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    Building, troubleshooting and testing of these amplifiers should only be
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Vacuum Rectifier Question

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Thanks, Tom! The 5W4 is exactly the sort of thing I'm interested in.

A Heath AA-161 carcass that's already missing the O/P trafo is being converted into a full function stereo preamp. The 6.3 VAC filament winding of the AA-161's power trafo can power a DC supply for 2X 12AX7s and 2X 12B4s. Choke I/P filtering the "raw" AC should yield something quite suitable for driving a LR8 regulated 250 VDC phono section B+ supply. A gyrator after the initial LC section will dump some Volts prior to powering the line stage. Less IS more, when it comes to dropping resistors

The 12B4s are CCS loaded at 20 mA. and an unbypassed 500 Ohm cathode bias resistor is used. I don't want to overstress the CCSes.

I thought I'd use this thread although the question is a little different;

I got a power tranny without a centretap on the sec. winding,
but I'd still like to use tubes for rectification.

Can I use two full wave rectifiers (EZ81's for instance) and
place them in a four-diode-Greatz-bridge-way ?



No, the EZ81 has a common cathode, so it can only half of the bridge - the other half needs the PLATES connected together, with separate cathodes. You COULD use two 6BY5s, which have two diodes with no internal connections - but why not use a hybrid bridge? There's no solid state diode recovery noise, since there's a vacuum diode in series. And half the voltage drop, better regulation, etc.
Eli's question has been answered, but just a word of warning about an "ouch!" I got some time ago.

That is about a Russian 5Y3GT I found, well and properly marked - but with an indirectly heated cathode inside! The voltage drop was quite lower than for the real thing. What the devil it actually was in USA terms I don't know.
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