Sola Sound Yellow Hybrid Tone Bender

[mdc]

Diode was indeed flipped in the schematic, thanks for the catch.

 

[Chuck D. Bones]

All of the voltage measurements make sense, just need one more.

Can we get a measurement of the zener voltage (voltage at D2-K)?

Is the TONE control oriented correctly? As drawn, clockwise rotation makes the sound darker.

Ya know... If this was built on a BMP board, we could have a gain recovery stage between the TONE and VOL controls. Just a thought.

 

[mdc]

TONE is correct - CCW is bass cut, CW is treble cut.

Voltage on the zener cathode is 4.86.

Also, there's a layout available here:

Colorsound Hybrid Tonebender 2018 Edition

Couldn't resist to draw a schematic and a layout for this interesting mutant of a circuit that just got traced. First two gain stages is a...

dirtboxlayouts.blogspot.com

 

[Chuck D. Bones]

Cool. We have independent confirmation of the trace. The schematic even has ref des.

Interesting that C5 has different values in different pedals. That would be a good place for a FAT switch.

 

[mdc]

I have about 6 or 8 OC140s on hand, when I get a sec this weekend I can get some hfe and leakage numbers from them. My recollection is that they're very consistent gain-wise and very low leakage.

 

[Robert]

 

[Robert]

Everyone who participated in this thread shoot me a PM and I'll get you a coupon for a free PCB.

 

[MGB]

Congrats guys !... That's a superb team effort and great show of talent as I watched this thread unfold.

Now, sorry for the noob question here, but doesn't that GC92H Ge diode fall in the unobtanium bin ?

Is there a known replacement or an equivalent part that would be easy to get ?

Thanks

 

[music6000]

Something like this :

 

[Chuck D. Bones]

SCHWING!

 

[Chuck D. Bones]

Congrats guys !... That's a superb team effort and great show of talent as I watched this thread unfold.

Now, sorry for the noob question here, but doesn't that GC92H Ge diode fall in the unobtanium bin ?

Is there a known replacement or an equivalent part that would be easy to get ?

Thanks

Corrected a typo...

Just do like we do with ALL Germanium devices: install sockets and try various parts. I plan on tweaking the 220K resistor as req'd to get the right bias on Q3 if I can't get there by subbing transistors and diodes. Here's a good starting point: go for low leakage on Q3 and fairly high leakage on D1. If Q3's Vc (collector voltage) is too low, then switch to a transistor with less leakage or a diode with more leakage. Do the opposite if Q3's Vc is too high.

 

[Bobbyd67]

Ahahaha I just noticed this thread xD Good job boys!!! (and gals possibly.... Chances are slim ... The hobby is great but you gotta admit .... It's kinda of sausage fest xD)

 

[mdc]

I was digging around the other day to try and find some specs on CG92H and on first pass I could only find this sidebar to a review of the Peak Zen50 diode tester in an old issue of everyday practical electronics:

 

[mdc]

OK, so!

I built the circuit on vero with the following parts:
Q1: 2N3440 / hfe 110
Q2: BC549C / hfe 513
Q3: OC140 / hfe 85 / leak. 0.00mA

D1: 1N270
D2: 5.1V zener

Q3 collector biased to 2.6V

Outside of those component choices, the only sub was a B20K for the W20K.

I honestly can't tell any meaningful difference versus the original. Sounds great, overall volume is about the same as stock - unity at ~2 or 3:00, good amount of output past that point. Extremes of the tone control sound about the same, and I can find a spot near the middle that's about identical.

I used the dirtbox effects layout I linked earlier, so consider that verified (fyi, the tone control is wired in the reverse from the original in that layout, but that might also be more intuitive...).

I'm stoked - thanks again for all the help in this!

 

[Chuck D. Bones]

Cool. I have not gotten around breadboarding this yet. I ran some sims and it did what I expected. No gating. Asymmetric distortion, lotta harmonic content. How does it sound with chords?

 

[mdc]

Quite good, I think—it's a pretty saturated-sounding fuzz, but there's a nice raggedness to the high end that makes it seem a bit more articulate than a big muff or something else with similar topography. It's an excellent bass fuzz, even with the 10nF cap in there. I've not played an original supa fuzz but I've built a copy of that circuit and found it too bassy to be usable; this is a much better sounding pedal and sits really nicely between what you might expect from a medium-gain TB circuit and an actual big muff.

 

[Julian A]

Took voltage measurements of my old build. They're pretty much where they should be. It has BC178C for Q1 & Q2 and a GT402B for Q3. 5.1V zener.
The GE diode is an AN307 (not that it changes much). I haven't made any changes to it, and will likely keep it as is. Would like to build the new NPN one though.

-9.24v input

Q1
C: -4.11
B: -0.645
E: -0.03

Q2
C: -4.37
B: -0.67
E: -0.047

Q3
C: -2.6
B: -0.147
E: 0

Note that Q3s voltage will vary with temperature. Good ol germanium. My room is a pretty cool ~60⁰F. After touching Q3 for 10 seconds, the voltage was around -2.35.

 

[music6000]

Quite good, I think—it's a pretty saturated-sounding fuzz, but there's a nice raggedness to the high end that makes it seem a bit more articulate than a big muff or something else with similar topography. It's an excellent bass fuzz, even with the 10nF cap in there. I've not played an original supa fuzz but I've built a copy of that circuit and found it too bassy to be usable; this is a much better sounding pedal and sits really nicely between what you might expect from a medium-gain TB circuit and an actual big muff.

So, PedalPCB layout Tone control as per Original cuts Treble clockwise from 12 O'clock & cuts Bass counter clockwise from 12 O'clock.

 

[mdc]

I mean to be fair they also put the input on the left hand side and drive on the wrong side of the road.

 

[music6000]

OK, so!

I built the circuit on vero with the following parts:
Q1: 2N3440 / hfe 110
Q2: BC549C / hfe 513
Q3: OC140 / hfe 85 / leak. 0.00mA

D1: 1N270
D2: 5.1V zener

Q3 collector biased to 2.6V

Outside of those component choices, the only sub was a B20K for the W20K.

I honestly can't tell any meaningful difference versus the original. Sounds great, overall volume is about the same as stock - unity at ~2 or 3:00, good amount of output past that point. Extremes of the tone control sound about the same, and I can find a spot near the middle that's about identical.

I used the dirtbox effects layout I linked earlier, so consider that verified (fyi, the tone control is wired in the reverse from the original in that layout, but that might also be more intuitive...).

I'm stoked - thanks again for all the help in this!

I agree that the Tone control makes more sense Reversed so Treble is Clockwise from 12 O'clock

On all other Sola Sound Tone Bender's it is labeled as TREBLE..............BASS, not TONE.