Hum level with Absolare amps

97dB horns with powerful tube amp isn't a good match at all.
You either need lower-powered amp or you need SS amp. Solid states are usually more quiet especially for very sensitive speakers.

not in agreement with Czarivey. I run a pair of 98dB/w/m, 16ohm nominal impedance horns with 2 x 15" woofer per channel. I've experimented with a number of SETs amps. best overall match went to a pair of 60wpc OTL amps - even though these cost significantly less any of my SET amps.

SS & horns are a diff matter altogether.

I heard Atmasphere amps are very great with noise floor just like solid states, but was generalizing rather than being particular. I also believe that Berning ZOTL amps that are substantially lower in power, but also have great noise floor parameters. I believe that >100dB is the number to go after when dealing with sensitive speakers.

The Absolare amps are very quiet and you should be fine. These amps sound wonderful, good luck with trying solid state, would not be my first option.