stupid simple overdrive two

[pinkjimiphoton]

so i worked up a new version of the ssod today. one input cap, one output cap, one resistor, one pot and a transistor. so stupid simple i don't even need to draw a schematic for it.
you need
1 ac176 or similar germanium npn transistor
one .022u input cap
one .1u cap
one 500k resistor
one 200k resistor (optional)
one 50k linear pot, and some passives... switch, case, power supply, jacks etc

ground emitter. i used the back of the 50k pot as a star ground.
to base, connect .022 cap (put your audio in to the free end of this cap) and at that node, run a 500k resistor to ground.

run 9v into the input of your 50k pot, wired as a variable resistor. take the wiper to the collector, and from this node add your .1u output cap. the free end of this cap is now your output.

the 50k pot works as a bias adjustment for the single stage amp, and lets you sweep thru the entire useable bias range of the transistor... kinda like a superhardon, but more in the overdrive/fuzz school than a booster. simply sweep the one knob til it sounds good, that's it! does volume and distortion in one shot. add in some true bypass switching, and suddenly the SSO2 is born.

if you're anal about stability and willing to give up a little balls, add another resistor, sayyyyy 200k or so from node at base input to b+, and that's it. hows it sound? really @#$%in good, believe it or not. nice very natural distortion that is amp like and cleans up well from the guitar like all good fuzzes should. the 500k resistor not only helps stabilize the biasing, but also acts as an anti pop resistor.
as you sweep the knob, you can get some crackle. that's ok, the output cap blocks any damaging dc from the rest of your signal chain.

[midwayfair]

Just want to clarify that people will need to use a Ge transistor, and it will need some leakage -- a silicon will require positive base bias. This uses leakage current for its bias. I'd actually use as big a resistor as possible for the base to 9V, but that's just me.

[pinkjimiphoton]

hi jon!!!
yep, that's why i said ge.  has to be to work.

here's a cheezy schem:



and i got it easily into the 1590a from the original one. the main dif is this has a bias knob for volume, the original was pretty much full blast with a volume control hung on the end of it. this way seems to work and sound better...
and you can just sweep it til it sounds good, WEATHER BE DAMNED!

[Granny Gremlin]

Sup dudes.  I was thinking of trying this out because it is so simple, but I play mostly bass (some guitar).  ... so I suppose I'd need to up the value of that 100n in front of the output, right?  Anything else?

[pinkjimiphoton]

you could up it to wherever sounds good, try maybe .1 on the input and .22-.47 on the output. more bass at the input will make it distort more,
i'd breadboard it and maybe use adjustable input and output caps.... like, maybe .022 to pin 1, 2.2u to pin 3, of a 100k-1m pot,  tie the arse ends together (negative or positive depending on pnp/npn) and put your input to the wiper... as ya turn the pot, you can fake an adjustable capacitor and tune it to wherever it sounds good. you can do the same thing on each end if ya want to i'd imagine.
values are arbitrary, i just pulled them ones out of my arse.

i'd imagine you'd wanna roll off a little bass on the input, and let a little more thru on the output depending on what you're trying to do with it.

[smallbearelec]

yep, that's why i said ge.  has to be to work.

Hi Jimi--

Does the device have to hit RM gain buckets? If so, it's an expensive part. If not, this build would be a super candidate for cheap, low-gain NPN ge connected as Darlington pair. The multiplied leakage of two devices might be enough to bias it.

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonRMs/BreadboardGeDarlingtonRMs.htm

Would ya measure the one you used and let us know? TNX.

[Granny Gremlin]

Thanks Jimi.   Yeah, I was gonna breadboard it first. 

I kinda play bass like a surrogate rhythm guitar (chords, well up the neck) a lot of the time but I do want to have the woof when I need it.

[pinkjimiphoton]

yep, that's why i said ge.  has to be to work.

Hi Jimi--

Does the device have to hit RM gain buckets? If so, it's an expensive part. If not, this build would be a super candidate for cheap, low-gain NPN ge connected as Darlington pair. The multiplied leakage of two devices might be enough to bias it.

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonRMs/BreadboardGeDarlingtonRMs.htm

Would ya measure the one you used and let us know? TNX.

might be a little tricky as it's p2p in a 1590a i dunno if i even kept it.

but i've built a bunch of these suckers, any old pnp or npn seems to work, as long as it's ge. low gain is fine, high gain is fine... they sound different, but it doesn't really seem to matter... ya get whatever the max gain of the transistor is by grounding the emitter. you can use a bigger pot than i did i'd imagine.

[smallbearelec]

i've built a bunch of these suckers, any old pnp or npn seems to work, as long as it's ge. low gain is fine, high gain is fine...

Thanks for the reply. I will try this out when I can make time around 62 other projects. I would be interested in coming up with a "recipe" for specific transistor gain/leakage, adding an output level pot and packaging in a Bare Box #1. There's a lot of low-gain NPN ge out that does not leak much...I'll have to experiment. If I think I have something commercial, I'll ask your permission to use the idea.

[pinkjimiphoton]

i've built a bunch of these suckers, any old pnp or npn seems to work, as long as it's ge. low gain is fine, high gain is fine...

Thanks for the reply. I will try this out when I can make time around 62 other projects. I would be interested in coming up with a "recipe" for specific transistor gain/leakage, adding an output level pot and packaging in a Bare Box #1. There's a lot of low-gain NPN ge out that does not leak much...I'll have to experiment. If I think I have something commercial, I'll ask your permission to use the idea.

won't work well like that. the leakage is what makes it bias, tho npn's seem to be fine still. i'll breadboard one up if i get a chance at some point over the next couple days. an output level is overkill. it's not all that loud, it's just a little above unity gain really, tho that depends on the transistor and the size of the gain pot. fwiw, i didn't really care for the output volume, just changing the bias to c works and sounds better.
i use nos JAN ge transistors that are stupid cheap... 15-25 cents a piece routinely. i haven't tried with any good transistors i don't think.

ha, scratch that... lol.... i just looked at the layout i posted, for an npn version using the ubiquitous ac176, there's plenty of them to be had for cheap still out there. i've built so many of these things i guess i forgot. it's just a nice simple cheap overdrive that sounds real warm and natural to my ear.  you can literally leave the 500k and optional 200k resistors out if you want, and it still works and sounds pretty much the same. they just were added cuz i noticed i could stuff just about any ge in there that way. in it;s simplest form, all you need is an input cap to b, ground the e, and stick an output cap and the pot on c with the pot going to B+ and you're done.

i would have to think about commercial derivatives to be honest, as i generally release this stuff into the wild for DIY use only. i'm not averse to it being used commercially, but it would have to be a "pay it forward" kinda thing in some respect to something charitable. or a shit load of money. just kidding on the last part. i'd rather see people get their courage up and take a dive building something than see 'em wasting all their money on shite like ep boosters. (don't get me started)   the GOOD thing?'  is you could probably make it as a kit that sells for around 30 dollars with everything and still make money. the most expensive part is probably the casing. switches and jacks etc are cheap.

[pinkjimiphoton]

looking at it, you could leave out the diode, and use a non polarized cap for the power supply filter (say, 2x100u with the cathodes connected together would make one 200u-ish non polarized cap)  and then run it npn or pnp at your whim by reversing polarity to the circuit and switching the q's i would imagine. in that case, maybe add a big ass (again, non polarized) cap between e and ground, but i haven't tried it. that would isolate the q enough where i'd imagine you could run it either way off a standard kinda daisy chain, but i'm probably wrong.

you guys, even you NEW guys prolly know way more about this stuff than me i'm just more willing to @#$% around and let the magick smoke out.

[pinkjimiphoton]

hey small bear, i checked it out, hfe around 80. i say around cuz it changes if ya breathe near it or touch it.

[smallbearelec]

hey small bear, i checked it out, hfe around 80. i say around cuz it changes if ya breathe near it or touch it.

Thanks for letting me know! I'll be interested in seeing whether your idea likes Darlington pairs that are tweaked into that range. As I noted, the leakage of the devices multiplies as well as the gains, which might be advantageous here. If still more leakage is needed, there are lots of otherwise-throwaway devices (like those used for FZ-1 clones) that would work.

[pinkjimiphoton]

me too, that would be great for a lot of worthless trannies

[pinkjimiphoton]

this is what's on my breadboard right now, currently mk 4



depending on the transistor, you may need to adjust the 3.3k up or downward. you can also ground the emitter no diff other than stability. also, i ended up with 4.7n instead of 100p on it. nice, quiet, stable. sounds like a nice overdrive, and you can control it from your guitar perfectly.

[pinkjimiphoton]

here's a stupid simple vero for the mk4 ssod. haven't built it yet, but i know it's right, matches the schematic and breadboard node for node.



if ya  build it ptp, should be able to fit in a 1590 ok i'd imagine.