Wondering whether your LCD2.2 is good or bad will lead to Audiophilia Nervosa.  And that's not a healthy condition.

I don't worry about it too much.  It's good to me and I'm currently satisfied with it.  I trust my ears to know that it doesn't completely suck.  If someone has a better LCD2r2 than mine that doesn't make mine worse.  One way that I judge the value of gear to me is on my personal goosebump scale.  Music played using certain gear is able to give me goosebumps as I listen.  Better gear on that scale gives me more goosebumps.  That measure has lead me well as I've tried to find gear.  It hasn't lead me astray yet.  My LCD2r2 rates highly on my goosebump scale.  To me it's a good headphone.  I know and recognize its faults.  Its faults do frustrate me at times.  But it gives me goosebumps and good listening enjoyment.  And that's good value to me.  I'm on the lookout for a headphone that is technically better but that headphone also needs to rate very highly on my goosebump scale.  It's not easy to find a headphone like that.

I think this is good advice. I have something like the goosebump scale and the LCD-2.2 has always scored very high on that. I'd call it the "fuck yeah" scale. The result of the very unscientific comparison of the LCD-2.2 with the HD650 was that the former resolves like a muhfucker, as does the latter. Both resolve more than the HE-500 I have, I think. I'd say my LCD-2.2 is roughly = to my HD650, though the HD650 might handle congested passages a bit better. I'd need to listen more to figure that out. Listened to both out of my UHA-6S MKII with GO450 as DAC. Low-gain in each case. But there are a lot of things I'm not controlling for, so my impressions are worth very little.

Ok, this is good to know. I've wanted to ask about gain settings but was worried it was n00bish. When I'm monitoring the dB level (with just an iPhone 6, but I've no idea how precise that is - my suspicion is that it isn't exceedingly so), I usually max out in the high 80s. Sometimes I might push it into the 90s, but not for long. I was operating with the idea that you'd up the gain setting only if you ran out of gain on the low setting. Usually, I don't push the dial much past noon (if I do) on low gain with the HD650. If I engage the high gain setting, then the dial would hover around nine - sometimes past, sometimes before.

Use high gain on those HD650s, set them free!

I'm going to go ahead and ask the n00b question:  How should one choose the gain setting on an amp for the HD650?  Is it a tradeoff between more gain is better until the volume knob is so low that channel imbalance rears its head? I have a Magni 2 (non uber, but has a gain switch)...

I'm going to go ahead and ask the n00b question:  How should one choose the gain setting on an amp for the HD650?  Is it a tradeoff between more gain is better until the volume knob is so low that channel imbalance rears its head? I have a Magni 2 (non uber, but has a gain switch)...

not picking on you lmader, but going to poke some fun at this common question.

ok, this is the advanced pyrate method for determining optimal gain switch settings. Use at your own risk. I will not take any responsibility for misuse or abuse of this method. This method only works for male geeks. The following equipment is required:

1. Hardwood seat stool approximately 80 cm high
2. Sound Level Meter with max SPL capture mode
3. Tripod for SLM positioning
4. Darts varying in range of 14 to 32 grams
5. Dartboard
6. 8.8 Kg sledgehammer

Position the hardwood seat stool in the center of a room, maintaining a 100 cm sphere of clearance in all directions excepting the floor.

Mount the SLM on the tripod, positioning such that the SLM microphone is 100 cm from the stool, aimed at the stool, at the same height as the stool.

Set the SLM for A-weighted, Fast response, Max SPL capture mode.

The inquisitor now positions themselves such that they are on the opposite side of the stool away from the SLM. Now the inquisitor places their [redickted] on the stool and pounds it with the 8.8 Kg sledgehammer.

Note the maximum SPL captured on the SLM. This should be in the range of 100 to 120 dBA.

Multiply the SPL by the 4th root of 2 and divide that result by 5.

Using that result, pick a dart whose weight most closely matches the result. Should be in the range of 14 to 32 g. Standing at regulation distance throw the dart at the dartboard and score.

Add 19 to dartboard score and then divide by 10. Noting the knob positioning of 1 to 10 following the olde analog clock notion of 1 = 7 o'clock, 5 = 12 o'clock and 10 = 5 o'clock, adjust the gain knob to the position most closely matching the last computation.

set the amplifier gain switch to the lowest setting. Plug in headphones. Listen to programme material. If sound level is too low and the gain knob greater than 5,  adjust the gain switch to the next setting. If the sound is now too loud, adjust the gain knob downward to a comfortable setting.

how should one choose the gain setting on an amp for the HD650?

You'll have to think about headphone specs, linear drive need, dynamic capability of the phone in question

Well I was asking specifically about the HD650 headphone...
Are there any generalizations, like, do higher impedance cans generally do better with gain, etc.  Anyway.