# Percolation Station -> Karma Suture (sort of)



## Chuck D. Bones

This is my attempt to replicate the Catalinbread Karma Suture using the Percolation Station (Harmonic Precolator) board.  Catalinbread offers some tantalizing clues in their adverts as to what they did to create the Karma Suture from the Harmonic Percolator.  I have not been able to find a Karma Suture schematic, and so far, I've been too cheap to buy a KS to trace myself. So this is my best guess. The KS adds two knobs: DIODES and DENSITY.  I put my own spin on it and added a diode switch.  With DIODES and DENSITY dimed and the DIODE switch set to GE, it's a stock HP.

The DENSITY control rolls back the bass at the input, which has a huge influence on the tone.  I replaced C2 with a 3.3nF cap and then wired a C100K and 47nF cap in series and connected that in parallel with C2.  I put the DENSITY pot, and two caps on a little Vero board.

The DIODES control is simply a C50K pot connected in series with the clipping diodes.  When DIODES is turned down, the clipping diodes have less and less effect on the tone.  Volume increases, distortion and compression decrease.  For fun, I wired in a SPDT on-off-on switch to select between Ge diodes, LEDs or Si diodes.  I also increased the BALANCE (Volume) pot from A50K to A100K so there's a little more signal available to push the diodes.  I used red LEDs and 1N4743A zeners for the Si diodes.  The zeners are wired in parallel, so they only conduct in the forward direction.  Zeners tend to have a larger forward drop, that's why I chose them.  Any Si diode will work, such as 1N4148.  I left the diodes and R5 off of the PCB and put the diodes, R5 and DIODES pot on a little Vero board.  It would have been neater, but the LEDs were thrown on as an afterthought.  The LEDs are pretty subtle; you have to crank the HARMONICS, DENSITY and DIODES controls for the LEDs to do anything.

If you set DIODES and DENSITY to zero, BALANCE to max, and use HARMONICS as a Boost control, it makes a decent treble booster.

Here's the schematic and some pix.  I went with side-mounted jacks so I'd have room for the Vero boards.  Top-mounted jacks would probably have fit, but I wanted easy access to the two new pots and Vero boards.  As you can see, it's a very snug fit between the jacks and the stomp switch.  I had to grind the jacks down a bit and mount the stomp switch rotated 90 deg.  I recommend socketing both transistors because this pedal's tone is very sensitive to the transistors.  Lower hFE gives less compression and more headroom.  I currently have a Russian P28 and 2N2222A installed.  One day, I'll paint and label the box. The controls layout is the same as the KS.









And here it is painted and labeled (finally!).  I went with the KS control names.


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## Mourguitars

Cant you add a small trim pot / bias control to adjust the sensitive of the transistors ?

I think i had one of those on the side of my Twin bender.....Very cool build btw !


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## Chuck D. Bones

Thanks!  I'm planning to do an acrylic pour, but I'm also kinda digging the industrial bare metal look.

What do you mean by "sensitive"?  There are a couple of resistors that could be tweaked to accommodate higher gain transistors.  I usually avoid trimpots as much as possible because they don't stay put and are not all that reliable.  I think you are better off trying different transistors than messing with trimpots.  Just my opinion.


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## Mourguitars

I thought those transistors are weather sensitive...like in Fl humidity ....if the pedal sounds bad adjust the bias to them. Thats pretty trick what you done...all in CDB fashion , great layout with the side jacks.

Only trick i done was stand up the broom yesterday ...lol...it worked !


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## Chuck D. Bones

Thanks, Mike.

Ge transistors are temperature sensitive.  They should definitely NOT be sensitive to humidity.  The transistor die is hermetically sealed inside the metal packages.  Plastic package devices are not sealed quite so well.  Believe me, if any moisture gets in there, the transistor is history.


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## Cucurbitam0schata

@Chuck D. Bones - where'd you end up sourcing the transistors and diodes? I tend to be a bit leery of hard-to-find-parts designs, but this one's really intriguing! 
@tcpoint - you mentioned in another thread that the GE diodes had to specifically be 1n695, how'd you come up with that spec?


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## Chuck D. Bones

I bought a set of transistors: 2N3565 & 2N404 from Small Bear.  Also got the 1N695 diodes from Small Bear.  I tried those transistors and some others I had, settled on 2N2222A (from my NOS stash) and P28 (bought on eBay from a guy in Ukraine).  I don't recommend buying semiconductors on eBay unless a) you know how to test them and b) you are a gambler.  Feel free to experiment with different transistors and Ge diodes.  I found that medium HFE (60 to 100) transistors bias better in this circuit than high HFE.  The Ge transistor needs to be low leakage. It's a cool dirt pedal and makes some bitchen tones.  Have fun!


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## tcpoint

Cucurbitam0schata said:


> @Chuck D. Bones - where'd you end up sourcing the transistors and diodes? I tend to be a bit leery of hard-to-find-parts designs, but this one's really intriguing!
> @tcpoint - you mentioned in another thread that the GE diodes had to specifically be 1n695, how'd you come up with that spec?


The 1N695 is the diodes used on the "Steve Albino" version.


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## Chuck D. Bones

I think it's Steve Albini.  He has all of his pigment.


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## tcpoint

Chuck D. Bones said:


> I think it's Steve Albini.  He has all of his pigment.


That's what meant to type.  Ha.


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## Cucurbitam0schata

Okie dokie, I'm working on sourcing parts for this percolator - this is the first project of mine that would use transistors like these. 

Some noob questions for you all:

*Sockets* - in order to play around with transistors, you use sockets, right? If so, do you use a socket like this from Small Bear?

*Transistor Experimenting* - I like the idea of swapping transistors and hear different sounds, like @Chuck D. Bones did. I'll try the original transistor pairs ( 2N404A / 2N3565 ) and some other pairs... any suggestions on _how to pair rando transistors _would be greatly appreciated. Can you just swap NPN and PNP transistors to your heart's delight? I cruised through a few sources, and there are (duh) so many to choose from. 
 - For example, if I wanted to use a 2N2222A (NPN), could I pair it with just another medium Hfe PNP transistor? 
 - Any other pro tips or reading material or youtube vids would be appreciated, if that's easier. 

Thanks, ya'll!


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## Chuck D. Bones

Those SB sockets are the ones to get. 

As for pairing transistors, there are as many opinions on how to do that as there are transistors!  Just get a few and try them.  Don't be surprised if many of the combinations sound the same.

My goal with the Percolator was to get the highest collector voltage on the NPN for maximum headroom.  Both transistors influence that.


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## Cucurbitam0schata

Another question on the Percolator: that 50 nF cap... can I use a 47 nF cap? As much as I want to attempt your sweet mods, I may opt to go an easier route prior to some next level wizardry...


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## Chuck D. Bones

47nF is plenty close.  This cap has a strong influence on the tone at high HARMONICS settings.  Smaller caps let in less bass so the sound is clearer and less muddy.


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## Cucurbitam0schata

Awesome - now you're really tempting me to try out your mod! Sounds fun to be able to mess around with that setting...


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## Chuck D. Bones

I finally finished the painting and lettering, see 1st post...


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## Cucurbitam0schata

Looks really good, Chuck! Gotta investigate this type of finishing. Just soldered up the vero boards for Chuck's mod. I'll post a build report soon.


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## Chuck D. Bones

Thanks, Man.  Have fun with yours.


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## NoizeNiche

Hey! I just picked up this same clone and I'm wondering how you were able to do everything. Going to be trying to use your photos and info to make one for myself!


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## Chuck D. Bones

Here are my Vero diagrams, if that helps. Should be pretty obvious where to make the cuts.  These are viewed from the component side.


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## NoizeNiche

Wow thanks! As soon as my sourced parts come in, I'll get started!


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## NoizeNiche

Well I've got my order on the way. Ordered from Stomp Box Parts. Enough for like 10 of those things haha. Anyways, now I need to order my enclosures. Any idea where I can get some from? Preference for powder coated?


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## Chuck D. Bones

Tayda.  Most of the enclosures you see in the Build Reports came from Tayda. Pay the extra couple of bucks for DHL shipping.  If you are cheap (and patient), wait for their next 15% off coupon.
Small Bear is also a very good source for enclosures, but they are offline at the moment.


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## cooder

Awesome stuff, thanks yet again for sharing all that stuff and writing it up! I'm getting more curious about this circuit now, just not sure how the tones would work for me.... but I guess I gotta put it on the list and find out!


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## Knotty Pine

Chuck D. Bones said:


> Here are my Vero diagrams, if that helps. Should be pretty obvious where to make the cuts.  These are viewed from the component side.
> 
> View attachment 4646
> 
> View attachment 4647


Hey Chuck could you mark where the cuts are? (I’m not as savvy to where they should be made) I’m about to build this PCB and I want to implement the mods you’ve added.


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## Chuck D. Bones

The top Vero has one cut between the orange trace and the magenta trace.

The bottom Vero has one cut between the orange trace & the blue trace.  

You also need to bridge pad Dn1 to pad Dn2 with a jumper.

Is this your first Vero?


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## Chuck D. Bones

Aion has just published a trace of the Karma Suture - both silicon and germanium editions.  So my guess on what was inside wasn't too far off...

Karma Suture trace


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## fig

Chuck D. Bones said:


> Aion has just published a trace of the Karma Suture - both silicon and germanium editions.  So my guess on what was inside wasn't too far off...
> 
> Karma Suture trace


Never had a doubt.


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