On 2008-07-08, Jim Lesurf wrote:
In article , Eeyore
wrote:
John Phillips wrote:
I often see texts that imply or state outright that ringing in
time-domain audio waveforms, usually associated with time-domain
discontinuities, is to be avoided. I wonder what is the basis for
this.

Ringing on square wave inputs may be a sign of maginal stability.

Key phrase here is "may be". I recall reading in the past more than one
review of a power amp where the writer assumed that 'ringing' on a square
wave was a sign of marginal stability. Whereas in many cases it simply
showed that the amp included a series inductor on its output to ensure safe
and stable operation into naster RF loads. Another example where it was
possible for writers to jump to conclusions based upon limited
understanding.

My impression is that it has been common for digital filtering in domestic
items like CD players to use FIR arrangements. Stability should not be a
problem for these. But may be more of an issue for IIR designs. Indeed, if
I recall correctly, some of the high order delta-sigma modulator (i.e. ADC)
arrangements published by Sony and Philips for DSD/SACD had potential
instability unless used correctly.

So, in summary it seems that there are some causes of time-domain audio
signal ripples ("ringing" as a description of the observed phenomenon)
that may indicate problems in an audio system. One of those problems
may be "ringing" as a cause of the observed phenomenon, associated with
marginal stability in both an analogue and a a digital sense.

However it also seems clear that the Pavlovian response sometimes seen
in audio contexts to the observation of a "ringing" waveform is probably
not necessarily appropriate.

--
John Phillips