Friedman Pedals - a circuit comparison

[NickC]

The cleanest way to do it is buy a Brown Betty board and build it to Thermionic specs.

Another option is to stack a Thermionic and a VarioBoost.

I thought you could just add some components to the thermionic to bring out a mid control @PedalPCB what do you think about it?

 

[Chuck D. Bones]

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.

 

[Danbieranowski]

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!

 

[megatrav]

[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)

 

[Chuck D. Bones]

Easily accomplished.
Reduce R13 to 10K
Increase R6 to 100K
Decrease R15 to 2.2K
Decrease C8 to 120pF
Decrease C9 to 100pF

 

[spi]

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:

Circuit	R13	C8	C9
Thermionic	10K	120p	100p
T Deluxe Channel A	10K	120p	220p
T Deluxe Channel B	27K	120p	220p
Dirty Sanchez	27K	220p	220p
Brown Betty	27K	470p	220p
Little Debbie	27K	470p	220p
Smallbox	27K	120p	220p
Aion Tempest	27K	120p	220p
GuitarPcb	10K	120p	100p
Fuzzdog	22K	120p	100p

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?

 

[Chuck D. Bones]

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.

 

[Robert]

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.

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.

 

[NickC]

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

 

[Chuck D. Bones]

I'd recommend reverse audio (C-taper) for both.

If you want more gain, you can bump R6 up to 220K.

 

[NickC]

thank you, basically i would like to have a thermionic + mid pot in 125b enclosure

 

[Chuck D. Bones]

To make it like Thermonic, follow the details in post #16.

 

[vmazz]

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?

 

[Chuck D. Bones]

Please ask this in the General Questions forum, not here.

 

[megatrav]

I know this thread is old, but is anyone familiar with the Friedman Naked amp?
I believe it is basically a Naylor Superdrive into a Marshall power amp section.
I would love to have that tone in a pedal.

I've looked at the schematic and I'm not sure if any PPCB current offerings could be modded easily to it

 

[Chuck D. Bones]

Other than being a Friedman product, the Naked amp question is off-topic.
But since you brought it up...
1. How accurate is that schematic?
2. Friedman pedals are designed to sound like a Friedman amp. They are not based on the amp schematic. In order to make or mod a pedal to sound like a specific amp, one must have said amp in their possession for measurements and listening comparisons.

 

[megatrav]

Other than being a Friedman product, the Naked amp question is off-topic.
But since you brought it up...
1. How accurate is that schematic?
2. Friedman pedals are designed to sound like a Friedman amp. They are not based on the amp schematic. In order to make or mod a pedal to sound like a specific amp, one must have said amp in their possession for measurements and listening comparisons.

That is totally fair. I hadn’t considered that!

Also, the schematic is from Amp Garage

 

[brightlight]

I've built basically the essential lineup of these now. Several thermionics, several complexes, a little Debbie, and a golden pearl.

I'm about to finish up a few more thermionics and another little Debbie and it got me thinking. Is there any value (no pun intended) in socketing the LEDs? Are different, usable results to be expected from trying out different color LEDs in these circuits or is it a waste of time?

 

[Chuck D. Bones]

Sure, why not? Going to a color other than red will raise the clipping threshold. If you do that, you may end up causing one or more opamps to clip before the LEDs kick in, which will totally alter the tone. You can also try asymmetric clipping which will add even-order harmonics.

 

[brightlight]

Sure, why not? Going to a color other than red will raise the clipping threshold. If you do that, you may end up causing one or more opamps to clip before the LEDs kick in, which will totally alter the tone. You can also try asymmetric clipping which will add even-order harmonics.

Ok cool! I'll take it as an opportunity share the results. Thank you!