Vulcan Build

The Vulcan is a heavy over to distortion by Joe Davisson. Check his Analog Alchemy page for more of his designs. Here’s a discussion of the circuit over at the DIYStompboxes forum.

I created a PCB you can order at OSH Park.

PartValue
C1100n
C2100n
C3100n
C42n2
C5100n
C6100n
C722µ
C822µ
C922µ
C10100µ
C1147n
D11N914
D21N914
D31N914
D4LED
D51N5817
Q12N5089
Q22N5089
Q32N5089
GAINA1M
VolumeA100K
R11M
R21M
R34M7
R410K
R51K
R6470K
R71M
R84M7
R910K
R101K
R11470K
R121M
R134M7
R1410K
R151K
RLED1K-10K (adjust to taste)
Vulcan Parts List
Wiring for Vulcan PCB

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.

Shocktave PCB

I have been thinking about making Joe Davidson’s Shocktave for many years now. I have yet to build it, the PCB in this post is unverified so far. I’m finally getting around to it.

I had built a BSIAB II while back that had all of the transistors in a row. This made for a fun layout. It also made it convenient to use a single 15 peg milmax header as a socket for all the transistors. This worked out well, so I thought I’d try the same idea here. It works out especially nice since all the transistors are the same and face the same way. Hard to put the wrong one in the wrong place or backwards. Not that I would ever do that.

I’m sorry the values are hard to read to in the layout. I’m a beginner with Eagle. If anyone knows how to arrange the values are part names individually please post a comment and let me know.