Preamp using MC33172N instead of OPA2134

The MC33172 may tolerate higher supply voltages but the Data Sheet specs are inferior to the OPA2134 in the areas that matter to audio. You can probably find a high-performance audio opamp that is rated for +/-22V supplies, but I'd look into regulating your +/-20V rails down to a lower voltage.

This is very bad advice, BUT... In my experience, Ti's products are very conservatively rated. The OPA2134 is rated up to +-18V, I'm pretty sure it will work fine at 20V.
EEeeek! Make sure you have some spares!

Can't believe no one mentions OPA2604 :confused:

Made for audio
drive 600ohm

opa604 2604 sound quality.png

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. . . Can't believe no one mentions OPA2604
A very good choice! I knew there were some suitable parts out there but I was too lazy to wade through several selection guides when I suggested regulating the supply rails down to lower voltages. I think there are one or two "high-voltage" parts in the (formerly) National LMExxxx series, and I believe the time-tested NE5534/NE5532 can live with +/-20V supplies. And, they are cheap and easy to get!