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Old 14th March 2007, 05:38 AM   #1
regal is offline regal  United States
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Default Building Power supply for AA DAC

I am building a separate power supply for an AA DAC. It needs +/-15VDC for analog and +/-8VDC for digital. The DAC has some regulation inside but posts have indicated that the unit benefits from a linear regulated supply. Would a LM317 for each rail be good for a DAC ?
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Old 14th March 2007, 10:35 PM   #2
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I suppose you refer to the Audio Alchemy DAC?

If so, a friend of mine did this a number of years ago.
It responded very well to this improvement.
Its still a good inexpensive DAC.

As far as I know he used LM317/LM337.
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Old 15th March 2007, 03:11 AM   #3
regal is offline regal  United States
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yes Audio Alchemy DDE1.2. I bought for the HDCD decoding, hard to find in a DAC.
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Old 16th March 2007, 04:18 AM   #4
regal is offline regal  United States
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The only specs for this power supply I have seen on the internet call for 2A to the analog section and 1A to the digital.


This seems unbelieveably high for a DAC?
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Old 21st May 2007, 08:01 PM   #5
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Sorry Regal,

Been away for a long time, busy with other things.
My friends Audio Alchemy was the original DDE 1.0.
It was powered by an unregulated power supply of +12V and -12V if I remember correctly.
Internally the DDE 1.0 has a +5V regulator for some of the circuitry, so it takes more current from the positive supply than the negative supply.

I agree that 2A seems a lot. If so 2 x 15V x 2A would be 60W!
And thats only the analog section! The digital secton would be 2 x 8V x 1A = 16W, a total of 72W.
That seems unreasonable. Is this a proposed specification for a new supply or a specification of the origininal supply?

I really dont think that your DDE 1.2 takes 2A, but that the (if so,) proposed power supply is probably overrated which is always a good idea imho, then 1,5A capability will probably do the job.
I like to run things cool. Makes for higher reliability and longer life as well as better performance.

There are other voltage regulators that can supply more than the 1,5A the LM317 can, for example the LM1085IT-ADJ which can deliver 3A if properly heatsinked.
In addition its a low voltage drop reg, so it can regulate down from just 1,3V above desired voltage, less overhead voltage = less heat dissipation.

Also some versions of fixed regulators, ie 7815 can deliver up to 2A.

Unfortunately there arent that many negative regulators around that can supply more than 1,5A or so. There was one... I dont remember... I dont recall... If anybody knows, please let me know.

Hmmm.... Why not two in paralell?? Has probably to be fixed or carefully calibrated adjustable, otherwise they will fight each other... we dont want that...

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