Tonebender MkIII (Pastyface with 3PRR)

[Bret608]

Hi everyone,

Here is the latest, a Pastyface with a 3PRR. This is a really nice utility board. I tested the fuzz with straight-up positive ground wiring before I boxed it, so I can attest that the voltage inverter makes no difference in sound, whether you're using a wall wart or battery. I basically did the Sola Sound parts values, with the addition of the 1m pulldown resistor and the jumpered 220k output resistor from the Soulbender.

The drill template I sent to PPP was just slightly off, so I had to work at the pot holes with a file to get it to fit. But in the end I'm pretty pleased with how it turned out. It's PPP green hammertone, which looks almost teal in person. The pictures were just me dorking around, "posing" it on my guitar kind of like Prymaxe does.

I like the sound; less gain than my Buzzaround but also a bit more raw and '60s-sounding. From what I was reading at DIYSB, I may need to try a leakier transistor in Q3 to get it to bias up a bit nicer. Right now I have some old G.E. 2n1305s in there; the hfe range 46-49-100 for Q1, 2 and 3 respectively. They're all under .80mA, so quite low leakage. I just need to get the rest of my germanium stash tested. What have other folks' experiences been for Q3 collector voltages?

[playpunk]

Looks like you figured out those jacks


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[angrykoko]

I love that enclosure color!  Looks great with those knobs.
I have those knobs too, wasnt sure what color to put them with.. now I know

Great Looking build, has a cool vintage vibe to it!  Very clean inside and out!

Cheers
Koko

[mgwhit]

Fuzzes just scream out for hammertone colors, don't they?  Nice to see you can fit all that in a 125B with, apparently, room to spare.  Cool build -- and cool Mustang, too!

[selfdestroyer]

Nice build. Those GE trannies look awesome also.

Cody

[Bret608]

Thanks for the kind words, everyone! Yes Andrew, I got those stereo enclosed jacks figured out with your help. This pedal is pretty quiet so I think they were a good choice.

It had to be hammertone for sure! Although they don't have it on their website, PPP apparently have grey hammertone as well. I'll probably grab that for the Supa Fuzz I built. Mike, either of the green or the grey should look cool with these Marshall knobs.

Glad you like the Mustang, Matt. All it needs are some of Timbo's pickups and it's good for another twenty years! 

Cody, I seriously don't want to break up this triumvirate of germanium awesomeness, but I think the collector voltage on Q3 is just a hair low. I'll try out some more and see how it goes. Damn, I really wanted to keep them together, if only for aesthetic reasons!

[Rockhorst]

Hey Bret! Interestingly I've been working on the same circuit as you have probably noticed. I was also wondering about biasing. The green one I posted here a while ago had Q1 and Q2 biased to about -3.8V and Q3 to about -1.2 V. I build another one with my own board and omitted the trimmer. With R7 at 10k, bias was way too low, almost no sound. Pushed it up to 500k and got -1.3 and that seemed enough for a great sounding fuzz. If you compare the schems as Fuzz Central, they don't have R7 at all (right?), which corresponds to a very very high resistor. So I'm going to build a new one soon, leaving off R7 or making it at least 1M, see what happens.

I used OC47s with gains of 60, 70 and 90 with negligible leakage (around 3 uA).

So far for my 2c on Tonebenders curious what you think.

[Bret608]

Hi Rutger! I did notice you've built this recently.

I think you're right; I left off the trimmer and with R7 at 10k I'm only getting about 0.36v on Q3's collector. I have about the same voltages as you on Q1 and Q2. I got curious and read up on this at DIYSB; see this thread: http://www.diystompboxes.com/smfforum/index.php?topic=64677.0

If I am understanding this thread correctly, pushing that 10k resistor up is critical is you are using low leakage transistors for Q3. Mac states that 220k to 2.2m is the range to work with. The 10k would be if you had over 100uA leakage and you would have to play with the diode a bit in that case. Almost none of my germaniums have that much leakage! But he also says 1.5 to 2v is a good collector voltage, so I think your 500k was a good choice. It sounds like you and I both have appropriate collector voltages on Q1 and Q2.

I'm going to try a couple more from my stash and see what happens. I tried a few 2n217 (AC128-like) I have last night, even ones leakier than the 2n1305 I have in there now. They biased up even lower, some as little as .1v! So if that doesn't work I'll put a higher resistor there as you did.

[Rockhorst]

Cool! Missed that thread, good info I'm becoming a bit of a fuzz addict, whereas about a year ago, I didn't understand what all the eh...fuzz was about.

[Kinki fuzz]

Nice pedal... and guitar!! The mkIII is a killer sounding fuzz

[Bret608]

Thanks Kinki Fuzz!

For those interested (thinking about you, Rutger!) I dug a little deeper on this:

http://www.diystompboxes.com/smfforum/index.php?topic=109001.0

Long story short, I swapped the 10k out for 560k and am now getting 1.36v on the collector of Q3. Will rock it tonight and report back. I think most people will use the trimmer on this, so it's not a big deal, but if builders choose to leave it off as I did that 10k needs to be raised for this to bias correctly. It could even be socketed, since resistors with high leakage may not need the resistor at all and you could jumper it.

[Rockhorst]

If you compare the schems as Fuzz Central, they don't have R7 at all (right?), which corresponds to a very very high resistor.

Basically what I said above this should be an interesting circuit to test all those leaky AC germaniums I have and never use...very curious, I'm going to do one with silicon Q1 and Q2 and leaky AC germanium for Q3. From what I've read, that should work out well and save the much higher fidelity OC transistors for other builds.

[Bret608]

That is indeed what you said!  I just felt like we should raise it to the level of a PSA or something.

Here's one more option I thought about besides jumping that resistor when you have leaky transistors for Q3. If they're moderately leaky, you could use a 1m trimmer on the Pastyface board. Just a thought...sounds like the whole theory behind having resistance in that position is to get Q3 to behave more like vintage units. By the way, mine does sound fantastic now. I'm wondering how those versions with the 680k/100k bias string up front sound by comparison.