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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
ditusa's avatar
ditusa
1,883 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
1,883 posts
 
TWOLEFTEARS, +1
rwatson OP
6 posts
 
All good stuff—thank you, everyone!  I guess it’s pretty apparent that I’m new to some of this, so appreciate your patience.  That said, to millercarbon’s remark, I actually was a professional jazz musician in my past life (albeit a horn player so not involved in the electronics side of things except for moving other musicians’ heavy gear).  I’m 56 now so I don’t need to impress anyone—I just appreciate well-made and designed stuff, whether it’s furniture or appliances.  Anyhow, it doesn’t sound like there’s anything I need to be concerned about in terms of equipment health, so that’s the main thing.  Millercarbon, I’m definitely all ears if you have suggestions on single-ended interconnects.  And speakers, for that matter! 
ditusa's avatar
ditusa
1,883 posts
 
@ RWATSON, The reason for balanced cables are many, long runs no signal loss, rejecting EMI, EMF, stopping ground looping, and many more. That is why all good amps used them like your amp, pro amps, military amps, hospital amps. Or any engineer looking for the ultimate transfer function connection. Hope that helps...
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mrdecibel
3,063 posts
 
Rwatson, a few more comments. BTW, welcome to the "Gon. As you stated, the hiss is not audible from your listening chair, so I would not worry about it. Putting your ear close to the power amplifier, it is quite common to hear the transformer. A recent thread on " Tech Talk " here, about transformer hum, might be a good read for you. Replacing your speakers will be entirely up to what you like, and being a musician, just read up on manufacturer product descriptions, product reviews, both from professionals and consumers, and listen to stuff, if at all possible ( which can be difficult during the virus ). Always keep your room, a major part of the equation, as both size, and the acoustics, matter. Speakers that are more sensitive ( efficient, playing louder with the same power applied), will likely show a higher hiss level, just as an fyi. I am a little confused about your statement, relating to the Parasound, and the 5 amps, available from the wall, which is quite inadequate. and abnormal. As cleeds indicated, the term " gain ", and mc, with " signal to noise ratio ", is quite a lot, of what connecting this audio stuff, is all about. Lots of articles abound, about these subjects. Enjoy ! and stay safe...everyone. 
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