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Old 22nd April 2006, 01:54 PM   #1
Ryssen is offline Ryssen  Sweden
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Default Voltage doubler question

I have a trafo with 310v/0,8A output that I thought of using with a SV572-10 SE,if I use a voltage doubler I get about 870v right?
and then use a solid state regulator to about 750-800v.Will this voltage doubling have any affect on the sound,hum,e.t.c?
I think it´s a little low to just use single voltage,about 435v.What do you think?

I have one pair of SV572-10-do they still make them?
Otherwise I have pair of 811-A to use when they burnt out.
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Old 22nd April 2006, 02:12 PM   #2
EC8010 is offline EC8010  United Kingdom
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The trouble with voltage doublers is that they have very poor regulation (the output voltage varies widely with load current). You might think that's not a problem as you're going to use a regulator, but it means that the regulator has to be able to cope with that very large input voltage swing and that invariably means that the series pass device has to dissipate a lot of power. Try modelling your proposed doubler in PSUD to see how it behaves, then calculate the implications on the regulator.
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Old 22nd April 2006, 02:48 PM   #3
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The performace of a doubler is precisely the same as a full-wave bridge at twice the AC voltage, except that ripple current is higher in the input caps.

Expect about 250 mA max. Since the peak voltage on the transrmer is 900 or so, it must insulated for that - PROBABLY OK.
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Old 22nd April 2006, 04:45 PM   #4
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I'm more conservative than Tom Bavis. I would not plan on drawing more than 200 mA. of DC from a doubler PSU with that trafo. BIG caps. are in order in the doubler stack, as that keeps the rail voltage up and quite stable. As the doubler stack caps. increase in value, the conduction angle gets smaller. So, I^2R heating in the rectifier winding is significant.

Follow the doubler stack with a low DCR choke and more capacitance. Large caps. in the doubler stack reduce the ripple fundamental well, but introduce a fair amount of ripple overtones into the rail. The choke kills the overtones.

With higher working voltage parts, the topology used in the "El Cheapo" B+ PSU will do nicely. Schematic here.
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Old 22nd April 2006, 07:35 PM   #5
Ryssen is offline Ryssen  Sweden
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200mA hm...maybee thats what i need, 100-110mA/tube.So you think I
should use a choke instead of regulator,how much voltage will I lose in the Choke?I have 2 BIG capacistors they are 1500uF/each,how big should it be after the choke?
Maybee I could go on with my questions.
I have a schema that uses a EL34 as driver,in katodfolower config.will this work and will it sound good,its triode connected.It has a EF86 as voltage amp.But that I won´t use,I want to use 6SN7 or 6SL7 or I have 2 "76" is it god to use?,I like trodes better,but I think it would bee fun to try sommething new with the EL34.


If somme one has links to schemas with the SV572-10 SE I apriciate if you post it. [B]well 811 schemas too.
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Old 22nd April 2006, 11:55 PM   #6
kevinkr is offline kevinkr  United States
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Svetlana 572-10 are still available here in the USA. New Sensor has them, and if you can't source them locally let me know as I can probably get them for you at a reasonable price. The new international airmail service would put the shipping at less than $20 for the pair I think.
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Old 22nd April 2006, 11:59 PM   #7
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Whilst what EC8010 says about regulation is true and would deter me from using a voltage doubler to power a class AB1, AB2 or B PP amp, in your case your SE amp will perforce be operating in class A and hopefully the regulation will not be a problem.

As to your ideas about driver and voltage amp, I would think EL34 in triode-connected CF operation as a driver would be good and an EF86 voltage amp would also be good. I know what you mean about preferring triodes but many people have reported success with pentode voltage amp stages in SE.
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Old 23rd April 2006, 12:28 AM   #8
Ryssen is offline Ryssen  Sweden
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Quote:
in your case your SE amp will perforce be operating in class A
Yes it will be in class A.
The voltage tube,maybee one of these D3a, C3m, C3g, F2a.
The C3m maybee,I can get a couple of them I think,will they work?
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Old 23rd April 2006, 12:35 AM   #9
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Voltage doublers were good enough for McIntosh

http://www.kbapps.com/audio/schemati...osh/mc240.html
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Old 23rd April 2006, 12:48 AM   #10
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Ray,

The H/K Cit. 2 and Fisher's whole line used doubler B+ PSUs without incident. Stu Hegeman and Avery Fisher were anything but stupid and their PP AB designs worked just FINE, thank you.

FWIW, I followed Hegeman's lead in "El Cheapo". Large caps. in the doubler stack "stiffen" the rail. The choke cleans up both SS diode "hash" and ripple overtones.
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