Being an electronics tech and working on guitar amplifiers, I see voltages that are way too high for the designed circuit due to todays higher line voltages.

Nice looking bucking transformer with stainless cover! Two grounded outlets give you two choices, 3% or 7% voltage drop. All vintage tube equipment should be using this voltage reducer. Read on; After WWll and up until 1968, household voltages were 117 volts. Typically voltages these days range from 120-125. Your vintage guitar amp was designed to operate around lower voltages of years ago. You might ask yourself what is a few extra volts? Take into account that the power supply in your vintage device is multiplying those voltages many times so that the end result could be 20-30-40 volts more than the circuit was designed for. This could lead to transformer failure, component failure and shorter tube life. As you can see in the photo, the voltage reducer brought the voltage down from 124 to 116. This is approximately a 7% drop. Simply plug your vintage equipment into the reducer outlet.
Will work with devices drawing up to a total of 4 amps. Has protective 4 amp fusing, grounded metal case with heavy duty power cord and nice stainless cover. Simply plug into a switched power strip to turn device on or off.
An example; Photo shows voltage of Dynaco ST-70 at 467v on todays line voltage and then 438v plugged into the voltage reducer. Factory spec calls for 435v at this point. All other voltages are much closer to Dynaco factory specifications with the reducer.

The top outlet will give you a 3% drop and the bottom a 7% voltage drop. Do NOT recommend using both outlets at the same time.
Your device will run cooler and safer, extending component, transformer and tube life!

Bucking Transformer Voltage Reducer For Fender Marshall Gibson Vox Ampeg Etc.