I now have started measuring my old Marantz slim-line model NR1506 pre-out using my tiny and ancient M-Audio Transit USB card. I had some other issues with my portable Macbook Pro (battery change and I also resoldered the VCore GPU due to LCD blackout - and the most irritating, to remake an bootable USB OSX on separate drive since OSX Catalina no longer supports the M-Audio card).
The loop-back of the Transit played from Audacity and recorded in REW. I get -99 dB THD.
Looped back through the NR1506, volume set to around 80. Auto and Pure direct was essentially the same.
As noted there is quite some mains noise, but THD is at the same level as my card, around -99.5 dB. So actual distortion of the analogue pre out is lower.
I've put my optical cable somewhere, but cannot find it at the moment so next test will be the optical in and analogue out to test the DAC. Perhaps tomorrow...
The THD seems however quite a bit lower than the later issue of this unit, NR1510, that Amir measured. I wonder why.
And here is the Toslink in - pre out result. I had to reduce volume here since my card clipped, so it is only 0.8 of 1.0 setting in Audacity and 75 on volume of the Marantz.
Somehow these settings increased noise floor and the mains noise. But THD stays around -100 dB, i.e. the same level as the M-Audio Transit sound card. Same result with auto as with pure direct. I do not see the 100 Hz jitter as seen on the 1510 and 1710. See
I just made some simple measurements via pre out of my slim line Marantz NR1710. Not having much advanced equipment but my 18 year old M-Audio Transit DAC and ADC was used to test it in various ways. It only supports 44,1/16 bit when used both ways. Basically it confirms Amirs data that the...
It seems that distortion increases with increased signal out Toslink; this is volume 0.95 from Audacity.
But conclusion is, THD stays quite low even with the DAC playing with the NR1506, as with the 1710, and 1608 shown previously in this tread.
Edit: Just to confirm, I remeasured my NR1710, using Toslink in-pre out, setting 1.0 volume out in Audyssey (below). THD is < -100 dB, but there is 100 Hz PSU jitter, as with the NR1510. Would be interesting to find out what it is that makes the jitter difference.