A Discussion About True Power Summing for Stereo Compressors

Where we discuss new analog design ideas for Pro Audio and modern spins on vintage ones.
User avatar
mediatechnology
Posts: 3888
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: A Discussion About True Power Summing for Stereo Compressors

Post by mediatechnology » Wed Jun 12, 2019 10:15 am

Using the DI path to key the acoustic is a neat trick.
https://ka-electronics.com

"There's A War On For Your Mind" Banned.Video https://banned.video/
Meme World https://www.memeworld.com/
"Armstrong: Climate Change Has Been A Routine Scare Tactic Since The 1930s" https://www.zerohedge.com/news/2019-09- ... ctic-1930s

emrr
Posts: 520
Joined: Sun Mar 02, 2008 11:27 pm
Location: NC, USA
Contact:

Re: A Discussion About True Power Summing for Stereo Compressors

Post by emrr » Wed Jun 12, 2019 10:46 am

The only comp I can think of offhand with a weighting control is the Manley/Langevin ELOP.
Best,

Doug Williams
Electromagnetic Radiation Recorders

User avatar
mediatechnology
Posts: 3888
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: A Discussion About True Power Summing for Stereo Compressors

Post by mediatechnology » Wed Jun 12, 2019 11:04 am

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.
https://ka-electronics.com

"There's A War On For Your Mind" Banned.Video https://banned.video/
Meme World https://www.memeworld.com/
"Armstrong: Climate Change Has Been A Routine Scare Tactic Since The 1930s" https://www.zerohedge.com/news/2019-09- ... ctic-1930s

emrr
Posts: 520
Joined: Sun Mar 02, 2008 11:27 pm
Location: NC, USA
Contact:

Re: A Discussion About True Power Summing for Stereo Compressors

Post by emrr » Wed Jun 12, 2019 11:39 am

Dual single shaft pot I assume, has to be.
Best,

Doug Williams
Electromagnetic Radiation Recorders

User avatar
mediatechnology
Posts: 3888
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: A Discussion About True Power Summing for Stereo Compressors

Post by mediatechnology » Wed Jun 12, 2019 11:48 am

Yes, a single-shaft dual.
https://ka-electronics.com

"There's A War On For Your Mind" Banned.Video https://banned.video/
Meme World https://www.memeworld.com/
"Armstrong: Climate Change Has Been A Routine Scare Tactic Since The 1930s" https://www.zerohedge.com/news/2019-09- ... ctic-1930s

emrr
Posts: 520
Joined: Sun Mar 02, 2008 11:27 pm
Location: NC, USA
Contact:

Re: A Discussion About True Power Summing for Stereo Compressors

Post by emrr » Wed Jun 12, 2019 11:58 am

Thanks, will report back once tested.
Best,

Doug Williams
Electromagnetic Radiation Recorders

Post Reply