Balanced Line

Er, isn't a MM cartridge intrinsically differential in operation?

Not disagreeing with your comments about circuit design and thermal noise, but I thought a phono cartridge - in particular a MM - is the one thing in an audio system that is legitimately deserving of balanced operation.

As to why balanced line is popular... it's an American thing. They like to have their electronics in line with the listener, but the power amp in line with the loudspeakers. So they think balanced operation is going to offer lower noise. Unfortunately, there's a world of difference between proper balanced line operation and pseudo-balanced operation.

But I disagree that the XLR connection is inherently 'worse' than single-ended under all conditions. For whatever reason, Ayre equipment for example sounds a lot better balanced than single-ended.

 

I'm curious, who are so many DAC chips made with balanced outputs?

 

I said 'interconnection'. Stop using personal predujudice to disrespect anything I post.
How can a connection that rejects noise inherently not be a good thing?

 

The question must surely be, is balanced working beneficial to a home system?
In the majority of cases the answer must surely be no, given that we aren't generally using long interconnects and the noise environment is considerably more manageable than in for example, a studio where you might have lots of electronics crammed into close proximity.

For the average system with a couple of sources, pre and power amplifier and speakers I cannot see how there could be any benefit.

It can have some benefit with dacs (as Simon mentions above) where it can help lower distortion if it forms part of the design but I struggle to see any other benefits.

Many so called balanced circuits aren't - they are quasi-balanced. The single ended circuit has an operational amplifier tacked onto the output to to invert the signal, thereby giving what can loosely be termed a balanced output. However in all but extreme situation this gives no benefit and has obvious potential to sound worse since it adds active stages where they aren't required.

 

Exactly! someone who understands.

 

All conventional cartridges (except things like Deccas) are floating, this isn't quite the same thing as balanced. They will drive a balanced input but there is no advantage.

The idea, I think, is that you run a number of DAC cores in parallel, and if you run half of the parallel cores with a digitally inverted signal you get a balanced output with the effect of cancelling some errors.

Anyway there's l oads of technical stuff about balanced connections at http://www.douglas-self.com/ampins/balanced/balanced.htm

Paul

 

Richard, so a MC cart isn't essentially balanced in operation then, being a differential generator that only requires a reference mid-ground to be balanced.

Oh, I best email Nelson Pass and tell him that he's full of shit then...
And those idiots at Aqvox, they need to be put right as well.
Jeff Rowland, he's a clueless **** too.
God even that Muppet Graham Slee doesn't know what he's on about.
I can add the designers at Boulder, Levinson, Harman Kardon, and Linn to that list as well because they all design phonostages specifically for balanced input and operation.

They must all be wrong.

A cartridge, like a microphone is the perfect balanced generator and providing such low signal levels as they do are most likely to benefit from a balanced cable runs and their inherent noise cancelling ability.

I'll not bother asking your qualifications, it's obvious you have none.

 

Have any of those designers provided hard facts demonstrating the benefits of their approach?

You say 'most likely to benefit' - so do the stages above demonstrate intrinsically lower noise and distortion than other good single ended stages?

This is one area where the numbers are king.


...and those designers you mention might be wrong since far more adopt a different approach

 

And you know perfectly well you are playing games, this is nothing like a line level balanced line. It doesn't stop hum and rf pick up and all turntable arm cables are single ended which is why they use rca phono plugs, or Naim used single ended BNC plugs, one signal and screen per channel, nothing more.

You need 3 cables in balanced line configuration, which mean you need a 3 pin XLR or the like. Tell me how many turntables you have seen with XLR plugs or phono stages or amplifiers with balanced line inputs on their phono input, well I have seen none.

 

Richard, the Linn Uphorik phono stage has XLR inputs, and they do an arm cable with XLRs.

The cool thing is that, given the cartridge is floating, there is no need for an actual differential input. You get all the CMRR etc without. OTOH I've no idea how Linn have configured things.

Paul

 

OK obviously a gap in my education as I have no experience of this, but I really don't see the point.

 

It will sound better, that's the point.

 

Why, there is no logical reason, but I am blind as I have not heard it.

So how do you wire a cartridge when it has four pins, two per channel, one pos one neg, so how can you wire that balanced, it is single ended.

I have only ever seen one cartridge with extra pins but that is for a dc polarising charge for the magnets in that silly price Audio Note Io.

 

It makes some sense to wire a cartridge 'balanced', so you use screened twisted pair, the pair to the cartridge and the screen to earth. This is a natural fit with an XLR.

Paul

 

So we have some possible benefits from using screened twisted pair from arm to amp, but then need additional circuitry in the phono stage.

Be interesting to actually compare the effect of both outside of the theory.

 

Probably due to the potential of recording studio use. Balanced certainly has advantage there, especially when lots of kit is rack-mounted together with no gaps and loads of nasty PSUs lying about behind the rack. I used to joint own / run a small (ADAT) project studio and the wiring was a bloody nightmare, a completely random mix of balanced, unbalanced, 1/4" jacks, XLRs, RCA plugs, bamtam plugs, mini-jacks etc etc. Miles of often flakey wiring. I've still got a tub or two of filthy gaffa-tape covered leads knocking about.

Tony.

 

I think 'balanced' makes a lot of sense from the time when transformers were the most common input/output device. More to the point, floating. If you were to use them all with just a hot signal line and ground pulling the other side of the TX down, then all equipment would be connected at ground and loops could occur.

I don't know much about phono stages, but don't many of them use step-up transformers? It makes sense to me to wire the cartridge floating to the step-up transformer.

You could make a balanced input with an op-amp that doesn't introduce more circuitry too, although making balanced outputs tends to.

Richard, you wire it to an XLR using the pos and neg of the cartridge to the hot and cold pins of the XLR, the screen of the cable is then connected at the phono stage only.

 

Yes and this is actruly balanced connection. It's the difference between the signal wires that generates the signal. It does not require an earth for the signal that would unbalance it, as you say the earth is actually the shield.

 

Incorrect, balanced operation requires a difference between two signals, not a signal referenced to ground.

 

1) Cartridges are differential floating devices. If you connect them to a balanced load and a differential amplifier common mode noise suppression ensues.
I used to build my own differential-input phono preamps, and in those days never ever bothered to observe good grounding etc. Even with unshielded twisted pair between cartridge and preamp I never got any trace of hum.

2) This said, active differential input stages are 3dB noisier than the equivalent single-ended stages, as they have two inputs in series. The often-heard saying that "balanced has less noise" is blatantly wrong. It has more self-noise, and is immune to externally-induced common mode noise. That's all.

3) There are plenty of phonostages with XLR inputs. There are even some tonearms available with XLR connectors, wired differentially. Even so if an RCA-terminated cable is not connected to ground at the tonearm it can feed straightaway into a balanced input.

4) A seldomly-discussed property of a balanced circuit is that its signal load current does not pass through the power supply ...


http://www.michell-engineering.co.uk/reviews/rev_hfn_orbe2.html


http://www.tnt-audio.com/ampli/aqvox_phono2ci_part1_e.html