an amp without "electronic" sound

Most of the recommendations you'll get are going to be tubes. But class D amps did this for me. The Bel Canto eVo series in particular. I find the sound to be natural and non-fatiguing.
There are many makers out there now so I suggest you give one a try, if it's not to your liking you could sell it with minor loss. I did this with the newer Bel Canto S-300. Bought it used and sold it a month later for exactly what I paid. The compact size was a plus but it did not sound as good as the older eVo version IMO.

I think the Ayre amps will fit your description.

The Pass amps have a reputation for lacking an electronic/mechanical sound.

Asking an electrical/electronic box/unit not to sound like itself is like asking a Harley to sound like a Honda.Up late last night?I know what you mean,but do you know what your asking?Good luck,Bob