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!

Hi Terry9, did you end up doubling up the Duelund resistors to match the orig. power rating? My experience with Duelunds are outside of Quad mods but were you able to fine 20W+ Duelunds for the job or was your mod only for the input R and C before the split-tranny?

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

Good for you then cos I had to change out Duelunds on my friend's JMLab Micro Utopia in favor of Mills MRA12s. The Duelunds caused a major saturation in the sound when overdriven.

Howdy folks .

I have recently acquired a pair of ESL-989's and whilst mugging up on user tips and tweaks I came across this most informative series of posts, amongst others, recommending a number of modifications ,chiefly the replacement of the 220uf lytic with metallised or film/foil poly + associated resistor.

I was under the impretion that those componants would be reasonably easy to get at ala the 63's however I was kinda dismayed to see the components connected directly to the PCB

I'm pretty good with point to point circuitry however I tend to shy away from PCB work .

I would be grateful for any further tips regarding the safe removal of the 220uf + R15 together with any further info re securing the replacement polypropylenes into the circuit .
Any under the hood images post modification would be most appreciated.