TH Black Eye (Soldano GTO) prototype build

Another Member used the PPCB Simple JFet Buffer on the Input of their Black Eye and it fixed the Squeal?
I dunno, I just tried it and it still squeals with the gain dimed. It "helps" but doesn't make it go away as definitively as the Klon or Cornish buffer does.

This is what I tried.
 
Kinda interesting that the C-Buffer works as that is also a transistor based buffer. Ugh, I have a pedal that used a C-Buffer board on but I can't remember which one. Let me look through my notes.
 
So if I have this right, You have to have the Amentum Boost on for the Buffer on the Output of the Amentum to make it work?
I have the Simple JFet Buffer on the Amentum output and it does NOT work.

Ok some interesting findings.

WORKS:
General Tso (Thorpy Buffer built in)
Convex (Thorpy Buffer built in)
Oceanid (Cornish Buffer built in)
Cephus (Cornish Buffer built in)
FDIC (Fuller Buffer built in)
Any Klon (Klon Buffer built in)
TC Electronic Polytune3 Mini w/Bona Fide buffer
Boss RV-3 (retail)
Ceasar Chorus
Celsius Preamp

Does NOT Work:
Ember (TC Spark) Boost using PPCB Cornish Buffer daughterboard
Amentum Boost using Simple JFet daughterboard
Heavy Water Dual Boost (Thorpy buffer built in....not sure why this won't work)
Episode Booster
Clandestine Booster
Xotic EP Booster (Retail)

Edit: In the "Does not work" list it is to varying degrees. For instance, the EP style preamps all quiet it down to a low squeal with the gain dimed. So it's doing SOMETHING. The "DOES WORK" list completely removed any squeal at all and it's just "high gain noise".
Without anything in front of it, and the gain dimed, I can get Tokyo on shortwave........ :ROFLMAO:
 
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I built mine and used old stock usa 12ax7s and it squealed like hell half up. I put in jjs and shorten the wires from the main board to the switch and the squealing was almost all gone except at the very end of the rotation. Once i turned on the buffer from the bignoise swiss army fuzz the squeal went away.

I am going to either swap the pot out for a 500k or jumper the outer lugs with a resistor, I found it had too much gain for my taste.

Fyi it sounds outstanding and i am in love, just half way up 🥖💦😉
 
If I’m not mistaken @vigilante398 buys truck loads of JJ’s. So it makes sense that JJ’s are handling this issue better than other tubes. They must be more tolerant to something that’s going on. Maybe if we could dump a tad bit more gain out of the path we would be fine? Im happy keeping it after my Klon or after my General Tso as one of those two is always on my board. But it would be nice to solve the squeal for the people that don’t use buffers.
 
I built mine and used old stock usa 12ax7s and it squealed like hell half up. I put in jjs and shorten the wires from the main board to the switch and the squealing was almost all gone except at the very end of the rotation. Once i turned on the buffer from the bignoise swiss army fuzz the squeal went away.

I am going to either swap the pot out for a 500k or jumper the outer lugs with a resistor, I found it had too much gain for my taste.

Fyi it sounds outstanding and i am in love, just half way up 🥖💦😉
In a tube circuit the value of the gain pot doesn't affect the level of gain as it's effectively just a voltage divider, so the ratio determines the gain more than the actual value. To actually lower the gain of the circuit you have a couple options:
  • choose a tube with a lower amplification factor (12AX7 - 100; 12AT7 - 60; 12AU7 - 20)
  • lower the value of plate resistors (R11, R12, R13, R14; stock values are 220k, 100k, 100k, 100k respectively)
  • raise the value of cathode resistors on non-bypassed cathodes; first and second stages are bypassed in this circuit, but the third and fourth stages (39k and 2k2 cathode resistors respectively) are not bypassed.
I'm ordering a few different buffer topologies to try out, should have results to report in a week or so.
 
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TkIIWEn.jpg


This is my fix. Seems to work perfect for me.
 
In a tube circuit the value of the gain pot doesn't affect the level of gain as it's effectively just a voltage divider, so the ratio determines the gain more than the actual value. To actually lower the gain of the circuit you have a couple options:
  • choose a tube with a lower amplification factor (12AX7 - 100; 12AT7 - 60; 12AU7 - 20)
  • lower the value of plate resistors (R11, R12, R13, R14; stock values are 220k, 100k, 100k, 100k respectively)
  • lower the value of cathode resistors on non-bypassed cathodes; first and second stages are bypassed in this circuit, but the third and fourth stages (39k and 2k2 cathode resistors respectively) are not bypassed.
I'm ordering a few different buffer topologies to try out, should have results to report in a week or so.
Please reread your post regarding cathode resistors and fix it.
 
I don’t know if this is an option, but I’d be down with a hybrid SMD (resistor) / TH (everything else) board if that would help with routing. Since this issue is unique to the TH board and not the previous SMD production runs, that could help things.
 
So I got a handful of different buffer boards to try, and so far the Cornish works the best. I can get the gain up just past 3 o'clock before it squeals. So it isn't a 100% fix, but it's the closest I've gotten so far.
Are you connecting the Buffer between the Input Jack & Input pad on the PCB?
 
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