Advice needed tube rectifier

gottafewouts · Post by **gottafewouts** » Mon 07/31/06 7:56 pm

Hi,
I built a single ended el-84 w/solid state rectifier project some time back.
I want to disconnect the solid state rectifier and replace with a tube rectifier. My PT has 5v 3a taps for rectifier. What tube would you suggest to use. The build is a single el-84 and 1 ecc83s.
Thanks in advance,
MJ

what_wires · Post by **what_wires** » Mon 07/31/06 9:00 pm

Why don't you use the 18W circuit? The EZ81 can handle the current and if you have any problems with it there are a lot of people here that can help you.

s2 · Post by s2 » Mon 07/31/06 9:53 pm

That is a very interesting question. The easiest thing to do would be to put a sag resistor between the SS rectifier and the 1st filter cap. I would have to know more about your amp and PT, but you can play around with 100 Ohm and 200 Ohm (5W) values to see what you think about the sag. Actually, you won't get much sag with only 2 tubes, but you will get a smoother and "browner" sound BC of the lower voltage.

Otherwise... If your 5V tap is capable of 3A, you can try a 5U4, which is about the only rectifier that will give you any sag in that position. If it is capable of 2A, you can try a 5Y3 for less voltage or a 5AR4 for more voltage. A 5V4 is in the middle.

gottafewouts · Post by **gottafewouts** » Tue 08/01/06 1:11 am

Thanks all for the tips. I am gathering a part list to build a 18-watter.
Sorry for that question, I know its not a 18 watt question. Did not mean any disrespect to the community. But its my don't bother the neighbors amp. I'm a fan of sag and didnt know if I would be able to get any with this 2 tube configuration. I'm using a weber pt (w025130) as they make
pretty solid Transformers at a reasonable price. It does have 5v 3a taps for rectifier tube. I'm glad to be a part of this community and did join to learn more about 18 watters. And will be building some in the near future.

Thanks everyone for your time,
MJ

marshman · Post by **marshman** » Wed 08/02/06 3:48 pm

I am by no means an expert on such matters, but I'm pretty sure that somewhere I have an article written by one of the gurus ( I think it was a Hoffman or Aiken thing, but don't quote me) that stated that Class A amps, due to their nature, don't actually sag because the tube(s) are at pretty much full power at all times. Am I losing my mind?

Post by **markh** » Wed 08/02/06 11:55 pm

Marshman wrote:...somewhere I have an article written by one of the gurus ... that stated that Class A amps, due to their nature, don't actually sag because the tube(s) are at pretty much full power at all times.

That is correct. The current consumption of single-ended (real class A) amps actually varies little from no signal to full output, so the traditional "sag" effect does not take place.

Sag does happen on the "bogus class A" push-pull cathode-biased amps and fixed-biased push-pull amps, both of which draw significantly more current at full output.

--mark h

Cathode_Ray · Post by **Cathode_Ray** » Thu 08/03/06 7:48 am

gottafewouts wrote:Hi,
I built a single ended el-84 w/solid state rectifier project some time back.
I want to disconnect the solid state rectifier and replace with a tube rectifier. My PT has 5v 3a taps for rectifier. What tube would you suggest to use. The build is a single el-84 and 1 ecc83s.
Thanks in advance,
MJ

6X4 recto tube.

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