transmission overdrive

[pinkjimiphoton]

hi guys,

tinkering around with some crap, and i came up with this :



positive it's been done a gazillion times before. but one little twist... i added a simple control to be able to "pan" between the two clippers... one made with 1n4001's (slower clipping for the lows) and one with 1n4148's (faster clipping for the highs)... it works, kinda sorta.. it's more noticeable at some settings than others, it's mostly useful for dialing in "touch sensitivity"..
the tone control is what it is, fairly simple and crude... but for one freekin' transistor, it actually works pretty well!! at least i think it does..
i didn't put a master volume on it. you just crank up the gain to where ya want it. unity gain is about 8:00, above that it just kinda gets more saturated (and a bit louder)...

how does it sound? kinda like a tube screamer. which wasn't what i really expected at all... it's a kinda nasal middy overdrive, cleanish, but enough to bump an amp into a really nice natural overdrive sound.

i tend to like the knobs pegged.

if ya build this or mess with it, you may wanna mess with the diodes some... i shoulda put switching in this, but i wanted to do something without all the vegematic options for a change.

led's would probably work great in it instead of 4001's.

i tried every npn in the house... took a couple hours, and settled on bc547 having the most natural overdrive tone. sockets are your friends. higher gain transistors and darlingtons sounded great... 5089's even were fairly good..bc109's etc... but in the end the 547 won out to my jaded old ears.

i built it up on a vero, here:



it works. it doesn't sound too bad, even.... will shoot a SPT when i get a chance. you may wanna add a volume control to it.  if so, just add a 100k pot between audio out on the board and the footswitch.

the original idea for this i stole from here, pretty much. it's not quite the same circuit anymore, but fair's fair, and without this guy's work, i never woulda built this, so here's to you bro, whomever you are!!

http://3lectronics.com/overdrive-effect-pedal-fuzz-schematic-and-layout/

[bluebunny]

Hmmm... looks interesting Jimi.  Another one for the build list, I think.  BTW, is the 9V battery with two negative sides part of the mojo?   

[pinkjimiphoton]

it's a negative transmission... lol...

actually sounds fairly decent for what it is, lol...

[pinkjimiphoton]

[J0K3RX]

I like the clipping idea!

[pinkjimiphoton]

i'll take the credit where it's due... lol....

all i did was sub the voltage divider in the original design and change it to a pot.

but it was a cool discovery!! definitely worth looking a little deeper into...

[Gus]

Something that might be fun to try

instead of the wiper to outer lug of the balls control

use a cap from wiper to outer lug connected to the base + to the wiper

this disconnects the DC bias shift with adjustment of the control

you might like the DC bias shift and gain change as you have built it

Where did you have the B set to when adjusting the trim?  This would be close to the potentiometer value you might use with the cap wiper to outer lug.

I don't know if this will sound better than what you built but maybe something to try.

[pinkjimiphoton]

hi gus,
would that be more like an "attack" control that way?
sounds like it may be kinda cool!!

what i like about this is the gain control doesn't give much volume, just more compression and grit.. do you think adding that cap may make it a little more aggressive?

the battery was a fresh cheap alkaline, 9.65v... c ranges from 5.0 to about 7.62v with the 500k trimmer... i like it best right up at the top of the range. could almost make that trimmer another pot, as it controls the volume and sensisitvity of the transistor. i almost added a variable tone cap on the input (.0068u/2.2u tant) and a master volume control... but i was like... wow, that would be a LOT of knobs for one stupid transistor, ya know?

they were cool ideas, but not cool enough to implement (tho i did try them, and definitely learned in the process!!)

thanks for the advice support and guidance gus... it means a lot to me bro. rock on!!

oh, and i was thinking about the "shift" pot...

wondering if it would work better with a dual gang pot, so you could get the tone from  ge and the volume increase from some si, like, say ya used 1n34's for the treble side, and led's for the bass side... on the second pot, use 4148's with the '34's to "boost" back up the volume a little and maybe add some 34's to the 400X's or led's to give it a little more flavor...

or maybe it's overkill?

[pinkjimiphoton]

sorry bro, i misunderstood your question i think...

i will open it up and get some voltage readings.. i remember that c was about double what b was with no transistor in the socket.. 7.93 was c, b was 3.9_ something...
shoulda written it down, sorry!!

[Gus]

Lets say you set the 1 meg B control to the middle (and it is a linear potentiometer) when you set the trim
This would be 500K C to B(1/2 of 1meg linear control)
So change the 1meg to a 500K linear and use a cap from wiper to outer lug

It might sound "better" as you built it because you change the DC bias and gain
What I posted disconnects the bias from the gain

Something a little different

[J0K3RX]

You could try a fake variable cap for the 47u coming from the emitter like in figure 2, output to ground. Try like 47u and 1u or something like that

[pinkjimiphoton]

fig 2 is like what i did, but it just didn't justify itself. it was nice to gain the extra tone control over the midrange, but it made for too much gain loss to be worth doing it.
i wanted it to be simple and stupid... don't get much easier than one transistor and a couple parts.