Fuzz options

[Kipper4]

My AC128 arrived today and i tried them but it wont work its just really splatty.
when i use the only other PNP's (BC327)i have to test if the circuit works its fine lots of fuzz and gain. But the 128 sound intermittant and splatty farty.
The voltages at the collector of Q2 are 0.28volts with the AC128
the voltage at Q2 collector with the BC327 is 4.56volts
whats going on there



My NPN BC109 fuzz face sounds good.
and the Fuzz face with the BC327 sounds good too but i've spent the money (more than i wanted to ) on two pairs of AC128 for that germanium mojo.
It feels a bit like.
"Here i stand broken hearted. Spent a penny and only farted."

[Kipper4]

http://www.grindheim.net/electronics/occc/AC128.jpg

This is the pinout i've been using just in case

[bluebunny]

Pinout looks good to me, Rich.

[maddmann08]

I encountered the same phenomenon when trying out different transistor types in my silicon Fuzz Face. In my case, I used a trimpot for the bias resistor on Q2 so I was able to solve the issue just by lowering the resistance until the collector voltage was back up to where it should be. It seemed each transistor I tried needed a different resistance value to properly bias so I adjusted the trimpot accordingly. Maybe this is your issue as well. I am by no means an expert, I just built my first fuzz a month ago, I just thought I would share a similar experience in the hopes it might help. 

[LucifersTrip]

the .28 is so far off that it suggests a wrong pinout or bad or wrong gain/leakage transistor

even if you adjusted the .28 up to near 4.5 with a trim on Q1 or Q2, it most likely wouldn't sound great. just like with most effects, you should at least get close to working voltages before the final tweak wit a trim...

1st thing to do is measure the 128's

[Kipper4]

I will do.
they were suposed to be measured already and were marked up and should all be betweem 55 and 110 hfe.
i'll get my meter out and my other device tonight and try to remeasure.
if that doesnt go well i have a friend with a peak semiconductor tester
Cheers dude

[Henry89789]

I think I've seen some reviews (on you tube, I think) or forum discussion somewhere suggesting that the AC 128s aren't the best sounding germanium transistors to begin with.                               

[Henry89789]

After reading this thread on fuzz options and suggestions, I am thinking of building a Lunar Module Deluxe and a Tonebender. Does anyone have any suggestions on which are the best schematics to use to build these pedals? Thanks.

[nocentelli]

The exact schematic for the lunar module deluxe is hosted over at the other forum, but there is a version called the lunar fuzz at www.guitarpcb.com - i think the main difference is that the Skreddy lunar module has a (56k?) resistor at the input, the lunar fuzz omits this. As for a tonebender, that is a name given to a large number of different circuits by different manufacturers (vox, solasound, colorsound etc) with quite different topologies: MK1, MK1.5, MKII and MK3 versions all have different circuits, with the MKI being similar to an early Maestro fuzz, the MK1.5 being essentially a fuzzface, MKII is a booster slamming a fuzzface, MK3 has a tone control etc (I think that's right). The Lunar module is probably closest to a MKII.the details of exactly what each version contained can be found at fuzzcentral, or in much more exhaustive detail at the D*A*M forum. Bear in mind all were originally made with germanium transistors, the MKII can certainly be accomplished with silicon.

[Kipper4]

it depends on which bit of kit i use to test one say hfe 280 the other say around 100 hfe for the same transistors
i trust the DMM more and it says around 100>150 hfe
but it just doesnt work in my present build.
The AC128 just sound splatty and intermitant
i built the pnp fuzz face with the 470R
the NPN version has a 330R
I'm about to ive up on these transistors and use them in something else. Like building a second Deacy amp.
It's starting to cheese me off.

[samhay]

Welcome to the vagaries that comes with working with the planet's dwindling supply of Ge transistors.
If you want to get close(ish) to that sound using Si, you might want to luck into the 'piggyback' Fuzz Face (or whichever Fuzz for that matter). Google aught to point you in the right direction.

[Kipper4]

I feel like i've been had though.
Everyone goes on about germanium fuzz and 128s. Except its not a given even when you pay for specialy selected ones too.
I'll have a look at some of the others like the piggy back and the lunar module.
It (PNP) sounds good with si PNP transistors. i'll stick with those.
i'll order some AC125 also just to try them.

[Kipper4]

I tried a Hybrid solution.
Silicon in Q1
Germanium in Q2
that works.
I think maybe play around with the biasing a bit and i might be on to something.

When i put Ge in Q1 and Si in Q2 i might have well used Ge in both (disaster)