Can someone explain the difference between Opto and electro to me? I see
opto on vintage and tubed compressors as well as some plugins like Waves
Renaissance. Thanks!

Dave

DaveDrummer wrote:
Can someone explain the difference between Opto and electro to me? I see
opto on vintage and tubed compressors as well as some plugins like Waves
Renaissance. Thanks!

Well, an optoelectric compressor is one that uses a light source (sometimes
a neon bulb, sometimes an LED or an electroluminescent panel, sometimes just
a plain old slow incandescent bulb), which illuminates with signal, and then
a photoresistive cell that drops in resistance when light hits it, which
shunts the signal to ground when the lamp lights up.

This is one of the more common dynamic control designs from the days before
we had effective voltage controlled amplifier circuits.

Most of them aren't very fast, and most of them tend to have a fairly sharp
knee because the lamp turns on fairly abruptly, but that's about all they
really have in common in terms of general action.

There is a nice discussion of these things in the RCA Radiotron Handbook.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Hi Dave read this article by Paul White, it will answer a lot of your
questions.

http://www.soundonsound.com/sos/dec0...ompression.htm

Regards,

Sytze


"DaveDrummer" schreef in bericht
...
Can someone explain the difference between Opto and electro to me? I see
opto on vintage and tubed compressors as well as some plugins like Waves
Renaissance. Thanks!

Dave

In article writes:

Can someone explain the difference between Opto and electro to me?

Opto and electro? "Opto" is usually short for "optoelectronic" and
it's one of the gain control elements that are used in compressors.

The difference between them is the rate at which the gain (or
attenuation) of the element changees when the control signal is
applied. I wrote an article in Recording several years ago about the
inner workings of compressors. See http://www.manleylabs.com for a
slightly condensed (minus illustrations) version of the article.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article , (Scott
Dorsey) wrote:


Well, an optoelectric compressor is one that uses a light source

Optionally electro-optical, also known as el-op.

--
Jay Frigoletto
Mastersuite
Los Angeles
promastering.com

Scott Dorsey wrote:

DaveDrummer wrote:
Can someone explain the difference between Opto and electro to me? I see
opto on vintage and tubed compressors as well as some plugins like Waves
Renaissance. Thanks!

Well, an optoelectric compressor is one that uses a light source (sometimes
a neon bulb, sometimes an LED or an electroluminescent panel, sometimes just
a plain old slow incandescent bulb), which illuminates with signal, and then
a photoresistive cell that drops in resistance when light hits it, which
shunts the signal to ground when the lamp lights up.

Can also be configured in the feedback loop too since the controlled element is
essentially a resistor.

This is one of the more common dynamic control designs from the days before
we had effective voltage controlled amplifier circuits.

It's also very common now too. Increasingly so in fact. I've used nothing else
since hmmm well.... earlyish 90's.

I gave up on cheap VCAs ( transconductance amps ) after I found modern
'el-optos'. Expensive VCAs are ok - but an opto-cell always beats it on price.
No set-up probs either. I got the msg when I heard there was a 1 yr lead time on
the half decent VCA I might have used !

Most of them aren't very fast, and most of them tend to have a fairly sharp
knee because the lamp turns on fairly abruptly, but that's about all they
really have in common in terms of general action.

They are actually very good now. If the 'lamp' is a led - which it *is* now -
I've found you can plot a fairly reliable law between forward current and
resistance. There's been a shake-up in the industry making these cells. In the
past they were mainly made for the military. Now, they're mainly made for
consumer apps.

Leds are quick 'lamps' too.

The photocell is somewhat less quick but modern materials technology has
improved that beyond all recognition. Silonex ( Audiohm ) can offer special
cells for high speed.

The Chinese copies ( look in many Far East amplifiers ) are still a generation
behind the likes of Silonex but I suggest you visit www.audiohm.com for a brief
on the latest hot parts as used by Focusrite et al - also Studiomaster in the
past too - lol.


There is a nice discussion of these things in the RCA Radiotron Handbook.

Haven't got that one.

Graham