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Re: A Discussion About True Power Summing for Stereo Compressors

Posted: Wed Jun 12, 2019 10:15 am
by mediatechnology
Using the DI path to key the acoustic is a neat trick.

Re: A Discussion About True Power Summing for Stereo Compressors

Posted: Wed Jun 12, 2019 10:46 am
by emrr
The only comp I can think of offhand with a weighting control is the Manley/Langevin ELOP.

Re: A Discussion About True Power Summing for Stereo Compressors

Posted: Wed Jun 12, 2019 11:04 am
by mediatechnology
I think I figured out a simple way to do this.
Put two 10KΩ linear pots ahead of the RMS detector inputs to control detector level.

Hook the pots up in a potentiometric (3 wire) connection so one is reversed to the other.

The wipers go to the coupling caps in series with the RMS input.
The hot side of the pots connect to the input diff amplifier at the original RMS detector sampling point.
The third terminal of the pots are grounded.
Decrease the detector input resistors by 1/2.

The pot then becomes a detector weighting control with the center position being both RMS detectors at 100%.
Panned hard to one side one channel is at 200% and the other at -∞ weighting.

Whatever you do make sure that there's no DC path to ground at the RMS detector input pin.
The bias current from the RMS detector's input op amp should have no DC path to ground.
Bias current is supplied by the feedback path.
If a bias current flows out the input the DC that develops will upset low-level RMS measurement.

Re: A Discussion About True Power Summing for Stereo Compressors

Posted: Wed Jun 12, 2019 11:39 am
by emrr
Dual single shaft pot I assume, has to be.

Re: A Discussion About True Power Summing for Stereo Compressors

Posted: Wed Jun 12, 2019 11:48 am
by mediatechnology
Yes, a single-shaft dual.

Re: A Discussion About True Power Summing for Stereo Compressors

Posted: Wed Jun 12, 2019 11:58 am
by emrr
Thanks, will report back once tested.