Is the 5 volt USB supply from a computer clean

[bumpy]

I am looking to supply a bit of kit with 5 volts. I hate switching power supplies and the obvious answer is to swap to a linear power supply.

Currently the kit is powered from a laptop computer via USB but the computer itself is powered from the ubiquitous switching power supply. :doh:

I was thinking if I switch off the mains power to the computer and let it run on it’s batteries will I get a clean 5 volts or will the internal machination of the computer conspire to dirty the USB 5 volts

[Firebottle]

It won't be as clean as a linear, there will be some sort of switching converter in the computer to give the 5V.

[bumpy]

It won't be as clean as a linear, there will be some sort of switching converter in the computer to give the 5V.

Thanks Alan, just as I suspected.
There are a number of 5v linear supplies on ebay for about £50, but not surprisingly none give noise specs. Any recommendations from people

[LC1979]

There are a number of 5v linear supplies on ebay for about £50, but not surprisingly none give noise specs. Any recommendations from people

This is relevant to my interests! :)

I've almost pulled the trigger on a 5v IFI supply several times, but was waiting to hear more about the long promised 5v supply from Allo, which is still due to be released imminently, AFAIK. I would also be keen to hear views on the eBay LPS modules...

[bumpy]

This is relevant to my interests! :)

I've almost pulled the trigger on a 5v IFI supply several times, but was waiting to hear more about the long promised 5v supply from Allo, which is still due to be released imminently, AFAIK. I would also be keen to hear views on the eBay LPS modules...

OK Luke. We wait with bated breath :)

[bumpy]

With Hi Fi almost all opinions on kit are subjective. But here is a product that can be measured scientifically so that meaningful comparisons can be made i.e. value for money.

Why then do so few sellers quote figures. My guess would be, that the power supplies are not as good as their superlative descriptions would have you believe.

[Andy831]

On the back of the OP question, if an item of kit asks for 5v 3a to power it is it ok to feed it 5v 2a or will that cause problems?

[Lawrence001]

On the back of the OP question, if an item of kit asks for 5v 3a to power it is it ok to feed it 5v 2a or will that cause problems?Problems. Overheating on power supply and various issues with the kit depending on what it is.

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[Andy831]

Thanks Lawrence so its a no no

[Cycleallday]

I use one of these, along with a couple a similar ex Maplin batteries/chargers with all my Pi's and would not go back to any mains tethered device.

https://www.amazon.co.uk/HUAF-Portable-24000mAh-Capacity-Compatible/dp/B07M6JFCLZ


The HUAF in particular is one i like - it has a quality feel, amazing battery life and can power 2x 2.5 amp devices and a 1x 1amp device at the same time should you wish.

Its a bit bigger and heavier than it may look - about the size of an iphone 6 plus and slightly heavier.

Its also good for charging my iphone and bluetooth earphones so gets plenty of use.

Mel

[bumpy]

I use one of these, along with a couple a similar ex Maplin batteries/chargers with all my Pi's and would not go back to any mains tethered device.

https://www.amazon.co.uk/HUAF-Portable-24000mAh-Capacity-Compatible/dp/B07M6JFCLZ


The HUAF in particular is one i like - it has a quality feel, amazing battery life and can power 2x 2.5 amp devices and a 1x 1amp device at the same time should you wish.

Its a bit bigger and heavier than it may look - about the size of an iphone 6 plus and slightly heavier.

Its also good for charging my iphone and bluetooth earphones so gets plenty of use.

Mel

Thanks Mel, that's an interesting alternative. Would I be right in saying that as its a battery in complete isolation there can be no distortion noise, or does the fact its a sensing charger mean there is something else electrical going on.

[Cycleallday]

It is a 'smart' battery in that if the power draw is removed then the unit switches off. This i find useful as sending a power off command to the pi (via wifi) also switches off the battery.

I hear no degradation using this type of unit and would not move to anything else. I do have an Audiophinics linear psu but have not used it with the pi's since starting down the battery route.

Mel

[Firebottle]

On the back of the OP question, if an item of kit asks for 5v 3a to power it is it ok to feed it 5v 2a or will that cause problems?

Often the spec for kit in question will be over estimating what is required. I usually like to measure the actual current that the kit will take.

Also most Chinese power supplies over specify what you can actually get from them. The sellers presume that because it has a, say, 50VA transformer fitted then you can get V times A DC output power equalling 50, which you most definitely can't> There are losses associated with conversion from AC (the transformer rating) to DC (the output rating).
As a rule of thumb say 2/3 of the published current specification.

[Andy831]

Thanks Alan

Sounds a bit complicated I will just buy a 5v 3a supply I think.

Andy