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Old 1st August 2008, 12:26 AM   #1
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Default Power supply choke help needed

Could one of you experts help me make sure I order the right chokes for my very ambitious first amp project.
I am just half way up the learning curve, so don't roll your eyes if I make no sence.

I am getting together the parts to build a pair of JELabs 300B mono blocs. I have been reading for weeks and think that I have a very good understanding of how it all works, but the math will take a little longer.

Of all the different power supplies that I have come across, this is the one I want to use. Its a CLCLCRC, but of course I found two
that ended up with the same voltages, but using different chokes.

Here they are, this one is from Exquisiteaudio :
http://members.myactv.net/~je2a3/JELsc-300BDXPS.jpg

and for this one scroll down this page:
http://www.iol.ie/~waltonaudio/mk2300bmk1.html

As you see the first one uses a 10 and maybe 5H, but the other one uses a 20 and a 10H. I would like to use the 10 and 5, but the thing is I am not sure which 10 and 5 to get, as looking at chokes I see they come in various specs, like different resistance and current ratings. So I am afraid that not getting the right 10 and 5H from Hammond's list may screw up the voltages.

So could someone do the math ant tell me exactly which ones would end up right.

Also, although I want to use the 10 and 5H like in the first schematic, my caps will be more like the second schematic,
10uf-50uf-50uf-50uf, so work that in the equation.

Ok, so thats my first concern with the PS. My other one is that if posible, I would like to use a 5ar4 instead of the gz37, as the gz37 seems hard to find. Some tube data sites don't even have info on it. From what I read they are both slow start up, but the 5ar4 would make the B+ higher.

So If I did use it, what adjustments would I make dowm stream to the caps or chokes to end up with simular voltages.

Just tring to see what options would be, thanks for any help, I hope that I am not asking too much at once, but I did try to use that simulator thing on Duncans site, but I gave up.

AB.
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Old 1st August 2008, 12:43 AM   #2
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Join Date: Jun 2004
Location: Indiana
This should be helpful to you...

Duncan Amps PSDII
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Old 1st August 2008, 12:51 AM   #3
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Location: Ann Arbor, MI
hey-Hey!!!,
The 20 Hy/400 mA choke is going to be nutsy big and expensive. A 10 Hy/300 mA from hammond's 193-series will be fine, same for the 5 Hy...take 150 mA. Changing the voltage a little bit isn't going to make any difference, don't sweat the IR voltage drop/gain you might see.
cheers,
Douglas
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Old 1st August 2008, 02:45 PM   #4
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Doug,

Thanks for your help, so you are saying a little veriation in the voltages is no big deal.
I was tring to come up with the exact voltages on that Duncan simulator and it was driving me crazy.

AB.
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Old 1st August 2008, 03:22 PM   #5
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hey-Hey!!!,
I've found the Sim to come out within less than 5%, and when better values are put in, it is quite close. The rest of the amp does not much care; 10% is going to be OK, but a big enogh difference it might make you feel bad...
cheers,
Douglas
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