Balanced vs. Unbalanced Inputs

The whole point of balanced cable operation is to avoid interconnect cable interaction with the sound of the system and if the tenants of the balanced system are followed, it does this very well. This means that to sound right, the cable does not have to be expensive, it simply has to be correct!

Could you clarify this, because in my mind, the point of balanced is, and has always been common mode noise rejection.  Good cable construction will of course lead to consistency of noise on both cables ensuring common mode rejection.

Now w.r.t. studio balanced connections, i.e. AES compliant, that is not just about balanced, but a drive/load standard that is low enough impedance to dominate over cable parameters.

Technically a phono cartridge is "floating" which means it's neither balanced or single ended. It can be wired either way

This statement is false. A floating inductor like a cartridge is in fact a balanced source.

No, that statement is quite true. A floating source is not the same as a differential source. It would only be truly differential if you center tapped it and connected the shield to the center tap, such that coupling to the cable shield is similar for both conductors. That is not the case for a cartridge.

but the reason there are so few balanced turntables/phono stages is that there is diminishing return on splitting the signal to make it balanced, particularly when the signal from a cartridge is already so weak.

I disagree with the diminishing returns as the two channels are completely separate loops, hence if you connect them to the same ground (single ended), then you loose the benefits of independent floating loops and reduce common mode rejection.

Nice of you @nitroxpro to advance the conversation with circuit diagrams and your advanced knowledge of simple circuits.

See my previous two posts, clearthinker


The AES standard is balanced interconnect with differential signalling AND the source and load and cable impedance is defined. Really, at least to me, it is that defined impedance that justifies most of atmasphere's argument, with the balanced and differential taking care of the rest.

Defined and low impedance compared to consumer equipment impedance ensures that the relatively low capacitance and inductance of interconnect cables are essentially eliminated from the equation. Matching the cable impedance to the source/load impedance guarantee fast signal transmission with limited ringing and also makes resistance purely a level shift. By fast, we are talking so far beyond audio it is not worth even mentioning.

Balanced interconnection with differential signalling effectively eliminates noise, the only purported benefit of expensive cables.

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.

This statement is a common myth, and being a myth, is false. A center tap degrades the Common Mode Rejection Ratio, on account of the simple fact that no center tap is really centered exactly. For this reason, center taps are never used. This is true of dynamic mics, cartridges, tape heads and any other inductive source including input and output line transformers.

I never said that center tap would be better for noise rejection (though it absolutely could be). You appear to have have misinterpreted my use of center tap to imply a single ended ground reference, which is not the same as connecting the shield to a center tap to balance the signal w.r.t. the shield. That it is not used in audio (not needed) does not mean it does not work. It is used in other industries because it does.


https://www.pulseelectronics.com/wp-content/uploads/2016/12/G019.pdf

https://patents.google.com/patent/US20170131427A1/en

Certainly noise rejection is one aspect, but so is the rejection of ground loops (that is why the balanced line system ignores ground).

Grounds loops ARE common mode noise. Hence, the accuracy of my statement, to reduce common mode noise.

The problem here is that in order to obtain the benefit of balanced operation, your equipment must support the standard, AES48. Having introduced balanced line operation to high end audio, I can tell you that hardly any high end audio gear supports the standard and so you hear differences, and often degradation.

We are talking input to phono stages, i.e. cartridges, so not sure where you are going bringing this up. It is not applicable.


At this point we need to be pedantic since terms that are not interchangeable are being used that way, "balanced" refers specifically to the interconnect method, i.e. the signals are impedance balanced to the ground/shield, hence the noise on one is balanced and opposite to the other. That could be implemented with transformer coupling and shielded cable, or differential signalling and a shielded cable.
What is called a "balanced" input is balanced in the sense that it connects to a balanced interconnect, but electrically it is differential. The AES standard is a differential signalling standard coupled with a balanced interconnect.

Since the cartridge is already a balanced source, its a matter of getting the signal to the preamp without involving that signal with the ground system (the tonearm tube and turntable).

Which makes this statement as noted before inaccurate.  A cartridge is not a balanced source. It is a floating differential source.  If you twist the wires and maintain a consistent (w.r.t. each wire) shield to the amplifier then the interconnect would be balanced.

Because the cartridge is floating, and hence its output differential, going into single ended input, assuming you use the practices of balanced interconnection (with shielding), you can still have a low noise floor especially at low frequencies, because the common mode noise at those frequencies will be rejected. However, from a practical standpoint, this does not work well at high frequencies, due to parasitics. This is where the differential input comes in that will reject common mode not just at low frequencies but at high frequencies.

Unfortunately, too often balanced and differential are thrown around interchangeably and they are not and mean different things. This is confusing especially if you are trying for a deeper understanding.