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Old 28th January 2008, 12:02 PM   #1
engels is offline engels  Israel
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Question diode bridge - 10000uF cap - diode tube - small cap - HV+

HV secondary -> Silicone bridge -> Large reserve cap -> Diode tube -> small filter cap -> plate supply


Another noooob question:
I've never seen this kind of setup, is it wrong?

The idea is, of course, to-

1) Stick another sexy tube in the chassis
2) HV delay
3) Sag?
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Old 28th January 2008, 01:24 PM   #2
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Added cost and no real reason?

If your talking about sag I assume your talking about a guitar amp here. You certainly don't want that in hi-fi. If your looking for the added resistance of a tube rectifier then you can just replace it with a resistor of a value equal to that of a desired tubes resistance.

10,000uf? Dang! Thats for sure DEADLY in any high voltage supply and not advised. Not needed really, in fact most SE amps can get away with less than 100uf with a SS rectifier, or 10 uf with a tube. I can't remember the site but there is one on google that talks about calculating the first capacitor stage and how much is needed and it was very low indeed. After the first CR filter you can add as much capacitance as you want, but above a certain point it becomes useless and has no added benefit and just becomes cost prohibative. Where your going to find 1,000 UF caps rated at 450v or above is going to be hard, let alone finding 10,000uf caps. Expect to pay over $60 for something that large!

Another really simple way to emulate a tube rectifier at low cost is
Option 1: UF4007 diodes with a resistor in series and diode "slowing" caps (.22ohm resistor/.01 uf cap in paralell with the diode. READ: .22 ohm/.01 cap are SERIES connected and then the whole assembly paralelled with the diode-otherwise you have a fireworks display at best and a shorted transformer at worst. )

Option 2:

uh...tube rectifier and a small cap (60uf or less) , then the rest of your filter.
Hope this helps! Not trying to rain on your parade but its really unnessicary and pretty cost prohibative to attempt what you have devised.
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Old 28th January 2008, 08:17 PM   #3
engels is offline engels  Israel
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Default 100000000

okay, okay, I understand what you're saying. There's no need for tube rectifiers and I know that. I think I've made only three or four amps with tube rectification and I don't like sag either - even in guitar amp.

The 100000000000000 is, of course, just a joke - let's say, 100uF is a real number. And by the way, if you ask where to get 1000uF caps - I've got about ten 2000uF/450V Mallory caps from a UPS power supply and I've used one in a 18W amp (solid state bridge of course). Believe it or not - this is a serious improvement over any 22uF-100uF filter cap. 2000uF is a perfect filter and it looks fun too.

But the question is more theoretical: will the above mentioned hookup work - because sometimes I see "hybrid" rectifiers here and there but they usually suffer from the same problem - you cannot put a big cap after a tube.
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Old 28th January 2008, 08:27 PM   #4
Serge66 is offline Serge66  Switzerland
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A choke is always a good thing in PSU.
The minimum size in henries: L = U / (6 x PI x f x I).
U is the voltage after the choke
f is the frequency of your mains (50 or 60)
I is the total current drawn by the load.
In practice, we double this value.

The choke allows to reduce the size of your caps. In the industry, we count with 1000uF per ampere.

The UF 4007 are ultra fast diodes for switch mode PSUs. I do not know how they behave in a 50/60Hz circuit. The normal ones are 1N4007.

As for the diode tube, sorry, I have no experience with this thing. I believe they act like a zener and therefore need a series resistor to limit the current (?).

Do not forget resistors across the caps if you connect them in series. Values in the tens of kilo-ohms, 5-10 watts. To be calculated.

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Old 28th January 2008, 08:31 PM   #5
engels is offline engels  Israel
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Default diodes

Quote:
Originally posted by Serge66

As for the diode tube, sorry, I have no experience with this thing. I believe they act like a zener and therefore need a series resistor to limit the current (?).
sorry, by "diode" I mean a regular rectifier tube or a damper diode.
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Old 29th January 2008, 10:16 PM   #6
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Default 10000uF cap

In a KT88SE an 220+220 500v Black Gate and a " forbiden" and beautiful EPCOS (Elna+Siemens joint venture ) 2200uF 450V , half brige CREE inc SiC schottkys config , no matter the advisers , headroom stage became fenomenal . I tried the with and without Diy poor man method and i am sure that this is the most desired improvement we music dieharders want in first place . I didn' t notice signs of what could be the increased ringing effect problems . Go with it , but not 10000uf . I would like trying more 2200uF but they are expensive .
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