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.  
I’m pretty sure that your amp is a true balanced ("differential") amplifier, so you will get 6dB more gain using the balanced connections than you will from unbalanced. That accounts for the increase in noise which - if you only only hear it when your ears are a few inches from the speaker - is immaterial.
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!
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.

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.
@ 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?
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! 
@ 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...
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. 
Att rwatson OP

cleeds I’m pretty sure that your amp is a true balanced ("differential") amplifier, so you will get 6dB more gain using the balanced connections than you will from unbalanced.
Levinson 532H it’s +0.4db difference in favor of the RCA!!!.
What "could" be is that the balanced input is a balanced summing opamp feeding the single ended discrete input circuit. If so less noise and better sound if you go direct with rca, as this cuts out that balanced opamp with it’s added noise.

Stereophile measured Levinson 532H .
The voltage gain into 8 ohms was to specifications: at 26.8dB using the balanced inputs, and slightly higher, 27.2dB, using the unbalanced inputs.

Or it could be the same but to do with the dac, it’s se output is one less opamp compared to it’s bal output.

PS Here’s the answer, similar to what cleeds said but from the dac not the poweramp.
The Levinson’s 390S DAC maximum output level was 2.18V from the unbalanced RCA jacks, this doubling to 4.36V from the balanced XLRs

Cheers George
Thanks, @mrdecibel, I really appreciate it!  To clarify, I have a Parasound Max 5500 (actually, borrowed from a video set up in another room) that indicates (what I assume is) amps from the wall.  Again, forgive my lack of knowledge regarding electronics, but I've often heard of dedicated 15A circuits, etc., for audio systems.  Bottom line is that I don't have anything like that.  Perhaps it's a non-issue, or perhaps I need to have an electrician come in.  It sounds like you're saying the latter might be advisable?

Regarding speakers, I am really just looking for some initial manufacturer suggestions since synergy is another thing that is often discussed on this forum and I'm sure there are speakers which are particularly well suited to the Levinson gear.  It might be best to start another thread so we don't drift too far off topic.  But, for what it's worth, I really only listen to vocal and instrumental jazz and classical music.  I'm sure there are many modern speakers that are far more accurate and better sounding than what I've been using.  Piano, small instrumental and vocal ensemble music sound quite nice to me on the B&Ws and I can definitely tell which recordings are not particularly well mixed.  One area where I'm sure there's a lot of room for improvement, however, is in detail and dynamic range with big band and large orchestral recordings. 

Stay safe (and sane) as well!
@georgehifi, if I'm following you, the hiss can't be explained by the DAC since it's present whether the 390s is connected or not.  Thanks!

Ok then same noise if the dac is not connected to the amp just the speakers,
Then when it’s switched to XLR input (which is .5db lower gain than SE) as Stereophile measured, it has more noise to you from the speakers, it must be a Balanced to SE summing opamp giving the extra noise, and therefore should not only be quieter using the SE as you found, but also sound better because the summing opamp is not used.
I found exactly the same but other way around using Belcanto Ref600 monoblocks, the RCA input used a se to balanced opamp into the Hypex NC500 balanced input buffer module, the XLR input input did not use it and had the same gain, and not only had less noise but sounded better as well (less hifi’ish), because the opamp was not used.

Cheers George
Another point is that 12’ is not a worrisome length for unbalanced cables. In pro audio applications there can be 50 to 100’ of cable as in the mic drops in a big concert hall. Unless you have a proven source of RFI/EMI nearby, like a broadcast tower, you’re better off with the RCA connects. 
georgehifi has it right, in my opinion.  I would also suggest that you contact Levinson and inquire on the design of the amp on weather or not it uses an op-amp for the XLR inputs.  My guess is that is probably the case; that they do use op-amps to convert the incoming single-ended signal to a balanced design.  And if so, then simply revert to using RCA connections for the best signal integrity to the amps primary design.  In my own system the components are expressly designed for use with XLR cables.  Hence, they pulled that into the name of the brand, Balanced Audio Technology (BAT).  

I also have to question MC comment about Balanced XLR cables being more costly than RCA cables.  The cables I use are by Audioquest.  They can be purchased with RCA terminations or XLR terminations for the exact same price.  I imagine it is possible that some cable vendors have a difference in price based on the terminations, but obviously not all.  And indeed, there are a lot of quality cable vendors on the market by which you can choose from.  Just my two cents on this particular comment.
Nothing to worry about. I am not an engineer but I have owned amps from Adcom, Aragon, Proceed, 2 Mark Levinson 300 series and McIntosh, speakers from Martin-Logan, Sonus Faber Guarneri Homage & B&W 803 d3. Every system combo had low level hiss when my ear is 6" away and every amp has a low hum from the transformers when standing a few inches away. From listening distance 9 to 10' away, I hear nothing. If you can hear the noises from the listening distance, there may be a ground issue somewhere that is causing the hum or a part starting to fail  in the amp. The final conclusion is that amps are not silent creatures and you will drive yourself crazy trying to fix what is normal. If you feel that the noises are too loud, then contact the manufactures Technical support and they will, most likely, tell you that what you are experiencing is normal. I am sure they would be happy to give you an RA and  charge you $100.00 an hour + shipping to tell you there is nothing wrong with the Amp.Given the weight of the amp shipping cost can be prohibitive. Unfortunately, unless you live in Texas or California, there are no local service people for Mark Levinson. Try to enjoy the music and don't listen from 6" away and you will be fine.
Just because you have XLR connections, does not mean you are true balanced. Lots of company put the XLR connectors on their equipment, but they are not balanced from input to out put.
Interesting since I thought the point of using balanced interconnects was to reduce noise.  
Reducing artifact from the cables and reduction of ground loops are why.
I suspect George is right; that this amp uses an additional circuit for the balanced input which is an additional opamp circuit. If true this suggests that internally the amp is not fully balanced. A schematic would sort that out...

At any rate if you have to be within 3 inches from the tweeter to hear this, than you have no worries!