In fact, I'm feeling a bit lazy so sent this off to be fabricated ?



I'll have a spare board or two if anyone wants one.

Matt.

Having the PCB is one thing... Having the Germanium transistors is a whole different thing. ?

Lol the reason I made the board was I have 8 AC128's lying around ?

you sir are the mad scientist of pedals

Clockwork Orange......damn should have used that name already ? (good compressor name hmmm)

Why the use of a charge pump? You can use a standard Bosstype power supply (Battery sounds best with fuzz) Just do the circuit "upside down"

Mojo? with the caps maybe, but the Germs sound great for a reason. The low HFE mixed with a bit of current leakage, make them great for fuzzface type circuits, and clean up so well when guitar volume is backed off. No mojo with them, just fact.

I suggest using a reverse log on the fuzz control if you haven't done that already. Lin pot there is almost useless, even though its found on originals

Did you find a special mix of hfe's for your fuzzface?

Heyo

Here the charge pump is acting as a voltage inverter to give a "-9v" to the circuits.
I thought it would be worthwhile in case you need to daisy chain other effects.

Any reason batteries would be better for fuzz? Is it just the lower voltage? Or something complex and above my paygrade?
That's one of the mods on the next version - a voltage starve control. Works wonderfully on breadboard.
I remember reading somewhere that according to Mr ZVex, the starve pot pretty much does a spot on simulation of a battery due to the additional series resistance being characteristic of depleting batteries.

The "Stab" on the Fuzz Factory does just that - adds a 5k pot in series.
The previous "Fuzz Faceless" I used the pot as a voltage divider rather than series to shake things up.
But that's definitely just splitting hairs!

As to the HFE's, I haven't measured or experimented properly with different gains.
The AC128's I have do have the HFE's written down but I want to measure them myself when I have time.
RG Keen did a great article on it:
http://www.geofex.com/Article_Folders/ffselect.htm

That was also one of features I was considering for the next version - a 3pdt/4pdt to switch between 2 transistors and respective bias trimmers.
But still gotta do some experimenting to evaluate for example:
Just switch the second transistor?
Would 2 germaniums sound significantly different to justify a switch?
A mix of silicon and germanium transistors?
Would a germanium optimized circuit sound good if a silicon was switched in?
Which transistors to use?
Oh goodness, where does it end? ?

You are definitely right about the rev log pot - the useful bits really bunch up at the end of the lin pot.
Perhaps the lin was just used because different tapers may have been difficult to manufacture at the time?
That's why PNP was first used - NPN was apparently tough to manufacture consistently.

Even with daisy chaining, the charge pump ain't necessary to me. If you run the circuit 'upside down', it sees the +9v as its ground, and the ground is 'negative' in relation for the collector.
I've found the battery sounds better, battery dying simulation or not, but i'm really splitting hairs here.
Difference between germs in same circuit......yes vast. Do a switcher later.
Played around with gt309's,gt402's,ac127's,ac132's,0c75 blah blah sorry....

Even Eric Johnson's cheapy BC183C's if biased right sound decent. Also 2n2222. 2n3904 can sound harsh in standard fuzzface.
BC108's,(and 7,9) sound brilliant. All about the bias on the second transistor. Playing with bias on first is only really noticable when guitar volume is down....so its about the 'clean up' nature.

Ya if you run the PNP transistors with a negative ground, it does run the risk of oscillation.
From what I've read and experienced it sometimes happens and sometimes doesn't.

When I tried running my PNP transistors with negative ground they would randomly oscillate, especially when playing with things like the voltage.

Then again, as I understand it, that's exactly how the Zvex Fuzz Factory works.
Ie Mr Vex uses the oscillation to his advantage.

The 1044/7660 charge pump is 1 chip and 2 capacitors so even if it's just a precaution, the low parts count helps it rank higher on the cost vs benefit side.

Thanks for the advice regarding the transistors!
So far the only PNP ones I have are the AC128's. Might need to acquire more!

Oh what I meant was the switch would switch between 2 options for the second transistor. But each option would have it's own bias trimmer so you wouldn't need to rebias it every time.

Found a link to illustrate want I'm trying to say.
www.muzique.com/lab/fuzzface.htm

I've been able to mix PNP and NPN. With no problems.

Actually found this page and saw he also uses the term 'upside down'..... Promise I didn't take the term from him ?

psyx wrote: Having the PCB is one thing... Having the Germanium transistors is a whole different thing. ?

AC128s available from Build Your Own Clone parts store for $12 per pair. Let me know if you want and I will add them to my next order (minimum order $50)
http://www.buildyourownclone.com/storetransistors.html

bottledtone wrote:

I suggest using a reverse log on the fuzz control if you haven't done that already. Lin pot there is almost useless, even though its found on originals

I'm glad you suggested this because I've been wanting to find out who in South Africa stocks these things. I haven't been able to find any.