Stereomour for LOW EFFICIENCY planar headphones....?

[milosz]

There are now some headphones based on planar drivers - the Audeze LCD-2 and the HiFiMan HE-6 -  which are quite low efficiency as headphones go.  The Audeze LCD-2 needs around and amp that doesn't strain to deliver 1/2~1 watt into 50 ohms, and the HiFiMan HE-6 wants more, maybe ~2 watt capable amps, again at 50 ohms.  These headphones have been touted as, essentially, the best there is-see the HeadFi.org forums- and while opinions certainly differ regarding "best" headphones, there's no doubt these things are pretty wonderful. For example, the Audeze LCD-2, for example, does a better job at reproducing 300 Hz squarewaves than some tubes amps I've seen. LCD-2 is roughly +/- 0.5 dB from 10 Hz to about 2 kHz then +/- 2 db to 20,000.  Waterfall plot is basically perfect....  etc and so forth.

The Bottlehead Crack is nowhere near capable of driving these well, as you might imagine.  So I was thinking, maybe the Stereomour?

What kind of output is available connecting a 50 ohm load, I assume the best idea would be to use the 16 ohm tap?

[mrarroyo]

How about using the speaker out the Sex Amp?

[milosz]

SEX is probably not quite enough power for the HE-6.

[Paul Joppa]

We are looking at a SEX revision with a 32-ohm output, which should be able to provide 2 watts into 50 ohm headphones. The SEX amp has much less hum than is possible with AC heated DHTs such as the Stereomour, which is why I don't recommend the Stereomour for headphones in general.

The Paramount with 16 ohm output impedance will provide 2.5 watts into a 50 ohm load, and has DC heaters. It works well with the K-1000s, too.

[Doc B.]

We tried SEX with the LCD-2 and it was OK but the bass was soft. The only amp (so far) that I have heard make the LCD-2 have the punchy bass it was supposed to was a Benchmark DAC 1, which of course has a very low output impedance SS stage and probably gobs of feedback for a very high damping factor. So I think there will be some challenge to making a tube amp that will present the things the LCD-2 does better than other headphones without it being a pretty much LCD-2 dedicated circuit. I am not entirely convinced that it is the absolute best one out there (because like some very expensive speakers that are not so efficient, it may require electronics that are less than the best in terms of resolution) but it's a very, very good headphone with very impressive bass when the amp creates the conditions it requires.

All this said, the short answer about LCD-2s and impedance and tube amps is that I would try the lowest impedance output tap that I could get away with. I'd be more inclined to try Paramounts next time than Stereomour. In fact I may rig a pair with a headphone adapter cable for the Head Fi meet at Bottleheadquarters on March 5th, where I'm sure there will be quite a few pairs of LCD-2s.

[milosz]

Very interesting- both your comment and the fact that there's an upcoming Head-Fi meet there.

Don't forget to try the HE-6 on some of your amps, too.

[mrarroyo]

SEX is probably not quite enough power for the HE-6.

The production HE6 is much more efficient and easier to drive than the prototype HE6. I know because I had both side by side and compare them. A regular headphone amp producing at least 1 wpc (like the Musical Fidelity X-Can V2 or V3) is more than capable of driving the production HE6. Cheers.

[milosz]

While the XCAN is capable of running HE-6 pretty well, because it can produce better than 1 watt at 50 ohms, I still feel the SEX might fall short because I think it incapable of producing 1 watt at 50 ohms especially below 50 Hz. [I have an XCAN v3 and a pair of HE-6]

XCAN is a hybrid product, anyway- a tube voltage amp with solid state output stage- and I think we are here discussing TUBES.  (In particular I am interested in single-ended triode amps that can drive the HE-6 well.  I want to hear how the euphonic overtone "flavor" imparted by a SET would sound on the HE-6, and LCD-2.)

[Paul Joppa]

... I still feel the SEX might fall short because I think it incapable of producing 1 watt at 50 ohms especially below 50 Hz. ...

For the stock SEX, you are correct - probably 1/3 of a watt is all you'd get. With a transformer that has a 32 ohm tap, you ought to get 1.3 watts, and with a better (larger) output transformer it should go much lower than 50Hz.

That still does not address the output impedance question though. Does anyone have a link to impedance measurements on these planar phones? I'd expect, if they are low efficiency, they might have very flat impedance, in which case the parafeed capacitor can be optimized for that specific load.

[milosz]

All very interesting and informative.  I'm sure anyone looking to try a SET amp on their planar 'phones would find this information useful.

[mrarroyo]

While the XCAN is capable of running HE-6 pretty well, because it can produce better than 1 watt at 50 ohms, I still feel the SEX might fall short because I think it incapable of producing 1 watt at 50 ohms especially below 50 Hz. [I have an XCAN v3 and a pair of HE-6]

XCAN is a hybrid product, anyway- a tube voltage amp with solid state output stage- and I think we are here discussing TUBES.  (In particular I am interested in single-ended triode amps that can drive the HE-6 well.  I want to hear how the euphonic overtone "flavor" imparted by a SET would sound on the HE-6, and LCD-2.)

Well, it is all a matter of opinion and how we each hear/listen. You are entitle to your opinion and I to mine.

[milosz]

Hey, don't take offense! Um, the Xcan IS a hybrid amp, that's not an 'opinion' it's a statement of fact.

Maybe you're confusing my comment re: the Bottlehead S.E.X  amp with the Xcan?

Paul Joppa - the designer - has confirmed that the SEX amp can only produce about 0.3 watts into 50 ohms, which is clearly not enough to drive the HE-5, so that's engineering data, not opinion. The manufacturer of the HE-6 says that best results can only be obtained with amps capable of producing 4 watts at 50 ohms.  Since 0.3 watts is quite a bit less than 4 watts.... well, it's clear the SEX in it's current incarnation is not up to the task.

[Grainger49]

Guys! 

PJ did say that the stock SEX, intended for low impedance headphones.  From the product page they mention Grado (32 ohms) and Sony (? ohms).  But the impedance of the headset is only one factor, sensitivity is another, listening preferences are yet another.

PJ has also said that for "special needs" (my phrase) headphones a different transformer will match up and do the job.

I don't think mrarroyo meant that the X-Cans being a hybrid was opinion.  I believe he meant that the way we listen is a matter of personal opinion.  I listen to speakers that shouldn't be driven well in a larger room and I'm satisfied with the volume.  That is personal opinion.  Others say my system doesn't play loud enough and their system does.  That is personal opinion. 

So I am saying you don't know if it will do for you till you try.  You should be beating the bushes to find a SEX amp you can listen to.

[mrarroyo]

Guys! 

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...  I believe he meant that the way we listen is a matter of personal opinion.  I listen to speakers that shouldn't be driven well in a larger room and I'm satisfied with the volume.  That is personal opinion.  Others say my system doesn't play loud enough and their system does.  That is personal opinion. 

So I am saying you don't know if it will do for you till you try.  You should be beating the bushes to find a SEX amp you can listen to.

Exactly what I meant. BTW, I have been modifying the X-Can's for about 5 years thanks to the ideas posted by Mike (Pinkfloyd) at Rock Grotto so I know they are hybrids. Cheers.

[Spinifex]

... I still feel the SEX might fall short because I think it incapable of producing 1 watt at 50 ohms especially below 50 Hz. ...

For the stock SEX, you are correct - probably 1/3 of a watt is all you'd get. With a transformer that has a 32 ohm tap, you ought to get 1.3 watts, and with a better (larger) output transformer it should go much lower than 50Hz.

That still does not address the output impedance question though. Does anyone have a link to impedance measurements on these planar phones? I'd expect, if they are low efficiency, they might have very flat impedance, in which case the parafeed capacitor can be optimized for that specific load.

There are Headroom graphs for both the HE-5 and HE-5LE here:

http://graphs.headphone.com/graphCompare.php?graphType=7&graphID[]=2251
http://graphs.headphone.com/graphCompare.php?graphType=7&graphID[]=2161