On the p20 there’s a screen that says calibration at the top and has 3 voltage settings.
Top one is output voltage setting.
Middle one is input voltage reading.
Last one is output voltage reading.
The screen allows you to adjust each one plus or minus. What do these setting do and what are the proper settings? The audiophile need within me might
Have calibrated them incorrectly.
Thanks Mike
We do calibrate each unit before it gets shipped out so you shouldn’t need to do this. If you have a multimeter you certainly can re-calibrate it, but you shouldn’t need to.
How do I reset it to its original setting it was shipped with?
Mike
There is no way to reset it back to the settings it was shipped with. It get’s saved when you change it. Were you trying to fix something that was off? You’ll now need a multimeter to re-calibrate it.
No, actually I was just seeing if other settings would improve the sound. I’ve a voltmeter how do calibrate
To the right calibration?
Mike
I own two P20s, and stumbled upon the calibration screen by accident. I was also interested in fine-tuning the input voltage measurement display, output voltage measurement display, etc., but despite asking multiple times through another thread on this forum, received no helpful replies. Nevertheless, I figured it out for myself using trial and error strategies. Beware, there is nothing intuitive about the process, so take careful notes on a piece of paper, and eventually, you’ll get there. 
@John_H, what was the result after your efforts were complete?
Use your voltmeter to read what’s coming out of the wall and out of the P20. If those differ by a fair margin, use the plus and minus buttons to close that gap. John_H is right and do your best to write diligent notes. It will make it a lot easier.
Tony,
Here’s the link to the discussion thread (click the blue words “Wish List for P20 owners” below):
P20 (left)
Output Voltage Setting
-10, 230V
Input Voltage Reading
2, 226.3V
Output Voltage Reading
12, 230.7V
P20 (right)
Output Voltage Setting
-4, 230V
Input Voltage Reading
2, 226.3V
Output Voltage Reading
12, 230.3V
Above are the settings which I settled on (back in 2018-Dec), but perhaps they have drifted slightly and require another trim. I haven’t checked in many months…
My entire system has been powered down for the past few days because one of my monoblock power amps has gone back to the shop for repairs, so it’s not convenient for me to go through the calibration settings on my two P20s now. Maybe I’ll give it a go in about a month’s time. Let’s compare notes then.
Essentially, there are three parameters/settings which interact with each other inexplicably, so to hit the bulls-eye on all three, one has to employ quite a bit of recursive trial-and-error. The AC line voltage in HK is typically fluctuates around 227-228V, but I like it to be rounded up and locked by my P20s into 230.0V. I recall that the final settings were significantly different from those from the factory when I received them. So have fun with taking careful notes, and experimenting!
I checked my P15 manual now but I didn’t find any calibration as he asked about so I wonder if the P15 don’t have that thing so I don’t need to worry about “destroying my P15’s calibration”?
One thing I’ve noticed is that my “Voltage Out” on the “Status”-screen can differ by a few volt.
Sometimes it’s 228.x volt and other times it’s 233.x volt and is that normal or should my P15 ALWAYS give the same volt out, say 229.3 volt?
What are you attempting to do?
Does the music sound any different when the V out varies? Probably not. I would just turn off the screen.
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Attempting to do?
I just thought that a power regenerator would always leave the same volt out as you’ve told it to do, say 230 volt, and not differ 5 volt from time to time but I’ve no experience of power regenerators so I don’t know exactly what to expect from them either.
I see most of the point of the regenerator is the lowering of impedance and stable voltage
It really doesn’t matter if the output is 230 or 230.1 or 231v, the stability will be the same as will the impedance
In other words, don’t fret over ‘calibrating’ it, plus unless you have a calibrated volt meter you really have no reference
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Hi everyone! I’ve attached a screen snapshot of the calibration exercise I went through last week, to ensure that my two P20s are not only matched to each other in output voltage, but that each individual unit’s display of both input and output voltage are independently accurate. I discovered that the top-most variable “Output voltage setting” is the most critical one to trim using your voltmeter, and that it’s mutually exclusive (independent) of the other two variables, making the process pretty easy. I’m satisfied, having hit the target output voltage of 230.0 volts within 0.5 volts and having matched the two P20s’ output voltage to within 0.1 volts of each other. Hopefully, they will continue to track each other closely under a variety of conditions and not drift much. The information should be self-explanatory, but please let me know if you have any questions!
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Great! Also, I just wanted to add that the Output Voltage Setting and Reading are quite specific for each Multiwave and Sinewave options if you intend to go around the different settings.
Yes, thanks for pointing that out. I’ve got both P20s on sine-wave output, as JRDG is adamant that multi-wave will bust their amps (without bothering to elaborate why), so I’m playing it safe.
Under very similar output loads of ~175W the current output amperages between my two P20s are significantly different. Can anyone explain why the discrepancy (over 20%) is so large? I thought the relationship between wattage and amperage was straight-forward math. Is there something else which needs to be calibrated for my two P20s? 
For the same power output of 175W, why do my two P20s display very different current outputs of 1.06A and 1.30A ? The latter seems especially high, given that 175W over 230V is equal to 0.76A.
Just now, I have successfully updated the firmware in both my P20s with downloaded and unzipped files in a folder called “PWR_15_20_125_Release”. My data screens now reads:
Bootloader: 1.13.00
Main: 0.01.25
Power meter: 0.21.00
Oscillator: 0.57.00
Web: 1.22.00
Happily, the output amperage of both P20s are now nearly identical with similar wattage outputs. Specifically, for 170W at 230.0V, they read 1.10A (up from 1.05A) and 1.0A (down from 1.3A). Close enough - problem solved. Thank you, PS Audio! 