| Re: Bravo, great work! [message #31864 is a reply to message #31862] |
Thu, 30 March 2006 10:41   |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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Thank you for your kind words. Power supply schematic is in the Part 10. The easiest way to implement 2A3 is to use the same PS schematic, and not use C1 and C5 (first PS caps). Then you`d have a choke input PS, with about B+=312V we need (depends of the rectifiers). `Cos of that I specified "larger" chokes then we really need (250mA and 150mA) - cost difference is negligible.
The only problem is filament voltage - probably it is the best to ask for "modified Centurion" trafo with two 5Vct/2,5A (2,5-0-2,5V) filaments windings. The original has two 5V/1,5A windings, and one 14V/1A we`re not using and it can be ommited (we`d have two ct terminals needed that way).
Cathode resistor of output tube can be lowered with switch across 91R resistor, leaving only 820R or so by shorting 91R.
Driver Ia must be lowered to 10mA, we`d lowered Ua that way, maybe Rk must be changed also (`cos of lower B1+).
Huh, it isn`t too easy to build "universal" 2A3/300B amp, but it is possible...
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