# This Week on the Breadboard: The 'lectric Mama Flanger



## Chuck D. Bones (Sep 14, 2021)

I wanted to build something using the recently acquired V3207D and MN3102 chips, so here's the first pedal out of the gate.  It's a flanger based on the EHX Electric Mistress, with some updates and mods.  I remember tracing an Electric Mistress back in '77.  The design is both minimalist and clever.  Unlike most clock oscillators, the one in the EM modulates the period of the clock rather that the frequency.  That means that the pitch shift is constant across the entire sweep.  The LFO in the EM was too clever for words.  While it worked pretty well, it varied considerably from unit-to unit.  I deployed a more traditional LFO, including clicking prevention.  The freq range runs from 0.07Hz to 9.2Hz.  At the low end of the speed range, it's a chorus.  At the top end of the range, it sounds like a ring modulator.  The tone is quite smooth, despite the minimal filtering.  These V3207D's rock!  I added a balance trim to achieve the deepest notches.  I never had much use for the FILTER setting, but it does come in handy when adjusting the timmers.  Next, I'm going to try a sinewave LFO to see how that sounds.


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## jjjimi84 (Sep 14, 2021)

That seems like a minimal parts Flanger.... putting that on the to do list. Nice work!


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## Chuck D. Bones (Sep 14, 2021)

Thanks!

C2 should be film, Q1 & Q2 can be any high-gain Si.

Not shown: 

Anti-pop resistor on the input.
Power protection and filtering.  Use 100uF & 100nF for filtering.  
Switching and On/Off LED.


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## fig (Sep 14, 2021)

Very nice sir. Thanks for the labels on the picture as well!


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## cooder (Sep 14, 2021)

jjjimi84 said:


> That seems like a minimal parts Flanger.... putting that on the to do list. Nice work!


You betcha....


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## lrgaraujo (Sep 14, 2021)

Awesome Work, Chuck! How do you like the more _chorusy _sounds of it?
I might have found just the project for the couple of 3207 and 3102 I've recently gotten


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## Chuck D. Bones (Sep 14, 2021)

The chorus is a little dry sounding because the modulation is too precise.  Might be better with a sinewave LFO.


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## Chuck D. Bones (Sep 16, 2021)

I have tried a sinewave LFO and I find the results much more sonically satisfying.  The issue now is making a sinewave LFO that is tunable over at least 2 decades, fairly low distortion and reliable.  I have one on the breadboard, but it does not really meet any of the criteria.  I ran across a paper by noted Caltech professor Dr. R. D. Middlebrook that offers a solution. Once I get that working, I'll post an updated schematic.


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## cooder (Sep 18, 2021)

Chuck D. Bones said:


> I have tried a sinewave LFO and I find the results much more sonically satisfying.  The issue now is making a sinewave LFO that is tunable over at least 2 decades, fairly low distortion and reliable.  I have one on the breadboard, but it does not really meet any of the criteria.  I ran across a paper by noted Caltech professor Dr. R. D. Middlebrook that offers a solution. Once I get that working, I'll post an updated schematic.


It gets really serious when Chuck checks out what another genius has to say... I'm twiddling thumbs and trying to grow new neuron connections in anticipation.


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## Chuck D. Bones (Sep 18, 2021)

I had the good fortune to attend a 3-day class that Dr. Middlebrook taught at my employer's about 20 years ago.  It was a revelation.

Still working on the sine converter.  It's a fine line between getting it right and going total OCD.


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## fig (Sep 18, 2021)

...so you are going full-on OCD then?


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## Chuck D. Bones (Sep 18, 2021)




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## Chuck D. Bones (Sep 18, 2021)

Here's the latest version.  Took a bit of fiddling to get the sinewave LFO working, but it's working very well now.  This is not an easy build because for optimum performance, the four trimmers have to be adjusted using a scope and sig gen.  But you can get pretty close tuning them by ear.  U4 should be a rail-to-rail opamp.  A pair of CA3130s will work nicely.  The LT1490 I used is a great dual opamp, but it's a little pricy at over $5 ea.  This circuit can be made to work with a TL072 for U4, but the sweep range is diminished.  This circuit is picky about which JFET you use for Q3, and whatever JFET is used requires three resistors to be selected-in-test (SIT).  We want Q3 to have Vp between 1V and 2.5V (more is better) and Idss has to be less than 10mA.  R31 & R32 are calculated based on Vp and Idss.  R33's value depends on Q3's parameters and is chosen to get the maximum sinewave signal at U4-7 without clipping.  As my mentor Arpad used to say _"If it's do-able, somebody vill do it!"*_ If this Rolls-Royce version is a bit too much, then Q3, R29-R31 and D2-D3 could be replaced with four diodes and sound pretty much the same. No SITs and no TR4.






* The implication was that just because a thing _could _be done, that didn't mean it _should _be done.


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## Chuck D. Bones (Sep 19, 2021)

Version 0.5 post deleted - not quite ready for prime time.  V0.4 works great, but increase C9 to 10uF NP.  

Still working on a diode-based sine shaper. 🤞


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## jubal81 (Sep 19, 2021)

Would a uC StompLFO work in there?


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## Chuck D. Bones (Sep 19, 2021)

I'll bet it would work great.  I'll read up on it.  Have you used one?


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## jubal81 (Sep 19, 2021)

Chuck D. Bones said:


> I'll bet it would work great.  I'll read up on it.  Have you used one?


Not yet. I've got 3 or 4 of them sitting my desk that I haven't gotten around to messing with.


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## Chuck D. Bones (Sep 20, 2021)

I can get the chips from Mouser and the code from Electric Druid, all I need now is to know where to get the programmer.  No point in messing around with analog LFOs when this device is available.


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## Chuck D. Bones (Sep 20, 2021)

ED even has an LFO and BBD clock VCO in one chip.  Begs the question why I'm messing around with this analog shit.

('cuz I wanna, that's why)


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## duffy_lane (Sep 20, 2021)

Seemingly legendary resources by Dr. Middlebrook if anyone else is interested.
Have me questioning if I actually know how to read 😅






						Dr. Middlebrook's Website
					

Technical therapy for analog circuit designers, including Dr. Middlebrook's Structured Analog Design Course and the General Feedback Theorem (GFT) in circuit simulator software.



					web.archive.org
				








						Books, papers, CDs and DVDs - Resources
					

More information about technical therapy, Structured Analog Design Course and the General Feedback Theorem (GFT) and more



					web.archive.org


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## Chuck D. Bones (Sep 20, 2021)

The 3-day course I attended was a subset of that material.  Part-way into the first day, I turned to the engineer sitting next to me and said "You know, I was already doing some of this stuff and I just chalked it up to laziness."  He said "Yeah, me too."  It felt good to have our "lazy" techniques validated.

I'm going to download all of this stuff, thanks!


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## fig (Sep 20, 2021)

Premise

_"Not much of what you learned in school turned out to be much use"_


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## Chuck D. Bones (Sep 20, 2021)

So true, as least as far as electrical engineering was concerned.

At one point in the lecture he made a disparaging reference to "rotton old tubes" and then in the next breath allowed that they were a hulluva lot more linear than transistors.


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## jubal81 (Sep 21, 2021)

Chuck D. Bones said:


> ED even has an LFO and BBD clock VCO in one chip.  Begs the question why I'm messing around with this analog shit.
> 
> ('cuz I wanna, that's why)


OMG, you're right. I forgot all about his flanger project.


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## Chuck D. Bones (Sep 21, 2021)

I finally got the diode sine shaper circuit working the way I like.





Any further developments will employ the Flangelocious LFO/clock chip from Electric Druid.  That chip will replace the MN3102 and everything in the bottom half of the schematic. The only extra part it requires is a +5V reg.  Credit where credit is due, it was some design notes on the Flangelicious page that set me on the right path for tuning the sine shaper above.  Turns out that a sinewave is not exactly what we want.  What we want is a "bent triangle" wave.  Notice that the waveform below does not really flatten out at the top and bottom like a sinewave does.  We don't want the LFO sweep to stall at the extremes, which is what happens with a sinewave LFO.  Backing off on the shape trim makes the waveform a little more pointed at the top and bottom.





The shape trim lets us fine tune the "pointiness" of the waveform and compensate for variations in diode Vf.  The range trim lets us maximize the sweep range.  The waveform above was measured at pin 3 of the RANGE pot.  This is the largest control signal that the clock VCO can accommodate.  As I mentioned in an earlier post, U4 can be a TL072.  The only downside of using a TL072 is the amplitude of the waveform above will about be 2V to 3V smaller because the TL072 output cannot swing to the rails.  There is still plenty of sweep range available.  The only trimmers that are critical are the blend trim and color trim.  The others could be hardwired with only slightly diminished performance.

I should add that this thing has a HUGE sweep range, much more than commercial flangers.  At the slowest speed, approx. 0.011Hz, and a high range setting we get a nice chorusing effect.  For flanger effects, I turn the RATE up and usually set the RANGE below 10:00.  I might try a log-taper pot there.  The waveform above is max LFO speed.  I had to use a stopwatch to measure the slowest speed because my 'scope doesn't go that slow.


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## Big Monk (Oct 10, 2021)

Chuck D. Bones said:


> I finally got the diode sine shaper circuit working the way I like.
> 
> View attachment 16227
> 
> ...



I’ve been looking for something that gives me the classic Electric Mistress sound but with unity volume considerations and a blend control. This might be it!

Either that, or put a blender pedal on my Mooer E-lady.


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## JamieJ (Oct 10, 2021)

Any chance of this becoming a boneyard build @Chuck D. Bones ?


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## Barry (Oct 10, 2021)

JamieJ said:


> Any chance of this becoming a boneyard build @Chuck D. Bones ?


I added it to the wish list


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## Chuck D. Bones (Oct 10, 2021)

I have one more thing to try on this design and that is using the Flangelicious LFO/Clock chip.  Time to pull the trigger on that Mouser order so I can have some microcontrollers.


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## fig (Oct 10, 2021)

Oh goodie! I love shopping. Can I push the cart? Can I? Can I?


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## Chuck D. Bones (Oct 10, 2021)

You can ride in the cart if you promise not to stand up.


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## jubal81 (Oct 10, 2021)

Chuck D. Bones said:


> I have one more thing to try on this design and that is using the Flangelicious LFO/Clock chip.  Time to pull the trigger on that Mouser order so I can have some microcontrollers.


Sweetness! Exciting stuff.
Any chance you could explain how you're doing the programming for those of us less digitally inclined?


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## Chuck D. Bones (Oct 10, 2021)

I'll be doing it for the first time, so I should probably make a youtube video, including all of the fuck-ups. 

The initial setup includes buying a USB programmer on eBay, installing programming SW from MicroChip on my PC and downloading the hex file from Electric Druid.  So far, I have only accomplished the 3rd task.

After that, install the chip in the programmer, plug in the programmer, run the programming SW, load the hex file and press the PROGRAM button.


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## cooder (Oct 10, 2021)

Such a cool project, can't wait for the version with Electric Druid chip!


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## Chuck D. Bones (Oct 10, 2021)

The deal with ED is their code is free for personal use.  If you want to go commercial, then you either buy programmed chips from ED or pay a license fee and program your own.


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## danfrank (Oct 15, 2021)

I think they use Microchip PIC ICs. I'm surprised ED is giving out the code, it's very nice of him! These PIC ICs have an option where the programmer can "burn" the inputs to the chip after programming so the IC can't be copied but is still able to execute the code that was programmed into it.
Back in the '90s these type ICs were used to trick cable boxes into "test" mode so the box would decode all cable channels. What a hoot!!

One more thing... When using the ED (no! not that ED!) chip which has to be run at +5 volts, the 3207 also has to be run at +5 volts unless the clock signal is boosted in amplitude to the voltage that the 3207 is using.
Thanks for this thread Chuck, a very interesting read!


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## Chuck D. Bones (Oct 16, 2021)

That is correct, sir!


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## Chuck D. Bones (Nov 15, 2021)

I've got this flanger running with the ED 4KNOBFLANGE chip.  Works well except I'm fighting a noise issue.  There's some slight ticking that's tied to the RATE and DEPTH control settings.  Goes away if I disconnect the output of the BBD.  Standby for further developments.


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## cooder (Nov 15, 2021)

All systems on stand by ready to rip...


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## Chuck D. Bones (Nov 16, 2021)

[edit]
Thought I fixed it.  I rearranged the power distribution and grounding and increase the filtering on the BBD output a little.  Here's how it looks now.  The 5V reg is hiding behind a capacitor to the left of the LFO/CLK chip.  Compare the parts count to the all-analog LFO & clock gen.  The RATE, DEPTH & MANUAL controls have a huge range.  Only two trimmers req'd.  The RATE, DEPTH & MANUAL are voltage-controlled, which means they could be hooked up to an expression pedal or other control source.  I'm calling this close but no cigar.  I want to spend some more time playing it and reviewing the circuit design.  I'm considering the merit of adding an output buffer.  This circuit is layout-sensitive since the 4KNOBFLANGE chip puts digital noise on the power and ground rails.


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## Big Monk (Nov 16, 2021)

Chuck D. Bones said:


> Fixed it!  Had to rearrange the power distribution and grounding and increase the filtering on the BBD output a little.  Here's how it looks now.  The 5V reg is hiding behind a capacitor to the left of the LFO/CLK chip.  Compare the parts count to the all-analog LFO & clock gen.  The RATE, DEPTH & MANUAL controls have a huge range.  Only two trimmers req'd.  The RATE, DEPTH & MANUAL are voltage-controlled, which means they could be hooked up to an expression pedal or other control source.  I'm calling this 99% done.  I want to spend some more time playing it and reviewing the circuit design.  I'm considering the merit of adding an output buffer.  This circuit is layout-sensitive since the 4KNOBFLANGE chip puts digital noise on the power and ground rails.
> 
> View attachment 18668
> 
> View attachment 18669



Boneyard Edition!!!!

EDIT: I've got all the major pieces for this one so I'm hoping you do decide to make a board of it.


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## Chuck D. Bones (Nov 16, 2021)

Output Buffer: who wants one?

This circuit needs an output buffer if you're driving a low-impedance load like a Fuzz Face or Range Master.

A simple output buffer requires four more parts: two R's, 1 C and an NPN transistor (or JFET).


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## Big Monk (Nov 16, 2021)

Chuck D. Bones said:


> Output Buffer: who wants one?
> 
> This circuit needs an output buffer if you're driving a low-impedance load like a Fuzz Face or Range Master.
> 
> A simple output buffer requires four more parts: two R's, 1 C and an NPN transistor (or JFET).



Can't hurt! Just picked up the ED chip. I already had the 3207s I bought for my upcoming Cepheid build.


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## Chuck D. Bones (Nov 16, 2021)

You buy the chip from ED?  Isn't shipping a bit expensive?  Or are you in the UK?


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## Big Monk (Nov 16, 2021)

Chuck D. Bones said:


> You buy the chip from ED?  Isn't shipping a bit expensive?  Or are you in the UK?



Nope. 7 euros total. About $8.34 USD shipped.

Bought it direct from ED.


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## Big Monk (Nov 16, 2021)

If you do end up doing a board for this, would you consider making the Blend an external control?


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## Chuck D. Bones (Nov 18, 2021)

OK, not completely fixed.  There is still a slight tick in the LFO/Clock chip near one end of the sweep.  It's an artifact of the chip code.  I must reluctantly remove the 4KNOBFLANGE chip from the design because once you hear the tick, you can't un-hear it.  Standby for further developments.

Regarding the external BLEND control, what exactly do you want it to do?  Bear in mind The 50/50 mix provides the deepest flanger tone.
a) Sweep from 100% dry to 100% wet.  The wet end would be pure vibrato with no characteristic flanger tone. We'd want a pot with a center detent so we can easily find the 50/50 mix.
b) Sweep from 100% dry to 50% wet.
c) Sweep from 50% wet to 100% wet.


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## Big Monk (Nov 18, 2021)

Chuck D. Bones said:


> OK, not completely fixed.  There is still a slight tick in the LFO/Clock chip near one end of the sweep.  It's an artifact of the chip code.  I must reluctantly remove the 4KNOBFLANGE chip from the design because once you hear the tick, you can't un-hear it.  Standby for further developments.
> 
> Regarding the external BLEND control, what exactly do you want it to do?  Bear in mind The 50/50 mix provides the deepest flanger tone.
> a) Sweep from 100% dry to 100% wet.  The wet end would be pure vibrato with no characteristic flanger tone. We'd want a pot with a center detent so we can easily find the 50/50 mix.
> ...



Dang! That's a shame about the ED chip. It was foolish of me to order one without the design complete. 

As far as the sweep, I think b) captures what I have in my head.


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## Chuck D. Bones (Nov 18, 2021)

I agree, it's disappointing.  
You might want to breadboard the circuit and give it a listen.  If you avoid the top-end of the sweep range, there's no tick.  Unfortunately for me, that's the end of the range I prefer to use.  Plan B is to try using the STOMPLFO chip and the original clock osc.  The advantage of the STOMPLFO chip is we have access to 8 different LFO waveforms, so that could be fun.  Plan C is to revert to the all-analog design.


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## Big Monk (Nov 18, 2021)

Chuck D. Bones said:


> I agree, it's disappointing.
> You might want to breadboard the circuit and give it a listen.  If you avoid the top-end of the sweep range, there's no tick.  Unfortunately for me, that's the end of the range I prefer to use.  Plan B is to try using the STOMPLFO chip and the original clock osc.  The advantage of the STOMPLFO chip is we have access to 8 different LFO waveforms, so that could be fun.  Plan C is to revert to the all-analog design.



Either way, I'm pumped. Plan C would not bother me at all as I just purchased the same chips for the Cepheid and would only need to grab a few more things for the LFO. Ordering the STOMPLFO is not a deal breaker either after finding out shipping direct from ED is super reasonable.

Keep us in the loop. This is very exciting.


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## Chuck D. Bones (Nov 24, 2021)

At long last, I think I'm done massaging this beast.  Presenting *The 6-knob Flanger*.

SPEED - DEPTH - MANUAL - COLOUR - BLEND - WAVEFORM

Per Big Monk's request, I installed a BLEND control and it comes in handy with some of the more "out there" settings.
The LFO is realized in the Electric Druid STOMPLFO chip.  ED provide the HEX file for free to DIYers.  I burned the code into a PIC 16F18313.  That chip sells for a little over a buck.  The schematic is on two sheets to make it more readable.  The audio path is on sheet one. The power supply, LFO and clock gen are on sheet two.  I annotated the voltages I measured on my breadboard.  I designed it with all B100K pots.  Most of the eight waveforms available from the STOMPLFO chip are useful. The sine and triangle produce the traditional flanger sweep.  The two random waveforms are fun.  There is a hyperbolic "sweep" waveform that is of no use with this clock VCO because the VCO has a hyperbolic response to control voltage.  If you only wanted two or three waveforms, that could be achieved with a few resistors and a SPDT toggle switch in place of the WAVEFORM pot. The STOMPLFO chip also has a Tap Tempo input that I did not use.  It basically overrides the SPEED control.  Any of the four control pots on the STOMPLFO chip could be replaced with an expression pedal or an external 0 to 5V control voltage.  The SPEED, DEPTH and MANUAL controls have a huge range.  I typically set SPEED below noon and DEPTH below 10:00.


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## music6000 (Nov 24, 2021)

Chuck D. Bones said:


> At long last, I think I'm done massaging this beast.  Presenting *The 6-knob Flanger*.
> 
> SPEED - DEPTH - MANUAL - COLOUR - BLEND - WAVEFORM


Something like this:


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## Chuck D. Bones (Nov 24, 2021)

That didn't take long!  If only I could work that quickly.


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## Big Monk (Nov 24, 2021)

Boneyard, Boneyard, Boneyard!


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## JamieJ (Nov 24, 2021)

How does it sound @Chuck D. Bones - can we get Electric Mistress tones from this circuit?


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## fig (Nov 24, 2021)

The proximity of the capacitors to the IC note...is that to reduce inductance between them? If no, perhaps a brief explanation please?


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## zgrav (Nov 24, 2021)

fig said:


> The proximity of the capacitors to the IC note...is that to reduce inductance between them? If no, perhaps a brief explanation please?


I think it reduces noise and might stop any oscillations.  Just guesses based on other schematics I have seen.


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## Chuck D. Bones (Nov 24, 2021)

I increased C23 to 560pF which moves the clock VCO range lower and the Electric Mistress tones are definitely there!  Set the WAVEFORM to Triangle, MANUAL to zero, BLEND to max and you're there.  Put a fuzz in front of it for the full jet-engine effect.  So far, I've tried a Servo FF and Chuck's FZ-1 and they both sound bitchen.  With other control settings, we can get a nice chorus or some spaced-out atonal synth effects.

Controls L-R: WAVEFORM - SPEED - DEPTH - MANUAL - COLOUR - BLEND

Chips L-R (top row) STOMPLFO (U6), clock VCO (U5), clock driver (U4), BBD (U3), 5V reg (U7).
(bottom row) mixer and Vref buffer (U2), preamp and pre-emphasis (U1).

Colour & blend trimmers are huddled under the COLOUR control.

The top power bus is Vdd (+5V).
Blue row below that is digital ground.
The middle red/blue pairs are Vcc & analog ground (2 rows of each)
Bottom red row is Vref.
Bottom blue row not used.

The notes about cap placement are to keep the digital noise originating in U6 from getting into the analog circuitry and to keep U6's control inputs from being upset by any noise pickup.


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## jubal81 (Nov 24, 2021)

The Wish List request is now live and you men all need to do your solemn duty and go vote the hell out of it.


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## Big Monk (Nov 24, 2021)

jubal81 said:


> The Wish List request is now live and you men all need to do your solemn duty and go vote the hell out of it.



It is done.


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## Chuck D. Bones (Nov 24, 2021)

I have a little more testing / tweaking to do.  I put the Flanger after a pedal containing a charge pump and the charge pump's switching freq was beating with the BBD's sample rate and making it "squeal like a piggy."


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## Chuck D. Bones (Nov 26, 2021)

Investigation & Findings:
The pedal that contained the charge pump mentioned above was a modified Chela as described here and here.  I tried another pedal with a charge pump in it, the Crunch Captain Deluxe and observed the same squeal. Next, I replaced the 'lectric Mama with a commercial Flanger, a Monoprice yellow Flanger which appears to be a relabeled Mooer E-Lady. It exhibited the same squeal behavior.

The cause of the squeal is some of the charge pump's 40KHz switching noise sneaks out of the pedal via the output jack.  When that 40KHz noise gets into a sampled circuit, like a BBD delay, chorus or flanger, the 40KHz signal is aliased down into the audio range when the sample clock is within ~10KHz of the charge pump noise.  When the flanger clock is swept toward the longer delay end on the range, that's exactly what happens.  Noise problems like this can be attacked on two fronts: the transmitter and the receiver.  

We can make the transmitter end less noisy by filtering the signal before it gets out of the box.  The modded Chela, which Cooder aptly named "Rippa," has a PRESENCE switch at the end which varies the high freq cutoff.  Either the up or down position of the PRESENCE switch provides enough high freq attenuation to kill the squeal.  The Crunch Captain Deluxe has no output filter on-board, so I will have to kludge one in. 

We can make the receiver less susceptible by filtering the signal coming in to remove as much of the 40KHz switching noise as possible.  I improved the 'lectric Mama's filtering upstream of the BBD by increasing R2 and C4, and adding another filtering stage with R7 and C5.  I had to retune the filtering on the output side of the BBD (C9, C10 & R12) to restore the overall freq response.  While I was at it, I tweaked the Vref voltage (increased R19) to maximize the BBD's headroom.  While all of this helped, it was not sufficient to kill the squeal.  It is also necessary to make sure that any pedal containing a charge pump does not transmit excess switching noise.


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## Big Monk (Nov 26, 2021)

My 4 Knob Flange chip just came in so not to bad on shipping time. May order the StompLFO chip just to have it.


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## fig (Nov 26, 2021)

Thanks, that answers a lot of questions (I think). If the charge pump is the source, wouldn't _all _circuits utilizing similar charge pumps, BBDs and clock chips exhibit similar results?


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## jubal81 (Nov 26, 2021)

10 votes on the wish list guys. We can do better.
Remember, the voting is done on the top right area of the post, not the normal "LIKE" for a forum post.


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## Barry (Nov 26, 2021)

jubal81 said:


> 10 votes on the wish list guys. We can do better.
> Remember, the voting is done on the top right area of the post, not the normal "LIKE" for a forum post.


It's got 16 votes on the one I posted for it


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## fig (Nov 26, 2021)

Mine shows 11. 😖


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## Barry (Nov 26, 2021)

So that makes 27


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## fig (Nov 26, 2021)

+ jubal's 10...37!


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## music6000 (Nov 26, 2021)

Chuck D. Bones said:


> Investigation & Findings:
> The pedal that contained the charge pump mentioned above was a modified Chela as described here and here.  I tried another pedal with a charge pump in it, the Crunch Captain Deluxe and observed the same squeal. Next, I replaced the 'lectric Mama with a commercial Flanger, a Monoprice yellow Flanger which appears to be a relabeled Mooer E-Lady. It exhibited the same squeal behavior.
> 
> The cause of the squeal is some of the charge pump's 40KHz switching noise sneaks out of the pedal via the output jack.  When that 40KHz noise gets into a sampled circuit, like a BBD delay, chorus or flanger, the 40KHz signal is aliased down into the audio range when the sample clock is within ~10KHz of the charge pump noise.  When the flanger clock is swept toward the longer delay end on the range, that's exactly what happens.  Noise problems like this can be attacked on two fronts: the transmitter and the receiver.
> ...


 Strymon might have to look at this!!!


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## jubal81 (Nov 26, 2021)

Barry said:


> It's got 16 votes on the one I posted for it


Man, I looked and didn't see that.


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## Chuck D. Bones (Nov 27, 2021)

fig said:


> Thanks, that answers a lot of questions (I think). If the charge pump is the source, wouldn't _all _circuits utilizing similar charge pumps, BBDs and clock chips exhibit similar results?


I would have thought so, but I just tried a ModTone Space Flanger and a Moen Chorus after the Crunch Captain Deluxe and the modded Chela.  No squeal.  One possibility is that neither one sweeps the clock freq low enough.  The Space Flanger _may _have more filtering, I'll have to open it up and see.


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## giovanni (Nov 27, 2021)

Chuck D. Bones said:


> The 3-day course I attended was a subset of that material.  Part-way into the first day, I turned to the engineer sitting next to me and said "You know, I was already doing some of this stuff and I just chalked it up to laziness."  He said "Yeah, me too."  It felt good to have our "lazy" techniques validated.
> 
> I'm going to download all of this stuff, thanks!


Late to this party, but what were the “lazy” techniques?


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## Chuck D. Bones (Nov 27, 2021)

We would think of components in terms of their impedance or admittance, whatever made the equations simpler.  We would express impedance and admittance as the Lapace transform.  For instance, a capacitor's impedance is 1/sC.  ("s" is the complex frequency, expressed in radians per second).  We would express parallel components are their equivalent admittance and create a substitute variable to use in the equations.  Example, the admittance of a cap and res in parallel is X1 = 1/R+sC.  It's a lot easier and cleaner to write X1 instead of 1/R+sC.  Lastly, we would arrange the equations so that each term had a clear physical meaning.  This term represents the DC offset, that term represents the AC gain, that sort of thing.  The whole idea was to turn a complicated calculus problem into a simple algebra problem.  We didn't invent the technique, we just exploited it to make our jobs easier.


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## Chuck D. Bones (Nov 27, 2021)

I'm going to have another bash at filtering the signal before it goes into the BBD to see if I can more effectively kill off the squeal.


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## fig (Nov 27, 2021)

Ooooo wait a minute Chuck! We could _feed_ mayonnaise to the tuna. This is big!

That's not what I was going to suggest....hang on......ahhh there it is...

Could the ESR of the caps in the circuit play a role in poor DC filtration of the charge pump's incessant swine wave?

Forgive any ignorance that _may_ be involved with that thar question.


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## Chuck D. Bones (Nov 27, 2021)

It's possible, but I use good caps for the charge pump.  No cap is perfect, so there is always going to be ripple on the 9V coming in and on the -9V, +18V, or whatever voltage we make.


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## Chuck D. Bones (Nov 30, 2021)

I should change the title of this thread to "This Month on the Breadboard."  I think I'm about done polishing this turd.  It's come a long way from the minimalist Electric Mistress based design to where it is now.  The EM is a good design and it sounds great, but it's susceptible to 40KHz noise from the charge pumps in other pedals.  I've done what I can to filter out the charge pump noise, and it's pretty effective, but if you listen real hard you can still hear it when the clock sweeps down to the bottom-end of its range.  Some pedals are noisier than others. 

Presenting version 3.5.2.  As I state in the notes, L1 is optional.  It helps reject charge pump noise, but if you don't have a 750uH choke (Tayda sells an 820uH, that's plenty close), just use a jumper there.  I changed BLEND to C-taper.  B-taper works, but most of the useful range is up near the top.  Just about any JFET will work for Q1, you want something with Vp below 2V and Idss above 2mA. You could even use a MOSFET.  Voltages marked are for reference only.  Gain is unity.  The active filters before and after the BBD are 3rd-order 8KHz low pass.  This circuit has the usual pre-emphasis (C4-R6) and de-emphasis (R13-C8) to reduce BBD noise.


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## jubal81 (Dec 13, 2021)

Got my BBDs today in the GPCB sale. 
I'm ready.


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## Bricksnbeatles (Dec 13, 2021)

Can’t believe I missed this thread for months somehow. Would I be correct in assuming that with minimal tweaks this could be adapted to accept the big-boy Tap-LFO chip for additional control over waveshapes via the distort input of the chip, as well as tap-tempo subdivisions, and an additional bank of 8 waveforms?


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## Chuck D. Bones (Dec 15, 2021)

Yup.


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## Driz (Dec 18, 2021)

Chuck D. Bones said:


> Yup.


Awesome looking circuit! When applying this modulation section to another flanger, would the voltage supplied to pin 5 of the BBD need to be 9v as it is in yours? I've seen other flangers where the BBDs are being fed 5v at pin 5 i.e the ibanez FL5


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## Driz (Dec 18, 2021)

Chuck D. Bones said:


> Yup.


Would also love to hear a demo


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## Chuck D. Bones (Dec 18, 2021)

The 3207D will run on 5V or 9V.  Higher voltage = more headroom.  The BBD & clock driver have to be powered by the same voltage.  When I used the 4KNOBFLANGE chip to provide the clock, I had to run the 3207D on 5V because the 4KNOBFLANGE runs on 5V.


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## Chuck D. Bones (Dec 20, 2021)

I haven't forgotten about this pedal.  I'm still sorting out the filtering.  The last version lacked the raw intensity of the Electric Mistress and I think I've figured out why.


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## JamieJ (Dec 20, 2021)

Take your time @Chuck D. Bones 
We can all wait patiently. We just want it to be just right. I have my chips waiting to go!


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## fig (Dec 20, 2021)

JamieJ said:


> I have my chips waiting to go!


Instant image of 2 dip-8s sitting side by side, one tapping it's pins, the other smoking a cigarette..


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## cooder (Dec 28, 2021)

It's ok if it won't happen this year...


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## music6000 (Dec 28, 2021)

cooder said:


> It's ok if it won't happen this year...


Hey Chuck, I think that means you only have 3 more days to sort it out!


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## Chuck D. Bones (Dec 28, 2021)

*UPDATE:* I added C17 from Vgg to GND in accordance with the V3207D datasheet.  Schematic has been updated (no change to page 2 except for title block).

I believe I'm done.  Spent some time yesterday reacquainting myself with Bill's Law.  If all you want is a triangle wave from the LFO, then the WAVEFORM pot could be replaced with two resistors or a trimpot.










All resistors are 1% metal film.
All capacitors less than 1nF are silver mica.
All capacitors from 1nF to 1uF are film.
C17 is tantalum.
All other electrolytic capacitors are aluminum.


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## cooder (Dec 28, 2021)

Ooooh man we might be ending 2021 on a high note then! Sweeeeet!


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## Chuck D. Bones (Dec 28, 2021)

I tried MOSFETs and BJTs for Q1, they all sound the same.  If you use a BJT, get one with a high HFE so it biases correctly and doesn't load the 3207.

I experimented with C29, which sets the clock freq range.  Larger values of C29 gets this circuit into chorus territory.  I went as high as 1nF.  

The filtering is a compromise between being bright enough and filtering out charge pump noise from other pedals.  The best solution for dealing with charge pump noise is to reduce it at the source.  Easier said than done.

I spent some time studying the interaction between the BLEND and COLOUR controls.  The two controls will always interact because the COLOUR control changes the peak amplitude of the wet signal.  I configured this circuit so that when BLEND is dimed, the mix stays balanced for all COLOUR settings.  When COLOUR and BLEND are set to zero, we get 100% dry signal.  Advancing either control from zero adds in some wet signal.  For high settings of the COLOUR control, BLEND changes the timbre more than it changes the mix.     

If you don't have a scope, you can set the trimmers by ear and get close enough.


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## benny_profane (Dec 28, 2021)

Chuck D. Bones said:


> I experimented with C29, which sets the clock freq range. Larger values of C29 gets this circuit into chorus territory. I went as high as 1nF.


Would it be worth it to have two capacitors on a toggle? Also, do you have a clock range to bias with frequency measurements instead of a scope?


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## cooder (Dec 28, 2021)

@Chuck D. Bones awesome stuff, so would it be a good idea to put C29 onto a three way toggle to have say 150pf in middle position, add 220pf (total 370p) in down position, add 1n in upper position (total 1120pF)?

PS: kudos for spelling COLOUR the correct way ....


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## cooder (Dec 28, 2021)

@benny_profane ... just posted that too, great minds think alike...


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## Chuck D. Bones (Dec 28, 2021)

Oh, so 6 knobs isn't enough?  You guys want a toggle switch too?  

The RANGE control has a huge, well, uh, range.  My advice is build it and see for yourself.  You can probably find one capacitor value that does what you want.



benny_profane said:


> do you have a clock range to bias with frequency measurements instead of a scope?


Not sure I understand the question.


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## cooder (Dec 29, 2021)

_"Oh, so 6 knobs isn't enough?  You guys want a toggle switch too?" @Chuck D. Bones _

.... and onboard relay bypass...

We'll see how this all pans out then!


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## Chuck D. Bones (Dec 29, 2021)

You should be able to share the +5V reg between the STOMPLFO chip and the relay controller.


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## benny_profane (Dec 29, 2021)

I meant is the clock frequency range defined (i.e., min/max expressed in Hz). I misinterpreted what you meant when referring to setting up with the scope. I thought you meant setting up the clock.


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## Chuck D. Bones (Dec 29, 2021)

I can measure the min/max clock freq if you're interested.  The clock freq is inversely proportional to C29 (for reasonable values of C29).  The BBD delay is 512 / Fclk.


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## cooder (Dec 29, 2021)

Got my work cut out, right. I better hurry up if I want to get a layout done still this year then....


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## Chuck D. Bones (Dec 29, 2021)

I measured the clock freq range on my breadboard.
Fmin = 28.7KHz
Fmax = 272KHz

Those clock frequencies produce a BBD delay time (td) from 1.88ms to 17.8ms.

Flangers produce a series of notches in the freq response.  The lowest freq notch occurs at 2 / td.  The higher freq notches occur at odd multiples of the 1st notch freq.  For instance, with Fclk = 51.2KHz, td is 10ms and the notches are at 200Hz, 600Hz, 1KHz, 1.4KHz, 1.8KHz, 2.2KHz, 2.6KHz, etc.

The bottom end of the RANGE control produces enough delay to get into the chorus range.  Bumping C29 up to 680pF or 1nF will produce a stronger chorus effect.  Be aware that slower sample rates produce more distortion and noise.

This article is worth a read:
https://www.sweetwater.com/insync/chorus-flange-and-phase-pedals-difference/


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## Bricksnbeatles (Dec 29, 2021)

Bricksnbeatles said:


> Can’t believe I missed this thread for months somehow. Would I be correct in assuming that with minimal tweaks this could be adapted to accept the big-boy Tap-LFO chip for additional control over waveshapes via the distort input of the chip, as well as tap-tempo subdivisions, and an additional bank of 8 waveforms?


I’ve just realized that the tapLFO lacks the offset CV of and depth CV inputs of the stompLFO, which are arguably the most important controls to have in a flanger, so while the additional 8 waveforms, wave-shaping ‘distort’ feature, and tap tempo subdivisions would be nice to have, it would be much more trouble to adapt to Chuck’s design than I initially was thinking about. 
The stompLFO also has double the max speed of the TapLFO, so that’s pretty cool.


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## cooder (Feb 4, 2022)

What. A. Crazy. Mofo. 
In the best sense of the word.
Dial on the wave knob and it takes you through weird and wonderful whacky worlds of flanging LFOs, I wasn't quite prepared for how whacky it can get, lol....
Of course there's the more 'normal' flanger sounds as well that I better start myself off with to get fully into it, and yes having the blend knob is definitely a good move to be able to get it calmed down a bit. 
The colour knob makes a massive difference too and dialing the top range of that with internal trimmer is important; it scared the beejezuz out of me first when I dialed that up and got into feedback zone.
Awesome design, mad genius I'd say. And I'm glad I had another spare 3102 left here after Chuck hooked me up (via a generous you know who person here) to a 3207 as well.
It's all go, hold on to the swoosh and swirl. Time to celebrate with a bit of photobombing.
































As you can see in the gutshots she's a bit of a tight affair in there, I had two caps mounted underneath board and the inductor was meant to go underneath as well. However, I had only a 1000uH inductor which measured on the CCCT 840uH. I might replace that with a closer to optoimum 750uH when I get some.
Thanks so much for the awesomesauce projects here, all hail Chuck and the Boneyard me thinks.


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## giovanni (Feb 4, 2022)

cooder said:


> What. A. Crazy. Mofo.
> In the best sense of the word.
> Dial on the wave knob and it takes you through weird and wonderful whacky worlds of flanging LFOs, I wasn't quite prepared for how whacky it can get, lol....
> Of course there's the more 'normal' flanger sounds as well that I better start myself off with to get fully into it, and yes having the blend knob is definitely a good move to be able to get it calmed down a bit.
> ...


Which PCB is that? Some existing flanger board that you used to build Chuck’s circuit?!?


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## Chuck D. Bones (Feb 4, 2022)

Cooder designed the board and the graphics.  Excellent work, as always!


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## zgrav (Feb 4, 2022)

soft bypass too?  wowza!


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## giovanni (Feb 4, 2022)

Wow! Really nice work @cooder!


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## jeffwhitfield (Feb 4, 2022)

Me want! Where can I get a PCB for that? Lovely work! 👍😁


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## Fingolfen (Oct 16, 2022)

Yeah... ummm... where can I get a board or 3????


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