APOCALYPSE AUDIO - PANZER FUZZ

my latest creation is an uber-high gain fuzz-tortion designed around the soviet GT308B germanium transistor. since this seems like one of the more common russian germanium transistors that people buy, i thought it would be a good candidate to include in my next project. the 308B has a gain that usually hovers around 75 in most specimens that i have seen, except for some batches marked with red dots that have a gain of around 20 points less on the Hfe reading. as with most other soviet Ge's, their leakage is pretty much nil, this allows for excellent stablilty, easy biasing without trimpots, and no need to do tedious gain/leakage checks. i thought the 308 would be the perfect candidate to design a high gain fuzz around because of it's relatively high gain compared to other russian Ge's, and i haven't done anything along those lines since the Toecutter, which although it is doomy as hell, it is in itself not all that terribly high gain anyway.

the controls of this guy are as follows- gain, lo drive, hi drive, tone, and volume. the lo drive control is basically a full range gain control for the 2nd stage, and the hi drive control is i gain control for the 3rd stage that is concentrated only on the high frequencies. with all of the gain and drive controls turned up, you get an all out doomy grind with plenty of bite for on the top end. rolling back the gain control gives you a great crunch tone that i would describe as medium-high gain. the tone control is a heavily modified version of one that i saw on the AMZ site. i added 2 more caps, and adjusted all of the values for a nice even sweep. turning it all the way up also brings in a little bit of low end as well, so you get what sounds like a little dip in the midrange, too- adding to the metal tone of circuit. don't get me wrong though- this isn't one of those ultra-scooped metal zone P.O.S.'s. this thing has a ton of low end and has been tuned to have a bump in the high mids as well in order to cut through the mix and add some nice grind to the tone.

i did this write up of the basics of the schematic for culturejam's new circuit design forum circuitworkshop.com.
it can be found HERE.

the input cap(.033) was chosen to roll off just the bottom end of the input signal, there will be plenty more of that to come. the first stage is a basic booster using feedback biasing(1M resistor), and a .47 uF bypass cap for more gain throughout the full frequency range of the guitar. the emitter resistor(1K) was chosen to limit the amount of output from the first stage, and the 470pF cap rolls off some highs and stabilizes any oscillations that might happen.. next we have the gain pot(500K) and a 2K2 resistor setting the minimum amount gain available. the .01/220K combo allows highs to pass easier than lows trimming some of the fat off of the boosted signal. stage 2 is biased the same, as is stage 3. i find this technique of biasing easy and simple, allowing for fewer components as well. the .047uF cap rolls some high end off of this stage. the lo drive pot is a 10k pot going through a 47uF cap to ground. this isn't really just low end getting boosted per se, more of a full range gain control for this stage, but with the lows rolled off by the .o47 cap it definitely has some of that feel to it. the 100K/.1uF combo are doing negative feedback duty, reducing the overall gain a bit, as well as taming some noise and adding stability. next, the .0047 cap is more low pass filtering, and the .068 is hi pass,interstage coupling, and DC blocking. stage 3 also has some more high end filtering grom the .0022 cap to the 9V rail, and the bias values have been tweaked by ear a little. the hi drive pot is a 1K connected to ground through a 100uH inductor. turning this up adds a decent amount of sizzle to the sound. the 680/.1uF to ground were added to round out the frequency response of this stage a bit. the tone control is a tweaked version of jack orman's swtc2. i changed some values and added the .0033 and .01 cap to ground. the final .001 cap is rolling off a bit more of the very top end. finally the volume control has a 2K2 resistor to ground to limit it's lowest value. the mosfet and 1M resistor are there for reverse polarity protection, and the 100uF cap is for power filtering.

attached is a pcb layout, that is of yet unverified, but it has been checked in eagle, so it should be good. i'm going to try and get some clips done soon- they won't be the highest of quality though, but you should be able to get the idea of what is going on. hope someone out there can give this one a shot- it's really a killer!


XXXXXXUPDATEXXXXXX  it looks like the size printed on the layout is a bit small.  if you measure it out to that size, then increase by 10% you'll be perfect.  sorry about that!

freestompboxes manifesto

i thought i'd print this bit of text that explains how and why my favorite forum- freestompboxes.org- was created. here ya go, the Freestompboxes Manifesto!


Freestompboxes.org Mission Statement (June 17th, 2007) Another Forum? It really takes nothing to set up a forum nowadays... No money, no knowledge, just a borrowed computer will do. There are more then plenty of them on every subject all over the internet. Probably rightfully so, because newsgroups and forums are the heart of the internet: people from all over the world with the same interest have the opportunity to exchange ideas. With libraries abound, the internet did not do so much of spreading the canon of official canonical information. Rather, it turned out to be a great medium for the exchange of underground stuff. Building your own guitar effect stompbox is a prime example. Stompbox project Info on the internet Most of the circuits have been around since the beginning, but mostly in DIY magazines and they never really caught the guitarists' eye. They just walked in and grabbed their Guitar Player magazine. The online guitarist googling for 'vintage stompboxes' nowadays is bound to meet the DIY stompbox community sooner or later. And if you are true tonefreak rather then a show-off name dropper you get very happy at the thought that you can build your own 'boutique' stompbox and tweak it to your own taste for a fraction of the money you would pay for a boutique box. Backlash of the DIY pedal craze Big commercial pedal manufacturers are dropping their prices like they're hot, boutique pedal makers are getting nervous and begging the diy community to safeguard them certain commercial death. Or so they think... Recent turbulences and censorship of certain commercial schematics (although they are all over the net) has caused great upheaval at the mother of all stompboxsites, aron's diystompboxes.com causing some 'heretic' discussion to flee to the kind German Musikding.de forum. Copyright, Patent and more Of course often the artwork and the graphical layout of the pcb of effect are protected, but redrawing or tracing a circuit is by no means illegal. Patents on effects do exist, but they are not some common. Most of them have expired by now. There are some examples here on the forum, so do check them out in you are interested. Maybe this quickly setup board can provide a space for unabridge, free discussion about any stompbox design.