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

Showing 8 responses by renisnceman

renisnceman OP
50 posts
 
I purchased an ebtech hum-x and it made no difference. The Bluesound is quiet but the dac isn’t up to par with the Jolida.  I have a feeling I’m going to have to stay with the passive pre- it’s just a little frustrating knowing improved sound quality comes at the cost of speaker hum.  Might just mean I’ll have to tweak tubes or cables instead, as I’m not sure where to go from here.
renisnceman OP
50 posts
 
The hum is non-existent with the volume down-  I’ve got nos Telefunkens in the dac—wondering if switching to lower gain 5751’s would make a difference?
renisnceman OP
50 posts
 
@georgehifi- 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 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.
renisnceman OP
50 posts
 
From Michael Allen at Jolida/Black Ice- “the spec is 47 K ohm.”  The volume control is analog. 
renisnceman OP
50 posts
 
No hum from the Bluesound....
renisnceman OP
50 posts
 
I put the pre-amp back in the loop.  Dead quiet- decided I couldn’t live with the hum. FWIW- and I don’t clearly understand the logic behind this, if I keep the amp connected to the speakers and disconnect the dac from the amp, the hum is worse. Disconnected every that might contribute to the hum- no change.    I may just look at better IC’s from pre to amp to see if I can wring some improvement.  It’s really a pretty good system as it is- I may just need to tweak with the pre in the loop.
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