JAY X

vca fader and compressor
« on: July 11, 2018, 04:21:36 AM »
Hi!

Attached to this message is a sketch of a fader/compressor schematic taken from the THAT design notes. My idea is to build a stereo fader with a simple compressor.  The controls are: Gain (volume), threshold, and  compression.  I will build it around a 4305 RMS detector and two 2181 vca's.

But a question arises:

If you combine fader volume and compression into a single circuit, the compression...¿is pre-fader?...¿post-fader?...¿in-fader?...¿what-fader? ???

¡¡Thank you for your advise!!

Jay x.


Re: vca fader and compressor
« Reply #1 on: July 11, 2018, 08:32:58 AM »
Hi Jay

Have a look at Studer 900 series schematic, there is a fader (VCA) with compressor

There is no pre or post here, all gain change, volume CV, compression CV, group CV drive the same VCA
You "just" need a CV summing amp from all source.

The audio SC for compression is taken before the VCA.

Best
Zam

JAY X

Re: vca fader and compressor
« Reply #2 on: July 11, 2018, 11:32:55 AM »
Hi Zam!

¡Thanks for your explanation!. In any case, i see i can place an insert after the vca output.

Another question i have: ¿is it ok to sum the two sidechain signals L&R that enter the RMS detector?

Jay x

Michael Tibes

Re: vca fader and compressor
« Reply #3 on: July 11, 2018, 01:19:06 PM »
The SSL mix bus compressor is a combination of compressor and fader as well and it is pretty well documented here. Maybe this is good for inspiration as well?

Michael

Re: vca fader and compressor
« Reply #4 on: July 11, 2018, 01:23:59 PM »
is it ok to sum the two sidechain signals L&R that enter the RMS detector?

That's exactly what is done at the schemo you show!

Best
Zam

JAY X

Re: vca fader and compressor
« Reply #5 on: July 13, 2018, 03:30:10 AM »
Hi!

Thanks for all your advise! Now is time to design...and build... 8)

Jay x

JAY X

Re: vca fader and compressor
« Reply #6 on: July 16, 2018, 05:01:18 AM »
Hi Again!

As always... too much enthusiastic... ;D

Revising the schematic, and other compressor schematics, i think it is possible to place a slew limiter, to add attack and release controls, after U3b, and then, the buffered output of the slew limiter goes to control the EC- control port of both vca's...¿right?

Jay x


 

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