| 300B Push Pull [message #10049] |
Fri, 28 December 2007 19:20  |
SteveBrown
Messages: 330
Registered: May 2009
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Grand Master |
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Does it get any better than this? PP 300B's - no feedback, all class A? I built a similar design a few years ago and really liked it, but for some reason moved to something else. I always remembered this design as something special, so I rebuilt it this week, but this time using 300B's instead of EL34's or 6550's which I'd used originally. Now, I'm sure some of this is "proud Papa" stuff, but I'm really liking the sounds I'm hearing. Bass is very solid and articulate. I've put a pot in the cathode of the output to balance it better, and I'm using a different power transformer and consequently had to rework the power supply a bit. My changes are to use a beefed up Dynaco ST70 power transformer (rated for 300 ma). I also used a 5AR4 instead of SS rectifiers and a 3H choke instead of 10H. I have not added a cap bypass on the cathode R yet, but will do that tomorrow to see what, if any, improvement it makes. I was thinking of trying 40uf from the top of the cathode R to the center of the OPT, any thoughts? Anyway, I have a great deal of respect for Allen's stuff, and I'd really encourage folks to try them out. I think it is pretty generous for a manufacturer to share details like this - really nice sounding stuff. Of course, I have no affiliation, just a happy builder.
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