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I'd like to try a different rectifier in my phono preamp in place of the originally specified 6X4 (or EZ90). I can't ask the original builder, so here I am...I seems that the Western Electric 412A -- with a pin adapter, of course -- is a near substitute for the 6X4. That said, I understand that the 412A draws more heater current ... specifically, 412A = 1 A while 6X4 = 600 mA [edited].
Thinking that this might present a problem, I called the manufacturer of the phono preamp's power transformer (DeYoung outside of Seattle) and asked. The company's design engineer told me that the PT's 6.4-volt tap is rated for 2 A. So, his message to me was that even the 412A's higher current draw is still well under limits. He also clued me into the fact that, in general, the designer/builder always over-specified his PTs.
So, I'm fairly confident. I guess I just want, as a double-check, to get a consensus recommendation on whether this is safe and reasonable. I always try to stay within an "original" tube's limits ... and my proposal entails a 65% [edited] increase in rectifier heater current draw. And maybe this isn't even the only potential pitfall?
Thanks for your help!
Edits: 05/27/17Follow Ups:
The 6X4 draws 600 mA. of heater current and is capable of supplying up to 70 mA. of B+ current.
Changing the rectifier type will alter the B+ rail voltage, which can lead to unpredictable (including damage) results.
IMO, change for its own sake is highly suspect.
BTW, let's assume no damage will occur. If PSU voltage regulation is part of the design, genuine sonic change is unlikely to occur.
FWIW, types electrically similar to the 6X4 are the Octal 6X5 and Loctal 7Y4.
Eli D.
The 6X4 draws 600 mA. of heater current and is capable of supplying up to 70 mA. of B+ current.
Thank you for (very politely) correcting my combination typo and careless reading of a data sheet. I've edited my post to reflect the correct heater current of the 6X4.
Changing the rectifier type will alter the B+ rail voltage, which can lead to unpredictable (including damage) results.
The Sylvania manual (link below) indicates a 22 V voltage drop for the 6X4. But, I can't find voltage drop for the 412A. Maybe you or others know?
IMO, change for its own sake is highly suspect.
I should be more circumspect. I try. To be honest, the only times that I've managed to better (I think?) a designer's/builder's original tube specification have come when that specification has rejected a potentially better alternative based on its high price and/or low availability. When a change from spec happens in those circumstances, I think that everyone's motive makes sense from his own perspective.
Thanks, Eli!
If you're going to do something like this, the type 6CA4 is also an option. 412's and 6754's are not exactly common. the 6754's primary benefit is in its looooong warm up time.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
And... they last forever. As long as the electrical requirements are met.
8^)
If the unit can use a 412A, there's this 6754 rectifier by Bendix...8^)
Edits: 05/26/17 05/26/17
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