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Old 11th October 2011, 12:19 AM   #31
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Quote:
Originally Posted by kmaier View Post
You're correct on both counts... and yes, the B+ will come up before the input and output tubes heat up. This will give you a surge on the filter caps (no load) so be sure the caps can handle the surge. I prefer to use either a 5V4G or 5AR4/GZ34 as they typically have a good 10 second delay before B+ builds up and it builds slowly. Your current draw is high for a 5V4G so I'd stick with the 5AR4.
Sorry to resurrect this thread, but I had my last 5AR4 do weird things (too much hum), so I'm thinking about using the solid-state rectifiers that I built in...

Won't the solid-state rectifiers also put a lot of B+ out before the tubes warm-up?

Any recommendations? Thanks! Dave
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Old 11th October 2011, 04:57 AM   #32
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Yes, the SS rectifiers will apply B+ instantly, and this may give problems.

The modern-production GZ34/5AR4 seems to be less than perfectly reliable, too - so many of us here use "damper" (efficiency) diodes - either 2 tubes in a full-wave rectifier, or paired with (eg) UF4007 SS rectifiers in a hybrid bridge.

The 6CJ3 and PY500A are examples of good rectifiers in this position. They not only delay the application of B+, but also cause it to appear very slowly across 30 seconds - meaning you don't get unpleasant surge currents, as well as protecting the signal-valves while their heaters/filaments warm up.

There's lots of different dampers to choose from - but please use Duncan's PSUD2 to find out the repetitive peak current in your power supply, to make sure the damper can handle it. But suffice to say, the diodes named above can cope with 500Vdc supplies with 50uF directly after the rectifier, and still be working years later. The reliability of dampers is much better than 5AR4s!
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Old 23rd April 2017, 03:48 PM   #33
sunil is offline sunil  India
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Hi, hope its not too late to ask this. Can we use the 5U4G instead of the GZ34 for the SSE build. The mains are 370-0-370.
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Old 23rd April 2017, 04:18 PM   #34
zman01 is offline zman01  Bangladesh
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Sunil,

Any particular reason you want to use the 5U4G?

I am not an expert, but from memory I recall that with a 5U4G tube you'll drop the voltage by another 30 volts vs the 5AR4 and you shall have to limit the first filter cap value to a maximum of 40uf (others please correct me if I am wrong).
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Old 23rd April 2017, 04:31 PM   #35
sunil is offline sunil  India
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Thanks ZMAN. I don't HV the GZs and they're expensive.
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Old 23rd April 2017, 04:40 PM   #36
zman01 is offline zman01  Bangladesh
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Sunil,

I recall George (Tubelab) recommending the Sovtek 5AR4. Have you checked the price for that one?
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Old 24th April 2017, 01:21 AM   #37
sunil is offline sunil  India
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The Sovteks average $16.

Can the 5U4G be used with different components on the SSE, a different cap value, think it was less than 40uF.
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Old 24th April 2017, 01:41 AM   #38
zman01 is offline zman01  Bangladesh
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Quote:
Originally Posted by sunil View Post

Can the 5U4G be used with different components on the SSE, a different cap value, think it was less than 40uF.
Yes possible to use 5U4G in SSE as long as maximum value of C1 is 40uf. IIRC a friend of mine had his SSE with a 33uf cap and 5U4G.
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Old 24th April 2017, 08:26 AM   #39
sunil is offline sunil  India
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I've got some NOS Russian tubes and really keen to use them here.

Since there's about 40v drop in voltage, does it make sense to increase from 375-0-375 to 400-0-400 or is that a bad idea ?

With EL34s, whats the kind of output we can expect with the SSE ?
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Old 24th April 2017, 08:47 AM   #40
zman01 is offline zman01  Bangladesh
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Hi Sunil,

Even if you have 370-0-370 transformer, you can give it a go. Your B+ might be a little bit on the lower side for the EL34, but the amp will run fine.

What power transformer and output transformer are you planning to use?
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