I think in real world conditions 220 or 240 settings wouldn't sonically matter much.
I like the higher setting idea.
The unit sees lower voltages (cooler, more reliable).
If you have bad low voltage issues , you can get a CVT (constant voltage transformer)
They are kind of costly.
People have lived with this issue for years.... "Gee why does my System Sound great one Day and like crap another day...."
All this said.... I never lived with 230V.... Just in part of New Jersey that had bad power for some time..... and that drove me nuts....
The country in questions 50 Hz , yes? So that degrades the power supply even more..... that is 16% less time for the Main Filters to be Charged.... More time for the Rail Voltage to Sag...
A bit too problematic for my totally Nerdy Audio Brain. Me? I would just get a correctly sized step down transformer or a proper regulator ( NOT A CVT )... Take the 230 to 220, set the amp for 220 and set the bias after verifying where the AC is normally. Or at least run in a steady 230V.
Build my own step down if I had too... Might even try a old PS Audio PPP 230V version...NOT CHEAP WHEN NEW. They had an adjustment adjustment pot that you could lower/raise the output some. It is a true regulator. Least I would never see the worst case of 253Vs going to my 220V gear designed for a max of 242..... The regulator will keep it in the set range, but regulators have limits too.
Or a cheap ADP or Furman for 230.... They are not the greatest regulators, but at least they will try to prevent your gear from seeing 253Vs.... they will try to keep it at around 230ish.
I bought a NEW IN BOX ADP 120V audio grade Regulator for 100$.... for my Home theater LOVE IT FOR THAT PRICE.... I have a PS Audion PPP for the main system.
DON"T USE COMPUTER GRADE UPS stuff.... they usually output Square waves.... VERY Bad for audio.....
So think of it this way....
Your Unit is set up to run 240v....
The Bias was set on a day that the 240V was at/near its peak but still within spec by a Tech that did not check his AC Line voltage at the time..... 264V which is 10% high.
You are now running your unit in a country with 230 voltage standard and the power company is having a bad Summer day.... so its 207 but still in spec.....
Your unit was Bias adjusted with a line voltage of 264V but is now running on 207Vs .... My bet you will surely hear it....
That is a 57V voltage swing.... or 22% difference. Your DC rails will drop by that 22% which absolutely affect the Bias-ing of the outputs. And the Tonal quality....
These units were not design to operate on power that is 22% low.
Even if the unit was biased at 240 and is now on 207 cause a bad summer day... that is -14% and is out of spec ...
Sure you can get by. Sure it will work.... But your mileage WILL vary and will leave you scratching you head ...
"why does this sound great some days or Nights...and like crap other days?"
If I was in a country with 230....and did not get/build a step down or regulator. I would Set the BIAS while the amp was set up for 240v and the Wall Voltage was at a known Average for your area, hopefully 230V.
To me that is the best no Cost solution I would try.... That way on high voltage days you are not risking the CAPs with too much rail voltage and yet have a good Bias setting.... SURE THIS HAS BEEN DONE THOUSANDS OF TIMES BY PEOPLE IN 230V countries.....
But I would label the Vintage Gear as being "Biased was Set for 240V Mains but plugged into 230V". So that when it is plugged back into the correct 240 voltage the BIAS should be reset.
By the way, you should never use a CVT transformer on Diode/Rectifier based power supply Like in Audio gear.... CVTs are designed to work best with Resistive loads, like heaters or incandescent lighting or some motors. They will not regulate properly with a Vintage stereo. They actual lower the voltage and create noise in response to the brief load created by the Diodes turning on for a short period of time. The Diodes in our Power supply only turn on for a brief period of the Sine wave at the Peak....which the CVTs don't like. Additionally they tend to put a Square wave.... which has a very different NOISY frequency content than a clean Sine wave....Which equates to more noise....
By the way, I tested a CVT with an amp.... It actual caused the amps transformer to buzz.... Not good....
A CVT is very different than a Buck/Boost Transformer/regulator like the cheap ADP Audio regulators.... those are some what ok.... but not designed to take 230 and make it 220.... But might work if you can find a 220V version....
Than you have the Monster Voltage Stabilizer they sold years ago.... Or a Variac .... but why?
Gee.... Glad I don't have to worry about this and especially with tube gear too.... Heater voltages being lower in addition to bias settings.... The 240/120 we have was crapy enough times.
WAY TOO MUCH INFO BUT WHAT THE HECK, I GOT THE FLU TODAY.....
