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Balanced Not really and Ground Hum

I have read that some balanced outputs (coming from any component) are not truly balanced, rather the manufacturers use RCA output wiring hard wired to the XLR output making the XLR unbalanced or not a "true balanced signal".
Is this a common practice and anyone come across this if so were?

The reason I ask is that I have been fighting that elusive little call "Hum or Ground Loop".
I have tried everything to solve it, disconnecting everything, adding Power Conditioners, Filtered AC cables, different RCA’s and now Dedicated Power (try explaining those three “Gotta Have It” words to the wife) but I can still hear the Hum.

So I am going to sell a bunch of my equipment and buy a preamp with balanced XLR out to my monoblock (Manley Snappers) which have XLR in.
I just don’t want to find it does not solve the problem because the XLR was wired from the RCA output.

Question: If the XLR is wired from the RCA beside the obvious audio consequences will it nullify the XLR = Less hum fact?
punkuk
samujohn's avatar
samujohn
291 posts
 
Hi,
Before you burn down the barn to get rid of the mice, get sombody with a technical background to come over and help. You are probably making the same mistake over and over, and a fresh mind may solve the problem easily. Recently I visited an MD with a hum problem that had defeated him. It was solved in five minutes by replacing his very expensive unshilded cables with cheap, but well shielded, interconnects.
regards,
kjweisner's avatar
kjweisner
293 posts
 
You are also correct that not all balanced outputs/inputs indicate truly balanced design. In fact, it's probably not "some" but "most" outputs that are not truly balanced. Companies such as BAT (Balanced Audio Technology) do build fully balanced designs whereby there are complete circuits for both the pos and neg "legs" of the run. Keep in mind that to leverage balanced, everything in the system, from source to amplification should be balanced. The primary benefit for full balanced is when there are long cable runs (which become antennae) a balanced line will cause interference introduced by this antenna effect to self cancel. I believe that balanced design may also enable the signal voltage to also be higher. You don't mention the lengths of your runs, but if you have a long one, then balanced may solve the issue.

If, on the other hand, your hum is a ground loop, this will make no difference. Spencer makes great points, especially concerning TT--I would add that if there's any cable TV, satellite or other video-oriented sources where RF cable is involved, they can be a source as well.
newbee
4,811 posts
 
Are you saying that you totally disassembled your components and then added them back into the system, one at a time, and you didn't notice the reappearing hum at the time the offending was reinserted into the system? I agree with the above re ground loops v balanced.

If you start with sources, removing one at a time, you should notice when the cause disappears. If not, then when they are reassembled, one at a time starting at the amps it should appear. Just let some time lapse between each change - sometimes hums take a bit of time to reappear due to warm up issues, etc. (I have amps which hum immediately, and others that start to hum after substantial warm up. The former I have been able to 'fix' with cheater plugs, the latter not at all absent some overhaul, if that, but much depends on level and speaker sensitivity.

Once you ID the source, the solution is probably a walk in the park.
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punkuk OP
52 posts
 
Thanks problem solved well 90%
The culprit was the Bam for the Merlin VSM's Speakers.
I never disconnected this unit from the power it just did not occur to me that it would be the problem.
I have found that using it in Battery mode cuts down the Hum by 90%.

The original question is still what makes a balanced system, as Kjweisner pointed out that few companies make truly balanced systems in addition ALL components need to be balanced (Not an easy feat)
If the latter is true is running balanced from the Pre to the power amp and exercise in futility, also running a “not truly balanced" signal (see above) is this also a waste of time.

Case in point; I have a " Clearaudio Symphono " Phono Stage that offers RCA in and a choice of RCA or balanced out,
As my Turntable (Nottingham Dias) only has RCA from the tonearm would using the Balanced out be pointless.

And lastly apart from the lowering of outside noise what sonic advantages does a balanced IC offer over RCA IC's.
Without starting the how much is an IC worth thread, I see a multitude of balanced cables with the usual wide ranging of price, but is a $500.00 Balanced IC more desirable than a $2k RCA IC (The price is just hypothetical)
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