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Sennheiser HD 800 Redux

The Monkey

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"Drain wire" always makes me think of that Dilbert cartoon with the boss emptying the bit bucket.


Also, that's not what I was taught -- that's more to prevent ground loops (my understanding -- could be wrong -- wouldn't mind knowing the reasoning behind that).  My knowledge comes from my dad, and my dad's business was satellite communications, and two-suitcase satellite telephony (80's), so a lot of systems had to be "standalone".  Unfortunately, I never fully understood the difference between star ground and daisy chain ground, so I will admit that I never "got" grounding schemes.

Well the common mode rejection applies with no ground as well.  It's the difference between the two conductors that matters so any interference will be applied in equal amounts to both conductors and thus cancelled out.    



You're right.


I just conducted a thought experiment, and if you only look at the headphone cable and headphones, and treat the amplifier as a black box, then as long as you don't have a DC offset (which you don't want anyway for a variety of reasons), you're right, it "doesn't care", and should by its very nature be symmetrical, and cancel out common mode interference.


Huh...now I gotta rethink why they use balanced cables on microphones so avidly.

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Well, microphones (at least those not powered) deliver fairly low level signals. Any RF interference could be problematic.  But the RF induced voltage/current into the mike cable would have the same polarity on both conductors. In other words the received radio signal is in-phase on both wires, or is in common-mode. If the mike is a balanced emitter of signal into a differential amp on the receiving end (or the primary of a transformer), then that differential amp input is only seeing the difference in voltage between the two conductors. The common-mode (in the same polarity on both conductors) RF signal is rejected by the differential input of the amp. (Common-mode rejection)


So, mikes use blanced signal trasmition for is common-mode rejection capability to rid signal of induced noise on long cable runs. (Not only RF from radio, but RF from flourescent lights and refridgerator motors as well.)


But with headphones, the high signal levels and low output impedance of the amp make developing an RF signal on the wire much less of a problem. Balanced is use on headphones so that you can rid yourself of cross-talk from the common ground with normal headphone wiring. Also because you have two amps slewing in opposite directions, you effectively double the slew rate of your electronics. Unfortunately, it also doubles the output impedance of the amp, so it lowers the damping factor. Lastly, it tends to cancel out some of the even order harmonic distortion products of the amp. To me that's why it's kind of stupid to build tube balanced amps that have amp stages for both + and - channels. But we're getting way off topic now.

Edited by Tyll Hertsens
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Twice the voltage would help as it offsets the natural cable loss.  Mics also follow the same basic line as cartridges so more voltage means more problems.  Nothing that can't be over come though but most are also balanced as in there are just two conductors for the signal. 


I do agree with Tyll that some balanced amps make no sense at all and could never surpass a properly done SE unit.  People want tube amps for the "tube" sound and running a quad of single amps will not give you that.  Working on the Stax side also spoils as those are true balanced amps where the channels are linked internally and there is no individual drift between the two outputs.  I really like the idea to use Susy on these newer SS amps as it just improves their performance so perhaps it is time to do something similar to a tube amp... 


As for going off topic, isn't that what we always do?  :) 

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There are a couple out on loan right now. I am of course hoping that the people who have them buy them, but in the event that that does not happen, we can do a little loaner program. Just PM or email (my user name at ecpaudio.com) me. Dibs to people who might want one permanently, but I am happy to send them around to anyone willing to cover shipping expenses.

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A UK member posted this on the ECP thread, so I guess Doug can do it:


Doug made a 220-240VAC DHSA-1 for me last year and jumped thru hoops to comply with the strict European Union regulations - use of lead free solder being one such requirement. He's a genuinely lovely guy to deal with and the DHSA-1 combines the best of solid state to sound 'tube' like but without the euphonics associated with thermionic gear.

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None of that is really needed for small scale production or a one off piece but following what the stupid people in Belgium say can't hurt. 


As for 100V, it would be easy enough to order a transformer with 100V windings or just taps.  The PCB would have to be changed or simply bypassed as the current voltage selector wouldn't work but it's a minor issue.  Doug might have to look into some gold anodizing though for the Japanese market...  :D

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I've long since disabused myself of the notion that audio is subjective, and that I need to hear things to know whether they are good.  You guys know what's good, and you share that info.  People do not seem to listen, which is stupid, but you share it nonetheless.  One of my first posts here I asked which Stax amp to buy, and you all said "Blue Hawaii".  You were right, of course, and history has clearly demonstrated that.  The only better amp is a better Blue Hawaii.


So is this L2 the HD800 amp to buy?  Shipping things is a fucking hassle out here, and I don't intend to barter around. I don't want to plug them in and love what I hear, but always know that I should be enjoying it less than I do because I obviously have the wrong gear.  That's what I do now.  You all know what I'm talking about.


Here are my requirements for an as yet unpurchased amp:


1) It needs to have some provenance.  I won't buy an amp from someone more than two degrees of separation from me (i.e. either I personally know he's awesome because I met him, or one of you knows he's awesome and I know you.)

2) It needs to happily drive my HD800s.  Single Ended is fine, but in a perfect world it would be balanced.

3) It needs to be sturdy enough to get boxed up carefully every year or two and moved across an ocean.

4) It needs to be unique in a way that transcends fungibility.  This probably means handmade.


A few things fit that bill more or less -- the aforementioned Balancing Act, a good GSX, something Naaman built, etc.  This L2 has me super intrigued, though, as some of you guys really seem to like it.  I know you all don't waste time with budgets, preferences, flavors of months, or practical concerns of any sort.  So what say you, collective -- is the L2 the amp?

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I quite like the L-2 but with the HD800 I have a complaint and that's to do with the top end.  Set the amp to high impedance (as it should be) the top end is squashed lacking both extension and presence.  This extends down into the midrange and makes it less "there" than it should be.  This is why I use the amp on the lo setting as it opens up the top end quite a bit but it's not as extended as the Dynalo (aka GS-1 type amp) with an impedance adapter. 


The HD6xx (built from different parts but 650 drivers) I have here is just fine though and with plenty of top end.  It's odd but should be noted as I'm not really a fan of extended treble though it should be "correct", what ever that means. 


Outside of this I do like the L-2 quite a bit.  It lacks the presence and 3-D nature of even a basic Stax rig but that's more a transducer issue and something the Dynalo is also guilty of.  It pretty much lets the nature of the source and the transducers stand out (as an amp should) and doesn't sound overblown and bloated like so many of the OTL amps.  The bass might even be a bit on the lean side neutral but I'll take that over exaggeration every day. 


The build quality is outstanding and the minimalistic look is very cool.  I was just giddy when I saw the small amber LED on the amps front panel... it's just perfect.  :)  Then there is just the utter silence of the amp, no hiss, no hum... no nothing.  Welcome change from ohh so many dynamic amps.  I also like the tube choice and the side product that tube rolling really isn't possible, which is a good thing. 


For me this would be a choice between the GS-X Mk2 and the L-2 and you can't really go wrong with either. 

Edited by spritzer
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Thanks, gents, that's all excellent news.  I'm glad you're pleased with yours, Jacob.


Birgir, I appreciate your thoughts.  Your thoughts on build quality especially, as I know you've been inside every amp under the sun.  The pictures I've seen of the amp all look stunning, and Doug's a great dude.  


As to the top end, that's a complaint I've heard levelled by a few folks I trust.  Tyll is adamant that a little bit of acoustic damping helps out, and I know you have had luck with an impedance adapter (albeit on the low setting.)  


In any case, super cool amp.  I think I'ma get one. 

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If somebody gave me $15K to get an amp for my HD800s with the proviso that I must return all unspent money and could not ever sell the amp, I'd buy an L-2.  I might try to get Doug to do a one-off "L-2 SE", but would get an L-2.


Fortunately, I have a DSH-1 and it's right up there.

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