Re: [LAU] question related output level and sound card

On Monday 16 December 2013 16:44:26 Fons Adriaensen did opine:

> On Mon, Dec 16, 2013 at 01:10:31PM -0500, Joe Hartley wrote:
> > Headphoune out is a different impedance than line out, it's really
> > easy to overload a line input. I'm a little suspicious of the level
> > into the main mixer though; you should have had more than enough
> > signal for the board.
>
> Headphone outs are very low impedance, which is perfectly OK for a
> line input (pro line outs are low Z as well). Most HP outs today are
> designed for 32 ohm earbuds and should be able to provide sufficient
> signal to a mixer line in, at least if the mixer has an input gain
> control on the line input, as most have.
>
> But an HP out won't provide a real 'pro' line level. And beware of
> the specs of some sound cards. They claim 'pro' level line outs at
> +4 dBu. But more often than not, that means their peak level is +4
> dBu, while in the pro world that is the _working level_, with peaks
> being 12..15 dB higher.

But the average sound card, running on the system 5 volt bus is all tapped
out at +4, clipping anything that goes above that. Some may tap the system
+ and - 12 volt for the output stage, so those will, if everything is
right, still clip at +20 or so which in some music can be hit even if the
meter only says +4. To hit + 30dbm takes about 16 to 17 volts on each
supply rail. No computer offers that much at its pci sockets. And some,
in an effort to be as power miserly as they can be, will have significant,
see it on the o-scope, cross-over distortion at any level.

Driving the average earbud, they can get away with murdering the music &
few can hear the diff. Sad but true too many times.
 
> > I suspect there was some user error at the mixer.
>
> Yep. Or the system just wasn't as powerful as the OP believed it was.
>
> Ciao,

Cheers, Gene

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