[MRC001]

  Also, is it safe to assume that headphones have varying efficiency at different frequencies? Would this explain why planars seem to sound more full with more power? I.e. that a more powerful amp can handle less efficiency at lower frequencies?

Some headphones do, but the LCD-2 do not. If a headphone has flat frequency response it means its sensitivity is the same at all frequencies. But its efficiency might not be the same at all frequencies - it might not have a flat impedance curve. However, orthos (including the LCD-2) do have a flat impedance curve, so their efficiency curve has the same shape as their sensitivity curve.
 
Consider the LCD-2: it has flat impedance vs. frequency and also has flat sensitivity vs. frequency. Thus it should require the same power to produce any frequency at the same level.

 

[Androb]

   
Little Dot VI+ - If these had a UK supplier I'd own one already (might take a gamble)

You can't go wrong with that amp. It's amazing!

 

[d marc0]

I can only afford a Schiit MAGNI right now.
I hope it's good enough for the LCD v2.2.
Has anyone tried this amp with LCD?

 

[Loquah]

  Some headphones do, but the LCD-2 do not. If a headphone has flat frequency response it means its sensitivity is the same at all frequencies. But its efficiency might not be the same at all frequencies - it might not have a flat impedance curve. However, orthos (including the LCD-2) do have a flat impedance curve, so their efficiency curve has the same shape as their sensitivity curve.
 
Consider the LCD-2: it has flat impedance vs. frequency and also has flat sensitivity vs. frequency. Thus it should require the same power to produce any frequency at the same level.

 
OK, thanks. I wasn't sure if impedance vs frequency was directly applicable to efficiency as well

 

[jodgey4]

  I can only afford a Schiit MAGNI right now.
I hope it's good enough for the LCD v2.2.
Has anyone tried this amp with LCD?

As far as I know, it has the most power of any amp in that price range. The LCD-2's are best paired with an amp that can put out between 1 and 4 watts... though these cans are generally forgiving on ideas such as synergy. I'd suggest saving up for something that can do those cans justice. 

 

[MRC001]

   
OK, thanks. I wasn't sure if impedance vs frequency was directly applicable to efficiency as well

I believe they're related just not directly, based on my basic understanding of EE. EE gurus correct me if I'm wrong:
 
Consider a hypothetical headphone with flat frequency response and impedance of 50 ohms at 20 Hz and 100 ohms at 1 kHz. The flat freq response means voltage sensitivity is the same at all frequencies. Yet impedance at 20 Hz is half what it is at 100 Hz.
 
Suppose we give this headphone 1 V at 20 Hz and at 1 kHz and see how much power it draws. At 20 Hz, R is half what it is at 1 kHz, so it draws twice the current. Power is i^2 * R, so twice the current squared is a factor of 4, times half the resistance, is twice the power. This this headphone is half as efficient at 20 Hz as it is at 1 kHz.
 
Or do the numbers we get the same result: the headphone is half as efficient at 20 Hz as it is at 1 kHz.
At 20 Hz: i = V / R = 1 / 50 = 0.02 A. P = i^2 * R = 0.02^2 * 50 = 0.02 W.
At 1 kHz: i = V / R = 1 / 100 = 0.01. P = i^2 * R = 0.01^2 * 100 = 0.01 W.
 
With the LCD-2, both the sensitivity AND the impedance curves are flat vs. frequency, so its efficiency must be flat vs. frequency as well. Edit: this is an oversimplification because it ignores HRTF. A headphone with subjectively "flat" frequency response must follow the HRTF curve which isn't flat so the headphone cannot have a flat sensitivity vs. frequency response.

 

[Loquah]

 
I believe they're related just not directly, based on my basic understanding of EE. EE gurus correct me if I'm wrong:
 
Consider a hypothetical headphone with flat frequency response and impedance of 50 ohms at 20 Hz and 100 ohms at 1 kHz. The flat freq response means voltage sensitivity is the same at all frequencies. Yet impedance at 20 Hz is half what it is at 100 Hz.
 
Suppose we give this headphone 1 V at 20 Hz and at 1 kHz and see how much power it draws. At 20 Hz, R is half what it is at 1 kHz, so it draws twice the current. Power is i^2 * R, so twice the current squared is a factor of 4, times half the resistance, is twice the power. This this headphone is half as efficient at 20 Hz as it is at 1 kHz.
 
Or do the numbers we get the same result: the headphone is half as efficient at 20 Hz as it is at 1 kHz.
At 20 Hz: i = V / R = 1 / 50 = 0.02 A. P = i^2 * R = 0.02^2 * 50 = 0.02 W.
At 1 kHz: i = V / R = 1 / 100 = 0.01. P = i^2 * R = 0.01^2 * 100 = 0.01 W.
 
With the LCD-2, both the sensitivity AND the impedance curves are flat vs. frequency, so its efficiency must be flat vs. frequency as well.

 
Ah, my confusion was that I don't think I've ever seen a graph of efficiency versus frequency. Or is it called something different?

 

[SilverEars]

 
I believe they're related just not directly, based on my basic understanding of EE. EE gurus correct me if I'm wrong:
 
Consider a hypothetical headphone with flat frequency response and impedance of 50 ohms at 20 Hz and 100 ohms at 1 kHz. The flat freq response means voltage sensitivity is the same at all frequencies. Yet impedance at 20 Hz is half what it is at 100 Hz.
 
Suppose we give this headphone 1 V at 20 Hz and at 1 kHz and see how much power it draws. At 20 Hz, R is half what it is at 1 kHz, so it draws twice the current. Power is i^2 * R, so twice the current squared is a factor of 4, times half the resistance, is twice the power. This this headphone is half as efficient at 20 Hz as it is at 1 kHz.
 
Or do the numbers we get the same result: the headphone is half as efficient at 20 Hz as it is at 1 kHz.
At 20 Hz: i = V / R = 1 / 50 = 0.02 A. P = i^2 * R = 0.02^2 * 50 = 0.02 W.
At 1 kHz: i = V / R = 1 / 100 = 0.01. P = i^2 * R = 0.01^2 * 100 = 0.01 W.
 
With the LCD-2, both the sensitivity AND the impedance curves are flat vs. frequency, so its efficiency must be flat vs. frequency as well.

Yes, since R is constant since the impedance is flat throughout the spectrum.  That means it only depends on voltage even for efficiency, although V^2.  This all depends on if voltage is constant at all frequencies.  
 
What I'm not understanding is the FR graph not being flat, why is that? 

 

[MRC001]

  Yes, since R is constant since the impedance is flat throughout the spectrum.  That means it only depends on voltage even for efficiency, although V^2.  This all depends on if voltage is constant at all frequencies.  
 
What I'm not understanding is the FR graph not being flat, why is that? 

Unlike loudspeakers, a headphone with subjectively flat response does NOT have objectively flat response. Because the headphone is attached to your head it has to compensate for sounds traveling through your head and bypassing your ears in ways that actual sounds in the real world don't. That's called the HRTF curve. Essentially, the headphone has to have a response that is the opposite of the HRTF curve in order to sound subjectively "flat" or neutral to the listener.
 
That means a headphone with subjectively "perfect", neutral flat response (the LCD-2 is close to this) does NOT have a flat sensitivity vs. frequency curve. Its sensitivity is different at different frequencies, and since the LCD-2 impedance is actually flat, its efficiency is NOT flat. Thus it requires more power at some frequencies than others.
 
Some loudspeakers also need to have non-flat response in order to have flat response at the listener position. For example, Magnepan 3.6 speakers have a response bump at 50 Hz. You place them the right distance from the back wall so the back wave is 180* out of phase with the front wave which cancels the bump. If you measure them near-field, you see a big bump at 50 Hz, but if you measure them far-field at the listener position you get flat response (if they're correctly positioned). Similar concept as headphones with HRTF corrected response, just a different application.

 

[HeadphoneAddict]

  I can only afford a Schiit MAGNI right now.
I hope it's good enough for the LCD v2.2.
Has anyone tried this amp with LCD?

 
I think you will enjoy it as long as your DAC is better than the Modi DAC (which is slightly lacking detail and energy vs an AE D1 or uDAC-2 SE).

 

[d marc0]

I think you will enjoy it as long as your DAC is better than the Modi DAC (which is slightly lacking detail and energy vs an AE D1 or uDAC-2 SE).

Thank you! I'll check them out...

 

[Poladise]

  ^^^    Lyr with Amperex tubes.    I had the original tubes and swapped them out a couple of days ago and oh. my. lord.....

 
What was the difference you noticed?
 

   
Little Dot VI+ - If these had a UK supplier I'd own one already (might take a gamble)

You can't go wrong with that amp. It's amazing!

 
Yeh, I bet it is. I've just become a little paranoid about shipping tube amps overseas. I'm very close to ordering one though.

 

[PTom]

  So the updated list of the most widely recommended amps for the LCD 2 within different price ranges is:
 
Below $2000:
 
- Auralic Taurus
- Beta 22
- Burson Soloist
- Burson Conductor (DAC/amp)
- Bryston BHA-1
- Decware Taboo MK II/MK III
- M2tech Marley
 
Below $1000:
 
- Audio GD SA31SE/MFB 6/Master 9
- Audio GD NFB 28 (DAC/amp)
- Centrance DACmini (DAC/Amp)
- Lake People G109
- Little Dot  MKVI+/MKVIII
- Meier Concerto/Classic
- Nuforce Icon DAC (DAC/amp)
- Schiit Mjonir/Lyr
- Violectric V200 
- Yulong A18
 
Below $200:
 
- O2
- Schiit Magni/Vali
 
As mentioned before, I'm looking for the most widely recommended amps for the LCD 2. Any more suggestions? Are there any in the above list that should be removed since they are not universally praised with the LCD 2 or are uncommon?
 
Update
 
Added: 
 
- Bryston BH1
- Auralic Taurus
- M2tech Marley
- Yulong A18
- Decware Taboo MK II/MK III
- Nuforce Icon DAC 
- Centrance DACmini (DAC/Amp)

Based on the above nominations, I've started a poll to find Head Fi's favourite amp to drive the LCD 2.
 
To vote in the $200-$1000 category click on the following link:
 
http://www.head-fi.org/t/716576/head-fis-favourite-amp-for-the-audeze-lcd-2-200-1000-poll
 
For the $1000-$2000 category click on the following:
 
http://www.head-fi.org/t/716577/head-fis-favourite-amp-for-the-audeze-lcd-2-1000-2000-poll

 

[vkalia]

  What was the difference you noticed?

 
I didnt do an A/B comparison with specific songs, so can only provide general impressions, based on long-term listening at different levels before and after.   
 
With the Amperex, the Lyr started sounding more like a single-ended-triode tube amp - voices had a fullness that sounded closer to live than recorded, instruments gained a presence that they did not have before.  I am guessing the lower mids gained some.    In short, the music has gained more "weight", realism and greater dynamic impact/slam.    
 
I am actually quite surprised - i was expecting a much smaller difference (I am the guy that typically takes all the talk about huge differences between amps, DACs, cables, etc with several grains of salt).

 

[G600]

   
Would you like to elaborate on what you did? Was it difficult? Expensive? And what types of improvements did you get?
 
Thanks.

Hello, and apologies for late reply.
 
Yes it was quite painful. Not that difficult but it requires patience and care. The soldering job is not a problem, but unscrewing and tearing the amp's PCB down is not easy.
 
After that you can replace the 8*330 Ohm 5W resistor, which are very poor. I chose Kiwame, they are well built, heavy and sound excellent.
I've also upgraded the 4 Wima MKP coupling caps for Audyn true copper caps (decent prices, good reports on the net). You can also choose Russian NOS paper in oil caps. Just increase the capacitance for a slightly better bass response, but beware of the space inside the chassis (some caps are huge).
You can find some tweaks and reviews on the MK VI's thread, and I'll post some photos some day.
 
For the improvements, unfortunately I've done the 2 tweaks at the same time, so dunno who's who.
The VI's big soundstage became bigger, more air in the stereo image, more defined and better bass. The neutrality of the circuit is still there, but everything is more natural, more defined and refined. The highs are less dry, and more detail retention. And finally there was an increase in dynamic.
It's indeed a big big improvement in sound quality, affordable, and with no drawbacks for me (the tweaks stays at your own risk). One MUST give it a try before selling the amp, or ask Sword Yang at Little Dot to build a custom MK VI+ (you just send him the parts).
And the differences in tubes are more obvious.