Below are the first notes on my ESL project. I just wrote down the things I am planning to do and some questions that came up in the process. I'm building an ESL, which I would like to drive directly by a HV-amp, so no audio transformer.


The amp

For a reasonable low frequency response, I probably need voltages of about 3-5kV, so probably a transmitter-tubes based amp. Maybe a cascaded version with 'normal' tubes or FETs? As you can see I haven't made anything yet, only some small test parts. For the first version amp I'm planning to build the HV-amp of Neil McKean I think the quality of this amp isn't great, but it's easy for a first step. Later maybe with a tube. For the final version, I'm planning to include a DAC, so I can connect a CD player (or SACD (super audio) player) directly, digital. For all the amp/filters I'm trying to make them differential. For the supply of the HV-amp I'm using a transformer out of a broken microwave oven, which has a secondary voltage of 3 kV(AC).


I'm planning to build an ESL with a wired stator. The membrane I have is 5 um mylar. No transformer. The frame I'm building has an adjustable stator/membrame distance, for tuning. Each stator-wire can be driven apart from the others, which can give a better HF spreading. For the first try all stator-wires are connected to each other, after that I connect the amp to the middle stator-wires, and connect a resistor between each neighboring stator-wires. Maybe later bi-amping? The size of the ESL will be something like 30x200cm. I want to make the mylar some conductive by graphite. Maybe other alternatives? I don't know yet what will be the best method of stretching.

HV power supply

For the HV supply of the ESL membrane there are a number of options. I want it to be adjustable. Probably I use the HV supply of a television unit, which can generate 25 kV, with a frequency of 15 kHz. Of cource this is sufficient. At my working place we borrow some HV lab supplies/amps, which I can use for some first tests.


Who has experience with direct driving an ESL? Is mylar the best membrane to use? Is graphite the best conductor for the membrane? Which HV tubes should I use? (572B?) What material should I use for the frames? which wood/steel? many other Q without A......