Quad ESL Cap mods


Hello,
I have a pair of Quad 988 I'm considering replacing the electrolytic 220uF Capacitor for a film cap...

For those who have done it -- what caps give you the clearest extensions in the highs and improved mids without mudding the low???

Also, who makes a 220uF film cap? All I seem to find is lower values? Is it best to wire a bunch of lower value caps together for a total 220uF (if so, should you mix electrolytic caps with film caps - like some modders do) or is it best to have a single 220uF cap?

I do see Mundorf has 200+uF caps in their Tube Cap line -- are these Mundorf Tube Caps appropriate for the Quad ESL application? how do they sound?

Thank you guys very much for any and all input into this, as I'm just beginning my Quad mod journey...
128x128grateful
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.
i have a photo attached to my Quad listing on my system page that shows my caps mounted - maybe this will give you an idea. Best mod
Hi Tsushima1, if you need some photos of the quad 988/989 mods/info, I can email photos of the mods I installed. I would leave the stock electrolytic cap/resistor in place and clip out the PTC that connects them on the PC board to the wire going to the step-up transformer, then reroute the speaker input wires. You need to wire in a separate bank of film capacitors/input resistor that are ideally mounted in the base (an not on the PC board).
My apologies for the Tardy Reply gents , I have only just returned to this project and thread.

Terry9 and MKsj2 , Thank you kindly for your assistance, I have emailed you both .Likewise Grateful , just off to admire your system.