Music Tech DIY • Yusynth Dual Balanced Modulator modification

So it always bugged me that this module was so offset that it took a lot to run it as a VCA or signal inverter. For instance, with an audio signal in the A input the B input CV would have to be offset by 10V to get zero output. If I put the signal into input B and a CV into A, the CV would have to be offset by something like -5V. This was not ideal. The solution to removing these offsets can be attained while calibrating the module. The trick is to ground the opposing input while monitoring the output. So if you are trimming the A input, ground the B input. If you are trimming the B input, ground A. With that said, I had to offset the A input a little to get this to work. This was accomplished by adding a resistor from pin 10 of the LM1496 to V+. If anyone is interested, I can add a photo of how this was done.
This is what to expect if you modify your circuit in this fashion:
A(dc,saw), B(none)- reversed phase, gain x1
A(ac,saw), B(none)- reversed phase, offset -7.5V, gain x1
A(none), B(dc,saw)- normal phase, gain x2
A(none), B(ac,saw)-normal phase, offset -7.5V, gain x2(clips a 10V p2p similar to rectification)

If you only use the DC inputs, the circuit works as a phase inverting VCA. Positive CVs will give you the input phase of the signal. Negative CVs will flip the phase.

Now here is the wacky stuff. The AC coupled inputs act differently because the LM1496 isn't centered around +/- 15 V, but we calibrated the circuit to be centered at 0V(ground).
A(ac,saw), B(dc,+10V envelope)- normal phase, gain variable till x1 @ 5V then begins to clip(positive)
A(dc,+10V envelope), B(ac,saw)-normail phase, gain variable x1 @ 5V around 7V begins to clip(negative)
A(ac,saw), B(dc,-10V envelope)- reversed phase, gain variable till x1 @ -5V then begins to clip(negative)
A(dc,-10V envelope), B(ac,saw)-reversed phase, gain variable x1 @ -5V around -7V begins to clip(positive)

Statistics: Posted by Benjamin AM — Sat Jul 27, 2024 10:13 am

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