psyduck

I think they'll be too scared of the high voltages 😁

I think the metal film resistors will work, they're used on the cfaelectrostat board in google drive. It's quite a bit bigger and you need two of them for one channel.

The thick film resistors are still bit of a problem cause of drift. Even with the dn2540, turning the trimmer a little too high or low will still cause it to drift.

Does your board have a ground plane?

I'm curious about the pricing and how it compares to the ES-2a.

Though running it close to max bias will probably damage your hearing.

I've used Vishay's CRCW 2010 and 2512 resistors rated at 400V. They are thick film resistors. Unfortunately due to political issues.

When adjusting the trimmers, make sure they're balanced to minimize DC offset between outputs, recommend having another DMM for that. To measure the current, you need to measure the voltage between the 100R resistors and divide the voltage by 100. The total current for one side is the sum of all 4 of them.

There's an updated board on google drive that has a 10k trimmer with dn2540 that you can adjust the current till it's stable. https://drive.google.com/file/d/16cuirLgLsadI1xa9c6OoaIqW6KevyZPa/view?usp=drive_link

Unfortunately the resistors drift with temperature as I've tried building it before. I'd recommend adding a fan to cool the top side.

Hello @jamesmking. How is the current limit calculated from the current sense resistor?

Happy Birthday!

I can build a Megatron XXL with 300B tubes for a fraction of that price.

This is a couple a months ago but a Woo Audio energizer blew the driver of a SR-X9000.

You can buy them on Taobao here: https://item.taobao.com/item.htm?ft=t&id=694554929492