Subject: Re: USB sound cards From: Neil Adams <adamstcs@xxxxxxxx> Date: Tue, 16 Dec 2014 15:20:08 +0800 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY><html> <body> Dick, the loss you are looking for is in the resistive component of the transducer impedance. For example, in a moving coil loudspeaker this might be on the order of .5 to .8 x the nominal impedance.<br><br> In order to provide maximum damping from the source amplifier, zero output impedance is a step in the right direction but negative output impedance can considerably improve on that (with the risk of instability if taken too far). <br><br> From long ago memory one UK Hi-Fi amplifier back in tube days had a variable damping control which enabled output impedance to be varied from plus several ohms to minus several ohms (was that amplifier the Pye 'Mozart'?).<br><br> NeilA<br><br> At 01:30 PM 12/16/2014, Richard F. Lyon wrote:<br> <blockquote type=3Dcite class=3Dcite cite=3D"">On Sun, Dec 14, 2014 at 6:= 15 AM, Bob Masta <<a href=3D"mailto:audio@xxxxxxxx">audio@xxxxxxxx</a>> wrote:<br> <dl> <dd>However, if instead of disconnection the leads were<br> <dd>*shorted* after the pulse, the generator would be driving<br> <dd>all its current into the zero-ohm load, giving a maximum<br> <dd>damping effect.<br><br> </dl><br> I'm not buying that.=C2 A zero-ohm load is lossless, just like an open circuit.=C2 Damping requires loss.=C2 Whether higher or lower resistance makes more damping depends on the nature of the resonance.<br><br> Dick<br> =C2 </blockquote></body> </html>