Slight hum

[stanbp64]

Originally Posted by jaymanaa

I apologize for that Scuzzer. Here is a clean pic (to the left of the red dotted line) of what I used (which is what the amp had originally). Also a couple topside pics of the amp after testing for golana.

Holy cow, That's a nice looking amp!!

[jaymanaa]

Originally Posted by stanbp64

Holy cow, That's a nice looking amp!!

Thanks Stan, I just need to get it "finished" for poor old Ken. He has had the patience of a Saint throughout this build. I think I could have called it "good" once or twice already, I just want it to be the very best that I can do. I think I'm good to go though, as soon as this power supply issue is ironed out. This is the first time I've ever utilized a doubler, and like everything else, they turned out to be way more complex than first glance let on. For instance, now we know why the PT is so freekin huge. With a doubler it has to be able to make twice the current as a TX used in a more conventional power supply.

[JonL]

That is a beauty. Have you used those power switches before? I got one that looks like that from "The Shack" for a non-audio project once and it gave me a lot of trouble.

[jaymanaa]

Originally Posted by JonL

That is a beauty. Have you used those power switches before? I got one that looks like that from "The Shack" for a non-audio project once and it gave me a lot of trouble.

Yep, I've used them a couple times, but not the radio shack brand. I can't think of the brand right now, but I buy them at KC Electronic Supply. They have a blue LED built in, but you have to supply the resistor.

[ultralc]

Originally Posted by Scuzzer

I don't understand why you'd use a half-wave voltage doubler vs. a full wave. They both have the same number of parts and I have to imagine the full wave would provide less ripple but heck, I'm sure I'm missing something.

In essence, they are both half-wave doubler, in the sense that they are full wave to the transformer, but half-wave to each cap. The one Jay uses is a universal one, meaning that you can cascade the diode/cap combo string to get higher multiplier out of it. The one you use is specific to a doubler. It is two half-wave rectifiers stack together. Most, if not all, doublers in vintage tube amps use this configuration since it uses cheaper lower voltage caps. The combined voltage ripple is 120 Hz instead of 60Hz, good if you add another cap or RC/LC stage after the doubler. The disadvantage is that two caps are in serial, so the effective capacitance (power reserve) for the amp is half (assuming they are the same value). With the "universal" one, the amp sees the full value of C2, but it is also in the full B+ voltage instead of half, and ripple is only 60 Hz.

I would put the motor run caps in the B+ location (after the choke, where signal is bypassed to ground) instead of inside the doubler.

[JonL]

The RatShack ones I've used had no LED. Sounds like the RS is just a cheap look-a-like.

[jaymanaa]

Originally Posted by ultralc

In essence, they are both half-wave doubler, in the sense that they are full wave to the transformer, but half-wave to each cap. The one Jay uses is a universal one, meaning that you can cascade the diode/cap combo string to get higher multiplier out of it. The one you use is specific to a doubler. It is two half-wave rectifiers stack together. Most, if not all, doublers in vintage tube amps use this configuration since it uses cheaper lower voltage caps. The combined voltage ripple is 120 Hz instead of 60Hz, good if you add another cap or RC/LC stage after the doubler. The disadvantage is that two caps are in serial, so the effective capacitance (power reserve) for the amp is half (assuming they are the same value). With the "universal" one, the amp sees the full value of C2, but it is also in the full B+ voltage instead of half, and ripple is only 60 Hz.

I would put the motor run caps in the B+ location (after the choke, where signal is bypassed to ground) instead of inside the doubler.

Thanks, I think I'm getting a handle on these now.

[golana]

She sure is purdy! Stainless steel, I ve done lots of work with metals, but would have thought SS would be hard to deal with, nice.

[jaymanaa]

Originally Posted by golana

She sure is purdy! Stainless steel, I ve done lots of work with metals, but would have thought SS would be hard to deal with, nice.

Thanks, it is hard to work with. You need sharp tools and a drill press that will turn them slow. I use a lube called metal mover as well, which helps tremendously.