Processing voltages

There are sexy, unusual modules that can be very interesting. Then there’s utility modules. Not so interesting, but useful. Here’s one: The design for this started out as a clone of the voltage processor from the ARP 2600 synthesizer. There are two voltage summing sections and a lag circuit. One thing that always bugged me […]

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VCO re^{n}dux

Having improved the LFO pulse width range yesterday, I went ahead and improved the VCO’s today. This time the fix was to increase the gain of the amplifier I’d added from 1.33 to 2.0. That involved changing out two resistors, but actually I decided it might be just as well to build a new amplifier. […]

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Actually LFO

OK, I think I’ve finished this Music from Outer Space LFO. I got some new PCBs in the mail today, including the corrected version of my auxiliary circuit board that contains the sync mod as well as the power header. The first version had the inputs to the op amp reversed, so the sync mod […]

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VCO victory surrender

I checked and as expected, the MFOS VCO has the same problem as the LFO: with an attenuator on the PWM CV, changing the attenuator changes the pulse width even with no CV plugged in. I applied the same fix, replacing the 100k pots with 25k and the 10k mixing resistors with 200k. I found […]

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Almost LFO

I changed the PW and PWM CV pots on the MFOS VC LFO from 100k to 25k, the fixed resistors on the PW pot from 100k to 22k, and the mixing resistors from 10k to 200k. Everything seems to work and changing the PWM attenuator (with no CV plugged in) doesn’t change the pulse width […]

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Not much to say about this one — the Music From Outer Space Dual VCA. I built it, I didn’t change anything (except to add a Euro/Kosmo power breakout), it works. It’s 75 mm wide, which isn’t on the list of official Kosmo module widths, but so what? I thought 100 mm would be too […]

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I swear, pulse width control is going to be the death of me. Hard to believe but it looks like there’s a rather serious design flaw in Ray Wilson’s Music from Outer Space Voltage Controlled Low Frequency Oscillator (or, as its friends call it, MFOS VC LFO). With no pulse width CV plugged in, changing […]


VCO build

VCO: Assembled. The PCB was pretty straightforward. The most novel part I did first, soldering the SOIC SSM2212. It went smoothly enough, didn’t even need my solder braid and all the connections were good. The tempco resistor went on top of it, with some heat sink compound to join the two. (The tempco is R24; […]

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