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Old 22nd January 2010, 05:11 PM   #1
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Default When you need +/- 15VDC and have only one pole

While I haven't built Pete Millet's Sound card measurement interface, I did pick up some of the MuRata DC-DC converters from DK which he used in his design. I pointed out on that thread that the NDTD2415C which I have (converts the 32V which I have in my Pioneer SX-838 to +/- 15VDC) benefits from a choke on the front end. While they have 12uH in the product data sheet, I picked up a little 12mH choke from a discarded switch mode power supply in the inductor junk box. Here's the before and after:

BEFORE
Click the image to open in full size.

AFTER:
Click the image to open in full size.

Load is 40mA on each side. The A-Wtd noise on the bottom is 2.6uV. Note that the scale on the top chart is 50mV vertical, the bottom 20mV.

Last edited by jackinnj; 22nd January 2010 at 05:14 PM.
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Old 22nd January 2010, 06:06 PM   #2
paulb is offline paulb  Canada
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What's the purpose of this thread?
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Old 22nd January 2010, 06:16 PM   #3
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What's the purpose of this thread?
I don't know. What's the purpose of the F5 thread?
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Old 22nd January 2010, 06:20 PM   #4
paulb is offline paulb  Canada
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I imagine the F5 thread gives some practical details for those who are building one, or considering to do so. And yours?
If you're presenting results of a power supply mod, how about a schematic?
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Old 22nd January 2010, 07:42 PM   #5
MRupp is offline MRupp  Germany
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Thanks for the info, very interesting. My first idea was to put filters on the outputs but this seems to work very well so I may not need to do this (I only have inductors with 3 Ohms resistance so would lose some voltage).

I still wonder whether it would bring any benefit to put some shielding around the PS components and/or move it to a separate board.
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Old 22nd January 2010, 08:01 PM   #6
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Just showing the implementation of the little Murata DC-DC converters -- with bipolar output. You can take 5VDC out of your USB jack and get relatively clean +/-15VDC for running opamps without bending yourself into a pretzel with a single supply configuration. A lot of Japanese receivers I've modded have a unipolar supply and use a bunch of electrolytics for coupling. This is easier.

12mH is not what Murata had recommended, and indeed it sucks a few mA more than the non-choke implemented supply...I was very surprised that the noise was as low as it was. Here's my implementation.

Click the image to open in full size.
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Old 22nd January 2010, 08:08 PM   #7
grufti is offline grufti  United States
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Thank you for the extra detail. I had seen your earlier post in the PM SCI thread.
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Old 3rd February 2010, 03:10 PM   #8
klewis is offline klewis  United States
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Quote:
Originally Posted by jackinnj View Post
While I haven't built Pete Millet's Sound card measurement interface
Jack,

Can you point me to the sound card measurement interface?

Thanks,

Ken
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Old 3rd February 2010, 04:54 PM   #9
tvrgeek is offline tvrgeek  United States
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Handy. I was not aware of this part.
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Old 3rd February 2010, 07:15 PM   #10
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Jack,

Can you point me to the sound card measurement interface?

Thanks,

Ken
Soundcard Interface
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