Interesting. I tried the HD650 straight out of my iPhone 4 and if it had been a horse--I would have shot it. Out of the op-amp headphone feed in my Pioneer receiver, it really opened up, but the Lyr--well, the Lyr lights up the HD650 like the 4th of July. I started with some Amperex orange globe A-frames--and they have a nice warm tubey sound. I was so happy with that combination and was skeptical of tube rolling--so it took me a while to try anything else. I recently switched to the stock GE 6BZ7 tubes and was surprised at the brighter sound. The 6BZ7 tubes give the HD650 a little extra bite, although they don't sound quite as smooth as the Amperex tubes. You guys with Lyrs should mention the tubes you're using.
Yeah, I've been through great swaths of that thread and it's not exactly...uh, user friendly, or HD650-oriented. I'm also not looking to spend $100/tube.
There's already a nice 275 page thread on that topic. Have fun.
The A-frame Amperex OGs were also my favourite tubes for the HD650. All midrange tubey goodness that the HD650 revelled in. I felt like a lone voice in that thread recommending those tubes for the HD650. I had the fabled Lorenz Stuttgarts that I found less engaging with the HD650. They were good for the LCD-2 but even then, not deserving of the hype they generated. If you want a more balanced sound with excellent transparency, try out the Amperex Bugle Boys. These had wonderful synergy with the HD800 and with that headphone I found them similar to the Stuttgart signature but with better clarity. They're abundant so you can get them on the cheap. Beware of counterfeits though.