[sdiy] Op amp notes

[Paul Higgins]

I know this has been on the list before in some other incarnation, but 
I've never seen it asked in this way.

What are people using for opamps:
1) in general purpose high-level audio circuits (e.g. EQs, summing 
amps)?
2) in critical low-level audio circuits (e.g. mic preamps, guitar 
pre-preamps/boosters)?
3) in CV-type circuits?

Also, are the low-offset opamps worth it (for CV applications), or are 
the parts specified in so many of the classic designs still basically 
good enough?

I know that some folks are partial to those opamps used all over the 
Mackies (NJR4560/4580?).  I've used an OP-27 a couple times for guitar 
pre-preamp designs, along with a FET for isolation (the pre-preamp 
mounting right in the guitar).  And years ago I saw a mod for one of 
the cheesy PAIA tube preamps (yeah, I'll admit I own one too) that 
replaced the 5532s with OPA-2604s, I think.  I never tried it, so I 
can't comment on whether the mod was worth doing.  (The mod was 
extensive and swapped out a lot of other things in the circuit as well. 
  Last I checked, it had disappeared from the net).

-PRH