I'm using a 1999 Headroom Maxed out Home to drive LCD-2 rev 2 phones. Audeze recommends 1 watt but I think that is more than than most people need because Audeze's assumptions are conservatively high. The LCD-2 is amazingly efficient for an Ortho, actually play slightly louder at the same voltage than the HD-600s. They're easy to drive and don't need much power, you want a super clean low distortion amp but it doesn't need a ton of power.
Audeze suggests your music has 60 dB of dynamic range. Sure you can invent sounds that have 60 dB or more of dynamic range but the only music I know of with 60 dB of dynamic range is something like the Carmina Burana or the 1812 Overture with cannons being fired. In this case if you listen with the quiet parts at 90 dB SPL the loud parts will make your ears bleed and possibly explode your head.
After saying that, Audeze provides a more realistic example: listen at 90 dB with 30 dB of dynamic range.
Power in dB is 10*log(ratio), here it's equal to 30 dB, so we have ratio = 1,000.
30 dB louder requires 1,000 times the power so that's 1 milliwatt to 1 Watt.
But listening with the quiet parts at 90 dB SPL is super freaking loud. Most people who listen that loud are listening to rock which has a lot less dynamic range (more like 12 dB instead of 30). So let's get realistic: suppose we listen with the quiet parts at 67 dB SPL and there's 30 dB of dynamic range.
Peaks will be 97 dB SPL.
The LCD-2 needs 1 mW for 90 dB, so for 97 dB it needs: 10 * log(x) = 7 --> x = 5. That's 5 mW of power. Five milliwatts. That's nothing!
Now if you really crank it up, suppose you listen with the quiet parts at 80 dB SPL, so peaks are 110 dB SPL. That's ear bleeding loud, but hey...
That's 20 dB louder than the reference 90 dB @ 1 mW, so we have:
10 * log(x) = 20 --> x = 100
So we need 100x more power, which is 100 milliwatts.
Still nowhere near 1 Watt of power. Any decent solid state headphone amp will put this out nicely, and most tube amps should too.
Of course the amp could run out of current and clip, so how much current would it need?
The LCD-2 has an impedance of about 50 ohms.
Power is current squared * impedance, so 0.1 W = i^2 * 50 --> i = 0.044. That's 44 milliAmps. Any decent solid state headphone amp should be able to do this no problem. Even most tube amps should.
Anyone feel free to check my math, but I can say the LCD-2 sounds absolutely freaking great with my Headroom Maxed out Home. It's a beefy little amp with super smooth yet detailed sound, ruler flat response with negligable distortion, perfect for high quality recordings of acoustic music. Those OPA627s are mighty smooth and clean and the little toroidal power supply shows nary a ripple on the DC. I'm not sure where it maxes out in power, but I've bench tested it to about 250 mW and 180 mA of current, at which it has no sign of clipping, all harmonics in spectrum at -85 dB or lower. That's way louder than I will ever need.
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