all PS audio electronics
Have to be both channel tubes to go faulty at once, highly unlikely. Don’t think PS Audio use common rectifier tubes for both channels, think that stage is all solid state.
The only common thing to both channels is the transformer, I doubt it’s that
https://www.stereophile.com/images/617ps.ins.jpg
https://i.pinimg.com/originals/df/f6/e4/dff6e4d089c2fd09309a560a722e52a6.jpg
Cheers George