[feathers]

I was reading the HCA-3500 spec sheet https://parasound.com/products/vintage-hca-3500 which states that the amplifier has a Damping Factor (DF) of 1000. I then read a Stereophile review of the amplifier stating that the amp's Output Impedance is 0.55 ohms. So where does 1000 come from? If DF = (Speaker Impedance) / (Amplifier Output Impedance), then the calculation does not yield 1000; rather, DF = 8 ohms / 0.55 ohms = 14.5

14.5 != 1000

The same Stereophile review https://www.stereophile.com/content/parasound-hca-3500-power-amplifier-specifications states that the amp's 'Voltage gain' is 31dB, whereas Parasound's spec sheet says that 1V (in) generates 28.28V (out) -- or 28.28dB.

28.28dB != 31dB

I would have asked on a Stereophile forum, but access seems broken.

[richidoo]

Stereopile is wrong.

Direct-coupled solid state amplifiers typically have Zo <.01 ohms

31dB gain = 35.48V ratio
28.28V ratio = 29.03dB gain

Welcome to AudioCircle, feathers!

[opnly bafld]

FWIW
Stereophile measurements:
"its voltage gain into 8 ohms was 28.5dB (27.9dB, balanced)."
"The maximum measured output impedance was 0.55 ohms (1kHz, 4 ohm load)—a slightly higher value than we normally see with solid-state amplifiers, but still low enough to have relatively little effect on the measurements with a simulated real load"

DF is one of those specs that may be useful for marketing, but not much else.

[feathers]

Thank you both [Richidoo; Opnly Bafld].