Pro Audio Design Forum

Sorry for these vague comments, but I haven't followed this project closely. Hearing hum when output is turned down, but not while turned up, if not just other noise masking the hum, may be a ground referencing issue between master local ground and output ground. If the output feed is properly diff...

Sorry for these vague comments, but I haven't followed this project closely. Hearing hum when output is turned down, but not while turned up, if not just other noise masking the hum, may be a ground referencing issue between master local ground and output ground. If the output feed is properly diffe...

Yeah Roger I did misunderstand. Not a whole mixer of 1x2 cards just optional add-ons. John: Would there be any advantage in the pan CV circuitry to use both VCA control ports? Could that eliminate some CV circuitry? For instance steer gain to Ec+ in one scale factor (e.g. 0 to +4.5 dB) and attenuat...

The scope of this project is still to be determined. For me it's mostly an academic pursuit, where I want to take my old current source summing to another level with VCAs, which appear to offer some extra benefits for system noise. Besides the bus noise gain being independant of the number of inputs...

One thing I like about the VCAs as current sources is when they are panned over or fader down, they will contribute very little noise to the bus output. This should be a clean machine... We may need to pay a little extra attention to PS etc. A good easy approach for VR is common three terminal with ...

pan2.JPG Yes, my subconscious technical editor didn't like all those parts either. Last night I came up with this pan, and fader this morning. I wouldn't throw away the early schematic for a possible control voltage based interface, but here is another much simpler way... While the pan law is not p...

So far I working from a KISS and KIA approach.

At some point it might be cool to make a digital interface so poop-tools or whatever computer could operate the mixer.

Solo could be executed destructively without adding any circuitry, just by muting all other inputs.

JR

I did a quick data sheet review and it (33078/9) looks adequate for all 5 slots... The noise voltage at 4.5nV is down with 5534. It's bipolar input so it has some bias current but probably < 1/2 uA over temp, and since we're probably going to see current errors larger than that from resistor toleran...

I have used lots of TL0xx in similar circuits but IIRC they could be pretty sloppy for DC offset voltage (10-20 mV). I would probably prefer some newer GP bifet or one of the funny cmos series opamps with OK noise and DC specs for the front three but nothing hi speed or ultra low noise... output pai...

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...