Tuesday, 28 February 2017

My Music From Outer Space Sound Lab - Update
I originally built it according to original spec to make "spacey effects" with my rock band. It was great but I couldn't capture the feel I wanted from a VCS3.  The SoundLab was too bright, too hard and not organic enough, even after going through a valve amp and tape delay.
I realized that part of the problem was the basic wave-forms, I needed sine or triangle. I couldn't even track a sawtooth with the VCF because it had linear CV response, not exponential like the VCO. So I drew up a list of simple mods and decided to add them, but I also wanted it it "patched out" so had that new panel made.
So far the LFO is done, it has an additional inverted output, range switch and LED. The AR also has an inverted output too, an external input with trigger threshold pot, a gated output to show when it is on, and an LED.  I added PWM to VCO1 and have yet to add the triangle wave output to both.
The VCF and VCA have been stripped down a bit so I can add exponential drivers. These were lifted directly from the MFOS modualr circuits, but I am still working on them.
I haven't address the VCO issue yet as I am only doing a bit at a time, but I have only used 1% resistors anyway, the two matched transistor pairs are fixed to vero pins so that I can easily swap them out and I plan to add the high frequency compensation circuit from the MFOS VCO, but I haven't worked out when to put them yet.
I started this a few years ago when I was off work with an injury for three months, but as I don't have a permanent place to work at home for now it is taking much longer than I hoped. The photo shows extension board 1, which has the LFO and AR extra components. The VCO panel is the other side of the shelf that the main PCB is mounted on and the VCA/VCF board is at the opposite end of the panel, mounted like the one shown, except that uses PCB connectors as it is more complicated.