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Old 16th September 2012, 08:21 PM   #1
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Default replace adjustable regulator with fixed?

Hello,

Is it possible to replace an adjustable regulator (like a LM317 ) with a fixed regulator?

The LM317 in circuit has +6v on the output, I'd like to drop in a +6v Dexa.

NewClassD UWB Regulator

I cannot think of any reason why this would not work, I just want to make sure I am not missing anything.

cheers
Kevin
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Old 16th September 2012, 08:45 PM   #2
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The LM317 has external components not required by fixed regs. You'll need to remove those after determining that they aren't needed for anything else. And the LM317 has a different pinout than its fixed output cousins.
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Old 16th September 2012, 09:00 PM   #3
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you need to flip the fixed ones 180degree.

you need to remove the trimmer and a resistor or 2.

Last edited by AudioSan; 16th September 2012 at 09:03 PM.
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Old 16th September 2012, 09:32 PM   #4
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The LM317 is a really good performer if properly bypassed, better than its fixed cousins. No doubt one can do better with a discrete design, but that's a lot of money to replace a 317. It's debatable if it will have an actual measurable benefit, but after spending that much, I'd certainly be convinced that it did.
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Old 16th September 2012, 10:06 PM   #5
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The NewClass D performed better (sonically) than the LM317 -- see the new issue of "Linear Audio"
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Old 17th September 2012, 08:10 AM   #6
RJM1 is offline RJM1  United States
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The NewClass D is only rated at 630mA where the LM317 is rated at 1A. Make sure you don't draw too much current.
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Old 17th September 2012, 09:20 AM   #7
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Quote:
Originally Posted by RJM1 View Post
The NewClass D is only rated at 630mA where the LM317 is rated at 1A. Make sure you don't draw too much current.
it's the LM78xx that is rated at 1A. LM317 is rated at 1.5A.
but they will work with higher currents to if one have som "bigish" sinks and
close rail voltage. i run close to 2A out of a LM7812. with 15V in.
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Old 17th September 2012, 09:47 AM   #8
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Quote:
you need to flip the fixed ones 180degree
That wouldn't account for the center pin, which is Ground for the fixed types and Out for the LM317.
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Old 17th September 2012, 10:11 AM   #9
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yes you are right
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Old 17th September 2012, 10:50 AM   #10
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by AudioSan View Post
i run close to 2A out of a LM7812. with 15V in.
What's the specification for an LM7812?

Are you suggesting that others copy you and operate devices outside the manufacturers specification?
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