Crown GPA-25 -- 1950s/1960s PA amp

[passaloutre]

Picked this up for a song at a local estate sale--I figured even if it was shot there'd still be enough tubes/iron to be worth it.

Anybody ever seen one of these? I can't find a schematic anywhere, but I assume it can't be too much different from other PAs of the day.

12AX7 - 12AT7 - 6C4 - 2x6L6GC with a 6CA4 rectifier

It's got 2 replacement electrolytic filter caps (Sprague Atom) dated 1964, so it's probably safe to say it needs new caps. Also the power transformer appears to be a replacement.

Just to try it out, I replaced one of the screw-on Microphone inputs with a 1/4" jack, jumpered the two mic channels, and played it with my guitar. It sounded pretty great cranked up, if a little muddy. Some nice blocking distortion makes for that good garage tone I love so much.

I had been thinking I'd rewire into something more guitar-centric, but I may just recap it, reduce some coupling caps, and call it a day.

[passaloutre]

The preamp and phase inverter arrangement seem not too dissimilar to this Bogen PA:

https://el34world.com/charts/Schematics/files/Bogen/Bogen_chb_50a.pdf

Big differences being my amp has cathode biased power tubes, and a tube rectifier. Some small differences in component values, but topology is essentially the same.

Any big changes you'd recommend for guitar use?