Today I was testing a different amplifier at the same power level. This different amplifier has four KOA 0.1R BPR56 resistors as opposed to the two in the L20.5
At 64W this different amplifier also had audible sound from those resistors but I would normally not have noticed as I needed to put my ear right next to it. I suspect the L20.5 is louder due to twice the current in the resistors and perhaps also due to brand related construction details. (Perhaps a higher temperature coefficient of expansion for the resistive element/wire?)
The zobel resistor is connected in series with the output. A 10 ohm resistor is connected in series with a 0.1uF capacitor.
So when your test signal frequency is high. The signal passing through this resistor will be relatively large.
It can be calculated by RC formula. Therefore, it is recommended that you reduce the test frequency. And use ring transformers whenever possible.
If a higher frequency signal needs to be measured. It is usually necessary to disconnect the 10R 2W resistance before measurement.
At this time, the resistance is equivalent to a small horn.
Avoid high frequency measurement as much as possible. This is not safe.
Usually we mean power at 1K frequency.
So when your test signal frequency is high. The signal passing through this resistor will be relatively large.
It can be calculated by RC formula. Therefore, it is recommended that you reduce the test frequency. And use ring transformers whenever possible.
If a higher frequency signal needs to be measured. It is usually necessary to disconnect the 10R 2W resistance before measurement.
At this time, the resistance is equivalent to a small horn.
Avoid high frequency measurement as much as possible. This is not safe.
Usually we mean power at 1K frequency.