3.3V PSU to drive PCM2706 USB DAC - Page 2 - diyAudio
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Old 4th February 2006, 05:54 AM   #11
Nordic is offline Nordic  South Africa
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Hey D, you must just keep on hanging around here, I'm realy out of my depth when it comes to digital circuits..., going to the shop quickly to get some Coke then I'll come enter what components I got for the PSU, If I have to guess, no LM regulators.. probably 78XX stuff.
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Old 4th February 2006, 06:46 AM   #12
Nordic is offline Nordic  South Africa
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Yep, 7808, 7805 and scc ez3.3 9330
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Old 4th February 2006, 08:22 AM   #13
Franz G is offline Franz G  Switzerland
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Nordic

I recommend you the following procedure:

First, use two or three NiMH in series, load them with 1k resistor and measure the voltage.

Anything between 3 to 3.9V is O.K.

Now you can try your USB DAC. When it works correctly, you can proceed to step two: make a fine PSU.

Franz
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Old 4th February 2006, 08:26 AM   #14
Nordic is offline Nordic  South Africa
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My hands stink now, just completed sawing off the excess PCB... Franz man, I still don't know how to thank you.
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Old 4th February 2006, 09:09 AM   #15
Franz G is offline Franz G  Switzerland
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Quote:
Franz man, I still don't know how to thank you.
Man, you promised me, not to talk about that in the forum!

For the others: I've sent some of my sample chips and smd soldering trials to Nordic (because I like his avatar)

The PCM2706 is already soldered in a adapter board, but he got a piece of four adapters, three of them unusable.

So, he had to cut it out.

Regards
Franz
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Old 4th February 2006, 11:03 AM   #16
Nordic is offline Nordic  South Africa
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Lol I'm sure they don't know what I thanked you for, but yeah, guys, Franz is my current hero... Boy do I have something to send to you, sadly its totaly legal.

BTW, you got mail
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Old 4th February 2006, 02:23 PM   #17
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Default Re: 3.3V PSU to drive PCM2706 USB DAC

Quote:
Originally posted by Nordic
Hey guys can you point me in the right direction to make a 3.3V regulated PSU suitable to drive the above DAC..
---------------------------------------------------------------------------------
If you want really low noise, go for the ALW regulator in this forum. Once you have built one, the rest are easy. NO packaged regulator can match it's performance.

My DAC sound much better powered by this even though it has multi stage regulation after a switching regulator.
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Old 4th February 2006, 07:50 PM   #18
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I'm no expert, but this much I have managed to find out: regulators don't do much to filter out high frequency noise, and that is a big part of the battle in a DAC. It is not that failure to filter it out will lead to a bad project, but that properly doing so will make it that much better. Also, while batteries help things, they are not necessarilly a panacea. They do still have some noise. Also, regulators are likely to add a little bit ofnoise, so even with a battery there will be some. A ferrite bead in series with the supply to the pin, and a decoupling cap very close to the pin can do wonders. But, as I say, you shouldn't let this hold up getting a project done, but you should consider it for the second try when you are trying to make improvements.
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Old 4th February 2006, 08:40 PM   #19
Nordic is offline Nordic  South Africa
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Thanks, I'm allready bussy with version 2, as I saw some problems with my first attempt, no harm done as I haven't soldered anything...got some ferite beads on a PCB from a PC screen somewhere, think I will pirate a few, why is there no seperate digital and analog power supplies... or is it not worth it...?
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Old 11th February 2006, 04:14 AM   #20
Nordic is offline Nordic  South Africa
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This morning I will start her up, think I soldered the last connection last night... also got a 3.3V supply working after a few tries... eventualy I used a LM317 a 240R resitor and a 1k pot.(and caps etc, but thats not important now). I have a 7.2V 1.2VA tranny connected to the regulator.

I also calculated that the second resistor should be somewhere over 600ohms... but strangely enough when I measure the two connected legs on the pot they read something like 260ohms...

As long as it doesn't break anything... anyone have any advice, measurements I can make with multimeter etc...?
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