Hi Max ,
I was very impressed with THS4081 at your suggestion . What a jewel ! Thank you! I am the retired designer for deHavilland and have been monkeying with OP AMPS for 20 years and I would like to tag my observations near your posting and I hope you don't mind . My application is in my own Metronome DAC as a buffer and in my Model 222 tape playback preamp, as a head amp ( gain of 4 to 8 typically) in front of the 12AX7s.
I prefer bipolar (BIP) generally over FET . I value transparency, balance , a warm sound, and delicate and sophisticated highs. I made an "A" list and "B" list and "C" list .
************** A LIST ****************
THS 4081 BIP . Transparent , full bodied , highs sing --voices float like angels up to the ceiling , really faultless. Has replaced AD 8597 in my mind. My personal choice. Tried THS4061 . Sounds rather gray compared to 4081 ....Don't bother.
OPA 827 FET . Dynamic , balanced , transparent , vivid without aggression. Best FET I know of --does what OPA627 does , but more and better. A wonderful device ,but does not sing on top like the THS 4081 . Not a sin of commission , but just not its nature.
ADA4004 BIP . Reminds me of THS4081 , perhaps a bit rounder and a bit slower. But a beautifully balanced and sweet musical amp. I could live with it .
AD8597 BIP Transparent and much like THS4081. I found it to be a bit light in the bass and always wanted more out of it , but it was my top choice. And I selected it over any FET but wanted more . And along came THS 4081.
AD744 FET Has been described as an "electrostatic sound " . I found it to be fast, transparent and sweet . But it put my attention on the highs and edges of the sound much like the 6922 tube . I prefer tubes like 6SN7 . But a very fine device !
************ B LIST ***************
OPA 627 FET Needs no introduction. Is on the B list only because OPA827 does what it does better with no downside.
AD4627-1 FET Nice amp . Maybe not as sophisticated as A list .
LME49990 BIP Very competent and transparent . I think its the best of the LME amps that I listened to. Somehow failed to grab me emotionally. Which is my general feeling about National Semiconductor amps ...
LME49710 , LME 49710HA . A bit bright especially the HA . Failing to grab me also applies.
************ C LIST ******************
BURSON V6 Classic . I tried the V6 briefly and the sound was good , however the pins on the Burson are approx. .025" in diameter where the industry standard for pins is in the range of .019" to .021" . They stretched and loosened my Mill Max sockets permanently and I may have to replace them . This was very disappointing and I sent the V6 units back.
OPA 602 / 604 FET . Big furry chocolate sound . My friend Sy , who hates anything even suggesting bright sound loves them . Easy to listen to , not terribly sophisticated .
OPA 134 FET Maybe the best old school BB below OPA627 . More accurate than OPA602/ 604
OPA 227 FET I don't remember , but probably like 134.
OPA 1611 BIP Failed to grab me . Not overtly bad .
OPA1655 FET Failed to grab me . Not overtly bad.
OPA891 BIP I had high expectations for this one after seeing the specs. but it turned out to be like LME49990. Left me cold especially in comparison to the THS 4081.
AD845 FET Nice chip , a bit crude .
ADA4898 BIP Very vivid and well balanced . I felt there was a bit of steelyness in the mids. Not a bad device.
LM6171 MC 1456 . Too many acid trips ago to recall them clearly , but I believe mechanical sounding and failure to grab.
LInear Technology LT1122 , LT1056 , LT1128 , LT1360 , LT1793 . As a group I thought some were very nice but at the end of the day , the HF character was always a bit unsophisticated.
Well, that is what is in my box of op amps , new and old.
Cheers.
Kara
