[zhgutov]

Yes, seems like an often discussed and in part cloudy topic. My original question was concerned with a USB DAC with single-ended outputs only (Chord Hugo 2) being hooked up to the SE inputs of the Violectric HPA V281 amp, then taking its balanced output to feed the Sennheiser HD 800 S.

The question was whether the V281 is a fully balanced amp as per category 1 in the a.m. posts by @EagleWings, which should make full use of the four amps in the V281. Unfortunately, there are not many DACs with balanced out (@Pharmaboy), especially not among the quasi-mobile ones; for sure Hugo 2 is to be seen as a TOTL DAC. Hints as referred to above (@lithiumnk, @Pharmaboy) do indeed indicate the V281 to be category 1. Thanks also to the other contributors (@rhern213, @LCMusicLover).

I used the words hints, indicate etc with a purpose - no clear-cut statement yet. Took a look at the V281 manual, too. Guess auditioning = musicality will have to decide over technicalities before a purchase ...

Seems like cross-thread discussion here
V281 is "1". It can take SE or balanced input signal, and output both balanced and unbalanced.

 

[Pharmaboy]

Seems like cross-thread discussion here
V281 is "1". It can take SE or balanced input signal, and output both balanced and unbalanced.

The real question in this discussion is whether all 4 amp sections of the V281 (which the manual describes as "4 Discrete-design power amps with 8 transistors per channel") are used when a single-ended input feeds signal to the V281 (whether the SE or balanced output is used by the headphone).

1. One possibility is that 2 of 4 internal amp sections are used when the SE input is connected; and all 4 internal amp sections are used only when a balanced input feeds signal to the V281. If this is true, than the V281 w/2 amp sections would be equivalent to the single-ended V220 in power output and sound quality.
2. The other possibility is that all 4 amp sections are in use regardless of which input (SE or balanced) is used.

I can't find the answer in the manual...

 

[zhgutov]

The real question in this discussion is whether all 4 amp sections of the V281 (which the manual describes as "4 Discrete-design power amps with 8 transistors per channel") are used when a single-ended input feeds signal to the V281 (whether the SE or balanced output is used by the headphone).

1. One possibility is that 2 of 4 internal amp sections are used when the SE input is connected; and all 4 internal amp sections are used only when a balanced input feeds signal to the V281. If this is true, than the V281 w/2 amp sections would be equivalent to the single-ended V220 in power output and sound quality.
2. The other possibility is that all 4 amp sections are in use regardless of which input (SE or balanced) is used.

I can't find the answer in the manual...

All 4 amps are used if you use balanced headphone output.
2 amps are used when you use SE headphone output.
It does not matter if you feed balanced or unbalanced signal.

 

[Pharmaboy]

How do you know this? Do the circuit diagrams in the manual support this?

(I can't read them...that's why I ask)

 

[zhgutov]

Do the circuit diagrams in the manual support this?

Yes.

Moreover, you can feed the same level to the balanced and unbalanced input and get the same level output.
And in all cases you can use both SE output. One is in phase, another is out of phase.
That's why it should work like I described. No way to be different.

 

[EagleWings]

Then, the amp falls in the category 2 in my list. Meaning, it is not a differential design, where in it would take a SE signal and use all 4 amps and output a BAL signal. Instead, it seems to use a circuit at the output stage to split the signal to create a Balanced output.

 

[zhgutov]

Then, the amp falls in the category 2 in my list. Meaning, it is not a differential design, where in it would take a SE signal and use all 4 amps and output a BAL signal. Instead, it seems to use a circuit at the output stage to split the signal to create a Balanced output.

http://violectric-usa.com/download/Balanced Headphone Amplifier Explained.pdf

 

[Pharmaboy]

http://violectric-usa.com/download/Balanced Headphone Amplifier Explained.pdf

Thanks, but I struggle to understand the pdf. This why I ask dumb questions (my IQ is apparently allocated to different topics/areas, not electrical engineering!).

 

[zhgutov]

Thanks, but I struggle to understand the pdf. This why I ask dumb questions (my IQ is apparently allocated to different topics/areas, not electrical engineering!).

I suppose, this means V281 is fully balanced ("1" in @EagleWings classification).
It can use 4 amps for both SE and balanced input signals.

 

[BLacklWf]

I think there is a confusion on what 'Balanced' means for the rest of the audio world vs the Headphone world, so let me take a bite at it. TLDR - please go to the last paragraph directly.

Balanced signal input is about the signal purity. Unbalanced inputs have 1 signal and 1 ground per Channel while as Balanced inputs have 2 signals and 1 ground per Channel. With Balanced, one of the signal has inversed (negative/reversed) polarity. The fact it involves the inversed polarity seems to confuse people - but the function of inversed polarity is totally different between Signal Input vs Amp Output. I won't be able to explain all the physics behind it for my lack of my knowledge, but the inversed polarity on Signal reduces electromagnetic noise. Also, 2x the signal = 2x the power which helps when a cable is over 50 feet. That's why the pro-aduio cables are almost always balanced because they tend to run long plus there are typically many electromagnetic nosie inducing equipments nearby. In the headphone world, due to the fact our input cables are much shorter (a few feet vs 50-100 feet) and typically not surrounded equpments using a couple hundreds or thousands watts, there isn't much difference as far as the signal quality wise on Balanced vs Unbalanced inputs. That's why some of the best audio engineers in the world are keep saying there isn't much difference between balanced vs unbalanced because they do not recognize 'Balanced' actually means something entirely different when it comes to Headphone output - that on the 3rd paragraph.

Balanced (or differential) amp output for speaker is about controlling the diaphragm better. It's not about signal integrity anymore. Using inphase and inversed polarities, the amp can push and pull the speaker diaphragm rather than push only/pull only - the difference is passively letting diaphragm return to its original position vs actively controlling diaphragm return - which in my opinion has bigger effect as the diaphragm gets heavier/bigger. Headphone diaphragms are much much lighter/smaller than speaker diaphragms and therefore some of the best audio engineers in the world again says there isn't much difference when it comes to headphones. But, clearly some headphones such as Sennheiser HD6XX benefit greatly from push & pull more than others in my experience. Inversed polarity is involved here but this actually has nothing to do with the inversed signal above. I will discuss it on the last paragraph.

On Headphone, Balanced outputs means one more thing. That is fixing one fundamental flaw of Unbalanced/SE headphone out. SE Headphone outputs have has 2 signals and 1 return per stereo. Which means the return paths are actually electrically shorted!! In my humble opinion, Headphone SE/Unbalanced output is just a purely stupid design which is just lazy, sucky, inferior, and just totally doesn't make any sense at all kinda of design. Why would anyone spend over $5,000+ on a headphone system and decide to short the wires together - that is beyond me! Ex) I spent $1,000+ on my input/USB cables so that they will totally shield out any electrical noise at the most microscopic level making my signal pure! Now, let's celebrate it by physically shorting two wires together!! F#%$!! Really... that's is totally beyond me... Again, sometimes even the best of the audio engineers are confused on what Balanced means for Headphone out and keep saying there is no difference between Headphone SE Out vs Headphone Balanced Out. One is Shorted and Other is Not!!! Duh!!! For Headphone, Balanced output means it's finally a proper engineering. On top of that a true balanced amp like V281 has differential design - therefore there is Push & Pull effect in driving the headphone diaphragm, but that's not what I'm trying to say here.

I just want people to know that Balanced Amp Output really has nothing to do with Balanced Signal Input. The inversed polarity for input is about the signal integrity. The inversed polarity of amp is about Push & Pull in order to control diaphragm better. On top of it, balanced outputs for headphone fixes the fundamental problem where the return paths are shorted otherwise. Someone may ask V281 has four amps (two amps for inphase and two amps for inversed), how does it then works with Unbalanced signals - where do inversed signals come from? The truth is that it flips and generate the inversed signals on its own - just like any non-headphone stereo amps do. Most audiophile solid state stereo amplifiers also have four amps, and they work perfectly fine with 'unbalanced' inputs just like V281 because the inverted signal is flipped by the amp regardless the input is Balanced or Unbalanced. Even when fed with Balanced signals, the amp only takes inphase signals and generate inversed signals on its own. The inversed input signal is only used to cancel the noise but not fed into the inversed amp. I said 'most' because there are amps which actually take the inversed signals from the balanced inputs, but to my knowledge those are rare and actually defeats the whole purpose of the balanced input design. The polarity inversion of the balanced signal input is about cancelling the noise and it was never meant to carry four signals to feed four separate amps - it was meant to carry two signals 'better'.

 

[EagleWings]

@BLacklWf , ^^^ this here is probably the best explanation I have come across on the subject. Thank you much.

Key-points from your post:
- The balanced signal that is fed as the input to an amp, is not the same as the balanced signal that the amp operates with (at least in most cases, as there are some exceptions, where the amp actually uses the inverted input signal)
- Regardless of the type of input signal (Balanced or SE), a fully balanced (differential) amp creates an inverted signal, which it works with in the amplification stage
- V281 is a fully balanced (differential) amp, regardless of the input signal (SE or Balanced), and so it belongs to the Category 1 in my list, as @zhgutov said in his recent post

Which brings us to the following key-points regarding DACs for the V281:
- When using Hugo 2 as a DAC to feed V281, the amp is operating as a fully balanced amp
- The performance of V281 depends on the quality of the input signal, regardless of whether it is SE or Balanced. So a DAC with a Balanced output is not completely necessary to get the best out of the V281
- Some DACs like Yggy, are known to output analog signal of better quality via the Balanced, than the SE output. In such cases, it makes sense to choose Balanced connection over the SE connection on the same DAC

 

[BLacklWf]

@BLacklWf , ^^^ this here is probably the best explanation I have come across on the subject. Thank you much.

Key-points from your post:
- The balanced signal that is fed as the input to an amp, is not the same as the balanced signal that the amp operates with (at least in most cases, as there are some exceptions, where the amp actually uses the inverted input signal)
- Regardless of the type of input signal (Balanced or SE), a fully balanced (differential) amp creates an inverted signal, which it works with in the amplification stage
- V281 is a fully balanced (differential) amp, regardless of the input signal (SE or Balanced), and so it belongs to the Category 1 in my list, as @zhgutov said in his recent post

Which brings us to the following key-points regarding DACs for the V281:
- When using Hugo 2 as a DAC to feed V281, the amp is operating as a fully balanced amp
- The performance of V281 depends on the quality of the input signal, regardless of whether it is SE or Balanced
- So to choose a DAC just because it can output a Balanced signal is pointless
- It is wise to choose the DAC based on its sound quality (and tonality), rather than its ability to output a Balanced signal
- Some DACs like Yggy, are known to output an analog signal of better quality via the Balanced output than the SE output. In such cases, it makes sense to choose Balanced connection over the SE connection on the same DAC

EagleWings - yes you've nailed my points! I could not have summarized it better myself. Just to add a few interesting tidy bits.. I have read V281 actually converts Balanced signals into Unbalanced signals, which is perfectly fine in my book because at the end of the day there are only Left vs Right signals. The purpose of Balanced signal is to send signals with less noise NOT to send extra signals. Fred who designs both amps and DACs clearly understands the both applications of the signal generation vs the signal amplification. I'm saying this because..

The other very well known amp designer made his balanced amp not to work with SE signals. I suppose he may think SE signal is not adequate for his balanced amp which makes me wonder if ever the inphase vs inversed signals differ for any reason (for most home application they would be spot on since signals travel like 3 feet in non-electromagnetic intense space) he would rather take the signals distorted as they are as his amp pushes and pulls the diaphragm.. rather than flip the inversed signals by the amp, which will sync both inphase vs inversed push and pull. Well.. some harmonic distortion may add to the sounds.. maybe he tried both and decided his ears like some harmonic distortion.. who knows?

The other very well known DAC designer refuses to have the internal balanced headphone output to his DACs saying his DAC is not balanced by design. I don't have expertise as to know if there is actually a balanced DAC by design.. So I'm not sure what his DAC lacks in order to have balanced headphone outs. But, most interestingly he has the balanced signal-outs but refuses the balanced headphone-outs! Perhaps.. he thinks amps use both inphase and inverse signals separately to drive the speakers... well regardless he already has both the signals! It really puzzles me because he is the best DAC designer of all time.. so who knows?

If someone starts to mention about the balanced grounds.. then the topic can get more complex.. but in my humble opinion the ground doesn't matter much vs how actual inphase/inverse polarity works (it doesn't even matter when the source is battery powered). But, I suppose someone can bring that or something else minuscules to say everything I ever said here is totally wrong.

 

[fdg]

Again some words about unbalanced and balanced signal.

In general it can be said that balanced signals are the better signals.
This is because of their nature.
Feeding unbalanced signals from one item to the other means that an electric signal is pushed from the transmitter to the receiver.
But the electrons which are in charge for this task like to go back to the transmitter because they are missing there.
And they do by using the screen of the cable.
That means that there is always traffic on the screen to accomplish equal potentials ( = ground) among all connected items.
And if some of these items are connected to different wall outlets with slightly differing potentials chances are high that his can be heard as hum.
Now imagine the same situation with balanced signals.
There is no need for the electrons to go back to the transmitter through the screen of the cable because they have a dedicated wire ( = out of phase signal) to do so.
And that means that there is no traffic on the screen – the cardinal reason for low(ered) hum !
Of course these effects are maximized for long cables – therefore professionals will exclusively use balanced signal lines, but also for 1-2 feet distances it is useful to drive them balanced.
Keep in mind:
- Only balanced lines will enable proper ground potentials
- Improper ground will generate crosstalk issues and hum

The features of HPA V281 concerning unbalanced and balanced signals:
The internal signal processing of V281 is unbalanced !
This is the only way to feed unbalanced and balanced input signals and generate balanced and unbalanced output signals.
The line-out circuitry and the headphone amps inside V281 are totally independent from each other and driven by a dedicated circuitry. That means that they will not affect each other.
For example you can feed an unbalanced signal and generate an unbalanced line-out signal and a balanced headphone signal simultaneously.
Or you can feed a balanced input signal and generate an unbalanced line-out signal and an unbalanced headphone signal.
Special function:
There are 4 headphone amps inside V281. These are left in-phase, left out-of-phase, right in phase, right out-of-phase.
They are connected to the 4-pin XLR headphone socket.
Further one phone jack socket is connected to the left and right in-phase signals and the other phone jack socket is connected to left and right the out-of-phase signals.
That means that two SE headphones will be driven by their own amps so there is no impedance mismatch.

Fully balanced amps:
These are amps where the internal structure is balanced, meaning they have two internal stereo paths: in-phase and out-of-phase.
They feature 4-way volume control and other 4-channels features.
If such gear is treated with unbalanced input signals only 50 % of the amp is active.
True “fully balanced” equipment is rare as there is no real profit to do so but lots of disadvantages.

Fully balanced D/A converters:
Such is simple as every better D/A converter chip offers balanced outputs.
This is an easy measure by the chip manufacturers to raise S/N ration.
All a designer has to do is to feed the signals coming from the D/A chip through some more or less complex electronics to the balanced outputs.
If the circuitry is a bit more complex (like inside Violectric / Lake People converters )
- a volume control is possible
- or different analog outputs levels whilst maintaining low output impedances
- or active unbalanced outputs which are derived from the balanced lines by using differential amps.

Cheers, Fried

 

[Fegefeuer]

I've referenced Fried's insight and explanations on the starting page. Will add the others as well. Please check page 1: technical insight and explanations by Fried Reim

 

[111MilesToGo]

Wow, what a lovely and lively discussion here, which started two pages back at https://www.head-fi.org/threads/vio...-durch-balanced.705318/page-248#post-14372270 and actually at
https://www.head-fi.org/threads/cho...official-thread.831345/page-898#post-14370938.

Thanks to all and esp. @fdg Fried Reim. Will have to digest first, being not a major in electronics...