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Old 17th April 2012, 04:00 AM   #11
Simon B is offline Simon B  United Kingdom
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Sounds a right pain Rick. Do you have any alternative power supplies you can try feeding this thing from apart from batteries and little switchers? Such as a linear supply with MOV spike suppression and some inlet filtering. It would be good to know if this is incoming mains noise, switcher noise or something else.

There are a couple of variables here, I have seen and heard strange stuff coming in on mains that just didn't used to be there, often unexplained, but including a neighbours fish pond fountain pump....(!). Data on power lines is another growing source of junk in the UK.

The iron and copper in linear warts provides filtering to some degree. Iron and copper are what's missing from switchers of course.

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Originally Posted by abraxalito View Post
Very interesting and enlightening observations, thanks
Methinks the onus is going to be on the audio designers to engineer their products to work with cheap switchers. Rather than the PSU designers to clean up their act - quality audio will always tend to be a minority sport compared to mobile phones and tablets.


I agree with you insofar as you're saying that cheap linear warts look like they're at least largely a thing of the past. But the sort of thing we're talking about here are commodity items, with ever changing designs, and very unpredictable emissions of broad spectrum crud, possibly to an extent that makes them a less than good idea for this application, sadly.

I know of big, good quality switchers being
used in recording studios as replacement psus for a particular make of mixing desk whose original power supply was not as well designed as it could have been, prone to eating now expensive sets of TO-3 series pass transistors, but this is a world away from a $2 item that weighs little more than the plastic case it comes in.

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Old 17th April 2012, 04:17 AM   #12
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Originally Posted by Simon B View Post
this is a world away from a $2 item that weighs little more than the plastic case it comes in.
$2 ? For a USB charger? You were had My last one (I bought a handful actually) was well under $1 and I didn't even begin to bargain with the guy.
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Old 17th April 2012, 10:10 AM   #13
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If you havnt already got an electrolytic decoupling cap ON the preamp board i suggest put one in , say 470uF and see if that makes a difference as you may not have enough decoupling near to the preamp circuitry .

Last edited by epicyclic; 17th April 2012 at 10:24 AM.
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Old 17th April 2012, 11:18 AM   #14
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thanks for the input! ive decided to make my own general purpose 12 and 9 volt power supply, i had no luck with anything anywhere, ive broken the circuit down and il try piecing it together bit by bit to see if i find anything but if i chose to develop this project, im just gonna go with putting the supply from the mains on the same chasis.
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