Voltage controlled crossfader (AMORE)

The prototype version of the board. There are a few differences compared to the final board.

This simple module basically consists of two VCAs and some contol voltage processing. You could patch a crossfade function with two standard VCAs and some control voltage processors. But it's not that simple to do and this means that you might not try to patch in a crossfader very often. So having a ready-made crossfader as a module makes a lot of sense.

The VCAs are based on the LM13600 (or LM13700) and produce a clean sound, with a fairly low noise level. The VCAs are DC-coupled so you can use the crossfader to process control voltages in addition to audio signals. 
This module has mix and mute control inputs. The mix function isn't terribly useful, it just mixes the two input signals at full volume. It essentially came for ”free” as I used the bypass/mute reusable circuit block.
The LM13600 OTA is rather difficult to find nowadays but the LM13700 seems to be still in production. I have tested the circuit with both OTA types and it seems the LM13700 has slightly lower gain but otherwise works exactly like the LM13600. So if you use the LM13700, you might want to increase the feedback resistor on the output op-amp from 47k to 56k or 62k so you get unity gain when CV is either 0 or 10V.

Trimming

There are two trimmers for nulling the DC offset of the two VCAs. Adjust the trimmers so there is minimal change in the DC voltage at the output when you sweep the CV.

Skill level required: LOW

This module needs no matching of components and uses no hard to find parts.

Circuit board layout (PDF-file)

Component placement (PDF-file)

Schematics