the b-17....do ya think it'll fly?

[pinkjimiphoton]

hi guys, i was doing a vero layout for a "tubesoundoverdrive" i found somewhere or other surfing around..

and well, i got to wondering how it might sound with two stages cascaded, and after some feverish typing, and a good bit of guestimation,
i came up with this thing.

i've gone over it a bunch of times, and re-did it a couple times...to make sure i didn't f it up too bad.

it's basically i think bootstrapped npn and pnp transistors, and a fairly simple circuit.

i figured since transistor stuff seems to be the opposite of tubes when configuring gain stages, i made the volume pot (crunch) a 500k, figuring it would give the circuit less gain.
i may try a 1 meg, too, there.

the trimmers i think are just set and forget, to dial in the pairs of transistors.

i went with a cap about half the size of the output cap for c3, figuring it would clean up the tone a little bit by letting less bass thru.

the diode clipper is probably unnecessary, but in for a dollar...do you think it would be better AFTER the output cap instead of before?

also made the emitter bypass cap of stage 2 100u instead of 22, figuring more filtering may help make it a little less hummy.

i know i need to breadboard this, for some reason i have an aversion to using the bb. i am a fool. an eeeeediot...a bloated sack of protoplasm..yada yada

anyways, i decided to call it the b17, cuz that's where the noise comes out of it.

advice appreciated before i take the plunge, after i take the plunge, whatever, i figure i'll learn something whether it's a waste of time and parts or not.



so....what do ya think?



do ya think it'll fly?



and my apologies and thanks to whomever drew up the circuit i based this on, they didn't put their name on the schematic...

here's the original schematic, in interest of giving props to whomever they are due to!!

[Ronan]

You might be one capacitor short of a take-off, I think the rail "i" needs a cap to the bases of Q3 and Q4.

Interesting circuit.

[pinkjimiphoton]

you know, you're right...i was looking at it, and realized i never connected the output of the crunch pot to the input of the second stage!!

brb....with the corrected version.

[pinkjimiphoton]

corrected. there's a couple of places i'm gonna try adding a diode clipper to.

also cut and pasted together a schematic.





gonna go give it a whirl i think, and see what happens...

[pinkjimiphoton]

it not only flies, it f-n' screams.

sounds ridiculously like an old marshall, very tubey...

i made a couple changes to the circuit, i added an 1n914 diode clipper just before the krunch pot, which is now 5k, not 500k...

got a 1 meg output atm, it's a little too big but was handy.

once the trimmers are dialed in, it's savage..lot of second harmonic, good compression, singing sustain that is absolutely nothing like a big muff.

i know, it shouldn't work. but it does. stupid pedal tricks are coming!

[bluebunny]

I think I need to give this one a try, if only for the inspired name! 

[Jdansti]

Got it on my long to-do list!

[R O Tiree]

C3... 0.047pF??? or 0.047uF?

Also, R2 and R4 should be swapped on your schematic?

[Earthscum]

That looks pretty sweet. The original seems to be a stripped down Pushme Pullyou. Never tried 2 cascaded, but drove one with a Octup and it sounded really sweet. Have you tried lifting the cap off the bottom of the first pair It should make for a nice sounding mod switch.

[pinkjimiphoton]

C3... 0.047pF??? or 0.047uF?

Also, R2 and R4 should be swapped on your schematic?

thanks, a couple mistakes, i'll fix and re upload soon.

c3 is .047u, there are no picofarad caps used on this build, all the values are microfarad.

also, r6 should be 220k....my bad, sorry for the mistakes.  i used 240k on mine.

there's distinct sweet spots on the trimmers...the first trimmer will be about half way up, and you can't adjust it too much...just try to get the best tone out of it possible.

the second trimmer seems to adjust the overall sound more, and here you can dial in from broken sounding to smooth and sustainy.

the diode clipper i added seemed to make a big diff, and probably why it sounds kinda plexi-ish.

mictester on the other forum told me this is the transistor equivalent of a long-tailed pair phase inverter/driver like on a tube amp...two of these, in series.

kinda neat...he didn't expect it to sustain well, or sound too good. we'll see when i'm done what's what...

to me, it sounds pretty good.

gonna try adding another asymetric clipper (probably a single led or something ) on the return from the krunch pot...thinking that may make the pot "blend" more.

remember, i'm a hack...so if ya go for this before i figure everything out, you're on your own.

but,, that said, it's already not a bad sounding pedal.

stay tuned!!

[Govmnt_Lacky]

there's distinct sweet spots on the trimmers...the first trimmer will be about half way up, and you can't adjust it too much...just try to get the best tone out of it possible.

Hey Jimi...

Curious suggestion. Since this is a Silicon tranny based build, and the first trimmer does not have a  lot of range for the circuit, would it be beneficial to replace it with a fixed resistor?

More space, cheaper part.. all be it that it is not THAT much cheaper 

[pinkjimiphoton]

hi dave,
i will try that!! see what it sounds like...but won't that cut the gain of the stage some? i try to find correlations between valves and transistors...they seem to be opposite, if you look at the e as a cathode in a triode..in tubes, bigger resistors = higher gain, with trannys it's backwards.

[pinkjimiphoton]

there's distinct sweet spots on the trimmers...the first trimmer will be about half way up, and you can't adjust it too much...just try to get the best tone out of it possible.

Hey Jimi...

Curious suggestion. Since this is a Silicon tranny based build, and the first trimmer does not have a  lot of range for the circuit, would it be beneficial to replace it with a fixed resistor?

More space, cheaper part.. all be it that it is not THAT much cheaper 

hi greg,
yah, you could do that...but you'd probably need to start with the trimmer to find the right resistor. every transistor i've tried in there so far has needed a little bit of a tweak, so i don't think there's one single value that will be a good fit.

gonna also try some GERMANIUM trannys in there and see what happens...in that case, the trimmer may be more important. also thinking the krunch pot may be able to be eliminated...gonna play with it some more before i update the schem and layout.

[pinkjimiphoton]

been messing with it for several hours...man...lotta possibilities.

you can get octave up/down out of it, some compression...and a serious fuzzy treble boost.

i tried various diode clippers at various points in the circuit, which will lead to some lo-fi fuzzy goodness...in some cases, all ya need for an octave down is to turn the guitar tone control all the way down.

but rather than get too crazy, i'm focusing more on the circuit as originally envisioned...and tried all the mods people suggested.

lifting the ground of the first electro doesn't work, it just makes it very buzzy and not very musical.

at the moment, there's an led diode clipper between the krunch pot wiper and ground (instead of input and ground) which sounds a lot better than the original idea of 2 1n914's to ground from the input of the pot.

a bat 41 in conjunction with the led's between  the input of the krunch pot and ground sounds very big muffish, in a good way...probably will keep it.

it needs treble dumped to ground early in the circuit...to my ear, sounds best with the guitar tone knob off, so i'm experimenting with values to find a good fit for a cap from base to ground...470n sounds great, but just a little muted..just tried 220, that doesn't work out so well either, neither did 100...so i bet about 330n will be the magic number...without this, there's so much treble that as a note sustains and blooms, a weird trebly feedback crackly noise seems to set in on the decay.

unacceptable.

so...almost done messing with it, hoping to get to trying some different transistors...have a feeling slipping a ge pnp or two in may sound really good.

the diode clipper with the switch is noticeable, but barely...man...gonna be a few compromises. will up the changes when i settle on them.

peace

[Earthscum]

it needs treble dumped to ground early in the circuit...to my ear, sounds best with the guitar tone knob off, so i'm experimenting with values to find a good fit for a cap from base to ground...470n sounds great, but just a little muted..just tried 220, that doesn't work out so well either, neither did 100...so i bet about 330n will be the magic number...without this, there's so much treble that as a note sustains and blooms, a weird trebly feedback crackly noise seems to set in on the decay.

unacceptable.

Maybe a cap across the 500k (L3) to ground could help shave a bit between stages, as well. A 220pF cap would be a nice middle ground, me thinks. Maybe even something like 25pF might get the right amount of highs out of it. 220pF across a 500k is about 11450 Hz in simple RC calculations. 25pF hits just under 13kHz (as an example of range).

[pinkjimiphoton]

hi dave,
good call;

as it turns out, messing with this thing alot, a 220n cap from the common base of q1 and 2 to ground did the trick.

i dumped the diode clipper, it really didn't help, tho i learned a lot, and have a couple more designs based on this now including octave up and down and buzz pedals.

ditched ALL the clippers. no need for them on this one. next one, definitely.

it has tons of balls without that stuff. tried ge and it just didn't sound good at all. pulling EITHER of the 3906's makes it a lot ballsier and puts it in fuzz land. replacing q3 with another 3904 sounds great too... more pedal designs.. one at a time.

i gotta fix the layout and revise the schematic, and i'll post 'em soon...but the basic design is verified, which is hip...and you can go from clean to scream from the guitar, it acts a lot like a fuzzface.

demo coming as soon as i can...gotta draw, then box it up.

[digi2t]

Video! Video! Video! Video! Video! Video! Video! 

[pinkjimiphoton]

any trannys around 400 hfe should work out fine i bet.

as drawn, this thing DOES work tho....add that 220n cap, and you're golden. use leds for the clipper on the first stage, and bat 41's between the wiper of the crunch pot and the input of the second stage...when ya turn your tone control all the way down, you should get an octave down buzzy fuzz...it's pretty sick!!

and if you want a really sick treble boost fuzz, try a 47n instead of the 220n.

here ya go guys,..correct complete and verified...



and the vero



watch for a stupid pedal tricks episode on a website near you soon....

time to box it up!

dino, video tomorrow, ok??

too late now, i don't wanna spend the nite in the hooscow!!! lol

[rutabaga bob]

[pinkjimiphoton]

awesome, thanks so much larry!!