Quad ESL Cap mods

I believe it is a coupling cap, acting as a high-pass filter (filters out the deep bass), therefore it is very important for sound quality.
220uF in film caps will be very costly and occupy a lot of space, about the size of four soda cans. The least expensive option is four Solen 47 uF / 400 Volts caps plus one Solen 20-30uF uF / 400 Volts plus one Mundorf Silver/Oil 4.7 uF, all in paralell.
Since the original electrolytic cap has a tolerance range of +/- 10%, this combo will be in the ballpark.
You may want to do the full combo with Mundorf Supreme caps and use a 4.7 uF Mundorf Silver / Oil as a high frequency bypass cap.
There are many cap comparisons on the net, most agree that Mundorf Silver /Oil is one of the best caps regarding clean and extended treble.
I have experimented Mundorf S/O as compared to Kimber, Auricap, Hovland and Jantzsen film caps in the tweeter network of my dynamic speakers, all those caps sound good but Mundorf is ahead of the pack IME.
I hope this helps

I have a 220uf Mundorf here and it's only the size of 1 soda can.

Face,
Thanks for the forum input. Is the Mundorf 220uF cap you have film or electrolytic? What is the reference/catalogue number? Where did you buy? Whats you'r application and how does it sound?

Thank you,
William

Casouza,
Thanks for the great info. Any experimentation with the Mundorf TubeCap? Is the TubeCap appropriate for this type of application?

and When I replace the cap in the Quads -- does it have to be 220uF or can I go less?

Thank you,
William

It is a film cap and is a #71348 available from Parts Connexion.

I used it in a similar application, to filter out bass from a open baffle speaker. I didn't notice any negative effect on SQ, but it was only used on a woofer.

If you use a smaller cap you will lower bass response.

A Mundorf tube cap is not made for this application.