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Old 9th August 2004, 12:32 AM   #1
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Default Can a tube rectifier handle a C dual LC?

I did one using ss diodes a while back and i'd like to know if this will work for tube rectifiers, such as 5AR4...

0-350V -> 5AR4 -> 10uF - choke - 100uF - left channel
....................................- choke - 100uF - right channel

reason is, i have two 100mA chokes instead of one 200mA for my 300B project.
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Old 9th August 2004, 01:43 AM   #2
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Yes, you can. You can also safely increase the 1st filter cap. to 22 or even 33 muF., as the 5AR4 is unusually tolerant of largish filter caps. for a vacuum rectifier.

2X 100 mA. chokes and separate 2nd filter caps. are superior to a single 200 mA. choke and a single large 2nd filter cap., as undersireable channel to channel interaction is reduced. Your arrangement is a pseudo dual mono power supply (PDMPS).

BTW, I assume your power trafo's rectifier winding is 350-0-350 V.
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Old 9th August 2004, 01:45 AM   #3
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All that matters is: the first cap is smaller than max. the rect. is rated for; the inductor(s)' reactance is higher than that of the cap (10uF @ 120Hz = 133 ohms; most chokes have a DC resistance on par with this, let alone the AC reactance! FWIW, in this case around .25H would be the minimum); and the total current draw is within rectifier ratings.

Tim
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Old 9th August 2004, 02:31 AM   #4
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hi eli, yes i meant 350-0-350. i have crappy fingers this morning

hi tim, sorry i forgot to say that the chokes are both 10H.

thanks!
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Old 9th August 2004, 10:57 PM   #5
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I like this topology also and have used it recently. The nice thing about it is that you can control your final output B+ voltage by varying the first cap. Gordon Rakin explains this technique in his Bugle amp. You might need to get a higher voltage PT but model it first using PSUD first to get you in the ball park.

http://www.wavelengthaudio.com/bugle.pdf
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Old 10th August 2004, 12:30 AM   #6
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i have a copy of that article and have built a bugle myself. how can i miss that? the version i made use one choke though as i don't have extra at the time of build.

now i'm faced with another issue -

i plan to use VR tubes (0C3 0D3) to have a 250V (or so) for my driver stage. i don't want to pull out supply from either of the B+ lines and wonder if the following can be applied:

350-0-350 -> 5AR4 -> 20uF -> 10H -> 100uF (Left)
-----------------------------> 10H -> 100uF (Right)
-----------------------------> R -> C -> R -> C -> VR (Driver)

any better approach than this?
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Old 10th August 2004, 11:13 PM   #7
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Hi,


Quote:
any better approach than this?
May I suggest this instead:

350-0-350 -> 5AR4 -> 20uF -> 10H -> 100uF (Left)
-----------------------------> 10H -> 100uF (Right)
---------------------------------------------------------> R -> C -> R (current set R for VR -> VR (Driver Right)
---------------------------------------------------------> R -> C -> R (current set R for VR -> VR (Driver Left)

R -> C for driver stage is probably not needed.

Never preceed nor succeed a VR tube by a shunt capacitance larger than 0.100F or it will osscillate.

Cheers,
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Old 10th August 2004, 11:31 PM   #8
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hi frank, thanks for the reply and sorry for feeding bit by bit information on this thread...

i only have holes for one each of VR150 and 105 tubes, hence, my dillemma because it is common for both channels of the driver.
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Old 10th August 2004, 11:46 PM   #9
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Hi,

Arnold,

Quote:
i only have holes for one each of VR150 and 105 tubes, hence, my dillemma because it is common for both channels of the driver.
I noticed you mentioned OD3 and OC3 which are both octal socket types.
However, in case you didn't punch the holes yet, both the 105V and 150V types also exist in a seven pin (pico seven) version as OB2 and OA2 respectively.

Otherwise I'd just leave the VRs out and keep the PS separate for both channels. There's little point in splitting it for the powertubes whilst having it common to the driver stages.

Cheers,
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Old 11th August 2004, 12:21 AM   #10
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hi frank, they're punched and sockets are in

can i just use two VR105 so that i can get my fixed bias voltage for my 300B?
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