[Gllug] OT: Digital Audio Switch

[Chris Bell]

On Tue 01 Jun, Pete Ryland wrote:
> 
> On Tue, Jun 01, 2004 at 02:54:24PM +0100, Chris Bell wrote:
> > On Tue 01 Jun, Pete Ryland wrote:
> > > On Fri, May 28, 2004 at 11:44:21AM +0100, Dylan wrote:
> > > > Hi All,
> > > > 
> > > > I know this is rather OT but I figure some of you will have experience 
> > > > in this...
> > > > 
> > > > I've got three audio sources with coax digital audio outputs, but only 
> > > > one input on my amp (when will the equipment manufacturers wake up and 
> > > > put more inputs on...) I've been looking for a suitable switch for a 
> > > > while to avoid the continuous replugging, but have only managed to find 
> > > > an optical switch.
> > > > 
> > > > Anyone know of a decent coax switch? Or would a standard phono switch be 
> > > > sufficient?
> > > 
> > > Better yet, invest in a mixer (expensive) or build your own (cheap).
> > > 
> > > Pete
> > 
> >    I have not searched, but are there cheap "mixer" IC's, etc, easily
> > available for digital audio streams? I was going to suggest some kind of
> > data switch IC, but I am not familiar with the standard signal levels used,
> > and did not wish to suggest something that may not work, or even possibly
> > cause damage. I would rather be safe than sorry until I could do a quick
> > check with the oscilloscope.
> 
> A mixer is just an op-amp in the following configuration:
> 
> I1 --R1--+--Ro-+
>          |   |\|
> I2 --R2--+---|-\___
>          | +-|+/
> I3 --R3--+ | |/
>            |
>            =
> 
> Where each of R1-3 is the pot for input volume and Ro is the pot for output
> volume.  Filters can be done by putting variable capacitors in series or
> parallel with each resisitor.
> 
> So, yes, you can buy an IC with an op-amp in it quite cheaply.
> 
> Pete

   That is OK for analogue audio, he says he wants to switch digital audio.

-- 
Chris Bell

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