Just wanted to share my good experiences - caveat: I do not have proper/professional measuring equipment, just working with acclaimed recording studio gear from RME. Details further below.
(Btw.: If you‘d like to chime in on a P12 upgrade question, you‘re also welcome to comment this post!)
Just compare the two graphs (ignore my notes in the pictures - the entire setup was identical between measurements!) - tube amp‘s phono stage before and after I powered it via the Stellar P3:
See the striking difference at 50Hz and it’s harmonics?
Setup (again: identical between measurements except the P3): RME Fireface UCXII AD/DA connected to the tape output of a Triode Tube amp. Set the input gain of the RME to level at 0dB with a 1kHz/0dB signal of a CD-Player, then switching to the Phono input. Set the RME to 192kHz sampling frequency / 24bit Bitdepth going into RME‘s spectrum analyzer software.
Not claiming, that noise level readings are ABSOLUTE levels - just making sure, that RME‘s gain is comparable between measurements. So please compare RELATIVE differences - they do speak for themselves, don‘t they?
Sound quality and soundstage also benefited majorly from the P3.
The only thing I need to find out is why there are some low frequency bursts every few seconds - they were there before the P3 as well, so it must be something inside the amp or the measuring chain. Seems to originate in the region of below 20Hz - or even a small DC burst? It‘s just one peak, then a pause of 2-5 seconds, then the next.
Anyway, just wanted to share the improvements in hum and noise levels the P3 brought with my tube amp.