harmonics and single-ended versus balanced audio cables

[Ron Resnick]

Do balanced audio cables tend to suppress second harmonics more than single-ended audio cables?

 

[DonH50]

The cable alone won't but if the driver and receiver are fully differential then all even-order harmonics will be suppressed.

IME/IMO the main reasons to use differential connections in audio systems are to reduce sensitivity to noise and break ground loops.

 

[opus112]

What Don said. The issue addressed by using balanced cables is noise control, not distortion reduction.

 

[RogerD]

Ron, a good explanation
http://audiosystemsgroup.com/InfoComm-Grounding2012.pdf
See technical grounding

 

[Ron Resnick]

But doesn't Don's answer, for which I am grateful, beg the question:

Do we lose more in sound quality by forfeiting all even-order harmonics than we gain in sound quality by reducing some noise?

(Let me make a prediction: devotees of SET amplifiers are more likely to vote "yes"; devotees of solid-state amplifiers are more likely to vote "no.")

 

[Ron Resnick]

What Don said. The issue addressed by using balanced cables is noise control, not distortion reduction.

I agree.

But that fact raises this second order question about second harmonics.

 

[RogerD]

But doesn't Don's answer, for which I am grateful, beg the question:

Do we lose more in sound quality by forfeiting all even-order harmonics than we gain in sound quality by reducing some noise?

(Let me make a prediction: devotees of SET amplifiers are more likely to vote "yes"; devotees of solid-state amplifiers are more likely to vote "no.")

This is my opinion from experience. All types of noise mentioned in the tech paper on grounding has the largest effect on sound quality by far. If you accomplish noise removal everything else is a preference.

 

[opus112]

But that fact raises this second order question about second harmonics.

I think there's some confusion on WBF between single-ended (not quite the right term, should be called 'unbalanced') cables and single ended amplifiers. They're quite different things.

The sound quality of SETs would I believe be the same or perhaps slightly better if they were run balanced. I also believe their desirable sound has nothing much to do with harmonics and everything to do with power supply.

 

[Ron Resnick]

I asked that question rhetorically only because devotees of SET amplifiers know that SET amplifiers exhibit higher distortion, especially at low frequencies, but they justify that result on the basis that second harmonic distortion is consonant with the music.

 

[RayDunzl]

But doesn't Don's answer, for which I am grateful, beg the question:

Do we lose more in sound quality by forfeiting all even-order harmonics than we gain in sound quality by reducing some noise?

(Let me make a prediction: devotees of SET amplifiers are more likely to vote "yes"; devotees of solid-state amplifiers are more likely to vote "no.")

I have Balanced Cable between my DAC and preamp.

I generate two tones, 1000Hz and 2000Hz at equal amplitude.

2000Hz is the second harmonic of 1000Hz.

If the "second harmonics" of the signal are being lost or attenuated in a balanced cable, why don't I see some drop in the output level of the 2000Hz tone?

 

[Ron Resnick]

I happily defer to the electrical engineers here to answer that question.

 

[Folsom]

I prefer SE, but I use something special that reduces the noise of them to below most XLR in audiophile setups. The qualities I like remain, but in a cleaner form.

How much you like 2nd harmonics is up to you, Ron. But I personally think XLR sounds weird, and not because of 2nd harmonics. It sounds... flat, to me. You have to accept that even though you lower noise, you double any faults of the circuit, and that's where I speculate the dullness comes in that I tend to experience on XLR use.

 

[Folsom]

There's a lot of equipment that is designed for balanced, and skips any effort for SE... It's totally normal that some manufacturers do that; as in it's common. Perhaps the reverse is true but I'm not certain of an example off hand. It's a factor to consider with the overall question.

 

[Ron Resnick]

I prefer SE, but I use something special that reduces the noise of them to below most XLR in audiophile setups. The qualities I like remain, but in a cleaner form.

How much you like 2nd harmonics is up to you, Ron. But I personally think XLR sounds weird, and not because of 2nd harmonics. It sounds... flat, to me. You have to accept that even though you lower noise, you double any faults of the circuit, and that's where I speculate the dullness comes in that I tend to experience on XLR use.

What is the length of your single-ended interconnects?

 

[DonH50]

But doesn't Don's answer, for which I am grateful, beg the question:

Do we lose more in sound quality by forfeiting all even-order harmonics than we gain in sound quality by reducing some noise?

(Let me make a prediction: devotees of SET amplifiers are more likely to vote "yes"; devotees of solid-state amplifiers are more likely to vote "no.")

You are confusing the signal and distortion. Differential circuits cancel even-order distortion terms. The signal itself is not affected, except that it has less distortion (and noise, due to both the additional 3 dB SNR provided by differential operation and the rejection of other "external" noise sources). Any even (and odd) harmonics in the signal will still be there.

Note the output stages of most power amplifiers are single-ended, tube or SS. And not all balanced circuits are fully-differential so offer the advantages of differential to varying degrees depending on their implementation. There is additional confusion because some manufacturers use the term "balanced" for amplifiers that are "bridged"; essentially, two single-end outputs operated in opposite polarity. The main reason for this is to produce twice the output voltage (and thus four times the power -- IF the power supply etc. supports it!) using the same voltage rails (and they can re-use the amplifier driver and output stage designs). Like other quasi-differential circuits, the amount of noise and distortion rejection depends upon the implementation.

The higher second harmonic distortion can make the sound "fuller" or "louder" (the latter is especially true for subs when the second harmonic is much more readily heard than the fundamental***) but you are hearing distortion, not the original signal.

HTH - Don

*** Note in subs, and in speakers in general, the distortion is more from the driver (speaker) than the amplifier. Speakers usually generate an order of magnitude (10x) or more distortion than the electronics and, except for rare balanced designs, are single-ended drivers.

 

[Ron Resnick]

You are confusing the signal and distortion. Differential circuits cancel even-order distortion terms. The signal itself is not affected, except that it has less distortion (and noise, due to both the additional 3 dB SNR provided by differential operation and the rejection of other "external" noise sources). Any even (and odd) harmonics in the signal will still be there.

. . .

The higher second harmonic distortion can make the sound "fuller"

. . .

I think this is why fans of SET amplifiers would generally not use balanced cables (assuming their equipment supported true differential signal handling) and would prefer to retain that second harmonic "distortion."

 

[DonH50]

The SET amplifier generates the distortion; whether you use a balanced cable or not after that no longer matters, save the potential for noise rejection. I would not bother with balanced cables on a SET, or really in most home systems, as the advantages are not generally required. And, it is real distortion, not something enhanced or obviated by a balanced (differential) cable as you seem to imply. I think you have the impression that differential circuits intrinsically "take away" something from the music but that is not the case; all they remove is extra noise and distortion. If implemented correctly. I could as easily make the argument that single-ended designs mask some of the microdetails in the music and blur transients. For audio circuits I would bet the big differences among components have much more to do with design and implementation details other than the difference between single-ended and differential topologies for the majority, probably the vast majority, of systems. If you have a high-noise environment (which may be more common in these days of dimmer switches and many other noise sources in the home) or have a ground loop, differential may help, but otherwise it is probably a wash.

This is not even a topic of debate in most systems because the benefits of differential circuits go well beyond the distortion and dynamic-range improvements. They also inject less noise into power and ground and are less sensitive to noise from power and ground, typically enable higher slew rates and greater bandwidth with less rail voltage (saving power), etc.

 

[microstrip]

I think this is why fans of SET amplifiers would generally not use balanced cables (assuming their equipment supported true differential signal handling) and would prefer to retain that second harmonic "distortion."

We have now three entities in the system contribution to sound quality - the differential outputs, the cable and the differential input.

SET users usually have not problem handing differential signals - they can use input transformers. In some applications they are are better suited than active stages - they offer very good common mode rejection ratio vs frequency, galvanic isolation, no power consumption and and immunity to very-hostile EMC environments. Besides their limited bandwidth can also be a bonus. Some SETs already have them at the input, wiring a XLR connector to them is an easy and perfect job! But yes, some users will object to using balanced because they consider that the circuit generating the negative phase of the output balanced signal changes the sound quality.

BTW differential mode input does not cancel the existing even harmonics. All circuits add distortion. When we say that "Differential circuits cancel even-order distortion terms" it just means that the added distortion due to differential input will not include even order terms, but the odd order terms will happily be added. And real life is not quite this perfect - the even order do not cancel, they are just attenuated. In some sense, real performance of a differential stage is harder to predict than that of a single ended one. This means that, as most of time, the final result is mostly due to implementation, not to the magic properties of modes.

 

[andromedaaudio]

Do balanced audio cables tend to suppress second harmonics more than single-ended audio cables?

Im not an expert on audio waveforms but you could have a point there.
It would also explain the appeal of analogue tape / records , its hidden in harmonics /overtones

 

[DonH50]

Not technically sound but whatever... It ain't the cable, it's the circuit.