2. tech-talk
  3. 1177210678

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
Post removed 
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)
davemitchell
253 posts
 
A truly balanced circuit has a pair of identical signal paths for each channel whereas an unbalanced circuit has only one signal path per channel. The duplicate signal path is for carrying an inverted version of the standard signal.

You can very quickly tell from glancing inside of an amp or preamp if it is a balanced or differential circuit. If it is, you will see four of every key part in the signal path (left channel +, left channel -, right channel + and right channel -). An unbalanced or single ended circuit will only have two of each component (left channel + and right channel +).

For a truly balanced system, every component from the source through the amplifier must have balanced circuitry. The noise reducing benefits of balanced operation occur when at the ouput of your amplifier, the inverted signal is inverted again and then summed with the standard signal. Any noise that was picked up via the signal paths in your equipment and any of your interconnect cables will be cancelled out, while the signal level will be doubled moving it 6db above the now lower noise floor.
More to discover