Try a PS Audio Ultimate Outlet and the P600 or P1200 Power Plant
Since you are trying to lower the operating voltage to keep the integrated happy how about putting a higher wattage (but non-noisey) load such as a 600 watt space heater on the line suppling the power to the amp. As an alternative you might also try an extension cord plug between the 383's power cord and wall recepticle to try to produce several volts of voltage drop.
Interesting how most of us are trying to preserve our supply voltage with dedicated lines and you have the opposite problem of trying to eliminate some of it.
I had a similar problem with an amp that hummed when the line voltage was too high. I called the power company and they came out and retapped the transformer out on the pole to solve the problem. The power company has to adjust your line if it is out of spec so you may wish to pursue that route. Since the weather is now getting cooler, it is only going to get worse with everyone not using their air conditioners.
I would also contact Levinson to see what the high voltage limit is since 126V is not really that high. It is hard to believe that Levinson would build an amp that can't handle AC voltage that is within spec. It seems to me that either the line voltage is out of spec or the 383 is.
You could also try an autotransformer to lower the voltage. They are commonly called Variacs. It is not actually a buck transformer but an adjustable inductive voltage divider. I used one with the amp above before the power company adjusted my voltage and it worked fine. If you live near Nashville I can let you borrow my Variac.
I would like to update this topic.
Checked with Levinson again and the Levinson's range is 120 V + or - 10% which indicates that it is satisfied up to 132 V. This voltage seems more like it.
The power company found a problem with a switching capacitor which is used for periods of high demand. It was not switching off.
Problem solved and I'm back in business. Life if good!!
Thanks to all who gave advice and moral support.