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Re: OTL for Tympanis

Posted by Slick (A) on November 29, 2005 at 05:58:45

In Reply to: Re: OTL for Tympanis posted by MIchael Samra on November 29, 2005 at 01:38:35:

Thanks for the kind and helpful words. I have made some error in modifying my Citation II, because I have limited HF response. I used a 6DJ8 constant current cascoded differential amp at 4.75mA per side for an input stage; 12AT7's as cathode followers, also with current sources @ 6mA per side as drivers; and the standard output stage, ultralinear, with triode mode switches. My power supplies are all regulated. I've used standard metal film resistors and coupling caps as diverse as 735P Spragues, Wimas, Multicap RTX and Auricaps. Highs are very rolled off and I am clueless as to why at this point. Transistor amps sound very detailed. I figured it was a transformer limitation. Maybe not?
I haven't figured out how to post a schematic here.
Regarding the Maggies, which I am devoted to for life, I'm curious as to the crossover mods Winey recommended. I put up a post on the Planar group, but got no response, asking whether the IVa crossover could be implemented in a IV since the tweeter is the same and the midrange LF rolloff is handled by my electronic crossover. I called Magnepan and spoke to someone named Wendell. He told me to stick with the (complicated and expensive) IV design because there might be minor driver differences, but he couldn't remember. I think he's wrong. I'm going to spice model both crossovers. If they are close, I'll build the IVa version using Jensen PIO's and foil inductors.
BUT, first I have to get a HF amp in place with some treble!

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