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Old 22nd November 2002, 04:18 PM   #1
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Default A less used approach

I looking for a bit more detail on external PSUs for power amps. It was raised in this thread,

http://www.diyaudio.com/forums/showthread.php?s=&threadid=3493&perpage=15&highlig ht=remote%20AND%20power%20AND%20supply&pagenumber= 1

but the thread then drifted off topic. GRollins and Fred Dieckmann both mentioned using extra capacitance in the amp enclosure.

Does this extra capacitance need to be a significant percentage of the overall capacitance? My aim is to use 26000uF caps in a C-C-L-C-C on each rail, where L=2-3mH. Could I simply move the last cap to the seperate enclosure? (I have the caps already, and am looking for a UK outlet for the chokes)

My other option would be to get an amount of smaller caps - 1000uF or thereabouts - and use those in addition to the existing caps.

All help will be gratefully accepted!!! Please!!!

Cheers

Paul
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Old 22nd November 2002, 04:31 PM   #2
tiroth is offline tiroth  United States
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Probaby half or more should be close by the amp. Reason: you need enough C by the rectifiers to absorb the spike (otherwise EMI probs and ohmic losses), but after that you ideally want to lower the impedance of the supply, which means keep the capacitance close to the circuit.
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Old 23rd November 2002, 08:21 AM   #3
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What spike?
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Old 23rd November 2002, 12:11 PM   #4
eLarson is offline eLarson  United States
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The spikes he refers to ride on the voltage
rail and are due to the rectification of the
AC mains.

A nice article about power supplies can be
found here:

http://www.tnt-audio.com/clinica/ssps1_e.html

It may go a long way toward answering
your questions.

Best,
Erik
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Old 23rd November 2002, 05:47 PM   #5
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Ideally we keep the transformers and first bank of
caps a few feet away, and then have another bank
of caps locally at the circuit. (This for Monos only...)

This also provides a nice opportunity to insert and R or
L to make a pi filter and take out some ripple.
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Old 24th November 2002, 09:12 AM   #6
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eLarson,

Thanks for that link, just downloaded and printed. I'll read that asap.

Nelson,

Do I take it that the chokes or resistors are in the transformer box or the amp box?

Everybody,

Thanks for your input.

Cheers

Paul

-------------------
Every step is one step closer to the prize.
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Old 24th November 2002, 01:33 PM   #7
eLarson is offline eLarson  United States
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If the goal is to get the power feed to the
amplifier box as clean as possible, I reckon I'd
put the bulk of the caps (with the choke
between the banks to make a pi filter) in the
PS box.

In the amplifier box I suppose I would put a
good sized cap (2200 or so) near the front end
circuitry, then one near each output device for
some "localized power delivery." (Honestly I'm
not sure how much that would really help, I've
never tried it with anything other than a
lineamp. YMMV)

Another thing to keep in mind is how to deliver
the power from the PS box to the amp box.
Allied with that concern is how to ground
everything. Keep the grounds for the lower
current front end circuits separate from those
for the output stage. I'm thinking the main
ground should be back at the PS box and the
others should connect to that one way or
another.

You may end up with an umbilical that looks
almost like an undersea cable by the time
everything is said and done!

Good luck with it,
Erik
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Old 24th November 2002, 02:41 PM   #8
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YMMV?
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Old 24th November 2002, 02:47 PM   #9
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YMMV

Your Milage May Vary

James
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Old 24th November 2002, 03:33 PM   #10
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Many thanks!!

Paul
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