PLAN B analog blog

There's a possibility that the NON VC Stereo Mixer - what's 
currently known as the Model 18 -  will be released regardless of 
how the poll swings.  It's too useful not to.

As far as a VC add-on, that would be doubtful if the poll goes to 
the larger carnation.  To reason being:

The way it's been conceived,  the 18A Expander (the add-on 
which adds VC to each channel) basically replaces the mixing 
circuitry of the host unit and adds external voltage controllability.   
When the 18A is *in*, the Model 18 host becomes knobs and 
jacks only  - all mixing, panning and control features are 
transferred to the Expander at that point.

Going into a little more detail - Manual panning requires a linear 
pot and  a few resistors. There's also a op amp summer, in 
there,  but those would be required regardless of pan or not.   
For voltage controlled panning your options are to utilize a multi 
channel VCA IC or perform that functionally semi-discretely with  
two OTA amplifiers, a larger handful of resistors, two transistors, 
two  trim pots and three ops amps - one to phase-shift the 
control signal, and two others for converting the current outputs 
of the OTA amps to voltage.  And that's only 1 of the four panners.  
I find it foolish to keep all those dormant on the host unit if VC 
isn't required.  Breaking it into two units seemed to be the logical 
option.

- P