Damping Factor - Interesting article

Today I received the Benchmark StarQuad XLR that is referenced in this article. They are replacing 2 Audience Au24 and Au24 SE cables that cost over $1000 combined some years back. The 2 StarQuad’s were $200. It should be an interesting comparison. I expect no difference with my Benchmark gear but audible difference with other gear.

Read my review of the Gold Note PA-1175 MkII Amplifier  with switchable damping factor. It appears at Dagogo.com 

@douglas_schroeder  Yes, the difference between DF=20 and DF=2000 seems to be huge, but not for the purpose of damping.  Amplifier with DF=2000 has very low output impedance and will provide steady voltage (ideal voltage source) at all frequencies while speaker impedance vary greatly.   It will affect the sound because of that.  Damping is different story.  When we apply positive voltage speaker membrane moves forward.  When membrane moves forward on its own speaker generates also positive voltage, but now current flows from speaker to amplifier.  Opposite direction of this current produces opposite action on the membrane and membrane stops.  This current depends on back EMF produced by the speaker and impedance in the circuit/loop.  This loop contains speaker internal impedance, impedance of speaker wire and the output impedance of an amp.   Let's assume for a moment that wire is perfect.  Total resistance in the circuit will be resistive portion of the speaker impedance - most likely 6 ohm for 8 ohm speaker and resistance of the amps output.  At DF=20 total resistance in the circuit will be 6 ohm + 8/20 ohm = 6.4 ohm  while for DF=2000 it will be 6 ohm + 8/2000 ohm = 6.004 ohm.   Ratio of braking current in the circuit will be equal to ratio of total resistance - in this case difference of 6.6%.  Is it audible?  Perhaps for trained ears, but it is not as dramatic as DF=20 vs DF=2000.  There will be more sound change from less than perfect driving, than lower damping IMHO.  For DF=200 vs DF=2000 difference in damping will be 0.6%.

@douglas_schroeder I don’t question what you heard at all. My experience is none compare to yours. I merely stated, that the sound difference you heard could likely be because of less stable output voltage while driving and not because of different damping.
As I said, the difference in damping between DF=200 and DF=2000 is only 0.6% but many people believe it is 10x more. The other question is how this high DF was obtained. The easiest way to lower output impedance is to increase feedback. Adding 20dB to feedback lowers output impedance 10 times, but there are consequences of that. One of them is TIM, that produces unpleasant higher order odd harmonics, that make sound bright and unpleasant. Even Benchmark in AHB2, that doesn’t have negative feedback in normal sense (feedback is non-recursive), settled only for DF=350@20Hz. Class D might have inherently low output impedance because output Mosfets always clamp output to low impedance (either GND or VCC), but for the other classes I would even avoid amps with very high DF (like 2000). Something has to give IMHO.