looking for a replacement for a broken power brick - the values seem confusing

Oh an effects unit? As in for audio?

While the supply in your photo is 9v AC, (at approx 700ma) you may be able to use a 9vdc supply as well.
Back in the 80s, switching regulators were way more expensive so many power bricks were AC and the regulation was inside the device itself, which started with rectifying the AC to turn it into DC.
This also means many things can use a DC power supply in its place.
HOWEVER, I'd recommend an AC brick regardless, as DC switch mode power supplies (like that multi select one you mention) often put out a lot of electrical noise, which may impact signal quality if it's for audio equipment.

Forget my bullcrap. Here's a near identical replacement 9VAC 1A

You'll need to swap the plug from the old one onto it, or find one similar with the 3.5mm plug

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