What is balanced? What are balanced amps? Do they sound better? Discussion for noobs and boobs.

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Marvey, Dec 5, 2015.

  1. Marvey

    Marvey Loves sex and records

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    CEE TEE warned me that this issue would need to be clarified sooner rather than later...

    Balanced Lines / Differential Signaling

    Technically, "balanced" simply means two wires with the same impedance to ground. That's it. Think twisted pairs used for telephone lines or Ethernet. Differential signaling is where the two symmetric (out-of-phase to each other) signals are used with each leg. Differential signaling is often used on balanced lines, so for the sake of discussion and common use, let's say that the term balanced implies differential signaling.

    Figure 1: Four Pairs of Balanced Lines
    twisted.gif

    Balanced Bridged Amps
    Balanced bridged is two separate amplifiers with each amplifier powering one leg of the differential signal. It's output is balanced. Calling this arrangement "fully" (from beginning to end) balanced is acceptable. Examples of this include many car amps or pro amps (many of which have a balanced switch to turn a two-channel stereo amp into a more powerful mono amp), "balanced" four channel B22s, the old Balanced HeadRoom amps, HeadRoom GSX, etc. Balanced bridged amps have twice as much voltage swing, twice as much distortion, twice the output impedance, and theoretically four times the power (although it's more realistically like two times the power) and less environmental noise.

    Figure 2: Balanced Bridged Amp with Balanced Output
    Balanced.png

    Looking at the above, it should be clear that we can actually buy two Magni 2Us and stick them together to make a balanced bridge amp.

    Balanced Output Amps
    It is possible for transformer coupled
    tube amps to have balanced outputs because the transformers are inherently balanced. This can be done by leaving the secondary windings floating. DNA and EC amps offer balanced outputs. Also, circlotron output stage amps like the Schiit Ragnarok are inherently balanced.

    Figure 3: Balanced Output from Single Ended Transformer Coupled Amp
    800x600px-LL-7ae651df_y6g2aSzh.jpeg


    Usage of the Term Balanced
    1. ACCEPTABLE: That amp is not "fully" balanced (the implication is balanced from beginning to end). Although it's probably better to be more specific on the architecture and the outputs of the amp.
    2. NONSENSE: That amp is not "really" or "truly" balanced. Need to be more specific.
    3. PARTIALLY CORRECT: The BA is not a balanced amp. Need to be more specific. The BA has balanced inputs and balanced outputs. The amp is single-ended, not balanced bridged.
     
    Last edited: Jun 6, 2017
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  2. Marvey

    Marvey Loves sex and records

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    Discussion of Sonic Merits of Balanced Amps

    This needs to be discussed on a case-by-case basis. But in a nutshell, an amp should be chosen on its sonic merits and according to its maximum capability (that is, if there is a balanced option, use it)*. Balanced output by itself (in whatever way, whether bridged, transformer balanced, inherent to circuit, etc.), does not and should not mean shit in your consideration for an amp.

    Here is another way to look at it:

    Great balanced > Great SE >> Good Balanced > Good SE >> Mediocre Balanced >= Mediocre SE >> Crap.
    Pick the amp or DAC first without consideration of balanced or SE. A mediocre or shitty amp is going to sound mediocre or shitty balanced or not.

    *For example, if you purchased a Geek Out V2, and you did not utilize the balanced output, you did not maximize it's capability. There is also the assumption that you would be willing to fork out extra money for adapters, re-termination, re-cabling, etc.


    Case-by-Case Subjective Impressions

    With the above taken into consideration, let's discuss balanced output advantages in specific cases:
    • Geek Out V2 Balanced: Better macrodynamics, sharper attacks, less soft sound. Significant improvement with HD650.
    • HDVD600: Better soundstage layering, separation, depth, and imaging precision. Moderate** improvement with HD800.
    • Balancing Act: Better soundstage layering, separation, depth, and imaging precision. Minor improvement with HD800. Zero improvement with Grados.
    • Ragnarok: Significant improvement across the board. (The Rag's SE output relies on extra summing circuitry after the circlotron that reduces the power output and constipates the sound quality).
    **Still quite small in the overall scheme of things. See this: http://www.superbestaudiofriends.or...iscussion-for-noobs-and-boobs.733/#post-18959


    Balanced Inputs from Sources with Balanced Outputs

    We need to be careful with sources with balanced outputs. This is less of a concern now, but there was a time not too long ago that balanced outputs from from big name brand CDPs usually consisted of opamps tacked on to their single-ended outputs. Yes, I know horrible. But some homework should be done in the first place to make sure the balanced output of sources are not cheesed.

    This question comes about often because people are concerned that they make full use of their DACs with balanced outputs.

    This is something that needs to be taken on a case-by-case basis.

    I will answer specifically for Gumby. Gumby provides single-ended outputs in addition to balanced outputs. The only thing between the balanced outputs and the single-ended outputs is a pair of transistors to sum the balanced signal so nothing will be lost. The question then becomes this: Will that pair of transistors fuck up the sound of the SE outputs of the Gumby so much that I will want to use a fully balanced bridged mediocre amp over an awesome amp with only single-ended inputs?

    Note that some single-ended amps like the BA offer to take balanced input via transformers (that sum the balanced input to SE for the amp). In this case, the question becomes this: "Will those transformers sound better than the pair of transistors / internal summing circuit in the Gumby?" I can tell you that Atomicbob measurements of the Gumby with a Jensen ISOBOX showed significantly more distortion in the bass, but yet he preferred the sound. (The distortion behavior is expected because the Gumby's out is so hot at 4Vrms and near the limits of those specific Jensen transformers.) So really, I think it's a matter of different.

    Bottom line is that the better amp is still going to sound better regardless. With a properly implemented source, the differences between balanced out and single ended out are not going to be significant. Choose the better sounding amp regardless of topology and don't worry about the chain being "fully" balanced throughout.

    To put it another way, in terms of discernible differences:
    Headphones > Amps > DACs > Source balanced out / SE out

    And if you are still stressing out about it, I will build you a box with bigger balanced to SE transformers that will handle the hot Yggy/Gumby outs just so you can bypass the two summing transistors inside those DACs. At the cost of $999. Just so you can get a "different" or perhaps maybe "better" sound.

    One Final Consideration

    Another way to frame the balanced vs SE argument (which is really balanced transmission vs. balanced bridged vs. balanced push-pull vs. SE) is this: How many great SE amps will you miss out on if you have only considered balanced (whatever implementation of balanced that may be).
     
    Last edited: Jun 6, 2017
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  3. PoochZag

    PoochZag The Shadow knows - Friend

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    This is really helpful, thank you @purrin. I just got into buying balanced gear (Mjolnir 2, and now a Gungnir) and it's nice to know exactly what I'm (over?)paying for. The satisfaction of plugging in those nice, beefy 4-pin XLR's makes it almost worth it on it's own :p
     
  4. Judeus

    Judeus Almost "Made"

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    interesting topic

    yes "balanced" is a word often thrown around when in reality it means a lot of different things

    to me the real meaning of balanced is dual mono and fully differential, for example the headamp gsxmkII
     
  5. Tyll Hertsens

    Tyll Hertsens Grandpappy of the hobby - Special Friend

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    This is a hot potato, me thinks. Mainly because I think the term "balanced", as we tend to use it, is technically incorrect.

    To some extent, I'm responsible for this word showing up in the world of headphones with the introduction of the Blockhead Many years ago.

    Bottom line: I don't think we can ever use this word in a technically correct way as it applies to balanced headphone amps. I guess I have to side with Steve E.'s take on the subject...technically...that "bridged" is the more correct term---but that horse left the barn long ago.

    To the best of my knowledge, balanced is a term to describe signal transmission lines that have transformers at both ends. In this case, you simply cannot put a signal on one of the conductors without having an equal and opposite signal appearing on the other line. It's also called a "current loop," as the current in the transmission line flows back and forth essentially trapped in the system. These current loops also typically had matched impedances at both ends so that it was very efficient.

    The word root also appears in the word "balun", which is a device that takes a single-ended and converts it into a balanced signal. IIRC, typical TV baluns convert 75 Ohm single-ended signal into a 300 Ohm balanced signal to be sent up twin-lead 300 Ohm cable.

    [​IMG]

    Differential signals are similar, but typically are associated non-transformer transmission using differential input and output circuits. They act quite a bit like transformer terminations, but are active devices rather than passive transformers. Most balanced transmission lines exist to reduce electromagnetic interference for long cable runs and/or efficient transmission with little loss---in the case of impedance matched lines.

    In any case, since we're not using the term correctly, it's probably a good idea to develop a mutually agreeable definition for ourselves.

    I'm not sure Purrin's statement that you get double the distortion is quite correct either. While odd harmonics might add, even harmonic distortion will tend to cancel in balanced amplifiers.

    My sense of it is that the greatest advantage of balanced amps is that it reduces cross-talk between channels as they no longer share a common ground.

    I'll add that single-ended tube amps with transformer outputs can technically deliver a balanced output, but calling it "fully balanced" is a misnomer in our world. That scheme, though, allows the arguably desirable euphonic even-order distortion not to be canceled out as it would be in a "fully balanced" amplifier.

    Thanks for bringing the subject up, Marv. You're right, it will likely be a bit of a mess.
     
  6. Marvey

    Marvey Loves sex and records

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    Someone added a quote from Doug. I deleted it. It was informative, but it was an opinion that pertained more towards design of amps (differential vs. 2x SE) and thus outside of the intent of this discussion. Maybe later.
     
    Last edited: Dec 5, 2015
  7. The Alchemist

    The Alchemist MOT: Schiit - Here to help!

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    I understand "Balanced" means two wires with the same impedance to ground. But what advantages sound-wise does it have over non-balanced amps/DACS?
     
  8. schiit

    schiit SchiitHead

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    Tyll, "balanced" and "differential" have been used interchangably in audio since before I can remember. The Sumo Andromeda II (introduced 1989) we referred to as a "balanced, differential" amplifier, for double the confusion. Other, earlier Sumo products were referred to as "differential." Theta always used "balanced" from inception—since 1985.

    Marv, "bridged", at least in the speaker amp community, is a different (and usually derogatory) term used for stereo amps that have been "bridged" to create a monoblock, either through the use of a bridging adapter (typically an op-amp phase splitter) or by driving one side of the amp through its feedback network. Both produced compromised sound, for obvious reasons.

    In our view, "balanced," and "differential" are equal, and refer to an amplifier that drives both the positive and negative outputs actively, in inverted relative phase. "Single-ended," to us, means an amplifier that drives only the positive outputs actively, with the negative being a common ground return. There is no judgement involved in either, as Marv is 100% correct in saying, "choose the sound, not the topology." There are advantages and disadvantages to both approaches.
     
    Last edited: Dec 5, 2015
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  9. The Alchemist

    The Alchemist MOT: Schiit - Here to help!

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    I know my Schiit Uberfrost and Valhalla 2 sound amazing, and they are not balanced - so I have to agree with the quote "choose the sound, not the topology."
     
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  10. Tyll Hertsens

    Tyll Hertsens Grandpappy of the hobby - Special Friend

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    Thanks Jason, it's nice to know I was not a complete idiot when I made the BlockHead. And thanks for your thoughts in this thread

    Curious to know if I'm on target with the thought that the term balanced came first with transformer coupled transmission lines; and differential came along with solid-state differential amplifiers?

    For others, here's a schematic of a balanced transmission line.

    [​IMG]

    You can see that the conductors in the transmission line have no connection to ground at all (in this case), so I'm thinking that the concept of equal impedance to ground is not really a good definition as it doesn't really address the characteristic of rejecting common mode signals.
     
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  11. Marvey

    Marvey Loves sex and records

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    The impedance to ground in the transmission line above is equal - effectively infinite.

    Also, there is this case below. Still balanced lines, but resistors to ground.
    bal2.png
     
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  12. SKiring

    SKiring Friend

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    Excellent write up Marvey.
    Just something of interest about this:
    I can say that while I entirely agree with the HDVA600 and HDVD800 benefiting from going balanced, when adding the Bimby up the chain the improvement was so much bigger that going balanced was less of an issue. I have been lucky enough to do a direct comparison to Gumby balanced vs. Gumby SE vs. Bimby and honestly at this point I found the differences between SE and balanced far less noticeable. While I was one of those guys consistently telling any owner of one to definitely find a "balanced" DAC.

    My best anecdote of not listening to HF or people that just write stuff without thinking from http://www.headphone.com/pages/balanced-headphones-guide:
    If this is what you expect the sonic differences are, the disappointment might kill you...
     
  13. Tyll Hertsens

    Tyll Hertsens Grandpappy of the hobby - Special Friend

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    Ha ha ha ha! I think I wrote that. Friggen marketing people, ya just can't trust 'em.
     
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  14. Marvey

    Marvey Loves sex and records

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    Thanks for stating this. You are right. The differences are not huge. I changed my second post a bit "HDVD600: Moderate** improvement with HD800."
     
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  15. Tyll Hertsens

    Tyll Hertsens Grandpappy of the hobby - Special Friend

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    Sure, you could also have center tapped transformers on the balanced line, and yes, the impedance to ground should always be the same, but it seems to me that's not the defining characteristic of a balanced line.

    And, FWIW, I'm not trying to be contrarian here; I'd like better clarity in my head on the subject so I appreciate the dialog. But if we're nit picking to develop a clear definition the details are important.
     
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  16. thegunner100

    thegunner100 Hentai Master Chief

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    Thanks Marv, it's great to have a post that we can direct people to when they have questions about balanced topology in dacs and amps.
     
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  17. Marvey

    Marvey Loves sex and records

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    For the purposes of this thread, balanced = differential in the scope of noobs and boobs trying to make amplifier decisions. I don't want to get too myopic on this.

    I know. :D There are some balanced headamps that do the opamp phase splitter thing from a SE input. There is another amp that I know of that will sum the balanced input so 2-gang pot can be used, and then do a phase splitter to feed the bridged amps.

    UPDATE: added "Balanced Inputs from Sources with Balanced Outputs" at the bottom of the second post.
     
    Last edited: Dec 5, 2015
  18. Marvey

    Marvey Loves sex and records

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    I figure this will save me some time in the future. I occasionally get messages along the lines of this: "Someone in Chinese audio forum says that BA is not balanced. But I know it is balanced. Please confirm." And then I need to make the effort of typing up everything that I just did in posts #1 and #2.

    The "balanced" thing goes along the same lines as the "43 driver IEM" or the "36bit -226db dynamic range on FFT DAC" thing.
     
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  19. GoldfishX

    GoldfishX Acquaintance

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    Just for the record, I blame David Mahler for the curiousity bug: :Violin:

    From his HD800 write-up on HF: "BALANCED MODE: I've found that the HD800 scales particularly well in balanced mode - better than most other headphones. With the HD800 in balanced mode, I clearly notice an added sense space and dimension." But in looking the only balanced amp he used with the headphone was the 307A/Pinnacle (the Manley Neo Classic he uses for the HD800 was SE only). So that was probably more a commentary on the amp itself, not the headphone...

    I imagine this had a similar influence on other people.
     
  20. murray

    murray Friend

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    There is also the problem where people are convinced that "balanced betters/demolishes/destroys SE" on a given amp because they are not aware that the balanced output has a higher level (typically +6dB). Or they are aware, but don't take the necessary steps to eliminate this as a point of difference. Many folks are not prepared to match output levels exactly (with tests tones and a measuring device) for critical comparisons. They will rely on their ears to "match" the levels approximately, but rely upon same ears to judge the balanced output to be far better. Even a small increase in level will provide a perceived advantage in sound quality (an old hi-fi salesman trick).
     

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