Output Linearity 600 Ohm +20 dBu Residual Spectrum:
AD797 (noisefloor @ -130 dB, 2nd harmonic @ -89 dB)
AD823 (-110 dB, 2nd @ -53 dB)
AD825 (-108 dB, 3rd @ -49 dB)
AD826 (-108 dB, 3rd @ -47 dB)
AD829 (-125 dB, 3rd @ -68 dB)
AD845 (-110 dB, 2nd @ -79 dB)
AD8599 (-130 dB, 2nd @ -68 dB; lot of spurious harmonics @ -70...-80 dB)
OP275 (-118 dB, 2nd @ -52 dB)
Audio-GD OPA-Earth (-122 dB, 2nd @ -40 dB)
Audio-GD OPA-Moon (-115 dB, all @ -40...-50 dB)
Burson Audio Discrete OpAmp Mk II (-120 dB, 2nd @ -40 dB)
LT1128 (-132 dB, 2nd @ -75 dB)
LM833 (-120 dB, 2nd & 3rd @ -75 dB)
LM837 (-120 dB, 2nd @ -70 dB)
LME49860 (-123 dB, 2nd @ -90 dB)
SGA-HVA-1 (-128 dB, 2nd @ -110 dB)
SGA-LNA-1 (-136 dB, 2nd @ -64 dB)
SGA-SOA-1 (-128 dB, 2nd @ -60 dB)
SGA-SOA-2 (-128 dB, 2nd @ -62 dB)
Signetics NE5532 (-115 dB, 2nd @ -58 dB)
TI NE5532 (-115 dB, 2nd @ -59 dB)
TI NE5534 (-120 dB, 2nd @ -68 dB)
Sound Skulptor SK25 (-114 dB, 2nd @ -89 dB)
Sound Skulptor SK99B (-133 dB, 2nd @ -97 dB)
OPA211 (-129 dB, 2nd @ -80 dB)
MC33078 (-119 dB, 2nd @ -40 dB)
OPA551 (-115 dB, 2nd @ -64 dB)
OPA627 (-120 dB, 2nd & 3rd @ -79...80 dB)
OPA827 (-120 dB, 3rd @ -86 dB)
OPA2132 (-115 dB, 2nd @ -62 dB)
OPA2604 (-110 dB, 2nd @ -46 dB)
RC4580 (-118 dB, 2nd @ -55 dB)
TL071 (-115 dB, 2nd & 3rd @ -40 dB)
For +20 dBu the best opamps are bolded, also good-enough opamps have been underlined. For 0 dBU about the same opamps are having about the same place in the list. Interesting that solid-state "opamps" (SGA-HVA-1 & SK99 & SK25) are measuring extremely well and the well-known LME49860 (LME49720 and NE4562) is just a tad lower in performance. +20 dBU means lot of gain, so these opamps should perform admirable when used in voltage amplification gain.