Add, subtract, multiply, divide, logic operations ...

[Magnus Danielson]

> 
> >  > But... And I'm refering to something further down in your message
> >  > and something you said earlier... In a mixer, if I split a 1v signal
> >  into
> >  > channel one and two, then given unity gain through the mixer,
> >  > what I hear on the output isn't a 2v signal.
> >  >
> >  > Is it?
> >
> >  Well, that depends only on how your mixer works, but yes - it should be.
> >  Don't forget that when you "hear" a 2v signal, it doesn't sound twice as
> >  loud as a 1v signal. The *voltage* of the output signal is doubled, the
> >  perceived *volume* the volume will be ahh, um, it'll be ahh....
> >  ....some sort of logarithmic amount bigger - but not doubled :)
> 
> *WHOA*... Hang on Christopher (btw, is "Chris" okay - Christopher sounds so
> formal)...
> 
> I run 40ish channels of audio at home... Now, if I split a 1v signal into
> 40 channels, and all inputs and the mixer masters are at unity gain, then I
> gotta say, that I will *NOT* be getting out *ANYWHERE NEAR* a 40v signal at
> the mains. In fact, I would bet money that I won't get anywhere near a 2v
> signal at the mains!
> 
> EEEEEKKK!!!
> 
> If I went with your way, we're talking about enough voltage at the outs to
> feed into a full wave bridge and then supply enough DC to run another
> synth! (obviously current is an issue, but...).
> 
> Ummm dude, I may be wrong in all this adding versus summing versus mixing,
> but I gotta stand fast at this point. :)

Mark, you'r on the rigth track here... even thougth the signals are added they
are also being scaled down do comply with the distorsion limits coming from the
active circuitry. Also, in many cases you does not feed the same 1 kHz into all
the 40 channels at once, so therefore migth the scaledown be less.

A standard mixer have from input to output normally three level scaling points,
that are the input gain, the channel fader and the main fader. The input gain
is there to scale the input signal for optimum headroom and S/N preformance in
the channel (and only to some parts as a preset level for the mix) and the
channel fader is there to adjust the amount of channel signal to go into the
mix and the output fader is to adjust the output level. A good mixer have a
separate output gain so that one can preset the output gain for optimum use of
the output fader sensitivity range.

But when the signals meet (the mixer bus) they are added...

Now, can someone please inform me if I have totally lost track of this 
discussion or weither I have got it rigth.... if not rigth please tell me what
the heck YOU guys are discussing....

> >  If yer average audio mixer does something different please clue me in -
> >  I've never looked at the schems for my Mackie (even though they're
> >  sitting in a file cabnet at home) but I think all those busses are just
> >  summing opamps.
> 
> Well, 32 of my input channels come from 1604's, and I agree that the
> channels feed the bus through summers, but the net effect can't be
> producing an increase in voltage to the point that we're talking about
> here. I'd be burning a hole right through the front end of my amp! :)

That depends on you amp sensitivity... nothing else... it could even be 
possible
to make amps which makes NO amplitude amplification but just does current
amplification, so that you would send it 60 Vrms in at 600 ohms impedance and 
it
would send 60 Vrms out to 4 ohms impedance...

Cheers,
Magnus