Here’s another in a line now of DOD pedal mods. For this FX55B, I decided to go for more of a BigMuff sound. Playing around with this pedal initially, I found it to be like most mass-produced distortion/fuzz effects. It had a very thin sound and that notorious volume drop that you may have heard on a high-school band’s first album. The lows were almost non-existent when the effect was engaged. I found the following schematic and, with a few simple changes, came out with a distortion pedal with considerable gain, massive lows, and a smoother, more rounded square wave.
Overall, the idea here was to get more from the pedal by employing some germanium to smooth out the harshness and to increase the overall output. The output is now considerably higher as long as the tone knob is set closer to 10 o’clock. At noon, the mixing is practically useless. At the 4 o’clock position, you get more of a thin, trash punk type of sound with an excessive noise floor. The sound sample demonstrates the effect with the tone set at about 10:30-11 and first contrasts the distortion setting. The third set shows off the tone below 10 o’clock. The last set shows what the tone does when you sweep through it.
this was the final build before it shipped out. circuit is a simple MOSFET (BS170) driver stage followed by two JFET (J201) recovery stages. i’ve included a sound sample of a similar reverb i built later without the second recovery stage and clipping diodes. it makes for a much more subtle reverb, but also tames the noise floor from the Belton module.
this is the actual first build. the “dirty verb” comes in towards the end which just switching on a pair of germanium clipping diodes. you get more reverb for your buck with the second JFET stage, but i haven’t found a way to cool down the noise just yet. that’ll be revision 5… maybe 7. [audio:http://abrammorphew.com/notes/wp-content/uploads/2013/02/reverb-test02.mp3|titles=sqrt reverb demo #02]
this is an older build now, but i wanted to post it while i’ve been on the subject to record the process. believe it or not, i still have some work to do on this one. i used a TL082 as a buffer for the mixing circuit. getting the gain set to my taste has been the toughest part. this one (unlike the last) is a bit low. it will all come in due time though. i’ve produced two solid builds this week (though really just debugging this one and one from scratch), and i’ll consider that a productive week.
a forced contract job for Ryan of Falcon Scott. he’s been having some issues finding an overdrive suitable to his hollow-body guitar. i just got a lot of BS170s and thought this might do the trick. the distortion is pretty squared off on the oscilloscope and crunchy. the left pot is post volume while the right biases the BS170. overall, it sounds pretty good and that’s saying a lot coming from someone who isn’t much into “distortion” (personal bias does make a difference. hah).
a big thanks to Jack Orman at Musique.com for laying out the basis. i modified his schematic a bit to get the “best” results for my ear, but i couldn’t have done it without his work.
two days worth of soldering and layout. it’s a combination of the Magnus Modulus and Rebote delay schematics. i couldn’t get the mixing circuit to really work from the Rebote schematic (an older version) without some serious distortion, so i just kind of reworked it on my own. here’s the schematic. i wouldn’t commit to it 100%, but it’s a start. tomorrow i’ll see if it level from bypass to effect works.