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Preamp valve rectified power supply

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I have two old British preamps I'm looking to use with the same power amp. Both are single valve, (EF40 and ECC40) and take supply from the power amp PT. I'd like to provide a valve rectified standalone power supply. Here are the specifications:

First preamp :
-6.3VAC at .2A
-420V at .6mA

Second preamp:
-6.3VAC at 1.3A
-440V at 30mA

The supply would provide either 420 or 440, but not concurrently. Should I find a transformer with taps for 6.3VAC at 1.3A and the capability to provide 440V after first stage filtering? Using a 50+50uf cap with an appropriate dropping resistor over to get 440V?

Are there schematics already available for such a unit build? GZ34 do the trick? Any transformer suggestions? Something older I could recycle into this? Thanks.
 
500 WVDC electrolytic caps. are available. 600+ WVDC metalized polypropylene caps. are available and could be a GOOD idea in a preamp PSU.

The 250 mA. 5AR4/GZ34 is overkill for this job. FWIW, I suggest a hybrid bridge rectifier with a 7Y4 as the "hot" legs and 2X 600 PIV Schottky diodes in the ground legs. The 7Y4 is very inexpensive. AAMOF the Loctal socket rates to cost more than the tube. ;)
 
Thanks. I was thinking the GZ34 might be overkill, considering the lack of output stage. I'd like to stay with valve rectification, however. Would EZ80 or EZ81 be more suitable? Paired perhaps?

Polypropeylene a good idea over electrolytic in the cases of preamp supply? Appreciate the responses.
 
The vacuum rectifier TOTALLY dominates composite behavior in hybrid bridges. Bridge rectification disposes of PIV limit problems.

A 6CA4/EZ81 would be in over its head too, working FWCT in a 400+ VDC PSU.

Keep costs down and performance up. Go hybrid bridge. :yes: Even crappy SS diodes work reasonably well. High PIV Schottkys are as quiet as vacuum rectifiers, without the forward drop penalty. :D
 
The #80 is electrically "equivalent" to a 5Y3, which means large forward drop and a 5 VAC supply, preferably with a CT.

Frankly, I don't understand people's "obsession" with looks. My thinking runs towards high performance, at low cost. Of course, butt ugly will not do. A 7Y4 is (IMO) pretty good looking and its inexpensive.
 
A hybrid bridge IS valve rectified. The SS diodes simply provide the path to ground.

Since you seem fixated on a vacuum rectified FWCT supply, perhaps the 6BY5 dual damper is the answer to the problem. Use a CLC filter, with only moderate capacitance in the 1st position. Use at least a 5 H. choke.
 
yes indeed, even with ss in there, it is still tube rectified....
i am not really obsessed with sexy tubes, just happened to have those...;)
might as well use it....

EZ_Bruecke2.png

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a loctal tube rectifier, 7X6 running off 6 volts is available and very cheap....http://frank.pocnet.net/sheets/127/7/7X6.pdf

jeez, am i supposed not to say this?:D
 
The 7X6 looks good for hybrid bridges. PIV limit is somewhat low. The type might make a decent voltage doubler for a preamp PSU. Triad N-68X isolation trafos are inexpensive and would get to about 300 VDC, when "full wave" doubled.

The 7Y4, like the 6X4 and 6X5, is good for 70 mA. The "big boy" of Loctal rectifiers is the 7Z4, which is good for 100 mA.
 
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