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Speaker hiss from power amp

I have a Mark Levinson 532H amp that is connected to a Levinson 390S CD processor only (no preamp).  Recently, I switched from single-ended to balanced interconnects (Cardas Neutral Reference) because it's a pretty long run (~12 feet) between the components.  The 532H has switches on the back for selecting balanced or unbalanced interconnects.  The switches had always been set for the RCA single ended inputs, so I just noticed that when the switches are set to balanced, there is a very slight hiss coming from my tweeters.  When unbalanced are selected, the hiss is substantially reduced, nearly but not quite silent.  Both speakers have an equal amount of hiss.  In balanced mode, the hiss is only audible when my ear is 3 or 4 inches from the tweeters so it doesn't in any way detract from my overall musical experience.  I should note that the hiss is evident whether or not anything is actually connected to the amp (other than the speakers, obviously), and there's no difference with gain when I have the 390s connected.  Also, the addition of a power conditioner has made no difference at all.  Two other things: there is a very slight hum coming from the amp (again, only audible if I'm very close to the amp) and the A/C power from my outlets seems pretty inadequate (probably less than 5 amps according to the Parasound).  Appreciate any ideas on why the hiss increases when the switches are set to balanced inputs and how it could possibly be eliminated.  
rwatson
rwatson OP
6 posts
 
Interesting since I thought the point of using balanced interconnects was to reduce noise.  I guess corollary questions, then, are: 1. Should I go back to single ended and potentially what could I be losing by doing so and, 2. Is the fact that I can hear ANY hiss possibly indicative of a faulty amp?  The second question is what’s really weighing most heavily since, as I said, the hiss isn’t audible at all from where I listen and, otherwise, everything sounds great to me.  Also, I was thinking of upgrading speakers (General suggestions on synergistic brands (my local shop sells Focal)?  Currently, I’m using older B&W Matrix 3 Series 2s that I purchased in the 1980s) and would hate for the noise floor to then become audible!
millercarbon's avatar
millercarbon
12,531 posts
 
Interesting since I thought the point of using balanced interconnects was to reduce noise.  

Then you have been misinformed. The point is improved signal to noise ratio. Its a ratio. That's why its written S/N. Signal divided by noise. A ratio. 

Okay technically the reason is to feel like you're all professional and everything, because everyone knows the pro's use XLR. Also to have twice as much of everything, because, well just because. Also a lot of people think the more you spend the better you are and balanced does cost a whole lot more. So its kind of a trifecta. 

Yes by the way glad you mentioned it you should go back to single ended. But not for this silly hiss reason but because you can buy so much more performance for your audiophile dollar.

twoleftears's avatar
twoleftears
5,313 posts
 
The hiss was already there.  The switch to XLR enables you to hear it more clearly.  XLR cabling reduces noise creeping in over the course of the run; what you hear is gain happening inside the amp and being output at the balanced socket at a higher level.
ditusa's avatar
ditusa
1,689 posts
 
@ RWATSON, Both mrdecibel and cleeds are right. The hiss is the amps dynamic range. To remove the hiss you will need gain controls on the amp. Or install them on the amp interconnects. The hum is maybe the amp transformer?
ditusa's avatar
ditusa
1,689 posts
 
TWOLEFTEARS, +1
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