Concerning the Quad 306
With CR2 now a LM317, op amp controlling offset ( although not in audio path )
can be substituted for one with better specification such as LME49710
To my ears, a marked improvement over the TLC271. From one amp alone
( I usually use one 306 per channel ) I immediately noticed improved stereo separation
and better sound stage, similar to when a 303 is used instead of a 405.

The bugbear of all other attempts at improving the TLC271 namely turn on turn off issues
has now been solved. The cause being insufficient current delivery by the standard CR2
a J503

Cheers / Chris