Friedman Pedals - a circuit comparison

Chuck D. Bones

Circuit Wizard
If adding some components was a practical option, I would have suggested it. The MID control in the Friedman pedals is an active filter. It required another opamp and there are no spare opamps on the board.


Well-known member
Let's take this to the next level and walk Dan through adding a Tube Screamer circuit to his Friedman Runt 50 head so he doesn't have to run one in front of the amp!


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[edited to add Little Debbie]

PedalPCB carries several Friedman pedals and for good reason, they sound great. My 2nd PedalPCB build was a Brown Betty. The Little Debbie, Dirty Sanchez, Brown Betty, Thermionic and Complex are all basically the same circuit with a few different component values and one or two knobs.

All have GAIN, BASS, TREBLE & VOLUME controls.
Dirty Sanchez, Brown Betty, Thermionic and Complex have a PRESENCE control.
Little Debbie, Dirty Sanchez, Brown Betty and Complex have a MID control.
Brown Betty & Thermionic have a TIGHT control.
Dirty Sanchez has a TIGHT switch.
Dirty Sanchez, Brown Betty and Thermionic have an internal gain trimmer.
Little Debbie has internal trimmers for Tight & Presence.

Thermionic has slightly higher gain and a little more bandwidth for more bite. The Build Docs call out 1N5817 schottky diodes for the 3rd stage. Some people use 1N4148s like in the other Friedman pedals.
Little Debbie, Dirty Sanchez & Brown Betty are in the middle gain-wise.
Complex has slightly lower gain and a mild treble boost at the end (C14/R20).

You can build any of the above on a Brown Betty board. I like having the TIGHT knob, but I think a TIGHT switch will do the trick in most cases. Some folks (you know who you are) like the sludgy sound and will leave TIGHT wide open.

If you want to see a side-by-side comparison of the Thermionic and Brown Betty schematics, look no further than the Thermionic Deluxe. Channel A is a Thermionic with a MID control; Channel B is a straight-ahead Brown Betty.
I know this is an old post, but what would you suggest to get the gain of the Little Debbie up to the Thermionic?
Basically I want to eventually build a Thermionic with a mid control if that is possible (like half of the deluxe version)


Well-known member
Resurrecting this old thread because my question seems relevant.

I get that high-gain/low-gain change is using either 10K or 27K for R13.
I'm kind of curious why the various Thermionic based boards have 2 different cap values (I'm talking specifically about C8 and C9 if you reference the Brown Betty schematic).

Here's what I observed:

T Deluxe Channel A10K120p220p
T Deluxe Channel B27K120p220p
Dirty Sanchez27K220p220p
Brown Betty27K470p220p
Little Debbie27K470p220p
Aion Tempest27K120p220p

My question is why do the variants (BB, LB) stray from the stock circuits? Or even why does the Deluxe channels not match the stock Thermionic/DirtySanchez (they're close but not exact)? Do these matter much in the circuit? I guess they control some of the gain of high frequency?
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Chuck D. Bones

Circuit Wizard
It's what you say, those caps tune the high-freq roll-off. It may be difficult to hear the differences, depending on the control settings. Friedman picked those values for a reason, but feel free to tweak them to your own preferences.

The gain setting resistor is R13 on the BB sch.
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Reverse Engineer
Staff member
Waaay back when the Thermionic was first drawn up the capacitors were monkeyed with a little as a band-aid to tame some oscillations that were occurring in some builds... Eventually the layout was improved and the modified values were no longer needed and returned to the correct stock values. After all, this was one of my first PCB layouts (intended for DIY building) so the fact that it worked at all is impressive enough. :ROFLMAO:

The differences in the hybrid pedals like the Little Debbie, and Brown Betty are most likely a result of these changes. Since neither of those were a direct clone they weren't updated.

The others reflect the measured values.

It looks like GuitarPCB has the correct values as well.

The Tempest appears to be a hybrid similar in vein to the Brown Betty, so that would explain the differences there.

It's possible that the Fuzzdog values come from one of the "best guess" schematics posted on FSB before all of the components were measured out of circuit.


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in the little debbie if I wanted to use normal pots instead of the 2 trimmers ( for tight and presence) i would have to use linear or reverse ones


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I’m curious about the closest pedal predecessor to these Friedman pedals I like the response of the complex I’ve built. I know a lot of the amp in box pedals are fet stages. These are ic stages What other pedals stack ic stages similarly? Anyone know a history?