By “somewhat popular” demand (having been asked for the schematics “several” times) we have made a PCB and kit available for the circuit we use to add 1V/Octave scaled input to the ElectroComp EML-100 and EML-101 synthesizers.
The EMLs use between 1.2 V/Octave and 1.4 V/Octave (varying from one unit to another) with an offset of between 4.2V and 4.6V. Our board allows you to feed in conventional one volt per octave control voltage from another synth, controller keyboard, sequencer, etc. and scales it up so that the EML’s second-voice oscillators (Oscillators 3 and 4) can track it. Using a sequencer especially opens up amazing possibilities for this already very powerful synth!
Our original version of this circuit just performed the summing and amplification and required the installation of a new external switch to turn the mod on and off. Our new version uses a multiplexer to automatically perform this switching task when a plug is inserted in the CV input jack. This means that it can be completely invisible– no hole needs to be drilled, and the synth functions 100% as original when nothing is plugged in.
The mod can be used on both versions of the EML-101. On the later version that has a “Sequencer” jack, the Sequencer jack becomes the 1V/Octave input, and on the earlier version, another jack can be selected to be the new 1V/Octave input (we use CM3).
We are looking for someone to help us take photos of the installation in an EML-100 in exchange for a free PCB or kit so if you have a 100 and are interested in the mod, please get in touch!
The PCB will come with schematics, bill of materials and detailed installation and tuning instructions with lots of full color photos. The kit will come with all of the above plus all required parts and the jack already partially wired (because this is probably the thing people are most likely to mess up!)