Thanks for the analysis, Germanium.
- mystery opamp is the original NJM 4556A.
- no, no hardware changes between 48k and 96k.
- was cleaning home-lab and couldn't just throw out clipped opamps.
- decided to try soldering leads to SOIC stubs and test new lead-free solder-paste, just for grins.
- would also serve as "stock" reference."
Sony MDR-D777LP, Denon AH-D1001, MDR-SA1000, closed earphones, eh?
- closed get too hot for me.
- considering building simple buffer amp with Burr-Brown/TI BUF634 to use with old Sennheiser HD-414SL open headphones.
Just a few more experiments left with this SB0460...
- might try a trick I used when designing LNA GaAs MMIC parts, ten years ago, based on "close-field" electrostatic theory.
- when I finish calcs, will send modification to you for trial and analysis.
- considering playing with either Auzentech X-Fi Prelude or E-MU 1212M (balanced-out).
Doesn't look like they performed to bad at all really (the JRC part). Worked better at 48KHz than the LME parts I feel but the LME parts seem to do better at 96KHz.