something like this?
How many watts/VA? Recommend at least double the capacity on the transformer as the equipment draw for audio. Standard US wall outlet is 1800 watts or 1.8 KVA.
Avoid cheap "converters". Weight/VA is a good indicator of quality.
Must be rated for 50 or 50/60Hz.
220 /110V or 240/120 is typical but 220/120V might require some creativity with multi-tap units (Signal, Hammond, Acme) but most of those are open and require enclosures . Cheapest way to do it well is to get a used "industrial" transformer, like a Sola or Acme off Ebay or whatever and a bit of DIY wiring.