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Old 28th June 2003, 06:33 PM   #1
Fuling is offline Fuling  Sweden
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Default 6AS7 Idea

Has anyone tried using two 6AS7/6080 dual regulator tubes as pseudo diodes in a fullwave bridge rectifier?
As I can see these tubes should be quite suitable for this, they have low Rp, high max. cathode current and high heater-cathode isolation voltage.

The reason I came up with the idea is that I have some power transformers with high current 6,3V windings and non-CT HV windings.
Using silicon rectifiers together with those transformers would result in an unusable high voltage, besides I want my tube amps to be as free from silicon contaminations as possible

On second thought, I guess one 6AS7 would be enough if it is completed by two silicon diodes (a hybrid bridge rectifier).
OK, I know what I just wrote about silicon butwhat the heck...
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Old 28th June 2003, 07:55 PM   #2
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H-K insulation will be insufficient for much voltage.

If you're concerned about excess voltage, use choke-input and a silicon FWB.

Tim
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Old 28th June 2003, 08:17 PM   #3
Fuling is offline Fuling  Sweden
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What if the heater windings lies at an elevated potential?

I have some issues against choke input filters, I ve never managed to tame the mechanical buzzing from the chokes...
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Old 28th June 2003, 09:43 PM   #4
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I presume you'd be wanting to use a 5U4 for the positive half of the FWB, and the 6AS7 for the lower? In that case the cathodes will be bouncing up and down (alternately) with the full AC voltage.
Better to use damper diodes, which have more than enough heater insulation, at least in one direction.

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Old 28th June 2003, 10:09 PM   #5
316a is offline 316a  England
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Default ???

Quote:
Originally posted by Sch3mat1c
H-K insulation will be insufficient for much voltage.

Tim

Hi Tim ,
If a separate filament winding is used for the 6080 and is connected to the cathode , there should not be a problem with h-k , although sectional matching of 6080 do not seem too good . There was a lot of debate about 6080 in this application on the Joenet . I agree that dampers are excellent and inexpensive

316a
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Old 28th June 2003, 10:16 PM   #6
Fuling is offline Fuling  Sweden
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Yeah, damper diodes, thats another idea.
IŽll see where this ends, I was just doing some brainstorming
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Old 28th June 2003, 10:36 PM   #7
316a is offline 316a  England
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Default Dampers

Hello ,
As you're in Europe , try looking out for some PY500a . Mullards are excellent as are Tungsram which appear to use the same tooling but have welded anodes . There are literally tens of thousands of these available . These were used in the last generation of colour TV sets , replacements were manufactured well into the 1980's so I doubt these will run dry for several years ! Benefits include low volt drop , high current delivery , low price .

316a
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Old 28th June 2003, 11:16 PM   #8
Joel is offline Joel  United States
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"Low price" 316a? Are you penny pinchers trying to advance the state of audio or not?
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Old 29th June 2003, 12:03 AM   #9
316a is offline 316a  England
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Default Huh ?

Quote:
Originally posted by Joel
"Low price" 316a? Are you penny pinchers trying to advance the state of audio or not?
Penny pinching and using valves which are cheap but have genuine advantages are two completely different things . I'm sure others out there can concur than PY500a is an excellent valve but I doubt you have tried them

316a
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Old 29th June 2003, 01:06 AM   #10
316a is offline 316a  England
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Quote:
Originally posted by fdegrove
Back to the 6080, sure you can turn any triode into a rectifier.
Just remember, as has been pointed out, you'd need to match this formidable dual triode and than use it as a rectifier.

Personally I'd rather put this excellent sounding valve to better use, after all there must still be tons of otherwise useless rectifier valve around...if ever that supply were to dry up than maybe, just maybe.

OTOH, it may be an interesting experiment nonetheless...provide both halve are reasonably matched.

Cheers,
I have some 7586 nuvistors , the only use for them I can think of at present is to turn them into cuff-links Class B is a topology I do not wish to dabble with , I do not need high power and would rather rely on a simple yet rugged power supply avoiding that nasty crossover stuff . Anyone wanting class b is welcome to it , I'll stick to pure class A
I wonder how a 6080 strapped as a rectifier would actually sound ? I'll have to dive through the archives on the Joenet to find out how the discussion there was concluded . With the cost of say a pair of EY84 , EY81 , PY801 or PY500a as mentioned I doubt it would be worthwhile even bothering trying a 6080 unless I was really bored

316a
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