TPA7498 amp suitable PSU for modding

Hi.
I have purchased a TPA7498 based amp and I try to re-use what I have laying around where possible so looking to see if this PSU is suitable.

I salvaged a few of these from when we had a telephone system upgrade at work.
They are Siemens PSUs and look to be very well made.

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As can be seen they are 54v output so..

Firstly are they suitable as an audio Power supply and if so what is the best way to reduce the output voltage?

Is putting the output throught a buck converter a no-no?

TIA

Anthony