Originally Posted by coli
***To put it another way, it's possible the Halo is re-producing your iPhone's noise floor in the most accurate manner compared to the other amp who lacks the resolution to reproduce it.
Sorry, not only wrong, but also delusional.
Originally Posted by audio4life
DS-21, that's a kind of test method that I've never thought of. All I can say is the Halo I have has no such noise on any channel.
I would expect that to be the case. I started the noise testing because I was looking for an amp to actively biamp a front trio of 12" Tannoy Dual Concentrics - designed by current KEF head engineer Mark Dodd - where the tweeter was more than 96dB/2.83V/1m . That's about 4x (6dB) more sensitive than any current KEF speaker! (And, for reference, about 15dB
more sensitive than a KEF R800ds surround speaker.)
As it were, it turns out that neither the cabinet width (12" driver + very large roundover for lower diffraction) nor the narrow pattern work in my current room. (My current room has sidewalls very far away from the speakers, so a wider pattern is better.) So that project ended up getting shelved for now.
But with typical domestic audio speakers at typical listening distances, noise floor won't be an issue.
Originally Posted by AcuDefTechGuy
So which amps were dead silent, and which amps had the hiss noise?
From memory, the Anthem Statement, Bryston, McIntosh, ATI, and Sherwood Newcastle were all basically equivalent in terms of noise floor through this test, though obviously that's more of an achievement for the Anthem/Mac/ATI than the Sherwood/Bryston, just because the first group is roughly 3dB more powerful than the second. Alternately, one could argue that it was a big achievement for the A-965's design team, because that amp was so much cheaper than its performance peers. That led me to buy one, though I did subsequently make a largely sideways move to an ATI AT2007.
The big Parasound was a shade worse, similar to an Arcam Class G 7-channel, an NAD 7-channel, and the ElectroVoice CPS8.5 "pro" 8-channel amp. (Though the EV does have fan noise.) The Adcom 2535 was bad enough that it caused me to look for a new amp. (I've owned it since 1994 or so, and started the project expecting to use that amp.) I never found the smaller Anthem 7-channel to test, or a Sunfire, or a Lexicon DD-8/Crown CT8150.
The Icepower-based Rotel 6-channel was really bad. Two samples of it were about the same. I don't know why, as other Icepower based I've tried (in integrated DAC/amps from Teac and Kanto) were much better. Even the Peavey IPR-3000, which has like 40dB of gain (a lot more than even, say, Emotiva) was better than the Rotel Icepower.Edited by DS-21 - 10/15/13 at 5:20pm