The ESL loudspeaker KESL1 (full range) has an OTL (output transformer less) tube amplifier without a step-up transformer and comprises to one unit with the panel. The tubes drive the foil directly. All you need is a preamplifier.
This in-house development is based on 20 years of experience.
For the active panel KESL1, we recommend the ESL preamplifier KVV1.
Also any other good preamplifier will work with the KESL1 just fine.
Please see the loudspeaker list on the left-hand side.