input, a (4) send connected to the input, and then three wires to connect the SFB to the three lugs of a pot. What do the other two wires on your board do?




And a followup question: Have you checked the continuity between all the wires that are supposed to be connected by the circuit and all the traces. I just see a lot of solder globs that could be touching other circuits, and your pot wires look like they aren't going to the right places on the output side of things. It almost looks like white #2 is connected to 9v and like white #3 is connected to both of the other blue wires. This is where color coding wires is really helpful in preventing mistakes.


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## delackattack

Mike52 said:


> I don't understand the question. Have you read this post and his followup posts? He used your circuit and made it work on the real pedal.
> 
> 
> 
> 
> 
> 
> Adding a blend to a Promethium (HM-2)
> 
> 
> I modded my real HM-2. The schematic at the Peperspedals link shows it wired right in between the flip flop switching (Q4 & Q10).  The Promethium also has the in and out buffers, so it should work the same.     You can see where "send", "return" and "output" are wired, when using the Tagboard...
> 
> 
> 
> 
> forum.pedalpcb.com
> 
> 
> 
> 
> 
> He may be wrong, or he may be right. But you can figure it out by linking the two circuits to your breadboard as I described above.
> 
> As to your wires. Your picture shows that you have 9 wires coming off the circuit. As I look at the schematic, I can only see seven wires at most (and one is redundant in this specific case). There should be a (1) +9v, (2) a ground, an (3) input, a (4) send connected to the input, and then three wires to connect the SFB to the three lugs of a pot. What do the other two wires on your board do?
> View attachment 20188
> 
> And a followup question: Have you checked the continuity between all the wires that are supposed to be connected by the circuit and all the traces. I just see a lot of solder globs that could be touching other circuits, and your pot wires look like they aren't going to the right places on the output side of things. It almost looks like white #2 is connected to 9v and like white #3 is connected to both of the other blue wires. This is where color coding wires is really helpful in preventing mistakes.


Sorry, juust got back  to this. The extra two wires are send and return. This is also the past circuit ive made that i had mentioned placing wires in the wrong postions


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