Balanced headphones, the Blockhead, and Electostatics vs. Dynamics
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JML

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I'm not sure this belongs here or in the amp section, but figured it has more to do with cans than amps.

After listening to the Blockhead & balanced HD-600 yesterday, re-reading the new Stereophile review, but not yet plowing through the HeadRoom information, I started to wonder. Could the vaunted transparency and low distortion of electrostatics somehow be more a product of their wiring -- i.e., the lack of a common return, than what we've presumed to be the cause (the driver design)? The electrostatics I've seen and used all had DIN 5-pin plugs, which means no common return for the circuit, right? Left and right, + and - for each, and a ground. Until the Blockhead, were we all missing something that may be obvious, but only retrospectively?
 
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jopi

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I'm not an expert, but I thought balanced equipment makes sense only when all components are balanced starting from the source all the way to the speakers or headphones.
What I've heard is, that electrostatics sound very good regardless of whether you have a balanced or unbalanced source.

And even the Stax's amps, I don't think those are balanced amps, are they?
 
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JML

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The standard headphone jack and plug has only three connectors -- right +, left +, and a common negative return from both drivers. I'm no electrical engineer, but look at your speakers' cabling -- there are separate returns for both channels, right?
 
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Nezer

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Quote:

Originally posted by JML
The standard headphone jack and plug has only three connectors -- right +, left +, and a common negative return from both drivers. I'm no electrical engineer, but look at your speakers' cabling -- there are separate returns for both channels, right?


Sure, it would be inconvienient and expensive to share...

However, they are usually joined inside the amp so they, in fact, do *usually* share a common signal return.
 
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Matt

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...very much thinking the same thing (the "lack of a common return" issue) in relation to the fact that I hear my Staxs as the most channel separated I've yet heard. The lack of a common ground thing was my theory, but obviously that's not possibly it. Is it possible, though, that the common ground meeting sooner, closer to the transduction stage, in "regular" headphones causes some sort of channel interference? Is that even possible? It seems like it would have to warp time or something do affect something that's already happened (i.e. those electrons have already passed through the transducer and they've already made their sonic mark).

- Sir Mister Matt
 
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jopi

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The little that I think I know is, that with a balanced system you have a separate plus and a minus cable for each channel to transmit power. You've got a separate ground for each channel on top of that to reduce hum and noise.

With an unbalanced or single ended setup you've got only one line for each channel and the voltage difference between the line and common ground (shared by both channels) transfers the signal for each channel. In this case any ground noise will affect line quality since it's part of data.

Again, I'm no expert by any stretch of imagination, but it doesn't really matter where in the chain of equipment you connect right and left channel grounds to make the whole balanced design collapse. I guess there is some equipment that produces balanced output out of unbalanced input (I believe the Sony SCD-1 SACD player does it that way and is therefore not considered a true balanced player) and perhaps that's what the Stax amplifiers are doing. Perhaps somebody can enlighten me on how that could work. How can split up a common ground into two separate grounds?
 
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Matt

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HeadRoom got on the front page of Stereophile this month, and in the article (about the venerable BlockHead), Tyll describes the common ground phenomena. Very interesting.

- Sir Mister Matt
 
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jopi

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I'm eagerly waiting for my copy, it hasn't arrived yet.
 
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Quote:

Originally posted by Matt
HeadRoom got on the front page of Stereophile this month, and in the article (about the venerable BlockHead), Tyll describes the common ground phenomena. Very interesting.

- Sir Mister Matt


big congrats to headroom!
 
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I mentioned this to Tyll and got a chuckle from him.

I know that the Blockhead represents the design philosophy of completely isolating the stereo channels.
This is done right down to having separate chassis and power cords for each channel.
Doesn’t the addition of crossfeed seem like blasphemy after going through all this trouble?
I put it to him this way.
“I don’t get it. You went to the extreme in separating the channels (in the Blockhead) only to muck it back together with crossfeed in the end.”
I got a smile out of him.
 
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At the DC show, Tyll was talking about a balanced Airhead for Etymotics. If he pulls that one off...
 
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I haven't seen the Blockhead yet, but from what I've heard crossfeed is established by connecting a cable between the two sound boards and you can still get a true balanced design by unplugging that cable.
Can anybody confirm that? (I'll see for my self next month).
 
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jopi

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Quote:

Originally posted by Hirsch
At the DC show, Tyll was talking about a balanced Airhead for Etymotics. If he pulls that one off...


Where do you get a balanced portable source?
I guess you could use two identical portable players, use a special cable that taps into one channel at each player, connect it to two airheads and only use one channel in each and feed it separately into the right and left Etys.

The biggest trick is to hit both play buttons on the players at exactly the same time.
 
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Hirsch

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Quote:

Originally posted by jopi


Where do you get a balanced portable source?
I guess you could use two identical portable players, use a special cable that taps into one channel at each player, connect it to two airheads and only use one channel in each and feed it separately into the right and left Etys.

The biggest trick is to hit both play buttons on the players at exactly the same time.


Given that Tyll said little more than the one sentence, I have no idea what he's planning.

However, what I'd do is not bother with a balanced source. Gear the amp to a PCDP with optical output, and include DACs with the amp. With the source optically isolated, you could keep the channels completed separated electrically, each with its own battery pack...
 
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You don't need balanced equipment all the way through to enjoy balanced interconnection's benefits. What I'm going to describe applies only to interconnection, and not to things like driving headphones or speakers.

The purpose of balanced interconnection is to reject common-mode noise that may be injected into the interconnect between two components. That is it. Everything else is a byproduct of the implementation. However, those byproducts can be beneficial:

1. XLR connectors used for balanced are more mechanically secure and positive than RCA connectors.

2. XLRs make ground before signal, and break ground after signal, so you can hot-plug and -unplug XLRs with no pops or funny noises.

3. XLRs provide a way to separate chassis ground from signal ground, unlike RCAs, and so can pretty much guarantee freedom from ground loops and associated noises, provided the balanced I/O on interconnected equipment is properly implemented (ie. no pin-1 problems). You also don't have to monkey with the shield/ground to filter off RF noise since the chassis shield is kept separately.

4. Commonly, balanced interconnections are driven differentially, ie. the positive signal on pin 2 and negative on pin 3, so you gain some extra SNR. Differential connections are not necessary to get balanced's benefits however, only balanced common-mode impedances. For example, I'd still get as good noise-rejection if I just drove pin 2, and left pin 3 alone, and made sure pin 2 and pin 3 impedances to ground are equal (balanced).

Some people believe that components have to be internally differential to take advantage of balanced. This is completely false, as the differential summing has to be done right at the inputs for the balanced connection to do any good. If not, then you can introduce common-mode noise into the component where it can use up valuable headroom by making the amp amplify and pass it along. Not to mention all the extra trouble CM noise can cause inside a component.

As far as the Blockhead and other differential output amps are concerned, I don't think it matters so much that they are balanced as much as they are differential output. That's because headphone input impedances are probably not balanced, and you lose out on noise-cancellation. Having a separate return may be useful if crosstalk is a perceptually important spec. I don't know if it is.

Does it make sense for the Blockhead to have such heroic channel separation, only to "muck" it up again with a crossfeed? One way to look at it is that it gives HeadRoom the option of only putting in the crosstalk they want, and not have to deal with any parasitic crosstalk.

--Andre
 
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