@amirm Perhaps you can make an exception, given how well this product measures? Bit of a shame if you don't cover some of the important features such as variable gain and bridged mode. After all, they add to the high cost.
Accuracy in the variable gain is something we have paid attention to. Personally I hate it if the left/right gain balance is altered when changing gain settings. Potentiometers are the worst!
We use dual Susumu 0,1% precicion metal film resistors for all gain settings per channel. (A total of 28 resistors).
I have measured the distortion in many resistors and the Susumu metal film resistors are the best.
Here is a picture of the input bufferPCB with all the gain resistors.
Every amplifier is run through a test where all gain settings are controlled before delivery. The maximum left/right error is 0,01dB on all gain settings.
I can see that Amir measured 0,02dB. I suspect that is due to small variations in cables and measurement setup. When I run the gain matching test I use a split cable to ensure the input is 100% equal on both channels.
The maxumum gain error from the abolute gain is 0,05dB.
If for example the gain switches is set to 21dB the gain *can* be 21,05dB on both channels, but the left/right error will never be more than 0,01dB
When it comes to bridging we can really just look at the stereo 4 Ohm performance. With an 8 ohm load the power performance will be exactly the same since both outputs will "see" the same load. The power supply will also "see" the exactly same load.
Usually the THD is even better in bridged mode since the unlinearities in the two NC500 modules will cancel each other.