joelorigo
Well-known member
Me too! I just ordered this PCB today.
Two Tone Fuzz transistor layout?
- Thread starter Kroars
- Start date
I wasn't able to source any GT402 transistors but did find 2 PT416 for Q1-2 and a 2N404 for Q3 all in the right hfe for this pedal but after populating board with resistors and caps I had it dawned on me I should of left R7 out so I could get voltage correct and collector of Q3. What kind of voltage should I be looking for for the Q3 collector? I've only ever done 2 tranny fuzz face type circuits before and know Q2 collector voltage is important in that circuit.
joelorigo
Well-known member
What is the right hfe for the pedal? I have a "3 Knob Tone Bender Set" I bought from Small Bear that are about 55, 78 & 95. Do they need to be higher?
PedalBuilder
Well-known member
A “3 knob Tone Bender” refers to a Tone Bender Mk. III, which has lower gain, low leakage transistors in Q1 and Q2, and a very leaky high gain transistor in Q3. Despite the similar name, it’s a completely different circuit than the Tone Bender Mk. I.5 and Mk. II circuits that comprise the Two Tone Fuzz.
For this pedal, I'd focus less on hFE and more on leakage; I've built great sounding Mk. II's using transistors with gains as low as the 30s and as high as the 400s(!), but they need to be leaky in order for it to bias correctly. There are lots of threads on Tone Bender Mk. II transistor hFE/leakage/voltages, so I'd recommend searching the forum to see what worked well for others.
joelorigo
Well-known member
I see.
When you say bias correctly, since there is no trimmer on this PCB your talking about having the correct leakage range on the transistors to elicit the proper voltage?
Also, in post #9 of this thread @DeadAirMD reports a great sounding pedal using GT402's from SBP which on their page lists "Most of these are very low leakage, anything leaky or unstable has been sorted out." It also says that "Leakage is below 300uA." What is considered "leaky?"
GT402 PNP Germanium Transistor
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So i finally populated the rest of my two tone and hooked up to my test box, nothing no sound at all. checked voltages and at r4 have -9.5v then checked collector of Q1 also -9v is that right ? I've got 9+ going into + on the pcb so to me that makes no sense. Going to get the probe out next and see if anything there. I've done a few tayda and madbean pedals and have always managed to figure out but the -9.5v has me stumped
Robert
Reverse Engineer
The charge pump IC generates the -9V supply. The fuzz circuit itself is a positive ground circuit.
Ok so having - volts going through is normal, this is my first PNP fuzz. Now I know why I streared clear of them
DeadAirMD
Well-known member
Also, in post #9 of this thread @DeadAirMD reports a great sounding pedal using GT402's from SBP which on their page lists "Most of these are very low leakage, anything leaky or unstable has been sorted out." It also says that "Leakage is below 300uA." What is considered "leaky?"
GT402 PNP Germanium Transistor
Top Quality Parts for Guitar Effects Pedals and DIY Music Devices. Knobs, Pots, Switches, Kits, LEDs, Enclosures, Jacks, Wire, Resistors, Capacitors, Semiconductors
Just buy the transistors for this pedal from SBP. One and done, sounds great. I didn't have to do any resistor biasing to make the transistors work.
Kroars
Well-known member
I consider anything under 100uA (.100mA) to be low leakage. Anything from 100uA to 300uA to be mid leakage and above 300uA to be relatively high leakage. I’ve found this categorization to “work” in a lot of GE circuits.I see.
When you say bias correctly, since there is no trimmer on this PCB your talking about having the correct leakage range on the transistors to elicit the proper voltage?
Also, in post #9 of this thread @DeadAirMD reports a great sounding pedal using GT402's from SBP which on their page lists "Most of these are very low leakage, anything leaky or unstable has been sorted out." It also says that "Leakage is below 300uA." What is considered "leaky?"
GT402 PNP Germanium Transistor
Top Quality Parts for Guitar Effects Pedals and DIY Music Devices. Knobs, Pots, Switches, Kits, LEDs, Enclosures, Jacks, Wire, Resistors, Capacitors, Semiconductors
That said, some circuits are more picky than others for particular ranges. This is a TB variant and I’ve had luck applying the general formula with Q1 and Q2 being low leakage and Q3 being on the higher side of mid leakage.
joelorigo
Well-known member
Good to know this, thank you!
joelorigo
Well-known member
I still might buy them to try but I kind of got lucky with the small amount I had on hand. Sounds pretty close to the real thing. Here's my finished build:
Kroars
Well-known member
Right on! I’ve got a ton of transistors and can honestly say, part numbers rarely, if ever matter. Some of the best GE fuzz pedals I’ve built were a total mixed bag of GE transistors, just in the agreed upon parameters for hfe/leakage. Even then, some circuits will sound really good outside of the established readings. The Fuzz Face, for example can be tweaked just a hair to sound great with transistors well outside the norm. Thats where experimenting is a ton of fun.I still might buy them to try but I kind of got lucky with the small amount I had on hand. Sounds pretty close to the real thing. Here's my finished build:
Check this guy out for reasonably priced GE transistors, he’s pretty well known. Look for his regularly held auctions for 10 transistor sets of all kinds, albeit mostly PNP. You can easily get multiple sets of 10 transistors for under $5 a set. The trick is to buy a few and he’ll combine shipping costs. I’ve gotten 8 or 10 sets at a time and if I over pay for shipping, he always refunds me.
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joelorigo
Well-known member
Thanks! I will check him outRight on! I’ve got a ton of transistors and can honestly say, part numbers rarely, if ever matter. Some of the best GE fuzz pedals I’ve built were a total mixed bag of GE transistors, just in the agreed upon parameters for hfe/leakage. Even then, some circuits will sound really good outside of the established readings. The Fuzz Face, for example can be tweaked just a hair to sound great with transistors well outside the norm. Thats where experimenting is a ton of fun.
Check this guy out for reasonably priced GE transistors, he’s pretty well known. Look for his regularly held auctions for 10 transistor sets of all kinds, albeit mostly PNP. You can easily get multiple sets of 10 transistors for under $5 a set. The trick is to buy a few and he’ll combine shipping costs. I’ve gotten 8 or 10 sets at a time and if I over pay for shipping, he always refunds me.
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