Morricab: that would be great if you can borrow a supply and so some comparitive tests. You are probably right in your suspecting the is afaulty cap in your Acoustat supply. Have a look at the Izzy Wizzy mods at this site http://www.izzy-wizzy.com/audio/spkr.html. More voltage will help but your limiting factor will be the condition of your PVC dielectric, same gors for a little extra current on the diaphram. The choke mod is a very good one and worth the twenty or so dollars it will cost you. Emco have switching supplies in the $60-80.00 range and you can have a look at this address http://www.emcohighvoltage.com/emcoindex.htm. Also (and you may have a hard time with this) you should try listening to your supplies with some top quality power cords as they too have a significant impact. I am biased toward the ones that I design but I am sure that a local high end shop can loan you a pair to try for a weekend. Please keep posting. Thanks and best regards. Moray James.