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  #1  
Old 22nd December 2011, 12:06 PM
bencat bencat is offline
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Default Cheap good quality Linear Power Supply

Many of the modern digital boxes that some of us use such as Dac,s , Media Streamers etc have either very cheap built in the plug power supplies or switch mode supplies. It is often commented and suggested that a good basic linear power supply replacement would give a good lift to the sound quality in each case.
However most of the ready made units offered for sale are priced above the cost of the original unit complete never mind the supply and this makes things difficult if you are on a budget.
Would it be possible to offer both a kit and fully constructed version which would be reasonable in cost but a real improvement on the original supplies ?
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Old 22nd December 2011, 01:57 PM
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pre65 pre65 is offline
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Default Re: Cheap good quality Linear Power Supply

It's not too difficult to build one if you have an understanding of how things work.

Might pay to set a few hours aside and search the Interweb, I'm sure you will find a few.
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Old 22nd December 2011, 05:26 PM
alnewall alnewall is offline
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Default Re: Cheap good quality Linear Power Supply

Quote:
Originally Posted by bencat View Post
It is often commented and suggested that a good basic linear power supply replacement would give a good lift to the sound quality in each case.
A good switched mode supply can also be very good.
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  #4  
Old 22nd December 2011, 08:13 PM
FreddieT FreddieT is offline
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Default Re: Cheap good quality Linear Power Supply

Having spent a good part of my days in EMC test chambers trying to qualify some kit for aircraft recently my suspicions about switched mode power supplies and wideband noise have been confirmed. The kit we were testing radiated very little, but the test equipment based around laptops with power supplies was awful and prevented us passing the tests. Running on batteries helped, but laptops seem to kick out substantial noise as well. Plug in the power supplies and oh dear.

We cured the problem by replacing the exit hole for the test cables from the chamber with a large metal plate to complete the Faraday cage with back to back connectors through the plate & feed throughs on all the lines (including power) to get some isolation from the ante chamber where the test kit was housed.

I agree that a good SMPS is OK, but I still worry about current harmonics in the local mains unless the filtering is very effective. Mind you a poorly designed linear supply can also lead to current pulses on th emains with the charging of the capacitors, unless a choke is used as well to balance energy storage. Now I wonder where that idea has been used before?

I've been toying with a wall wart replacement supply design with multiple isolated outputs (similar to that used by guitarists for their pedal boards but with better components) with choke filters. Not even close to the drawing board yet, too busy testing....

Merry Christmas!

F.
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Old 23rd December 2011, 11:11 AM
bencat bencat is offline
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Default Re: Cheap good quality Linear Power Supply

Thanks for all the comments and yes I do know that switchmode supplies can be very good indeed Chord Electronics use them but they are hugely expensive to design and build well which defeats the object as I need due to lack of funds to get as much bang as possible for my buck as the wonderful americans would say.

Philip - Thanks for the advice and I promise I have spent at least two or three days looking at different links on the internet and the conclusion is.
1. I do not know what I would be doing and do not have the knowledge to spot what is and is not good practise.
2. Everyone who does a design all think that their approach is best but how can you tell ? Go for the cheapest and keep your fingers crossed.

I can not afford the most exotic and what should be the best so what I think I and many others are looking for is a pointer to something that would be relatively easy to build and component source and could be made fairly cheaply to start with. Howeve if scope was left for upgrades of better components later that would be a useful thing to have as well. First and foremost though would have to be that it would at least be a good step up from the standard wall wart. Appreciate that most people are a little busy at the moment but this is not something that will change anytime soon more and more of the boxes we add are using these supplies and having a reasonable quality substutute would be something lots of people would value .
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Old 23rd December 2011, 11:20 AM
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pre65 pre65 is offline
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Default Re: Cheap good quality Linear Power Supply

What is the voltage of the item you would most want an improved power supply ?

And do you know the current needed ?

Also, is the start up current needed greater than the running current ? (it is on Squeezebox).
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