komrade boost

[pinkjimiphoton]

thanks paul, i actually understood all of that. thank you!!!

i had a play with this on the breadboard, and made some neat discoveries.

i suspected the presence of the signal at the base was what was turning it off or on. thanks for confirming that.

i played with a bunch of input/output caps, input caps with variable cap trick (like in the gagan easy face) with caps from 100p to 33u...

the more bass, the more distortion of course, i find it nice between 1n and 4.7n. above that, gets too woofy. but a .1u cap shorted across the input cap gives a nice big phat boost that's nice for leads!!

can ditch the rc network on e. just ground e directly as you suggested.

can also ditch the 1m gain pot! it DOES let you adjust the overall distortion amount if you don't use your guitar knobs, but if you do, it's really not necessary.

so we're down to

input cap to base

100k trimmer (which also determines the volume of the over all thing as well as the distortion)) and .047-.1u output cap to collector

grounded emitter..

so... two caps, a resistor/trimmer and a leaky ge transistor. that's it.

a 4 part fuzz?

tried transistors that were too hissy/leaky even for percolators, and they sound KILLER. the leakier would appear the better, as dave discovered!!

gonna try an npb version shortly, curious to see if it will work the same.

thanks guys. i can't believe i'm actually using my breadboard for the first time instead of committing crap to vero. god. what was i thinking???



oh yeah, paul, also i agree, it's not the SAME as a simple tube stage... it just kinda looked like one a little... with the bypass cap, blocking caps and + resistor.
i have gotta quit thinking i know anything. i don't and it's fairly dangerous.

[PRR]

> it's not the SAME as a simple tube stage...

There's key differences in getting it to work.

However, a very smart man wrote a book which treats tubes, BJTs, and FETs "all the same". They all have two input pins and two output pins (as they must) but three physical pins. There's a higher-power path from an emitter K/E/S to a collector P/C/D, and a lower power control path from G/B/G to K/E/S. A change of control voltage causes a change of collected current.

Main differences:

BJT Base is always leaky, hardly-no leaks in Grid or Gate.

Tubes JFETs and some MOSFETs have a "half-on" control level "below" the other control pin, BJTs and most MOSFETs have it "above" the other control pin.

[pinkjimiphoton]

thanks bro.


have you seen this?

http://www.radiomuseum.org/forum/the_trioderizer_a_solid_state_triode.html

it's probably my lack of experience that makes me think like i do,

i built a few stages of this cascaded and played with it a while and found some really amusing variations that cover most of the fuzz sounds i've ever found. amazing how a simple overdrive can  become an octave up if ya juice it hard enough.

three stages was amusing... blatty, gated, but with a decent sustain that sounded almost like a synthesizer... you can make it "swell" in. very fun.

not useful (for me)

so i of course added another stage. used the crummiest ge's i have, really leaky low gain that won't work in anything.

and in this, two of 'em in series sound KILLER.

when all's said and done, it's like the world's simplest fuzz.

ditched the input gain. don't need it. just use the guitar knob (tho it sounds better to my ear with a 10k resistor in series with the guitar signal)

so...guitar >> .0047u cap >> q1 b.

ground both emitters to b+

100k trimmer to c of each q from b-

.047u cap from q1 c to q2 b

.47u cap from q2 c to top of 100k pot

ground the bottom of it to 9v+

output is wiper.

so... 2 caps, 2 resistors, 2 transistors and a pot.

7 components sound pretty sweet!!

fwiw.... q1 c resistor 39k
q2 c resistor 68k

who needs a schematic?

loud, fuzzy, overdrive, sounds remarkably like early AC/DC.

turn your guitar down for clean(ish) and up for scream.

(can use the 1m pot for a gain control like my original idea if people don't like their guitar knob)

but more than two stages? forget it, unless ya like that kinda sound... i tend to gravitate more to tube-ish kinda sounds with a healthy midrange, and this has that in spades.


oh yeah... if anyone adds the third q, hook c directly to b-

have fun!!

[Shoeman]

I just breadboarded this after lurking for a week.  So simple and so good.  Used an AC128 Sony I had lying from an aborted Rangemaster project.  Still fooling with the caps to fine tune it, and I ditched the gain pot too.   Thanks for the circuit.  I'll box it soon and add it to the arsenal.

Geoff

[pinkjimiphoton]

hey geoff, thanks for the build report, and welcome to the forum!!!

i am really psyched you dig it. it makes a great little booster to cut thru when ya need to... not real loud, but nice tone!!
check the bias schmias thread too for an evolved version.

i'm gonna make an npn version for my pedalboard of this one, to me, it's a keeper!!

any noise issues? mine's a little hissy, in an "airy" kinda way... but it sounds so good i don't wanna f with it!!

[Shoeman]

Mine is loud.  I'll put the gain pot back in when I box it.  I also want to try and measure the leakage and gain of the 128.  Been looking at the method on Keen's site.  I did not hear excess noise, but the breadboard is not a fair test of that either, and I was playing it through a fetzer-ruby into headphones since the Misses was in bed.   I love all these different flavors of fuzz and boost you can make.   On my lunch break yesterday I was listening to BB&HC Cheap Thrills and one of the fuzz tones just jumped right out of the speakers and grabbed me.  Real 1968 nastiness.

[pinkjimiphoton]

i'm actually sacrificing some of the gain in it where i've got the juice turned. it's pretty sick. the bigger one actually has TOO much distortion, if that's possible. i've never heard anything slam an amp like that. it's like a reverse attack, it starts as fuzzy noise and then fades into distortion. loving it.

glad you're digging this.

rock on man

[Shoeman]

So far in mine the trimmer has very little effect on the sound other than loudness.  It does vary the voltage as expected.  I suspect the AC128 I have may not be optimum for the circuit.  Maybe not as crappy as it should be!   I need to see how it interacts with tube input stages and all the various pickups I have before I do any more tweaking.  Tough work, aint it

[pinkjimiphoton]

on mine, there's a couple spots on the trimmer where it gets all staticky and horrible... in a kinda cool way.  but yah, basically, just dial up the volume, and use that and the hint of ge overdrive to push your amp over.... i am loving it.. and when ya want velcro, hit it HARD.

[pinkjimiphoton]

this page seems to explain what this circuit is.

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part2/page1.html

and just found this, which is kinda a similar idea...

[dwmorrin]

You just posted a fuzz face schematic. 

[pinkjimiphoton]

yeah, it is, huh? lol

[Shoeman]

Spent the morning fooling with this again.  The .1uf input cap is my preference.  Fuller, louder, better imho.   Tried a really leaky NTE158 I had. I'm new at measuring leakage so I'm not sure I did it right, 230uA for the AC128 and 623uA (!!) for the NTE158.  Anyhow, swapping between the two made little difference in performance.  Buzzy like a bee, with hardly any more than unity gain and pretty fast decay on single notes.  I tried running it into a Mosfet boost to raise the gain, but that seemed to get rid of a lot of the circuits personality.  I tried the Mosfet Boost in front of the circuit and that was no help either.  So I was left thinking "interesting but not very useful" to myself.   
  Then I went back and reread all the posts and figured what the heck, let's breadboard the two Q version since I have them.  Took all of two minutes.  Well Mistah, as we say up here, that is a different kettle of fish.  Now it's loud.  Now it's fuzzy.  It swells, it gets gated on high notes, it's attack sensitive and it sounds pretty good. This kind of testing needs to be done when you're alone in the house I have found, because hitting the same chord over and over while you twiddle pots and let it ring out will drive any bystanders crazy.  It does not have the long sustain of a BMP or the Leeds.  It will give you the Satisfaction tone.  It's useful and a way to use those leaky Ge's that sounds OK. 
I have more cap tuning to do on it.  Gotta go.

Geoff

[pinkjimiphoton]

Spent the morning fooling with this again.  The .1uf input cap is my preference.  Fuller, louder, better imho. 

becomes more of a fuzz at tht point. i tried a bunch of caps before settling on the .0047 in the end... too big, it gets wooly and very buzzbox like for sure.

it should be about unity if ya used the 1m pot about 3:00 on the pot, and full about maybe 5:00 with the pot half up as noon.

 Tried a really leaky NTE158 I had. I'm new at measuring leakage so I'm not sure I did it right, 230uA for the AC128 and 623uA (!!) for the NTE158.  Anyhow, swapping between the two made little difference in performance.  Buzzy like a bee, with hardly any more than unity gain and pretty fast decay on single notes.  I tried running it into a Mosfet boost to raise the gain, but that seemed to get rid of a lot of the circuits personality.  I tried the Mosfet Boost in front of the circuit and that was no help either.  So I was left thinking "interesting but not very useful" to myself. 

think of how this thing works..

it's basically you have whatever voltage you generate from your guitar, hitting the base and opening the valve for all intents to allow current to flow and the transistor to amplify.
whatever the max gain of the transistor is is what it's gonna put out. the guitar is part of the circuit. so slammin' it in the front won't really help, and boosting behind it does kill it's character somewhat.  i agree. but i'm betting the hfe on those transistors is a bit higher than you're expecting.  i have a nice treble boosted buffer that boosts maybe 6 db when it's pegged.
i've built several of them  now, and your transistors are exhibiting exactly what i found with ac128s and mp16's etc. they are very buzzy and gated. try more like a .022u input cap... that should help some. you'll still get a fair amount of breakup and it will have more ass.

and you wanna have your amp cranked up some while twiddlin', cuz it sounds completely different at really low volumes compared to moderate stage volumes.

you need crappier transistors for this circuit to be happy.

i think.

 
  Then I went back and reread all the posts and figured what the heck, let's breadboard the two Q version since I have them.  Took all of two minutes.  Well Mistah, as we say up here, that is a different kettle of fish.  Now it's loud.  Now it's fuzzy.  It swells, it gets gated on high notes, it's attack sensitive and it sounds pretty good.

now try adding the little booster in front, and you have the ancient prophet, pretty much. i got exactly the kind of sounds you describe. it became much more controllable with a gain pot and a volume pot... in that case, turn the gain down just a little, and crank the volume up to the point it's useful.... make sure your amp is up a bit, cuz it'll react differently when quiet. sucks tuning in a good fuzztone with peeps around.

This kind of testing needs to be done when you're alone in the house I have found, because hitting the same chord over and over while you twiddle pots and let it ring out will drive any bystanders crazy.

  It does not have the long sustain of a BMP or the Leeds.  It will give you the Satisfaction tone.  It's useful and a way to use those leaky Ge's that sounds OK. 
I have more cap tuning to do on it.  Gotta go.

Geoff

the komrade boost can't give you that. it's just a simple boost to get ya a nice ge flavor with a little boost to it.

the fuzz variants tho, are different. the ancient prophet one was insane saturday nite. no problem with sustain. turned my guitar down when i needed clean, cranked it wheni wanted scream.
you'll get it. once ya find the sweet spots with the trims and the proper caps, it'll become self evident.

[garcho]

"permission to repost refused"

If it was anyone but FSB I'd give you a little razzin' Jimmy.  

[pinkjimiphoton]

sorry gary, i got it somewhere other than fsb, lol...

i just thought it was kinda neat how part of the circuit looked similar.

i will take it down if you want my friend!!

[garcho]

I don't care! I just noticed it and thought I'd poke a little fun, didn't mean to imply it's my drawing, it's not.

[pinkjimiphoton]

 

[duck_arse]

you got so many of these things going at the moment jimi, it's hard to know which one I tried. this is the 4 parter, yes? I tried a 2 stage with a pair of too high gain AC127 and the input pot. boy, there is a spot on the pot, you turn past that point and it goes shoowmmm rrrrrahhggg, I think it was. you just get extra. I tried 20k pots for the collectors as I was down around 4k and lower, esp when I wound down to 3V. still worked, but there was less diff between the 2 cap values, and it was getting quite dull.

I found an interesting sound with biasing odd that I'll need to listen to again to describe. and it is LOUD at all volts, pumping about 8V p-p w/ 9V. and no volume control? how the hell do you play this?

[pinkjimiphoton]

you got so many of these things going at the moment jimi, it's hard to know which one I tried. this is the 4 parter, yes? I tried a 2 stage with a pair of too high gain AC127 and the input pot. boy, there is a spot on the pot, you turn past that point and it goes shoowmmm rrrrrahhggg, I think it was. you just get extra. I tried 20k pots for the collectors as I was down around 4k and lower, esp when I wound down to 3V. still worked, but there was less diff between the 2 cap values, and it was getting quite dull.

I found an interesting sound with biasing odd that I'll need to listen to again to describe. and it is LOUD at all volts, pumping about 8V p-p w/ 9V. and no volume control? how the hell do you play this?

yes, this is the 4 parter.

you're finding some of the same things i found bro!!! yeah, crank the pot to a certain point, and the universe starts to oscillate... then it cuts off and comes back with one hellacious outta control fuzz.

i play mine with my volume control on my guitar, but the single stage is just a little above unity. you may need to add a master volume pot to avoid inducing mad cow disease or starting the zombie apocalypse.

i found if you bias it almost off... like just to cutoff... just past that it comes back with a really peculiar distortion that isn't as loud. that's what led to experimenting with adding more stages.

this is just meant as a simple booster,, but it's gotta twist. you can use it (the 4 part one) as a buffer, a boost, or an overdrive.

i believe the way it works is the transistor is biased on to whatever it's full gain is by the grounded emitter..... so a 20hfe gives us a voltage amplification of 20 at the collector.
as soon as you introduce a signal to the base, it's amplified 20x by the transistor. two stages we have 20x20 which suddenly becomes a huge voltage gain.

it's like them country guys who have a twin pegged, and their guitar barely on.

you have a lot of headroom, for a fuzz i'd imagine, cuz as soon as you open the gate, it's boosted by whatever the gain of the transistor is. so if ya boost it by 100, then do it again with another 100, man, suddenly you're parting hair at the back of the room.

and you're getting 8v p-p off a 9v battery you say? that's a hell of a return.

gotta figure out a way to use my oscilloscope or something to see what's going on. but i don't know squat about using it.