Now lets get into my impressions of the working P20 and P15 that I received. At least two of the three units I ordered were working!
Plugging in the functional P20/P15 I was greeted by a high pitched noise eminating from the back of both units as captured here: https://www.youtube.com/watch?v=HCOKExaQMwU&feature=youtu.be
Fortunately this is only audible when in close proximity to the units, I cannot hear it from my listening position. Unfortunately what I can hear from my main listening position is the transformer hum in my mono block amplifiers. For some reason the P20 is making my amps transformers sing louder than they do when pulling directly from the wall outlet. Prior to the P20 there was a hum in my amps but you had to be directly over them to hear it, now I can hear it anywhere in the room. It reminds me of my Grandmother’s fish tank’s pump hum. Keep in mind I have two dedicated 20A outlets running to my audio room. This is not a ground issue either as I tried a cheater plug and the hum volume remains the same. I can’t seem to modulate the hum loudness either in changing from sine to multi-wave output strength. Paul and Co. are in the process of helping me figure this one out, according to Paul this is the exact opposite of what he would expect to happen (the transformer should become quieter when connected to the P20). So that was a head scratcher for me and I spent three hours of trouble shooting this weekend by unplugging various SMPS to see if they influenced the hum level to no avail. I wish I could bill PS Audio for this time 
I proceed to upgrade the firmware to 1.23 and everything went smoothly. My in-home power was much cleaner than I expected it to be. The incoming power sine wave is just slightly clipped at the top and varies between 1%-2% THD depending on the time of day:
Now we can get to some positives! I took frequency response measurements before and after P20 integration with a calibrated microphone to see if I can put objective data to subjective listening impressions. I also listened to several of my reference tracks (Nils Logfren-Bass & Drum Intro, Ke$ha-Praying and Young Jeezy- Put On) prior to P20 installation so I could provide as close to an A/B impression as possible.
Even after my frustrating day and me wanting to be angry at PS Audio I have to say I was impressed. I wanted to dislike the P20 seeing as how I already had pretty clean power going in but it won me over nonetheless. The best way I can describe the sensation is as if you were listening to music from outside your room with the door closed. Adding the P20 opened the door. Everything was much clearer, cleaner and the bass was more dynamic/responsive. Now keep in mind that I described this as the sensation I felt, not the magnitude of that sensation. The improvement literally wasn’t as significant if the door was closed/opened. I would say the P20 improved my systems performance between 10-15% from where it was. At this point in the game (for me) that is a huge improvement when I am fighting for inches.
I expected the frequency measurements to reflect my subjective impressions. They did not. I ran a full range frequency sweep from 1-20kHz pre/post P20 integration. I also ran sweeps from 1-100Hz in 5% master volume increments from 30-55 master volume setting on my pre-amp as I figured this is where the power reserves of the P20 would be realized. The data is below and the differences between having a P20 and not are within error of microphone placement/measurement tolerance. Green traces are without the P20 connected and the Red traces are after the P20 was connected.
Now keep in mind frequency response does not tell us everything. If that were the case then we wouldn’t be lusting over speakers we can’t afford, after all most of the higher end speakers have similar frequency responses. To be completely honest, I thought prior to doing the measurements that the P20 had to boosted the loudness of my system in general. That’s what it felt like from my listening impressions, 25% on my master volume felt like 30%-the dynamics increased as well as the over all sound level. There is some magic happening here with the P20 that measurements don’t divulge. I am an Nanoscience Engineer by trade, so trust me I believe data is king and it can ultimately set you free- but something special is happening with the P20 in my system that frequency response doesn’t describe.
I was also impressed by the load the P20 could handle. With all my gear connected to the one functional P20 (even my 1600W capable gaming PC) I was only loading the P20 to 65%. I think you may see my other unit up for sale when I receive my replacement.
I had a similar experience with the P15 in my home theater set-up. The sound stage was more open and the bass more responsive. I also noted the picture on my 75" Sony HDR 4k set improve. All in all I will be a happy camper if PS Audio can explain/fix why my monoblock’s transformers are now singing louder when connected to the P20 and I receive the replacement P20 I am owed.
Cheers,
Tony
