Re: [linux-audio-dev] live pa questions - Linux-audio-dev

4 Apr 2005

Andres Cabrera wrote:

...
  Overheating of
the amp is nonsense. Most amplifiers operate in class A 
or AB anyway, and maybe in class D. Heat dissipation is independant of 
the input signal for these amps. The types that might build up a problem 
with heat (e.g. class H) aren't used in PA enviroments. And before the 
amp overheats, your speakers will be dead.

Thanks for clarifying. I remembered I heard about overheating somewhere
with DC, and thought it was on the amp.
Adding a small DC offset is one easy way of getting rid of denormal
problems (in programs like csound and pd), do you know if this small DC
offset is able to produce these effects?

 I don't know about the output stage of a soundcard. (Almost) every 
soundcard uses a delta-sigma DAC, which needs some sort of low pass 
filtering. It needs an output buffer to transform the rather high 
impedance of this filter to a low output impedance, so the question is 
if there is some sort of DC decoupling impemented in this buffer. I 
don't know, but using a voltmeter (or scope) while applying a DC signal 
to the card will answer that.
if you take a look at the specs of the EMU1820M it states "Frequency 
Response: 0.0/-.35dB, 20Hz - 20kHz" which would mean that it doesn't 
output DC signals.

But as far as I know, most audio input stages are capacitively coupled, 
thereby removing such DC offsets, so there is little chance that this 
type of signals will propagate through the entire signal chain.

Greets,

Pieter