2. amps-preamps
  3. 160894-109163

Passive preamp issues or?

I have a Nuforce STA 200 that I’ve been using with an Axiom Walker mod preamp for a while now.  Other equipment is a Bluesound Node 2 streamer and a Jolida dsd dac.  Nordost digital coax and Dueland Schroeder IC’s from dac to pre and pre to amp.   Last night, I disconnected the preamp and ran the IC’s directly from the dac to amp, using the volume control on the dac.  The change in detail and depth was not subtle.  Soundstage extended beyond the speakers- everything just sounded better.  However, with the high gain of the Nuforce there’s  a hum in the speakers- it’s not not audible when I’m not playing anything. I’m willing to live with it, but I’m curious why the sound improved significantly by pulling the pre- should I look at better IC’s from pre to amp or is the Axiom subtracting from the sound quality?
renisnceman
georgehifi's avatar
georgehifi
10,312 posts
 
I’m not saying a grounding issue, that’s why I asked for you to find out what the output impedance is of the dac (at all volume levels) as this sound like it’s the dac impedance match maybe problem, or it's hum in the dac just being presented.

Cheers George
renisnceman OP
50 posts
 
Output impedance from the specs page is 47K ohms
renisnceman OP
50 posts
 
Reread your post, I’ll try to confirm with Jolida.
georgehifi's avatar
georgehifi
10,312 posts
 
If it is 47kohm output impedance, that’s insanely high, never seen anything like it.

If you get no answer, also try another source with output rca’s like the Blue Note 2 streamer as it has volume control also, see if it still hums then.

Cheers George
atmasphere's avatar
atmasphere
11,756 posts
 
so when I turn the volume up, the speakers hum, mildly— then as I turn the volume up all the way, well past safe levels, the hum disappears and  I just get white noise hiss- again, not that loud.  If it was a grounding issue would the hum be there all the time?
@renisnceman


First off, the output impedance can't be 47K. It could be 4.7K (which is still high IMO). 47K might be the minimum it can drive with full bandwidth...

Anyway, the description in the quote sounds like a volume control problem. Is the control analog or digital. This does not sound like a grounding problem; if it were you'd have a different description.
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