Useful Synth Circuits SUB is a new modification that adds a sub-oscillator to the vintage and modern Oberheim SEM Synthesizer module (1974-1979 and 2009).
The Oberheim SEM is one of the most legendary analog monophonic synthesizers. In 2009, the original hardware was briefly reissued as SEM Pro. Numerous emulations of Tom Oberheim’s iconic mono synth exist.
Fifty-one years after the official release, Useful Synth Circuits has released an affordable modification called SUB that makes the SEM sound even fatter, the vintage and the reissue.
Useful Synth Circuits SUB
SUB is a new modification that adds a sub-oscillator to the Oberheim SEM Synthesizer. This modification has two versions: one for the 1974 vintage SEM and one for the 2009 reissue. With this non-destructive, fully reversible mod, your Oberheim SEM will get two octaves of sub-oscillator controlled by the EXT knob.
According to Useful Synth Circuits, this mod uses the existing Molex connectors underneath the SEM circuit board. It only requires one soldering point for the +15V supply. The other connections are already there and ready to be plugged in.
Once you have Useful Synth Circuits SUB installed, your EXT knob is a juicy analog sub-oscillator. Turn the knob to the left, and you will set the level for a -1 octave square wave sub-oscillator. Turn the knob to the right, and you can set the level of a -2 octave square wave sub.
It’s also possible to keep the EXT in as it is. In this case, you connect one of the connectors and will lose the -2 octave option of the sub-oscillator. How it all sounds could be heard in the linked video.
First Impression
This is an intriguing modification for the Oberheim SEM. If I had an original SEM, I would consider this mod because it is easy to install and makes the sound even beefier.
Useful Synth Circuits SUB is available now for 53,95€ + shipping on the official website and Reverb.com
More information here: Useful Synth Circuits
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