This is Joe Davisson’s Vulcan overdrive. Starting with a prototype board made at home with the Othermill, then turned this into a board from OSHPARK. Boxed up and is working well. This is an interesting overdrive with a couple unique circuit features.


Shocktave first impression

Shocktave Build

This worked right after I found a small solder bridge grounding the input cap. The PCB layout I posted has some very small traces that are very close to the ground plane. I thought this was going to be a nightmare to solder. It was actually not too hard. I found careful application of small amounts of solder worked well.

I had to sub a 2n5089 for a 2n5088. Since I only 4 2n5089s on hand. I picked the Q1 as the substitute.

My first impression was wow this is so distorted I’m not even sure that it’s working. After some testing I notice there is a very nice octave that comes out at times. Seems playing single notes around the 12th fret really brings out the octave, go figure. The octave sounds very nice under the right conditions.

Chords throw everything out the window. Playing a chord seems to make the sound explode into a barrage of noise, and not very musical noise at that.

Could be good for something. The mix is useful. Turning it down you can mix the octave to a pleasing level. Turning the mix all the way up produces a random arpeggiated note sort of distortion. This has some potential, but is hard to control. Q4 and 5 form an oscillator that is driven by the input signal. I wonder if  there were a control control the frequency of the oscillator if some more interesting sounds would come out.

The oscillator portion of the circuit stumps me. I don’t understand how this works and have not been able to find anything similar for reference.