Fuzzrite voltages seems strange to me

[gigimarga]

Hello,

I'd built the last night, for a friend, a Mosrite Fuzzrite using the schematic (and PCB) from FuzzCentral (thx Phillip Bryant!) : http://fuzzcentral.ssguitar.com/schematics/fuzzriteschem.gif.

I used two 2N2222 with the hFE about 160 (as i saw in a Dragonfly's post) and pots of 470K/47K instead of 350K/33K.

It sounds OK i think (i'd never heard an original one), but when i measured the voltages (using a 9.4V battery) i found both collectors at 0.57V, both bases at 0.51V and the emitters, of course, at 0V.
Are these values right or i must to bias the trannies at 4.5V,  like in a Fuzz Face?

Thx a lot!

[Sir H C]

Sounds a bit low, would think closer to .7 volts, but ballpark as the voltage across the base - collector resistor should be 1/160th of that across the collector - V+ resistor, so you get about the base-emitter diode voltage on the collector.  Usually this is in the .7 volt range, but with such a low collector current, .51 is equally probable.

[gigimarga]

Thx for your answers!

I will search for a soundclip to compare with mine and after that i will try or not to increase the collector's voltages...

[gigimarga]

 

[gigimarga]

 

[GREEN FUZ]

Not sure if this is any use to you as I purposely misbiased my circuit in an attempt to cop the tone of this soundtrack.
http://www.youtube.com/watch?v=YswkF-d2VZ8
Supposedly a lot of the early Fuzzrite`s weren`t biased very accurately which could account for the sound I was aiming for. What do I know except that it sounds great to me.

I think I got it fairly close.

For the record: My voltages.

Battery = 8.20v

Q1 2N3904 C = 2.44v                  Q2 2N3904 C = 6.86v
                 B = 0.64v                                   B = 0.56v
                 E = 0.0v                                     E = 0.0v

[gigimarga]

Thx a lot GREEN FUZ!

Your collectors' voltages seems very strange to me...mine are equal and more lower...i will check all!

[nico13]

Hello Gigimarga,

I also built a silicon fuzzrite yerterday using the same schematic as you and BC107A transistor and I've got the same problem

i found both collectors at 0.57V, both bases at 0.51V and the emitters, of course, at 0V.

and I found the effected sound very low.

Nico

[gigimarga]

At last, i like it as it is...any suggestion is welcomed!

[nico13]

Well I used this layout:




And I checked my build: everything was OK except a shortcut between rows 2 and 3.

I used 2N2222 transistors (with hfe about 170) and now I've got a good wild fuzz!

Here are my voltages for the transistors with an input voltage of 9V (regulated power supply):
Q1: C=0.59 / B=0.53 / E=0
Q2: C=0.60 / B=0.53 / E=0

[Marc.yo]

Well I used this layout:




And I checked my build: everything was OK except a shortcut between rows 2 and 3.

I used 2N2222 transistors (with hfe about 170) and now I've got a good wild fuzz!

Here are my voltages for the transistors with an input voltage of 9V (regulated power supply):
Q1: C=0.59 / B=0.53 / E=0
Q2: C=0.60 / B=0.53 / E=0

nice layout btw

[nico13]

Thanks Marc,

I tried to keep the symetry of the schematic.

This layout is verified.