Pro Audio Design Forum

The guts of this is a block of 8 balanced inputs, 16 VCA. I have scratched out a simple circuit to convert potentiometer position to pan and fader commands, and a more complex circuit (3 opamps more) to map 0-5V control voltages to pan and fader commands. I think that with the final output stages a...

So it looks like the (active) component count for a single channel is line receiver IC (THAT1246), two VCAs (2180) and a dual op amp for CV. The entire audio path is just a line receiver and the left/right VCAs. Sweet.

Cool! The way I set the 1K output bias current was to measure the emitter current of either the top or bottom transistor via the I*R drop across Re. Depending on the size of your heatsink you can set the class-A current from maybe 65 mA to 85 mA IIRC. WIth 3R3 emitter resistors that becomes ~ 0.21 V...

I originally wrote: These calculations are for a 6 or 12 spring system with an initial delay of 13.5 mS. I remember now that when I first checked the springs Accutronics sent me the "longest" spring (Accutronics longest) was ~37 ms. That's the last entry in the table. The 13.5 ms figure, d...

I've had an ancient piece in mind to couple with a spring reverb, which I spotted in an early '50's magazine. Circuit is a proper variable vibrato for organ or instrument use, and it cries out to be done in stereo, with stereo spring reverb path. Done with octal tubes, of course. Was that the work ...

Yes, my subconscious technical editor didn't like all those parts either. Last night I came up with this pan, and fader this morning.

OK, love it. I can live with that. Close enough for government work. Thanks John!

Solo could be executed destructively without adding any circuitry, just by muting all other inputs. As John and I have pointed out elsewhere a non-destructive in-place solo isn't really possible in this architecture using VCAs. Our choices seem to be either PFL or destructive solo. My vote, for KIS...

KIA also gets my vote for the signal path.

For the DC CV circuitry you can't beat the MC33079/MC33179. The '179 only pulls ~750 uA/OA and they're cheap, low noise and have good drive.

Accutronics supplied the whole sled for this project. They can be bolted together and suspended by springs or O rings. They sell them online - the last time I checked they had an eBay storefront. For twelve lines (springs) there would be four sleds since they have a three line unit. I was thinking t...

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

I think that's the new shiny hammer thread.

OK, we can just take the 5 op amp stage pan bender and mux that 8 times.