Pro Audio Design Forum

I am apprehensive about mux noise. If I follow your train of thought, 8x sets of controls MUXed into one set of (5) opamps that output a somewhat scaled up control voltage to make filtering and S/H easier. The two CV outputs are MUXed into 8x pairs of S/H buffers, driving final level shifting opamps...

If I hook up a PIC to VCA look out compressors.

JR

I'm supposed to be the guy who says " I can do that with a PIC"! Making a look up table or crude calculation would be pretty simple with a PIC. It might get a little messy sampling all the pots and switches, then turning around and putting out clean DC levels. Since these contriol voltages...

pan.JPG EDIT: added R values for 3 dB pan law, and 10 dB fader. Values still subject to tweaking. Top opamp on left side is one pan channel. Second opamp is simple inverted version of first and other pan channel Third opamp is fader control voltage. Fader and pan opamps, have 3 slopes. One slope fo...

Thanx Wayne... I really should be taking care of other "real" business, but I am working on a version combining the pan and fader V to dB control voltage crunching... I am already backing off my diff front end to take advantage of virtual earth diode steering available when + inputs all gr...

I was ASSuming 5V would be a common voltage for digital interfacing but nowadays a lot of modern stuff is 3.3V rails. Any d/a would probably use s/h to support multiple outputs so those can also be scaled in the process. O-1V instead of 0-5V is just scaling a few resistor values in that pan circuit ...

vca master.jpg Here is sketch of VCA master with LPF built in... I can't be real certain of the behavior of this filter since there are VCAs where 2 of the three resistors are supposed to be, and the VCA at least on inputs won't look like Rs... From the math the input R doesn't affect frequency cut...

mod_app (2).jpg Here is a simple mod to the THAT Pan app note #120 that cleans up the dependance on - supply voltage for pan mid point. Change the input opamp U5B from grounded inverting, to simple differential. The resistor from +5 to + input needs to be 49.2k (49.3k 1% sounds close enough). Just ...

I think the only useful metric of pan law is spl, and that is a moving target. Hence the fudge. I have a feeling I don't quite get your point though. Sorry if I'm not clear... Pan law is for the convenience of the mix engineer, so they don't have to drastically readjust the fader when altering the ...

OK, single opamps, at least for critical audio path. Yes I'm familiar with general practice in console design. My point about the pan, is irrespective of the target pan law, few (any?) are very strict about following even that target. In principle one could make an accurate derived -6dB pan law by s...