Quad ESL Cap mods

Sorry to be tardy - I just found this thread.

I started modding my 2805 and 2905 nearly two years ago. First I messed about with caps and resistors - metallized poly all sounded the same; the big difference came with using more film and foil. When I got up to 70uF film and foil plus 150uF metallized, the sound was dramatically improved. Duelund resistors were better than Mills WW.

The big breakthrough came with changing the step-up transformers to the Vanderveen design manufactured by Plitron. I used the 75:1. To my ears, the best sound came with using NO signal shaping other than an input resistor (as Vanderveen suggests). Best resistor in my setup was obtained by using nichrome wire as speaker cables - I have a monoblock behind each speaker, so short wires are feasible. Each of the two wires is a bit more than one ohm.

Best improvement of all was making my own low power monoblocks with low voltage rails. With this setup, it is physically impossible for the amps to punch a harmful spike into the speakers - so I could safely eliminate all of the protection circuitry. Sound is quite magical.

I hope that you are experienced with ELSs, because they can kill the unwary in several ways. Please be careful. All the best!

Hello Johnsonwu. I doubled the Duelunds to get the 20W.

My first Quad Mod was along the lines you suggest, Tsushima1. I simply removed the existing lines from the WBT connectors and insulated the ends. Then I routed new lines (15 AWG silver coated copper) from the connectors to the downstream side of the signal shaping network (cap and resistors). Then I put my caps and resistors in another box with WBT connectors on both sides, et voila! I connected amps to my new box, and the new box to the Quads.

To restore to original condition, one need only remove the new wiring from the WBT's, and re-solder the old, which you have carefully preserved in the black electronics box.

I found that the more film and foil, and the less metallized, the better. Changing to Plitron transformers was better. But, be careful, please. Since you are talking about modification, I assume that you know about the required safety practices. Otherwise, I suggest leaving it to a tech.

Sorry, I'm across the pond.