I've just figured out that these cans actually sound best with zero gain on my BCL Linear, but the knob turned up to 3 o'clock or so. For a long time I thought they needed high gain and low volume to sound best, but then realized that I was getting a bit of harshness and also a weird tingle in my right ear. I think this is a much better option.
Exactly my setting. I discovered this issue with my linear after few tests with the amp -5 years ago or so-. The gain, through feedback I suppose, is horrendous and put distortion that is noticeable with this cans. It doesn't matter. You put them on '3' and they sound wonderful (3 to 5, to the top, don't change volume, as you know. BTW it is the same setting for a variety of other cans like K712Pro, but this last one suffers even more with other problems).
There are few models in the market/(second hand?) that can offer this two things: supreme transparency, absolute supreme. Not as a super neutral or about clarity or full range. But transparency to the music intent. Few models let pass through what is that noise about, that vital information, and instead inform you about mike location, mixing decisions, or wonderful mistakes in your playback chain. It's all about the music for me (classical only). Second one is keeping quality in low-medium volume setting. The Beyer 770-250 can do that as well. Not many others. The AKG sings like nothing I have ever encounter. Many reports in the past said the next step up can only be Stax. Maybe I can test that assumption in the long future.
As an anecdote I had success powering them directly (in 2008, mind you) from a Sony VAIO laptop. Even more than with the Linear. Those laptops had fancy sound parts, some of them. And it seems that model sound chip amp delivered enough current. But there was, at the very limit of audibility, a white noise, a hum in the background, very very faint. Maybe the chip, maybe power lines, I didn't know, never cared.
I could find a NOS pair 11 years ago and I am a very happy owner since. I found and missed an opportunity shortly thereafter to purchase a second unit in a very bad old box, so even an older batch, not the final white/light copper/brown one.
I used them from time to time, to enjoy myself with that sparkling and magical midrange. Nowadays the K712pro enjoy more time on the head. But, sadly, I need a new/better fit amp for the AKGs. In the past not many amps where around, not many, that delivered more current, apart from voltage (I remember when the Beta22 was almost the default go-to for that feature). But after... 2012? or so, with the planars in the market, there are a lot of amps available that should driver them properly, in full capacity.
My new DT1990 (completely different thing) is well served from the Linear though.