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Trying to reduce noise while listening to tube phono

Let me start by staying that I'm in love with how my system sounds right now. Hagerman Trumpet and Decca London Super Gold (paratrace stylus) is a ridiculously good combo. The only "but" is that if I raise the level to 3 o'clock on the preamp (Herron) I start to get tube hiss... or some hiss from somewhere. It used to be worse but then I got all new very low noise tubes and it improved a ton but I want to see if I reduce it some more. I'm wondering if the issue is the amount of gain on my preamp? Should I try another preamp with more gain and see if that solves the problem? On other inputs there's no hiss even at full volume so there's nothing technically wrong with preamp.
dhcod
mijostyn's avatar
mijostyn
8,570 posts
 
goheelz why would a dedicated AC line eliminate noise problems?
lewm
13,039 posts
 
Dedicated AC would help, and usually does help, if there are other devices otherwise attached to the same AC line that produce electrical noise in the form of EMI.  It could make a big difference if you've got your refrigerator or dishwasher drawing from the same circuit breaker, for example.  For that same reason, the turntable motor should be electrically isolated from the preamplifier and amplifier. But these precautions would do nothing for inherently noisy tubes or a poorly designed noisy circuit.  
goheelz's avatar
goheelz
297 posts
 
+1 @lewm Who, unlike me, may have the technical expertise to explain *why* dedicated AC lines helped with noise issues. Thanks for your cogent summary of the way AC lines can be a factor.

Agree that phono stage design is likely a culprit in the OP's noise situation. But I'm sold on dedicated AC lines, whether I can explain their efficacy or not!


dhcod OP
710 posts
 
What is the reason to have unshielded tonearm leads?


I bought the M2-12R from the dealer who suggested rewiring it in this manner for better sound. It really makes a difference.... SME's wire has never been their strong suit. I'm super happy with the arm so I would definitely look everywhere else for solutions rather than rewire.
lewm
13,039 posts
 
If you live in a low RFI environment, you might not suffer for lack of shielding.  I use unshielded tonearm leads in my suburban environment, for some of my arms, and I don't perceive a problem.  Which is to say that my tonearms using shielded wire sound the same as those using unshielded wire, in terms of RF noise. If you live in a city or industrial area, shielding is a good idea. Furthermore, I would think that the SME arm wand itself acts as a sort of shield for wires traveling within it.  Not so, once those wires exit the base of the tonearm.  On the other hand, I have never read that SME used inferior wires.  Is there any reliable source for that info? (Is there any reliable source for anything in audio?)
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