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Re: USB sound cards

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.

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).

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'?).


At 01:30 PM 12/16/2014, Richard F. Lyon wrote:
On Sun, Dec 14, 2014 at 6:15 AM, Bob Masta <audio@xxxxxxxxxxx> wrote:
However, if instead of disconnection the leads were
*shorted* after the pulse, the generator would be driving
all its current into the zero-ohm load, giving a maximum
damping effect.

I'm not buying that.  A zero-ohm load is lossless, just like an open circuit.  Damping requires loss.  Whether higher or lower resistance makes more damping depends on the nature of the resonance.