The Germocide Fuzz was something I designed when a forum member asked about what he could build with some low leakage, but very low gain (less than 50hfe) PNP germanium transistors he had.
Monday, 18 February 2013
Germocide Fuzz
One more from the Dragonfly archives. This one is a must for us who have tons of low leakage, low gain germaniums on our hands. The name is describing the circuit well, as it takes 4 germs to get one ripping fuzz running. Note that this is "positive ground" circuit. You can always use a suitable pump to chain with your other boxes.
The Germocide Fuzz was something I designed when a forum member asked about what he could build with some low leakage, but very low gain (less than 50hfe) PNP germanium transistors he had.
The Germocide Fuzz was something I designed when a forum member asked about what he could build with some low leakage, but very low gain (less than 50hfe) PNP germanium transistors he had.
Surely there should be some breaks in the top row underneath the 1k and 470 resistors?
ReplyDeleteYes it definitely needs cut, but I think Miro is away for a few days so he may not have a chance to correct it straight away
DeleteInput to Gain 2 or Gain 3? I guess that would affect the green line Gain 3 too.
ReplyDeleteYup. This needs those two cuts, under the both resistors in top row, and input does go to Gain 3 - the label on bard is wrong.
ReplyDeleteI'll fix the layout as soon as i get back home...
+m
Layout updated. Should be safe to build now :)
ReplyDelete+m
Verified! Well, mine didn't work with the diode in it, I had to snip it and replace it with a jumper as no voltage was going through it. I take it it was included for polarity protection as the schem just shows it going to ground from -9v? Also this is quiet, really quiet, like having to crank the amp to 11 quiet. I'm going to replace the 68k resistor with something around the 22k mark and see if that helps as from the looks of things and having read the post on DIYstompboxes where I think this schem originated, Dragonfly recommends swapping it for a 100k pot to make it more tweakable. I'm going to change the 22nf output cap for 10nf too as at the moment it's got huge amounts of bass even with a tele!
ReplyDeleteAfter going through the original post it looks like it was designed as a Fuzz Face that uses low gain germaniums in a darlington pair configuration with a silicon pnp booster stuck on the front. It sounds pretty mean but I think there's scope for a little tweaking to get it sounding a bit sweeter, Dragonfly recommends that Q2 and Q3 have hfe around 30 and Q4 and Q5 around 50 so it looks like I get to play with my new toy again :D
Ok so the 10nf output cap was a good call and so was the 100k log pot in place of the 68k resistor (lug 3 going to Q1's 100nf cap, Lug 2 going to Q2's and lug 1 going to ground) but it didn't cure the volume problem it just turned it into a totally frickin sweet splattery fuzz. Now it can go from your classic warm germanium fuzz to a more modern tone by tweaking the new pot, I bet if you put a higher gain transistor in Q1 you could get into Death by Audio terittory. It's so damn quiet though :( I've probably done something idiotic like put in a resistor that's too high but I've checked everything, ah well it sounds pretty awesome so maybe I'll just stick a booster in after it too.
DeleteHaha. Stupid me. That's for polarity protection, and i have just placed it backwards.
DeleteI'll fix that tonight and tag it after i've posted the correction.
Thanks for the info. I'm pretty baffled about the quietness though....
+m
I updated the layout for correct polarity protection and tagged it.
DeleteIf you find something out about the level issue, let us know.
Thanks again!
+m
Will do, I think I can hear a couple of beers calling so I'll pick this up again in the morning.
DeleteRight, after an afternoon of modding and fiddling it came down to one thing and one thing only: it needs the 47uf cap next to the trimmer snipping out to get full volume. I think it's an error with the original schematic, maybe Dragonfly got a bit carried away after he put the booster section in. Anyway, I've made a few discoveries in the process of trying to debug this so I'm going to draw up a fairly modded version if anyone wants to give it a go.
DeleteThat's perfect. Let me know and i'll draw the mods as a layout...
Delete+m
Cool, cheers dude. I'm off out to Manchester for the night but I'm going to sit down with it tomorrow and try and get everything working in one circuit, there's a few tweaks that would apply to any Fuzz Face and I'm going for all out Germanium and replacing the 2n3906 with a darlington pair and possibly using a different booster circuit. I'm also toying with the idea of switchable input caps or maybe just a blend as there are different values that people would enjoy (I've got it socketed at the moment. Lastly I think it would benefit from having pots for the bias trimmer (to get those gated fuzz sounds) and the 1k resistor off the 22uf cap.
DeleteI'm going to build this modded version from scratch before I recommend any of the changes just to make sure they mesh with each other. I'm getting started on it now so hopefully I'll be able to email over the schem I've prepared later tonight :D
DeleteWhat would I have to change to use this for low gain low leakage NPN's? Reverse caps and transistors?
ReplyDeleteIs it simple enough to modify this for an NPN version? Similar to other fuzz circuits where you can swap caps,diodes and transistors around the opposite way?
ReplyDelete