Hello!
I just found out that my headphone amp (6DE7-based made by a famous manufacturer in New York) is using 330uf for the first capacitor and it's using a Sophia 274B. I know some manufacturers go beyond the limit but I've never seen a value this high. I don't see any flash on start-up but I'm worried about the rectifier. I'm assuming it's okay since it's not drawing too much current (?). I tried replacing it with 33uf but I got unacceptable hum. I'm thinking of adding a C-R in front.
Thanks.
I just found out that my headphone amp (6DE7-based made by a famous manufacturer in New York) is using 330uf for the first capacitor and it's using a Sophia 274B. I know some manufacturers go beyond the limit but I've never seen a value this high. I don't see any flash on start-up but I'm worried about the rectifier. I'm assuming it's okay since it's not drawing too much current (?). I tried replacing it with 33uf but I got unacceptable hum. I'm thinking of adding a C-R in front.
Thanks.
I don't know a whole lot about this except knowing that a tube rectifier shouldn't have too big a capacitor as the very first one it connects to, unless it's got a choke input.. Googling the name and part #, I found this:
http://www.sophiaelectric.com/pages/se/274b.htm
http://www.sophiaelectric.com/pages/se/274b.htm
Later text implies using it to run a power amp (300B), instead of a (presumably lower power) headphone amp, but still, that looks like it would have large peak currents during warmup.
Sorry I don't have a schematic. It uses a dissimilar triode (?) for each channel and an output transformer.
Yes, pin 8 of the rectifier goes directly to C1.
Can I put a resistor (~50 0hm) between the rectifier and C1?
My other idea is to put a ss diode instead of the resistor.
Any other ideas?
Yes, pin 8 of the rectifier goes directly to C1.
Can I put a resistor (~50 0hm) between the rectifier and C1?
My other idea is to put a ss diode instead of the resistor.
Any other ideas?
Maybe draw a schematic. I don't know much about headphone amps and what might make the first capacitor value less of an issue. But if this is a production amp and many were made and none are blowing up the rectifier tube, do you need to worry about it?
If you really want to fix this issue, I think you would be better off changing the first cap to the largest value you feel comfortable with, maybe 10uf and adding a CR after the second cap. As lowering of the first cap will likely lower your available B+, as will adding a additional CR, so make sure you have headroom. Changing to a SS rectifier will increase B+, possibly a lot, and may really change the character of the amp.
If you really want to fix this issue, I think you would be better off changing the first cap to the largest value you feel comfortable with, maybe 10uf and adding a CR after the second cap. As lowering of the first cap will likely lower your available B+, as will adding a additional CR, so make sure you have headroom. Changing to a SS rectifier will increase B+, possibly a lot, and may really change the character of the amp.
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