Author Topic: Low noise, portable +/- 12V PSU  (Read 1049 times)

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Offline moffyTopic starter

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Low noise, portable +/- 12V PSU
« on: May 08, 2019, 12:28:02 am »
I was trying to do some noise/distortion measurements on an audio VCA I had made but I was getting 50Hz noise from my power supply. I was looking for around 100/110db of resolution for my measurement system. Even if I moved the wires a little the 50Hz noise would fluctuate, obviously induced pickup. So I went for a simple, cheap solution. Bought 2, 12V/2.4AH gel batteries from Jaycar and some terminals, and voila, a low noise power supply which is portable and completely isolated, so no ground loops.
Testing went very well, unfortunately my VCA had around -80db of signal distortion. But the test setup, a Steinberg UR44 external sound card and my laptop had around 110db S/N ratio with the battery supply. For charging I already had one of those PRO type chargers that do multiple chemistries.
Perhaps others might share any mildly unusual battery supply stories, I'm sure they would be interesting. :) :) :)
« Last Edit: May 08, 2019, 12:29:51 am by moffy »
 

Offline NiHaoMike

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Re: Low noise, portable +/- 12V PSU
« Reply #1 on: May 08, 2019, 01:34:44 am »
Were those really cheaper than using NiMH AA batteries?
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Offline moffyTopic starter

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Re: Low noise, portable +/- 12V PSU
« Reply #2 on: May 08, 2019, 01:37:31 am »
Yes, especially from Jaycar. Simpler too, just cable tied them together no battery holders. :)
« Last Edit: May 08, 2019, 01:39:09 am by moffy »
 

Offline David Hess

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Re: Low noise, portable +/- 12V PSU
« Reply #3 on: May 08, 2019, 03:06:33 am »
I have used stacks of AA NiCd cells in the past to do the same thing.  Batteries make fine low noise floating power supplies.
 

Offline Gyro

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Re: Low noise, portable +/- 12V PSU
« Reply #4 on: May 08, 2019, 09:07:37 am »
You'd be well advised to add a couple of in-line fuses, otherwise it's only a matter of time before the insulation drips from your wires and the tracks lift off your PCBs. ;)

It won't hurt the noise performance.

This style is compact and easy to find... https://www.ebay.co.uk/itm/5x-Inline-Standard-Blade-Fuse-Holder-Splash-Proof-DC-12V-30A-Fuses-For-Car-Bike/132727931095
« Last Edit: May 08, 2019, 11:20:12 am by Gyro »
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Offline mariush

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Re: Low noise, portable +/- 12V PSU
« Reply #5 on: May 08, 2019, 09:30:03 am »
Seems like it would have been easier to use 4 x 9v batteries for +/- 11v..20v, followed by two linear regulators.
But i'm not aware of the power consumption.
Could have used 24 AA or AAA batteries, rechargeable batteries and battery holders are cheap.
 

Offline moffyTopic starter

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Re: Low noise, portable +/- 12V PSU
« Reply #6 on: May 10, 2019, 05:58:29 am »
2 by Pb-Gel in Oz are much cheaper and easier than 24 AA or AAA and remeber it has 2.4AH capacity. Yes the fuses are a very good idea, and I'll probably regret not putting them in somewhere down the line but I've gone minimalist i.e. Once I got something working I stopped(lazyness). One could put a set of regulators after the batteries for a variable supply.
I have used stacks of AA NiCd cells in the past to do the same thing.  Batteries make fine low noise floating power supplies.

Yes, they do work very well.
 


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