Step down transformers detrimental to SQ?

You won't need a transformer. Not if you're talking about line voltage. Line voltage is nominal, as in uncalibrated, as in it varies. What is called 110 here in the US can turn out to measure lower. (Occasionally even quite a bit lower, in what is called a brown-out.) Which, strangely enough, voltage running a little low like that turns out to be a much bigger problem than voltage that runs high.

This is because, first thing your amp does is run the incoming AC through its power supply. The power supply converts the AC to DC. Everything actually runs on this DC power supply. CD player, turntable, DAC, your laptop for that matter. It all runs on DC. As such it is all pretty darn near immune to AC voltage- unless said voltage drops too low. Damage from high voltage however only happens when voltage spikes crazy high. Think lightning. Some tens of volts though is nothing. I travel, and have plugged in many times to 200-220v, none of my 110v gear was ever harmed in the least.

@bsmg I was under impression that I need a step down because the voltage from my wall is higher than the amp spec. So it takes 120V down to 100V for amp intake? I could be wrong though. I've never used a transformer.

@millercarbon Are you sure I can operate a 100V amp in US? This overseas dealer has specifically told me it would kill the amp if I plugged it into 120V w/o transformer?

If your overseas dealer told you that then he's as electrically misinformed as, well as pretty much everyone else. You're talking to a guy who has wired a whole house, recently installed a panel, and has a whole system personally custom wired to run on a dedicated line that goes from 220v coming out the service panel to a custom solid silver step-down transformer that does drop the 220 to 110 just under my listening room. Not to mention built a 200 watt amp, modified lots of electronics. And yes I am sure.

But hey, don't take my word for it. Go try and find yourself a step-down transformer designed to go from 110 to 100. Good luck! They don't make one. For the simple reason there is no market for one. Because nobody needs one. Because it just doesn't make any difference.

Incidentally, and this is probably nothing, but I am curious to know if this is an older vintage type amp? And where was it made?

Again, there's no problem with higher voltage. Its lower that tends to cause problems. And since if you go back to say early 1900's America (or 'modern' day California) you were much more likely to encounter low voltage situations, its possible they were designing (and labeling) electronics for those somewhat lower voltages.

Either that, or it was made somewhere with substandard (by modern standards) electricity (like, you know, California) or maybe even somewhere foreign. Like.... all together now.... California.

Kidding. California would get the label right.

But seriously: vintage? Country?

@bsmg I was under impression that I need a step down because the voltage from my wall is higher than the amp spec.

Sorry; you’re correct. I misunderstood what you were asking.

Don’t know where millercarbon is but my power conditioner shows a digital voltage readout when it’s on and I’ve never seen it drop below 121V and most of the time it reads 123V,,,,,,in northeast TN hard by the VA border.

And you're lucky with that 220V stuff......I once plugged in a 110V blow dryer in Manila; it ran real fast for about 2 seconds and died.