Today I made some measurements of the power amp section. I soldered at 4 ohm resistance using 4x1 Ohm 50W resistors and made some measurements using the E1DA ADC and the Scaler. Source was the Topping D10s.
First a control measurement of the Pre Out of the NR1710. Volume setting was 75 (which is reasonable since I never pass this volume level in practice), and since we already know that the NR1710 pre amp section is no good above volume 80. Analog in at 0 dBFS (≈2V), direct mode gives a SINAD of 93.
Noise level increases on Pre out when input level is lowered (-20 dBFS).
Power amp section at 4.47V (≈5W) gets a SINAD of 74.
Using optical in and auto mode reduces SINAD somewhat (getting that jitter around the 1 kHz tone):
Increasing input level (to -8.5 dBFS, about 8.8V or 20W), analog direct gives around SINAD 77.
The same wiIth optical in, auto mode
In conclusion, power amp gives around SINAD 73-77 between 5-20W output. This is quite much higher than Amir measured on the sister amp NR1510 (SINAD ≈58-65) and the later incarnation Cinema 70 (SINAD ≈57-69).
As a side note the amp was measured in place in my rack, close to all other equipment with cables attached. I did not check whether this affected mains noise in my measurements.