Not exactly guitar amps ... but its got vacuum tubes ... my home system:
A stereo pair of Quad ESL57 electrostatic loudspeakers, manufactured in Huntingdon, Hunts, England, circa 1961.
No cones, no magnets, no speaker boxes. The speakers are only 2 1/2" deep.
The speakers have never been serviced or repaired, still going strong after 50 years.
Powered by a pair of Quad II-Forty valve amps; 40 watt mono amplifiers using a pair of KT88 output tubes each.
Quad was the nickname of the Acoustical Manufacturing Company