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Old 22nd January 2002, 11:52 PM   #1
hifi is offline hifi  Sweden
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Default Aleph 2 LC powersupply ...question..

i got hold of some pretty nice 1,1mH inductors (they way about 0,7kg each) and i want to use them in my ALeph 2 ps...witch "hook up" would be best?


Rectifier --- Inductor---Capacitor ---Aleph

Rectifier --- Capacitor --- inductor ---Aleph

would i gain much with?

rectifier --- capacitpr --- inductor --- capacitor ---- aleph

even though the first cap will be a smaller and of less quality than the later one?... (due to size)

/micke
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Old 22nd January 2002, 11:58 PM   #2
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Hi there,

If I learnt my lessons well , and before Grey wanders here , best would be the third, but if you can not afford a large cap immediately after the rectifier, the first one should be fine.

Cheers,
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Old 23rd January 2002, 12:54 AM   #3
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Grey shuffles in the door wearing his best aw-shucks look...
(No one [okay, <i>almost</i> no one] thinks evil of a Southern boy when he's got on his 'aw-shucks' look.)
Actually, it's a teeny bit more complicated than that. Depends on what voltage/current you want out of your power supply.
#1 will give you less voltage--in theory about .9 x VAC--but more current capability
#2 will give you something on the order of 1.4 x VAC, but with a bit more smoothing (think of it as a filter for a speaker--12 dB/oct)
#3 will give you the same voltage as #2, but with even better smoothing (18 dB/oct)
Given those three options, and assuming that you can make the voltages come out the way you want them to, I vote for #3, same as Francois.

Grey
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Old 23rd January 2002, 01:04 AM   #4
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Default Aleph inductors

I think the first would be the best since the inductance between the rectifier and the capacitor will tend to smooth out the pulse of current that goes into the capacitor on AC peaks. I would NOT use the second one. The amplifier wants to have a low impedance power supply and having the inductor between the capacitor and the Aleph raises that impedance. If the inductors have an iron core you might consider


transformer--inductor--rectifier--capacitor--Aleph

Iron can take a "set" if there is current going only one way through the coil. With the arrangement above you force the magnetic field in the core to reverse each cycle which might make the inductor a little more effective. This will not happen with an air core coil. I know this is a poor explaination, but I am not an engineer. Maybe an EE can bail me out. This idea originally appeared in Audio Amateur Four/87.
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Old 23rd January 2002, 01:27 AM   #5
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Default more on inductors

Grey got that post in while I was typing mine. In order to get the .9 X AC voltage you have to have a certain amount of inductance called a critical inductance. THAT is about the DC output voltage divided by the output current in milliamps. I don't think a millihenry is enough.

Aw-shucks Grey, you do a great job with this forum and I hate to be the Yankee boy who disagrees with you.
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Old 23rd January 2002, 02:09 AM   #6
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Some of my best friends are Yankees...but I try not to hold it against them.
Nobody asked me my choice for second best, just best.

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Old 23rd January 2002, 05:43 AM   #7
richt is offline richt  Puerto Rico
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hi folks !!!

very interesting discussion !

i have a tube amplifier with hv unregulated.
what design do i have to consider ??


power t + inductor + diode +cap

power t + diode + inductor + cap

power t + diode + cap + inductor + cap


i want the best ripple rejection but i want a stabler current
since hv is not regulated.

thank you folks

richt
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Old 23rd January 2002, 05:50 AM   #8
hifi is offline hifi  Sweden
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hmmm

what ratio should be used between the caps? before and after the inductor..??
/micke
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Old 23rd January 2002, 05:54 AM   #9
richt is offline richt  Puerto Rico
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thank you

do you mean hv caps mfarads ??

100mf on each can but i want to raise it !

thank you


p.s. i installed hexfred diodes but bass is more tight but his are
too harshy.

richt
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Old 23rd January 2002, 11:17 AM   #10
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Default It depends

The "optimal" solution depends on the application. Aleph pretty much draws a predictable current and so impedance of supply is not really important. I would expect number 2 below might be "more optimal" than some of the others.

TR - Ind - Cap - Aleph: "Best" if you have a small transformer as you will be using it more effectively

TR - small cap - ind - cap - Aleph: Kind of best of both worlds

TR - large cap - ind - large cap - Aleph: You don't really get to use transformer more effectively and you are still spiking current draw and attempt to filter it out later.

My favourite is:

-----small_cap --- ind --large cap --- ind large cap
Transformer
-----small_cap --- ind --large cap --- ind large cap

You can have as many sections as you like, but 1 section should be enough. If you prefer, you can do the following:

Tr--small cap--ind--large cap--ind--large cap--aleph

All these scenarios are most easily simulated using PSUD2 http://www.duncanamps.com/psud2/

Remember, to have maximum effect out of an inductor, you need to have ripple across it!


Petter
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