Bumble Bee Transistor Biasing???

[Gristlepig]

Hey folks,

So, I've been plugging away at this Buzzaround all day now, and finally have it completed. I just plugged in the transistors, and they sound kinda crappy...

I started with the set Smallbear sells specifically for the Buzzaround. Q1 is a Chinese 3AX31C, Q2 is an OC76, and Q3 is a 2n404A. Unlike the Tonebender sets he sells, it did not come with substitute resistors to bias the trannies.

They sound kind of gated, with a hissy decay to the sustain at higher gain ratings. Q3 only makes it up to about 2.8v with the Balance knob dimed.

Am I correct in my assumption that the Balance pot acts as a baising control for Q3?

After subbing a bunch of transistors in and out of the circuit, I found that the 3AX31C for Q1 is the likely culprit. The gain is labelled 71 on the bag without a listing for leakage.

Should I futz with the resistors for Q1, or is this transistor most likely bad? I plugged in an OC75 with a gain of 68 and leakage in the 200's and it sounded fine.

The circuit actually sounded fantastic just dropping in a SB Tonebender set of OC75's with no regard to the resistors supplied with the set.

I know SB accepts returns on hissy transistors so long as they haven't been soldered or clipped... I'm just not sure if this transistor qualifies.

And I know... I should have breadboarded it first. This is the last GE fuzz I build without first auditioning it on breadboard.

Though the OC75's sound great, I could only get the bias to on Q3 to 3.7v or so...
Anyone have any input as to the ideal voltage readings for each transistor, and which resistors to tweak to get them biased correctly?

Thanks!

[midwayfair]

I would just e-mail Steve. He might send a replacement. It's possible to have a transistor that tests fine but doesn't actually work every once in a while.

The balance pot is indeed a bias control; there are no significant biasing concerns in the Buzzaround.

Edit: actually, double check the pinout, too. Did you try sticking it in backward?

[Gristlepig]

I just tried sticking that Chinese Q1 in backswards. Effect wasn't as loud, and I got the same hissy, crackly whine on the note decay. I just stuck a trio of OC75's in there. Huge improvement. Still a bit of gating on most settings.

I guess I'll email Steve and see what's up re the Buzzaround GE set.

So, I shouldn't be concerned about voltage readings on the transistors? I know Q1 and Q2 operate as a Darlington and I don't know what correct voltages should be there, but shouldn't Q3 bias to 4.5v on the collector?

BTW, I've used your 3PDT boards on a few builds recently. I love em. Makes outboard wiring way less traumatic!

[Gristlepig]

Returned the Sino GE to SB. Built a nice Fuzz Face with the remaining Q2 qnd Q3 from the set!

Thanks for all the help. The Bumble Bee sounds pretty awesome with the Smallbear OC75 Tonebender matched set.

And now that I've played the pedal a bunch, I see what y'all mean about the volume mod. Absolutely essential... Some of the sweetest settings on this thing are loud as f*ck!

Thanks for all the help!