Originally Posted by The Monkey
The Parasound 1500 is a pretty good DAC. The only suggestion I have is maybe getting a switchbox so you can do some quick A/Bing. Obviously still a subjective test, but at least you can more quickly switch back and forth between sources. I use the Manley SkipJack for that and it works well. Certainly, long term listening tests are also necessary but maybe this will help you isolate some of the nuances.
Originally Posted by zenpunk
Proper level matching is the most important. Can you both feed them the same digital signal by daisy chaining them if one has a SPDIF out, or use a USB to SPDIF box with two outputs?
Thanks Monkey and zenpunk for the replies. I'm feeding them both from the optical out of my MBP and plugging both into my Stax amp using RCAs, so I just swap the optical cable and select the appropriate source on the amp. I found that with the NAD set to 0 dB, the Parasound was still a bit louder (in fact, setting the NAD to +2 dB would generate the same sound level, but of course I didn't do this in A/Bing for fear of clipping). So, yes, matching the sound level was a PITA.
It's perhaps worth mentioning for others trying to do this, that I did also try creating "multi-output device", and driving the NAD via USB and the Parasound via optical, so that I needed to only select the correct source on the amp. I found that OSX 10.7 would degrade the audio (it would become very choppy) after 10-15 minutes, so I gave up on that approach.
I'm going to do some more listening over the weekend, but the only difference I can discern is an improvement in the lowest bass, I'll have to decide if that's worth the extra $$.