I was going to write some quibbles, but instead I will just point you to this article from Roger Sanders. While the amp he talks about has long been superseded, the problems about ESL's and phase angles and currents remains true. http://www.enjoythemusic.com/magazine/manufacture/0702/ Best, E |
It has long been considered common wisdom that OTL amps are great with the original QUAD ESL. When I had just gotten my first pair of the speaker, I asked Roger Modjeski at an instore seminar for his view on amps well-suited for the QUAD. He had worked on many Futterman amps, and in the 1980's designed his own OTL, which he ended up selling to Counterpoint. He also worked on the direct-drive tube amp used in the Beveridge ESL, fixing some problems he found in the amp when he went to work for Bev. Roger said that though the OTL/QUAD combination was indeed considered by many to be a good synergistic match, he considered it to be the opposite---an OTL being the absolute worst amp design for use with that speaker. The reasons included the matter of the impedance swings in the speaker, of course. Roger has designed and currently offers an ESL with a direct-drive (no speaker transformer) tube amp, which I am dying to hear. |
I was told by out 80+ year old Sydney Quad speaker restorer Otto Major http://www.stereo.net.au/forums/uploads/monthly_12_2014/post-106213-0-29462600-1419899180.jpg who was good friends with Peter Walker, that yes original Quad 57’s were voiced with early Quad prototype tube amps and also maybe Williamson’s?, with not much current ability or wattage and high’ish output impedance’s (low damping factor) From what Otto told me the Quad 63’s was eventually released for sale in 1981 and were voiced around transistor amp/s of the time, and that the Quad 303 and later 405 amp was developed around it, much lower output impedance’s and higher damping factor and current drive than the tube amps were for the 57’s, I think they may have been Williamson’s. http://www.oestex.com/tubes/WW12-1943-BPT.jpg Cheers George |
