Hi,
you can add me to the queue of PS-2A users that encounter the same issue. I bought a used Power Station about 2 weeks ago. The guy who sold it to me had bought it new in Februrary this year from a reputable retailer here in Germany.
For the first two days, the unit worked fine. On the third day, the unit started to emit the typical crackle noises that we all know from failing tubes. So I replaced the whole tube set (it still had the original Fryette labeled tubes) with a matched set of 6L6GC and a 12AX7 from JJ. The unit worked fine again for about 5 days. Yesterday, while I was playing one of my amps through the Power Station, the speaker output started to emit the hum we hear in the sample in the OP. There is still output from the power amp, but now overlaid with this annoying hum.
This is a 230V unit powered from a 230V outlet (the actual wall voltage I measured yesterday was 231V). The hum is independent from what is plugged into the PS-2’s inputs. Even with just Speaker Out from the Power Station to a speaker, it emits this annoying hum. Tried different speaker cables to no avail. Replaced the new, working JJ tube set with the original Fryette tubes, which led to the hum becoming even more prominent. Tried a THIRD new tube set with the same result. Sigh…
The seller says this is none of his business and with this being a used unit the retailer doesn’t want to take care of it. Really really frustrating to say the least.