MATRIXSYNTH: Custom 5U Modded Vintage Oberheim SEM Module

Tuesday, August 22, 2017

Custom 5U Modded Vintage Oberheim SEM Module

via this auction

"Vintage Oberheim SEM built into a 8-Space panel.

This SEM is in near perfect condition except for the initials engraved into the face by a previous owner.

The panel was designed by Dave Brown at Dave built two of these for me. I am only selling this one. The panel has a few engraving flaws that can be seen in the pictures but over all looks very nice.

All of the patch points were brought out plus an extra CV per oscillator. The pulse mod patch points were not brought out because the external mod input already covered the pulse mod when SEM mod select switch is set to EXT MOD. Therefore, all CV inputs have attenuators.

The VCA is normalized the VCA CV IN. The Envelope Generator jacks are normalized to operate as they do on the SEM with Trig normalized to Gate, and EG2 normalized to EG1. VCO2 1V/Oct and VCF CV2 are normalized to VCO1 1V/Oct. The VCF normalization provides adjustable Key tracking of the VCF. This is a feature incorporated in most analog synthesizer's that was sadly missed in the original SEM.

The combination of the attenuated CVs and extensive normalization make this custom made SEM patch panel much more usable that the Tom Oberheim Reissue SEM patch panel version.

Utilizing the patch points with a full modular system opens up mind boggling possibilities for sound creation. This vintage SEM sounds so fantastic that words just don't do it justice. It still remains my favorite of all mono synths.

The SEM is powered by +/-18.5 volts so it either needs a special power supply or conversion. After I received my SEM panels Dave built another and came up with the idea to use an inverter coupled to a linear regulator to provide the required +/- 18 VDC power supply. I incorporated Dave's inverter power supply design in this panel.

The inverter requires 5 VDC @ 650mA. Theoretically the dotcom system power supply can be used since the 5 VDC is only used for LEDs. This assumes that the dotcom power supply in your cabinet can support the load. Mine could not so I added an additional 5 VDC power supply. I am including one in here just in case. The additional power supply can be paralleled to your exiting dotcom power supply AC input. Or can be plugged in separately. I have a regular two prong cord attached and ready to go. See Dave's website for more details about the inverter power supply and the SEM panel."

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