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Balanced vs. Unbalanced Inputs

I am trying to upgrade to a differentially balanced phono stage to compliment my Pass XP-22 pre and Pass X250.8 amp so as to minimize long cable artifacts and benefit from CMR. I do understand the it is the circuitry and not the input connection that determines wether a signal is balanced or not. I am looking at both a Pass XP-27 and AR Phono 3SE as possible options. Both have RCA inputs plus a ground post only. No XLR inputs. 

As far as my understanding goes, a balanced cable must have 2 signal conductors, a hot (+) and a cold (-) PLUS a ground for EACH channel. So, I sent an email to Pass Labs as follows:  

 ".... I want to confirm that there are TWO signal conductors PLUS a ground for each channel. Specifically, on each of     the RCA inputs, do the center pins and the shields carry the hot (+) and cold (-) signals respectively while the grounding wire/grounding post becomes the tone arm/turntable chassis ground connection common to BOTH channels? "

This was the response:
     "No. RCA shield and ground lug are contiguous connections."

But on the pass website is the following:
     "In order to minimize ground loop issues Pass Labs never manufactures equipment with signal ground and chassis ground contiguous."

When I email Linn about their pseudo balanced  LP12 T cable they responded with:
     "All Linn arm cables are terminated with a 5 pin DIN connector with the center pin being arm ground, which on an LP12 is also used as the chassis ground.  This is separate from the left and right channel grounds and hots which are on the other 4 pins."

Again, there is no (+) signal to be superimposed with an inverted (-) signal separate from ground for CMR. I Do have a technical background but I am not well versed on circuit design so please forgive my ignorance. I did get some very helpful advice from a member here, however, the further I inquired with the manufacturers the more confusing it became. As of now I am wary about emailing AR for fear of even more confusion. If anyone has any advice on how to proceed I would really appreciate it. Thank you all so much.

Bruce
brskie

Showing 4 responses by clearthinker

clearthinker's avatar
clearthinker
1,582 posts
 
Goodness me.  Opinions here are diametrically opposed on a question that should be straightforward.  The OP says he understands now but if that is the case then he is smarter than I am.

I had believed that running phono fully balanced brings a 6dB noise floor reduction and thus is very desirable given the very low level signals involved.  Having read the thread carefully and re-read it, I no longer clear that a phono output can even be run single ended (because of the cartridge 'floating' idea expressed in two posts).  Nor yet has any view been expressed here as to the respective SQ benefits of balanced vs single-ended operation  (Possibly premature as it has not been agreed what balanced operation is or whether it is possible).

I think I would be a great idea to ask the the great phono cartridge and phono amp designers to clear this up - hopefully they might all agree.  Question: precisely how are cartridge and turntable wired to the phono amp to obtain fully balanced operation?

Also it would be highly instructive to listen to the same system wired single-ended and then fully-balanced and to take noise measurements of each.
clearthinker's avatar
clearthinker
1,582 posts
 
Thank you for all the effort in that input @atmasphere and the benefit of your wide knowledge and experience.  It throws much needed light.  I am finding this discussion very interesting as well as informative.

A.    If I understand correctly, to summarise, you say yes most cartridge arms can be wired fully balanced.  Balanced operation reduces noise, particularly in long wiring runs.


B.   "[balanced operation] prevents interconnect cables from interacting with their audio system...Imagine all the cables sounding as good as the best you've heard: that is the benefit."

Ooooh, I can see that one is going to be controversial.  You seem to be saying SQ differences between different cables arise from running single-ended, as most audiophile systems do, and not from the cables themselves.
Is it going too far to draw some further conclusions from that statement:
1.  All well-designed cables sound (much) the same in a balanced set-up.
2.  Money spent on expensive cables is (largely) wasted in a balanced set-up.  Therefore:
3.  There are SQ differences due to cables in a single-ended set-up so expenditure on cables can be justified.  But if you choose a balanced system, this will gain at least the same SQ improvements as buying expensive cables, but without the extra cost.  Pace - I accept in principle it is more costly to build balanced amplifiers than single-ended.


C.   "your equipment must support the standard, AES48; I can tell you that hardly any high end audio gear supports the standard "

Are you saying that some amplifier hardware fitted with XLRs and said by the manufacturer to be 'fully balanced', is not fully balanced and does not support AES48?  Presumably XLRs could be put on for show without the correct wiring behind?  If this is correct, someone suitably qualified should start naming names.
clearthinker's avatar
clearthinker
1,582 posts
 
Thank you again atmasphere.

Given the haphazard wiring behind the XLRs and non-adherence to AES48 of many amps, I am indeed lucky (just that) to find my system is free from hum and other obvious non-matching artifacts and appears to have a very low noise floor - I hear nothing on no-signal until I turn the volume pot up a long way.

For reference, I (believe) I run fully balanced throughout.  Ortofon A90 on a Simon Yorke Aeroarm though a bespoke SY connection box into a van den Hul The Grail SB phono amp, Audio Research Ref 6, vintage Krell KRS200 monoblocks.

It seems wrong that getting the benefits of running fully balanced should be such an uncertain adventure.

And if nothing else, these exchanges have revealed the truth about the alleged benefits of high-end cabling.

clearthinker's avatar
clearthinker
1,582 posts
 
Hi @glupson, given what atmasphere says about wiring behind the XLRs in many amps, perhaps rather than for convenience, the XLRs are there for show.

It seems to me that guys like John Atkinson should report on 'balanced' amps that are not actually wired balanced and/or do not conform with AES48 just like he reports on speakers that are 4dB less sensitive than the manufacturer's spec.  We want to ensure manufacturers are honest with their specs and that those who are not are exposed.
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