Nice man, I am finding 13.24volts to be the absolute best with my Roc and LCD-2's....so you aren't far off from me.....and I tested a ton of different voltages.  
 
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currawong said:

Just thought I'd throw in that I have no complaints about my Phoenix/LCD-2 pairing.  I have, however, tweaked my system to be a little more lively, which works well with all my headphones. I've set the bias in the Phoenix to 14V, which is the lowest I want to go as lower makes the Magnums fatiguing and isn't going to benefit the HD-800s if I decide to compare them.
 
Just for fun, I plugged the LCD-2s into the Sparrow, and the result is quite good, all things considering.  The music comes as a wall of sound, and there isn't as much genuine punch in the bass and things get congested somewhat when the music gets busy, but it doesn't distort and is punchy enough.  If the LCD-2 weren't so damn big I'd have a good transportable rig with the combo.

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currawong said:

Just for fun, I plugged the LCD-2s into the Sparrow, and the result is quite good, all things considering.  The music comes as a wall of sound, and there isn't as much genuine punch in the bass and things get congested somewhat when the music gets busy, but it doesn't distort and is punchy enough.  If the LCD-2 weren't so damn big I'd have a good transportable rig with the combo.

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Great, that's the amp i'll be using them with. Am working hard to buy the lcd 2, and really can't afford a very expensive dac+amp.

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cya|\| said:

Great, that's the amp i'll be using them with. Am working hard to buy the lcd 2, and really can't afford a very expensive dac+amp.

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That can be taken care of down the track.

I don't find that the LCD2s are that hard to drive - any solid state amp that can drive the HD650/HD600/K701 will have sufficient output to drive the LCD2 to very acceptable levels.  The only real variable is trying to synergise the finer points to suit your personal preferences.  Two out of my five amps make the LCD2 sound amazing.  Both my full tube amps do no justice to the LCD2 whatsoever.

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sp wild said:

I don't find that the LCD2s are that hard to drive - any solid state amp that can drive the HD650/HD600/K701 will have sufficient output to drive the LCD2 to very acceptable levels.  The only real variable is trying to synergise the finer points to suit your personal preferences.  Two out of my five amps make the LCD2 sound amazing.  Both my full tube amps do no justice to the LCD2 whatsoever.

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Which tube amps are they?  Curious on the specs and ratings.

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tigzstudio said:

Which tube amps are they?  Curious on the specs and ratings.

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Cayin HA-1A, and MingDa MC84 - both are OT designs, both are able to drive speakers, the Cayin 2 watts into 8ohm and the MD 5 watts into 8ohms.  There is more than sufficient power and current drive to power the 50ohm LCD2s.  Both amps were my chosen amps for HD650 and K701 - but with the LCD2s - it relegated them into a mid-tier can with a massive soundstage - but mid-tier in terms of speed, slows and bottleneck the LCD-2, frequency extremes are significantly let down.

One for the techs out there...
From memory, the LCD-2s are 91db efficient. If this was a set of normal speakers, that figure would be a good thing (95db would suit my tastes better, however) Anyway, is 91db 'good' for a set of headphones? In comparison, how efficient are the HD800s? Does the efficiency of the headphone effect the amp/phone relationship in the same way as the amp/speaker relationship? If the headphones are too efficient, does the amp have a harder time keeping a 'grip' on them?
 
Supposing that 91db is efficient for a headphone, then the lower 'rated' output of some amps shouldn't be a big issue as long as they have fulsome current on tap, yes?

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tigzstudio said:

Nice man, I am finding 13.24volts to be the absolute best with my Roc and LCD-2's....so you aren't far off from me.....and I tested a ton of different voltages.  
 

 

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i saw in one of the Roc threads when people were starting to talk about adjusting the bias voltage...but what is that actually changing? is that changing how far into class a the amp is biased? 

 
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gogogasgas said:

One for the techs out there...
From memory, the LCD-2s are 91db efficient. If this was a set of normal speakers, that figure would be a good thing (95db would suit my tastes better, however) Anyway, is 91db 'good' for a set of headphones? In comparison, how efficient are the HD800s? Does the efficiency of the headphone effect the amp/phone relationship in the same way as the amp/speaker relationship? If the headphones are too efficient, does the amp have a harder time keeping a 'grip' on them?
 
Supposing that 91db is efficient for a headphone, then the lower 'rated' output of some amps shouldn't be a big issue as long as they have fulsome current on tap, yes?

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With all my amps, the LCD2 have the same overall sensitivity as the HD650 - similar degrees on the volume knob induces similar volume levels on both cans in all my amps.

 
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sp wild said:

 

With all my amps, the LCD2 have the same overall sensitivity as the HD650 - similar degrees on the volume knob induces similar volume levels on both cans in all my amps.

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Agree.
 
 
Take look on T1's spec, 600om. " they are efficient" quoted by many. In the reality, they are pretty hard to drive.
 

seamaster said:

 
Agree.
 
 
Take look on T1's spec, 600om. " they are efficient" quoted by many. In the reality, they are pretty hard to drive.
 

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The same spot on the volume might be being used for both the hd650's and the LCD-2, which represents the amount of voltage being supplied to the driver, but the LCD-2 is still drawing 6 times more current than the HD650's, which is 6 times the power

Wow! I didn't know that.
 
Kinda makes sense - because V=IR and increasing volumes is simple increasing amplitude - which is voltage in AC.
 
Still - how is it worked out that at the same dial position, the exact same voltage is being applied to 2 different cans - wont the varying the resistance affect voltage and current at a given level?

For simplicities sake I kept all that out lol yes the amount of voltage dropped across the headphone would change based on the output impedance of the amp and the impedance of the phone, but if you're using say a discrete solid state amp with output impedance below 1 ohm it's not going to vary much if at all.



Like I said I was just trying to keep things simple, and for approximations sake, a spot on the dial is for a given voltage output

Edit: I'm no EE though, but I do having a passing knowledge in electronics. If someone who knows more than I sees something wrong in what I wrote, please correct me

A few people are mixing a few things up here.

Most headphones define their "efficiency" (rightly) as the decibel level that can be achieved with a certain output which is defines in watts, or actually usually milliwatts, as we are talking about headphones. For example, the Beyer T1 has a specified sensitivity of 102dB at 1mW of power output.

Now, what determines how much power the amp can output is it's ability to deliver a certain amount of voltage AND current into the headphone. W = V * A - one watt (W) is the rate at which work is done when one ampere (A) of current flows through an electrical potential difference of one volt (V).

So if (and I am not sure its the case) the LCD-2's sensitivity is 91dB at 1mW, then the T1 would be 11dB more efficient if they were the same impedance. But of course they are not, and so what ultimately determines where the volume control will be set, as Soup pointed out, is how much power a given amp can deliver as different impedances. If an amp will deliver the same output power in milliwatts at every impedance, then the T1 will require less of a turn of the volume control than the LCD-2 will. But most amps deliver different output power into 600 ohms than into 60.

So unless you know a LOT about the amp in question, it's not simple to say headphone A will need this much volume and headphone B will need that much.

Your mostly right skylab, since sensitivity is defined as dB/mW and not dB/mV, which I think they should be, the impadance is already taken care of, because amplifiers don't output a certain amount of power for each notch of a volume knob, they output voltage, so current and therefor power are derived values. Because efficiency is defined in this way, having to turn the dial further does not mean necessarily mean that a phone is less efficient. It just means that it requires more voltage.

But i think at this point were pretty far off topic lol