Posted by TubeCraft [ 207.106.24.98 ] on January 11, 2005 at 12:53:32:
In Reply to: Re: Holy Toledo! posted by Wayne Parham on January 11, 2005 at 10:08:53:
"I guess there is probably some trick about setting the Q of the parafeed cap and transformer to keep it from getting tubby."
There's a small chapter in the Radiotron Manual (3rd ed.) on parafeed and sizing the cap to avoid resonance with the L of the transformer primary. Basically, it's easy, 'cause bigger is better, say 1-5 uf, some use up to 10uf. I use 400-630v Solens or vintage paper in oils. The Radiotron manual also mentions that one may want to intentionally size the cap to resonate to "increase bass response"...
There's also the Rp of the tube to consider and the quality of available caps!
The Rat Shack line transformer works great as a parafeed output - I'm sure something from allied or edcor would work just as well. Plan on experimenting with the various taps. I want to try using a PP OPT in parafeed.
BTW, I'm using the primary of the original Hammond 1627 opt as a plate choke.
Anyone who reads my posts, remember, I'm no EE or anything - I barely have the math to do anything correctly. Just an experimenter.
TC
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