Baffled by a switch mode power supply problem.

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I have the entry level Stax 252S energizer/amp and L300 headphone system.
Sounds great, but I would like to replace the el-cheapo 12 vdc wall wart that powers the 252s energizer. Also would like to eliminate having to use the 120vac to 100vac transformer, that now converts my USA mains voltage to Japanese 100vac mains voltage for the wall wart. I have built numerous regulated power supply's over the years, and put together a very nice supply using the schematic for the positive LT1085CT regulator circuit. It works great, supplying a constant 12.4vdc under about triple the load it will be required to deliver. Unfortunately, when feeding the 252S energizer, it won't even light up or supply any power to it. Plug in wall wart back in, and everything works fine. Recheck my diy supply, and it works fine under load on the test bench. I am guessing that the 252S amps switching power supply,(that coverts the 12vdc to the required 580v for the circuit), is screwing somehow with the LT1085CT voltage regulator chip.
The wall wart is marked 12vdc at 500ma output, and reads 22vdc no load on my Fluke meter.
Is it not possible to feed a switching power supply with a regulated voltage? Do you just feed the amp with 22 vdc unregulated, and have the SMPS pull down the voltage under load?
Don't want to damage the energizer/amp, but things should not be this hard I would think.
Anyone have any experience with this problem?
Thanks for reading this.
MG16

Edits: 03/29/21

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Topic - Baffled by a switch mode power supply problem. - mg16 10:28:12 03/29/21 (7)

RE: Baffled by a switch mode power supply problem. - jedrider 10:21:40 03/30/21 (1)

I think Jedrider has it right... - Lew 18:19:19 04/09/21 (0)

That is weird. Polarity reversed maybe? (nt) - Jonesy 10:56:27 03/29/21 (4)

RE: That is weird. Polarity reversed maybe? (nt) - mg16 11:32:19 03/29/21 (3)

Or... existing adapter is non SMPS? - Jonesy 12:28:44 03/31/21 (0)

RE: That is weird. Polarity reversed maybe? (nt) - Duster 15:42:19 03/29/21 (1)

RE: That is weird. Polarity reversed maybe? (nt) - mg16 08:35:35 03/30/21 (0)

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