See, to drive the worst case Hifiman HE-6 to 115 dB (a reasonable level for a hard impact), you need about 2 W power, therefore ~130 mA at 15V (+/-7.5V) (2W) per channel. Almost all opamps cannot do this unbuffered. It takes just about every ounce of power out of BUF634. Of course you'll also need near zero output impedance too.
But to drive something easier like HE-500, you only need ~30 mA at 15V (600 mW), which quite a few opamps can manage without a dedicated buffer, but not that AD8597, which can only source ~18 mA. Some opamps can source more current at lower voltages, but it is not one of them.
care to show the Veff equation you used? Plain old RMS, yes? But we were talking about peak drive.
Any GSM interference issues of note? OPA209 was atrocious in this regard... I could grab OPA1611 for a spin, as well as actual AD797s.
Posting my recent opamp impressions:4898-weighty, thick, and rich, maybe not as much as 627. Organic sounding. Better blackground, than 209 but less detailed/resolving, less plankton. 209 digs deeper. Vocals less dry than 1611 but still a hint of dryness. A bit muddled at times, but still decent separation. Slightly bigger sounding bottom end.209-Analytical signature, digs deep. Easier to hear recording noise and artifacts. String plucks and applause is more thin and brittle. Slight haze/veil despite picking up tons of detail. More blended, less separation and articulation of dynamics. Overall less refined signature than the others. Vocals less dry but could also because it stands out less in overall signature which is more coherent and balanced than the others. Therefore, any vocal issues could stand out/apart less. I do think vocals are more liquid than the others in actuality on more listening. 4627-Better dynamics and note articulation than 209. Perhaps best macro and micro dynamic balance of the bunch w/ lots of clear inner detail. Excellent timbre! Clearer, blacker than 209 w/ better separation and imaging. Widest SS of all. Less recording noise emphasis than 209 but actually more resolving. Superior resolution, excellent spatial precision, best blackground, fantastic macro and micro dynamics. Most natural and accurate timbre. The clear cut overall winner.1611-Very fast, best of the bunch. Analytical type sig. Decent timbre, not as good as 4627 or 4898 though, better than 209. Not sure why, could be a minute extra bit of treble brittleness, ringing type treble sound. Driest vocals. Wider SS than 4898. 4627 has cleaner, clearer note articulation and more accurate timbre. 1611 might have sharper, more precise sound but less blackground and timbre is less accurate and fleshed out. Note: All opamps have more than sufficient run time w/ the exception of the OPA1611 which has the fewest by far.
