Originally Posted by SVChucko
Meh. By my measurement (which may well be incorrect), S/N at 3V sensitivity is 97 dB below full power. It's only 91 dB at the 0 dbU setting.
Here are the spectra I got in testing. First one is the 3V setting, second is 0 dbU. The red line is the DP10Q, the green line is the D/A -> A/D loopback (residual). Note the 90(ish) Hz and harmonics thereof that dominate. I haven't figured out where they come from yet, but I bet it's in the power supplies. Get rid of those and the S/N would improve dramatically.
I've only heard actual music briefly on this amp, through some crummy PA monitor speakers. It sounded OK at low power levels, up to about conversational volumes. I had the amp a few feet away so there was no shortage of background noise. Of course I had the gain turned way down too.
Looking at how the peaks of the harmonics don't change when you change the input voltage, means it's generated after the pre stage, so it probably is a similar problem to mine, being present even when you mute the channels.
97db S/N would mean a noise equivalent of around ~45db@1m being produced by my speakers which matches my SPL meter readings (which are about 3db off compared to the UMIK, so that 42db reading matches the calculated 45db pretty well).
Does your noise sound similar to the noise in the video I posted earlier?
I think it's really just the speakers with their 110db/W/m sensitivity (8 ohm) which make my noise sound so extremely loud.
After all that's over 10db more than the 1899 and a noise of 45db compared to a noise of 35db is quite a difference.
It was far from being that extreme when I tested the amp on consumer PA speakers.
That being at a rated frequency response of 55-20khz (-10db) makes anything stand out really well.
Guess I'll have to drop 6 grand for the LA8 more sooner than expected.