Arbiter's Fuzz Face problem

[Akuma60]

I did the PNP, negative ground from GGG, with two AC128 and a DPDT for true bypass.

The problem is that each time I switch to the effect, I get an awfully gated sound and then, 5 to 10 seconds later, the effect kicks in okay!  I looked at gated fuzzes info, but I'd like to know if this gating problem rings a bell to anybody ?

Thanks

[jonathan perez]

check biasing

[tcobretti]

Most likely your problem is that one or both of the transistors isn't getting about -4.5v at its collector.  You have to adjust the values of the 33k and 8k2 resistors to get the voltages around 4.5v.  Germanium FFs are a little weird to tune because every Ge tranny is unique in its biasing requirements.  I'd measure the collector voltages with a digital multimeter, then lower or raise those resistor values as necessary.  You might want to socket those resistors to make it easier.

It's a great fuzz once you get it going, good luck.

[petemoore]

I did the PNP, negative ground from GGG, with two AC128 and a DPDT for true bypass.
  Some intractable problems may persist with this grounding scheme.
The problem is that each time I switch to the effect, I get an awfully gated sound and then, 5 to 10 seconds later, the effect kicks in okay!  I looked at gated fuzzes info, but I'd like to know if this gating problem rings a bell to anybody ?
  I would still check the bias and work with it, but building a PNP Pos Gnd FF will give 'FF' results more consistantly...I can't shed more light on this than suggesting to compare the results you get [after trying to resolve the issues..] to a regular FF...PNP Pos Gnd. or PNP Neg Gnd.
 

[mac]

Besides the noise problems of PNP neg gnd, some say that PNP pos gnd does not sound like NPN or PNP neg gnd. Comparing NPN and PNP must be done with complementary PNP - NPN transistors, ie ac127 and ac128. PNP neg and pos gnd differences, if any, is easy to test.

I would go for a PNP pos gnd.


mac

[tcobretti]

Yeah, I didn't mention it before, but the PNP Neg Gnd FF is pretty notorious for noise and oscillation.  You may be able to get it to work, I'm sure some people have managed it, but the likelihood of problems is far greater than if you built a PNP Pos Gnd.

Sorry for the bad news.

[petemoore]

  Not hard to convert to a "FF"...
  just get yer FF schem on it and only a few alterations, following the polarity of all the polarized's...
  How can you know how a FF acts if your FF acts up?...stick to the original grounding scheme, get a bias, tune for gain and voicing, mess with amp settings try tuning it again...they always sound different anyway, certainly can be made to do so.
  Maybe with carefully chosen parts etc. a FF can be thrown together and figured as optimized, but until it and other things have been messed with chances are there's a tone in it that may not yet have been found.
  Input cap for instance, it may be difficult enough to choose the value that a choice to have to selectable values is made.
  I like to keep a .1uf from signal path through 10kL to ground handy to adjust HF content at the output...that and a teeny cap on the input or ~a .047uf across the resistor between the C resistors [1k? see Axis Face].
  A little HF rolloff here...a little bass rolloff there...can make a big difference...add gain choices and it's a balancing act.

[Akuma60]

Thanks for the help!!

Unfortunatly, didn't manage to make it work!  Couldn't bias the transistors!  Get -4.5 volts one time, two minutes after that, I get a different voltage, try to find another resistance, good voltage, recheck, bad voltage, on and on and on and on...

Checked all the solder joints, did another Arbiter Fuzz, converted my last one to a positive ground!  Nothing works!  Well I guess you gotta know when to stop (after two days working on troubleshooting a single stompbox).  Guess I've got a bad karma with the Arbiter Fuzz!

Did the Easy Fuzz last week, pleased with the sound!  Hope enclosing it won't screw up the effect!   

I think I'll try the Rocket Fuzz for my next fuzz project!  I don't wanna see a germnium transistor for awhile!!

Thanks again for the help

[petemoore]

  Did the Easy Fuzz last week, pleased with the sound!
  Congrats!! This is a nice Fuzz Face.
  Hope enclosing it won't screw up the effect!
  Inspect the wiring that it doesn't touch the box anywhere, then test across the battery clip terminals with DMM in beep mode before attaching power, [checking for a short across the power supply] to help insure you won't burn battery up.
  Time isn't an issue to a circuit, figure it can take as much of your time as it feels like until you can get it to show you what's up with it.
  Counting connections at nodes on schematic and comparing that with the count the DMM confirms on the board...and schematic Vs measured resistor values...other than that it's all polarity/orientation of cap and transistor/power supply. Something on the board has to be different than what the schematic shows...one too many connects, misvalued R..usually any 'simple' little thing[s in a complicated network.