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In Reply to: RE: New Soul Sister pre posted by calsaint on February 20, 2017 at 15:13:45
510 VDC. When you operate a 5U4GB over 490 VDC of B+, you are going to have 5U4GB trouble, on a long-term basis, don't do it !!Its a wonderful rectifier tube, and I truly LIKE your idea of a BEEFY supply.
The higher the HY of a choke, the lower typically is its current rating, - due to many turns of thinner wire. How about if you get RID of any "C" or "c" ( large of small capacitor) device right after the rectifier, ( its a poor design idea - to be avoided ) and input the rectifier directly into a smaller than 50 HY choke, but one that still meets Critical Inductance ???
The smaller HY choke will have a higher current rating, and you may get a physically quieter ( non buzzing ) supply. Its hard for me, or anyone else, to tell whats going on - not being there, but operating the 5U4GB at 490 VDC or less, and a beefier L1, is what I THINK I would try out.
Also, spend $13 and Listen to the current JJ 5U4GB as a rectifier. It up-seated my Tung-Sol as a favorite. YMMV.
Have fun. I bought a Sutherland PH3D last month, and it runs on D Cell batteries, and - no tubes to worry about ! $700 NIB, on sale.
Jeff Medwin
Edits: 02/22/17Follow Ups:
I've got a couple of these in the PS of my 2a3 amp. I could pull the 2nd one from there and swap it with the first choke here and see how it fares.
That's something I was considering at the outset but I just didn't feel like messing with 2 PSs at once heh.
Sounds like a plan, right ?
I'll report back.
-Steve
To address Jeff's point, the 5R4GY works great and reliable at high voltage. If you have one kicking around would be plug and play replacement in this application.
I am not so sure it works great maxhifi. Isn't a 5R4 a whimpy high-drop tube ??
Higher drop than the 5U4, but it's far from whimpy... my RCA MI-12188A amplifiers have a 750-0-750 V power transformer, straight into the 5R4, then a choke input. They run at around 200mA with a B+ of 590V or so. Had them for 15 years and never changed the tubes. Still test good.
The 5R4 is a high vacuum tube designed for higher voltages than the 5U4 can handle. And all that with a 2A filament. It's a great tube. In a preamp it would be loafing.
with you and Fender telling me to drop in new rectifier tubes I'll certainly have some experimenting to do. Sounds great, thx.
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