The Toecutter

i used to be in a stoner rock outfit called Rise of Man, and i do sound for Indian, so every once in a while i get the itch for some heavy shit. usually High on Fire, Sleep, Electric Wizard, Boris, etc. will cure the itch, but i find myself gettin a rash for those tones to come heaving out of my amplifiers cabinet from time to time as well. so when the chance came up to design a circuit for the DIYStompbox Forum XFX contest i decided to "bring the sludge".

adding on to a previous design called Dirty Boots, i used a technique that i stumbled upon one night for biasing ge transistors by putting a ge diode in a feedback bias loop the "wrong" way- to such designs as the Bazz Fuss- with cathode to base, and anode to collector. i've been told that the leakage of the germanium diode basically acts like a big ass resistor. if my ears aren't deceiving, it adds a bit of compression as well, and a bit of nasty dirt on one side of the wave. all of this was done using Russian germanium GT313A trannys (which apparently have an internal resistor from base to emitter).
so there are 3 stages of those, as well as a bit of filtering on the high end. all of the filter caps are decent size, so as to try and slam as much bass as possible through the circuit in order to get that churning, folding on top of itself, crunch of doom. in the first stage there is a .1uF bypass cap to try and give a midrange boost before a full range boost in the second and third.
the one caveat of the contest was that the circuit have some sort of bootstrapping. this accomplished by the .1uF cap and 4K7 resistor going from from base of tranny 3 to emitter of tranny 2. i have recently been toying around with putting a variable resistor in place of the 4K7 and this can be cool for a kind of "shape" control. for a gain control i just put a variable R going from stage 1 to 2 and controlled the amount of drive that way. it's not on the schem, but i put a 500k pot on the input for an input impedance control as well. the third stage is biased by a pot from 9v to the collector and this also adds a way to adjust the color of the tone.
it's a pretty sick circuit, and sounds like the walls of babylon are falling down around you. give it a shot, russian trannys are cheap on ebay...for now.

shitty sound sample i recorded with a 5w amp into my computer's mic is available HERE.

Fuzz for the People!

HERE is a link to my compilation of eastern european diy and production fuzz boxes. there are some interesting designs, and a lot of original ways of doing things. i find it intriguing what rock and rollers and engineers on the other side of the iron curtain came up with in isolation. the build quality was spectacular in many of the production pedals, because the electronic parts that they used were military spec made for soviet war machines.
talk about over spec'd? how bout an A-bomb.
ahh, i can see it now- just the roaches and the fuzz...



also HERE is a great site with many Russian fuzz pedals posted. also tons of freaky guitars!

Kazan Booster

so i've been finding these strange fuzz circuits lately and kind of taking the under my wing. also, i've had an unhealthy obsession with eastern bloc diy and production fuzz pedals. so it's only natural that i take a look at the Booster from Kazan, Russia. it's a Soviet production model from 1977, and although it is called a booster, it is most definitely a fuzz. inside are 3 russian germanium trannys of 2 different types. 2 high gain, and one lower. there are pictures and more information on it HERE at the Cheezy Guitars website.
also from the above site-

"Here's a couple of words from the pedal' owner:
Booster is classic-looking fuzz pedal. It has two controls - tone and volume. Tone works only in two positions - it should be switch in fact, but it wouldn't look so cool;)
Volume output is rather low. Sound is real nice, my friend called it "organic", I would describe it as "rooty" - nice, old fashioned fuzz a'la Velvet Underground. When I bought Booster, it was not working. My friend, £ukasz, who is expert and magican of music gear, fixed it for me. It turned out, that effect has two "build in" errors. First was low volume output - maby it was designed for use rather with radio than guitar amp? Who knows. Second was not-very- professional bypas, which results in high noise level, when effect was switch off. Booster is build on Ge(germanium) transistors and built like a tank - about 1,5 mm steel sheet! Works on 9V battery only. Switch is non-profesional too - it's just an ordinary switch, like you can find in lamp."

Credits:
Piotr Salewski

what first drew me to this circuit was the odd diode configuration after the gain pot. i'll get to breadboarding this thing some time soon and do some more research. also, i have a vero layout in the works. here is the original schematic and parts list from the owner's manual.





i've thought about the volume drop that he speaks of and how it could be remedied. my best guess would be to delete the 150K resistor before the output pot which is probably cutting a lot of the signal. R17 seems a biy strange to me as well- a 300 ohm resistor to ground right before the output pot. this seems to me like it would be shunting a ton of signal to ground uneccesarily. the output pot itself is a 2K2 pot set up in a normal volume configuration. this seems like a quite low value, and also probably contributes to the volume drop, shunting signal to ground. R8 is missing a value on the parts list, so i'll probably have to adjust it to taste when i get it on the breadboard.
the transistors in this pedal are russian germaniums part no.s mp42b, and mp39b.
here are the stats for the mp42b transistor that i found someone selling on ebay.
pnp
200mW
15V
15V
150mA
85>C
1MHz
45/100
CSI
TO9

i have also found on the net that the mp39b has a gain of 20-60, and saw some possible equivalents- MP39A-> 2N273; 2N405/406; 2SB173/170/32.

i've been picking up russian ge transistors on ebay every once in a while, so maybe i'll pick some of these up and try this out with the real transistors. i'll post the vero layout when i'm satisfied it's correct.

cheers!

DOUBLE BEAT SCHEMATIC

a while back the stompbox god RG Keen posted a schematic of the Roland AD50. but alas, it looks as if even the gods have their weaknesses, because i noticed that the schematic was missing a master volume pot for the fuzz. then Analog Guru over freestompboxes.org enlightened me to a few missing parts and pot values.

so now, i present to you, finally unchained, the correct Roland AD50 Double Beat schematic.

DIYS Gallery

here is a link that has been the depository for most of my DIY ventures up until now.

it's the in the gallery over at the DIYStompboxes forum- an overwhelming cavalcade of DIY delights. you'll see a couple designs that i did as well as some articles, schematics, and layouts.

new vero layout- Roland Double-Beat Fuzz

i was workin on this thing the other day, finally got it finished. as of yet, unverified. hell, i haven't even put it on the breadboard yet. but the clips i've heard are pretty sick, and i have yet to see someone else do a layout for it so that makes me feel special. HERE is a link to the thread over at freestompboxes.org- my favorite haunting ground.

XXXLAYOUT IS NOW VERIFIED!XXX


this pedal originally had a wah after it, but this is just the fuzz section of course.

schemo can be found here.

and here is a clip. watch out for that fuckers toes though. they'll gitcha.

first post

well, this looks like it's going to be my new DIY stompbox site, and whatever else i feel like throwing on the heap. hopefully i'll have something worthwhile to check out every now and then, so yeah, cool. later.