[sdiy] noise gate?

[Roy J. Tellason]

On Tuesday 06 July 2004 02:41 am, Colin Hinz wrote:
> On Tue, 6 Jul 2004, Roy J. Tellason wrote:
> > Anybody got a schematic for a simple noise gate circuit?  I'd like
> > something that would be adaptable to providing a logic output when a
> > signa (say from a mic) exceeded a certain level...
>
> EPFM.

Eh?  :-)

> Less terseness? Oh, sorry.
>
> Craig Anderton's ELECTRONIC PROJECTS FOR MUSICIANS. The book is available
> from PAiA (and elsewhere, I'm sure, as it's published by Amsco, which
> should have good music-store distribution) and PAiA sells bare circuit
> boards as well.

I think I may even have a copy of that around here someplace.  I didn't 
remember there being such a circuit in it,  but maybe that just means that 
it's time for a re-read...

And that outfit is selling boards for his stuff?  Cool.

> But be cautioned, Anderton's circuit uses the now-unobtanium RC4739

Seems like according to my card file I have a couple of those on hand.  I 
remember those (and the 4136?) being used a lot in Tapco mixers,  and at one 
point I'd hooked up with them for service.  Probably still have a few other 
bits around too,  like knobs and such.

> which has the unfortunate distinction of a pinout which is as extinct as
> itself -- hassle-free substitution is not possible.

I don't see the attraction to using that part,  anyhow -- my inclination is go 
to with much more generic stuff whenever possible.

> Fortunately, it's not too difficult to handwire a "ordinary" op-amp IC in
> its place, but this does tilt the balance in favour of using "Vectorboard"
> instead of buying the PCB.

I tend to take that approach more often than not anyway.  I've seen some of 
the projects that people have done,  even some folks in this group,  and 
that's *way* more ambitious than I feel like getting these days!  I can still 
remember one page I viewed recently where the author was talking about knobs, 
and having a requirement for 300 (!) of them.  I don't think I have anywhere 
near that many pots,  nor would I want to have to buy that many...

> The circuit also calls for a CLM-6000 opto-isolator, but if you only need
> the "gate" signal, you won't need that chunk of (near)unobtanium.

What is that,  one of those incandescent-lamp-and-CdS-photocell deals?  I 
remember bumping into that in a *lot* of stuff way back when.  Damn,  I guess 
I should see if I can find that book...