Compressor Auto Release Settings

[Gary Vee]

I have a Drawmer 1968 Mercenary compressor. It has 3 program dependent release settings. 2 are described as semi-auto (200ms - 2sec and 500msec - 5). The 3rd is described as automatic (1sec - 10sec).

I am curious how these circuits actually work. I assume this is all done in the analog domain so what criteria are used to achieve these automatic release modes? I typically use this unit in linked mode with bass and bass direct signals and found 200ms - 2sec semi-auto mode works best.

[palli...@gmail.com]

Gary Vee wrote:
=============

> I have a Drawmer 1968 Mercenary compressor. It has 3 program dependent release settings.
> 2 are described as semi-auto (200ms - 2sec and 500msec - 5).
>The 3rd is described as automatic (1sec - 10sec).
>
> I am curious how these circuits actually work.
> I assume this is all done in the analog domain so what criteria are used to achieve
> these automatic release modes?

** It is said to be "program dependant".

The deeper the limiting the longer the release takes.

...... Phil

[Scott Dorsey]

Gary Vee <gar...@gmail.com> wrote:
>I have a Drawmer 1968 Mercenary compressor. It has 3 program dependent rele=
>ase settings. 2 are described as semi-auto (200ms - 2sec and 500msec - 5). =
>The 3rd is described as automatic (1sec - 10sec).=20
>
>I am curious how these circuits actually work. I assume this is all done in=
> the analog domain so what criteria are used to achieve these automatic rel=
>ease modes? I typically use this unit in linked mode with bass and bass dir=

>ect signals and found 200ms - 2sec semi-auto mode works best.

Calling this "automatic" is silly.

What is going on is that your signal comes in, and it goes into some kind
of envelope detector which produces a voltage that is proportional to the
peak value or the RMS value or something in-between. That is your control
voltage. After filtering, that is used to control the VCA.

Now, that controls signal gets filtered, and there is a low-pass network
and that switch is setting the time constant of the low-pass network.

The capacitor in that low-pass network (and we'll think of it just as a
single RC filter with one pole for the purposes of making the explanation
simpler) fills up at a rate proportional to the envelope of the signal and
discharges at a constant rate set by a load resistor.

A small peak goes by.... a small control voltage fills the capacitor up
a little bit and it discharges down quickly.

A large peak goes by... a large control voltage fills the capacitor up a
whole lot and so it takes longer to discharge.

Download and read the manual for the Orban 424, it explains the circuit
design nicely.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Gary Vee]

Thank you for the excellent reply Scott. I have not been too keen on the fully automatic setting. To my ears both the semi-auto settings are much better.

Also, thank you for the suggestion for the Orban 424 manual with a "Circuit Description" section. The only other time I have seen a circuit description in a manual is the UA 1176 reissue. Compressors have always fascinated me and thanks again for your explanation.

[Trevor]

> Thank you for the excellent reply Scott.
> I have not been too keen on the fully automatic setting.
> To my ears both the semi-auto settings are much better.

I agree with Scott though, "calling this automatic is silly". "Semi
Automatic" and "Fully Automatic" even more so! Looks like the only
difference between your 3 settings is the time constant, and the 3rd one
is probably too long for your usage, that's all.

[palli...@gmail.com]

Trevor who is clueless wrote:
================================

>
>Looks like the only
> difference between your 3 settings is the time constant, and the 3rd one
> is probably too long for your usage, that's all.

** A time *constant* does not change with signal level.

There is more going on.



...... Phil