Amplifier Suggestions for Electrostatics

For my ESLs I bought a used Crown DC-300A power amp. This amp is capable of 150 Watts per channel and has very low distortion. However, you must present the amplifier a resistive load. With a hybrid ESL (has magnetic woofers) this is no problem. Otherwise you must use a 10 Ohm resistor in parallel with your step-up transformers. Also, the Crown does not like it when extremely low frequencies are passed into the transformers( apparently due to some kind of feedback). I also auditioned my DIY ESLs with a McIntosh MC2105, and the "autoformer" sound is incredible.

Here is my ESL website, so you can see what I am using. It may be old and outdated, but the DC-300A still packs a punch. It also only cost $350.
It is indeed a monoblock design. The LM338K voltage regulators used in the power supply would not handle the current requirements of two channels. The design will drive conventional speakers just as well as it does the Quad electrostatics. The power output into 8ohm is limited by the supply rail voltage to a little over 20Wrms. This has been done deliberately due to the maximum 33Vp-p that can be handled by the Quad ESL57. The power output into 4ohm is about 40Wrms.

I hope to add a further development of this design to my website before the end of the year. This will supply 40Wrms into both 4 and 8ohm.

Yes, the construction costs of the version shown in the photographs are probably more than it would cost to buy a second-hand amp, but this was not the object of the exercise. Nick, who built the amp, wanted to retain the sound qualities of his lower powered JLH Class-A whilst being able to supply more current to meet the low (2ohm at 15kHz) impedance of the Quad ESLs. Nick also opted to oversize the heatsinks etc since he wanted to ensure (relatively) cool running and to minimise drift due to temperature variations.