Amplifier Output Impedance (Damping Factor) and Speakers

[mhardy6647]

The advantage of these T+A amps is that only the output impedance can be changed and nothing else. I can't imagine a better UUT for this topic.

Variable output impedance was a "thing" a long, long time ago in hifi, for those who weren't aware of it.

source: https://www.alliedcatalogs.com/flipbook/1959_allied_radio_catalog.html
UL listed, too!

 

[fpitas]

Variable output impedance was a "thing" a long, long time ago in hifi, for those who weren't aware of it.
View attachment 330872
source: https://www.alliedcatalogs.com/flipbook/1959_allied_radio_catalog.html
UL listed, too!

Output impedance of Large, Really Large, and "OMG the cone will never stop ringing"

 

[sergeauckland]

Pye amongst others made amplifiers with adjustable positive feedback that could reduce the output impedance to zero, or even negative if one wasn't careful.

I incorporated those ideas into a 100 wpc amplifier I designed in the 1970s and it worked fine, best set to a small value (like 0.1 ohms) positive. Still not as low as SS amps, but a lot better than the amp without it.

S.

 

[Deleted member 48726]

Output impedance of Large, Really Large, and "OMG the cone will never stop ringing"

The Forever Bass setting..

 

[egellings]

So if I read an amp manufacturer says they increased DF from 240 to 320 between version 1 and version 2 of an amp, does that really matter?

Nope, unless other more important audibly noticeable characteristics got improved as a byproduct.