Bridge patched as 4-quadrant multiplier

Hi. I am wanting to patch my Bridge module as a 4-quadrant multiplier. I am not quite clear on how I need to combine/patch the mixer section with the fader section. Any guidance or patch specifics is greatly appreciated.

3 Likes

A 4-quadrant multiplier can be created using the crossfader to crossfade between positive and negative versions of the same signal.

  1. Mult your input signal to fader B input and Mixer - (subtract) input
  2. Patch Mixer output (inverted source) to fader A input
  3. Patch control source to fader CV input

Now, when CV = 0, fader output will be negative source
When CV = 0.5V, fader output will be 0V (positive and negative sides cancel out)
When CV = 1V, fader output will be positive source

6 Likes

Ah, yes! Thank you. Makes perfect sense.
While we’re talking Bridge… does the divide-by-5 function on the mults cut out negative voltage from a -5/+5V source?

2 Likes

No, it does not. +/-5V will become +/-1V, which is fine for patching to LZX modules (and even desirable, in the case it’s a modulation source, since bipolar modulation can be nice.)

Behind the scenes: Bridge is one of the few Expedition modules with +/-12V power rails, so it can pass signals up to the same amplitudes as EuroRack audio modules on all functions.

8 Likes

Awesome! I’m in need of another #Multiplier and don’t always use the mixer & fader circuits of the #Bridge so this is a great hack.

@creatorlars
What other LZX modules can pass voltages beyond +/-1?
Any of the Cadets (besides some of the scaler configurations obviously…)/Castles?

3 Likes

The Expedition modules use ICs like ADA4851-4 op amps that will pass +/-5V and use clipping diodes to clamp any voltages outside of that, making it +/-12V tolerant.

Any of Cadet/Castle modules that have clipping diodes (1N5711) will pass 0-5V otherwise they can do +/-12V as LM6172s are tolerant up to that.

Edit: I might be forgetting a few exceptions with ICs where you can power them +5/-12V and use a diode clamp for the positive voltages.

4 Likes