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I just purchased a Yamaha A-S2000 integrated amp for my speaker setup. Besides being a terrific speaker amp, it turns out it also has a pretty decent dedicated headphone section so I started doing some comparisons to my Graham Slee Novo headphone amp. (DAC is VDA-2 from CIAudio and Cambridge Audio 651BD as transport.)


At some point during my comparisons I decided to try and feed the Novo from the A-S2000's preamp out. Wow. Much better than Novo or Yamaha on their own. The soundstage widened considerably with a better higher frequency/spatial resolution. Also better dynamics and more bass slam/oomph. After some experimenting, I seemed to get the best results when the Novo's volume pot was turned all the way up, using Yamaha to adjust the volume. 


Could someone kindly explain what is happening: 


1) By turning the Novo's volume all the way to the max, am I adding unnecessary distortion to the sound (something that I'm perceiving as good-sounding)? I don't know why, but listening to the Novo (on its own, without the preamp) there is some faintly audible hiss at 3 o'clock but then at full-on it's dead quiet again.


2) Is it "acceptable" in the first place to use a preamp with an integrated headphone amp (essentially chaining two preamps)? Naturally the signal chain should be kept as short as possible.


3) My Novo only has the standard switching supply, so could it be that the Yamaha's hefty toroidal transformer is responsible here (the unit weighs ~23 kg)?     



BTW, in case someone is interested in the A-S2000's headphone output (A-S1000 is the same but without the volume trim): though rated at a measly 30 mW / 32 ohms it can drive my AKG k701's well. I'm guessing the specs are understating it like with the main amp's power output (which in reality is 103 W RMS / 20hz-20kHz into 8 ohms with negligible distortion). Anyway, the headphone out sounds pretty good but has a very different sound signature from the Novo: less treble and more/fuller/rounder bass. More laid back and less analytical. 

Edited by anttipi - 10/3/12 at 3:39pm