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Old 2nd April 2008, 03:29 PM   #1
coresta is offline coresta  France
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Default 807/350B/6L6 PP amps PSU ?

Hi tubeholics I've been searching on the www the different schematics of this sort of amps. Most of them use a 5U4 or 274 rectifier . Should i use 2 x 5r4 to improve sonic results as i have them left (and the 5v windings) from a 900 CT Power Transformer ? I would put 10uF /5Hy/40uF for each block . Any opinion ?? Pierre ps : outputpower is n't the main goal as 20w is laaaaarge enough for me !
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Old 2nd April 2008, 06:07 PM   #2
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The data sheet say that both the 5U4 and the 5R4 are only food with 4uf of first stage capacitance. I had one die on me the other day because I overloaded it. They are both good to about 240mA which should cover almost all 807 designs.

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Old 2nd April 2008, 06:30 PM   #3
coresta is offline coresta  France
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ok Shoog, thanks for reply ! I said 10uF for two valves . But do you mean a twin rectifying will improve sonics ? regards Pierre
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Old 2nd April 2008, 07:16 PM   #4
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If your proposing to use two 5U4's per monoblock, I can't really see any reason why it would improve sonics. Also it may not be adequate protection against overloading as one may hog current as they age. If you need more than 240mA then go look for another rectifier.

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Old 2nd April 2008, 07:33 PM   #5
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Hi,

I have recently been testing a design using 450-0-450v 230mA transformer into a 5R4=>11uF=>17H=>500uF(excessive!) and i get about 520V on the anodes of the 807's in AB.

Seems to work well, although im a bit scared about the 11uF cap now i read Shoogs' comment.
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Old 2nd April 2008, 08:48 PM   #6
coresta is offline coresta  France
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yes , 4uF is a maximum/nominal value for the 5R4 . Then, 10Hy then 40 to 100 uF is perfect . Whats the idle current of your 807 at 0watts ? do you regulate screen voltage (max300v) or do you have another psu ? Pierre
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Old 2nd April 2008, 09:48 PM   #7
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You could use two damper diodes. Svetlana makes some nice ones that sound very good. I think damper diodes tend to sound better than 5R4s
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Old 3rd April 2008, 08:20 AM   #8
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I agree about the dampers. Svetlana's 6D22S can use up to 50uF with a C inout filter.
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