I have a power transformer that I would like to use in an EL84 PP amp. The transformer doesn't have a center tap in the secondary. I want to use an EZ81 rectifier tube. Is there a workaround for this transformer?
use silicon.
Or, partly use silicon. Build a bridge rectifier with two silicon diodes, and the EZ81 as the other legs of the bridge.
There you go - best of both worlds. Or worst of both depending on your pov.
The Valve Wizard
Or, partly use silicon. Build a bridge rectifier with two silicon diodes, and the EZ81 as the other legs of the bridge.
There you go - best of both worlds. Or worst of both depending on your pov.
The Valve Wizard
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Thanks for the reply, but I just realized the transformer doesn't have a 5v winding. So I'll have to go full bridge diode and forget the EZ81.
EZ81 is indirectly heated 6.3v
Although, your plan B makes a lot of sense for a number of reasons. But don't let me put you off.
Gregory,
Can you provide the membership with either a model number or a diagram for the power transformer in question?
Can you provide the membership with either a model number or a diagram for the power transformer in question?
This transformer was salvaged. It has no part no. I've found similar units on Ali Express from Zhifeng D Electron. It's marked "Hi Audio" and 0-275 @ 300mA, 3.15-0-3.15 @ 3A, 6.3 @ 4A.
Greg,
If you have that much HV current why not build a 6L6GC or 7591A amp? Use one filament winding for each channel.
275 volts silicon rectified will probably net more voltage than EL84s will be comfortable with. A half and half with an EZ81 will be pushing the limits of its 150ma current rating. An EL84 stereo amp will likely require about 150ma of current.
What are you considering for output trannies?
Steve
If you have that much HV current why not build a 6L6GC or 7591A amp? Use one filament winding for each channel.
275 volts silicon rectified will probably net more voltage than EL84s will be comfortable with. A half and half with an EZ81 will be pushing the limits of its 150ma current rating. An EL84 stereo amp will likely require about 150ma of current.
What are you considering for output trannies?
Steve
Getting around the 150 mA. limit of the 6CA4/EZ81 is easy enough. Use a 6BY5 dual damper that's good for 175 mA. per diode.
The Russian 6Π14Π-EB (6p14p-ev), AKA EL84M, is a nice sounding, true, 7189 equivalent that's very tough. Wherever the B+ rail comes in, that variant will hold up. The "best" option for that type just might be full pentode mode, with g2 B+ regulated at 275 VDC. Remember, the design center rating system used in the linked RCA datasheet is quite conservative and an increase gets you the design maximum numbers. A 12.5 W. plate dissipation is definitely safe.
The Russian 6Π14Π-EB (6p14p-ev), AKA EL84M, is a nice sounding, true, 7189 equivalent that's very tough. Wherever the B+ rail comes in, that variant will hold up. The "best" option for that type just might be full pentode mode, with g2 B+ regulated at 275 VDC. Remember, the design center rating system used in the linked RCA datasheet is quite conservative and an increase gets you the design maximum numbers. A 12.5 W. plate dissipation is definitely safe.