Who can convert single ended to balanced?

Wasn't there a company, I think it was JPS, that made a modification for the Thiel 3.5 EQ box called the Golden Flute? You might contact them--not sure if it's the same company as the one that makes cables now, but worth a try.

JPS made their own eq replacements for various speakers, B&W, Thiel, etc.. When I contacted them, they told me they no longer make them, and very few balanced JPS Golden Flutes were made for Thiel 3.5's. Thanks anyway.

I think there might have been another company that made upgraded EQ boxes for Thiel 3.5s (the speaker that hooked me on high end, by the way), but I don't recall them, maybe others might chime in here. Is it possible Marchand might do something like this for you on a custom basis (I know that my crossovers are custom made by Marchand for my particular speaker builder, and they include a bass boost with a variable low frequency cutoff)?

There was a retailer that was making eq replacements for B&W's, I believe it was called something like the "Maughan(?) box". Again this seems to be a dead end. The balanced Golden Flutes seem to be the best option, but I haven't had any luck finding them. I now have two extra Thiel 3.5 stereo eq's, so converting them seems to be the best option at hand. Thanks all the same.

Parts Express sells a balanced/rca converter by a company named ACT. I use it and it works well. It is a pricey little devil at $65.