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Old 19th June 2006, 02:30 AM   #11
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Quote:
Originally posted by AndrewT
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If you want 30W into 4ohms and it needs 15Vpk at the output why are you planning to run +-25Vrails? Is the chipamp that bad?
Actually, I used those numbers as a 'worst case' scenario for current draw. In reality, I will be using 8 ohm speaker with 30V.
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Old 19th June 2006, 02:30 AM   #12
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Quote:
Originally posted by ErikdeBest

For low listening levels...and for maybe 90% of the time these regulator would be fine...but, whenever there is some Peak in the music current draw will be larger! Think about it this way...why are the recommended trafo's rated for at least 4 amp on the secondary?
Point taken. Perhaps my mind was thinking "Class A tube" where the fluctuations in current are minimal.
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Old 19th June 2006, 04:22 AM   #13
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Use LM338 and use the schematic to get negative supply.

Gajanan Phadte
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File Type: jpg neg.jpg (16.7 KB, 522 views)
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Old 19th June 2006, 07:24 AM   #14
AndrewT is offline AndrewT  Scotland
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Hi,
just to pluck a couple of numbers, from the posts' worst case currents, could range from 0.66A to 5Apk.

Which end of these extremes do you design for?

I know which end I will aim for.

BTW. the current variations in a ClassA stage can vary from almost zero to double quiescent current. Again that is an enormous ratio that has to be accomodated by the PSU.
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Old 19th June 2006, 07:39 AM   #15
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I note that the minimum current from the 317T is 1.5A, but the typical maximum (for the Nat Semi LM317T) is 3.4A!

If you could parallel two of those suckers you'd probably be on the money - so the question is, will 2 operate in parallel? Or would you need two sets of rectifiers for each unit? Mind you, it's probably easier to use the pass transistor style hookup...
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Old 19th June 2006, 08:00 AM   #16
anbello is offline anbello  Italy
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Hi,
I think this can help you
LM338 regulated snubberized PSU for audio amplifiers

ciao
andrea
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Old 19th June 2006, 01:34 PM   #17
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Quote:
Originally posted by AndrewT
Hi,
just to pluck a couple of numbers, from the posts' worst case currents, could range from 0.66A to 5Apk.

Which end of these extremes do you design for?
Point taken. Thanks kindly for the response.
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Old 19th June 2006, 02:16 PM   #18
Wynand is offline Wynand  South Africa
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National does have a 3A negative regulator as well. I can't remember the number, but look at their selection tables.
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Old 19th June 2006, 02:23 PM   #19
Wynand is offline Wynand  South Africa
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Found it LM333

http://www.national.com/pf/LM/LM333.html

It's not 5A but it doubles the current capabilities.

-1.5 - -32V

Hope it helps.

P.S I ran two TDA2050's off a single pair of LM317/LM337's
I don't recommend it though.
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Old 20th June 2006, 06:44 AM   #20
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Maybe it would be possible to use a nice transformer with nice caps No regulators?

Can't you put regulators in parallel to get more amperage? I think that would work too.
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