Linear USB power supplies...

[jack]

I'm after a decent low noise linear PSU with USB outputs to power an Focusrite Scarlett 2i2 4th Gen interface...

Currently it's fronting a RPi which is generating a load of hum, rather drowning out the faint audio I'm trying to record. The box uses USB C to connect to the Pi and uses the same cable for power unless there's another PSU plugged into a power-only USB C socket, in which can it uses that for power.

My logic is therefore to use a linear 5V USB supply in that second socket. Obviously, I could build one, however by the time I've done that and boxed it nicely, I suspect I'd be £50 and a load of time into it, so I might as well buy one.

What to do?

Edit: moving the power from the Pi to a "less digital" source has improved matters greatly ... still some hum though...

[Morgan Jones]

I've just discovered I have a need for a linear USB supply. But I looked and a ready-made one is £50. And it looks as though it will be pretty poor. I cannot understand why people like toroidal transformers with heatsink fins. If the transformer gets that hot that it needs fins, it's poorly designed. What did you do in the end?

[jack]

See the post at: viewtopic.php?t=2137&start=17580#p217559

I got one of these:

Creadvent 25W Dual Usb 5V Linear Power Supply Talema/YHDC Low Noise for DAC Audio Amplifier LPS Hifi
https://a.aliexpress.com/_EJgz8aE

But I only paid £49 for it and then got a £29 refund as they sent me one with a slightly different PCB.

My logic is that the case/xfrmr/sockets etc would cost me that or more, even before the time it'd take and it's then really easy to improve the PSU filtering etc as and when you want.

It's a really nice case. The fins on the xfrmr are not for cooling - it's just moulding - the footprints of these small toroids are pretty standardised, so small toroids are still on a standard footprint.

[Morgan Jones]

Thanks for that, but I see the price has gone up significantly.

[jack]

Thanks for that, but I see the price has gone up significantly.

There are regular substantial "offers" on AliExpress (as you'll be aware) and generally multiple suppliers. Just hang on a bit.

[ed]

Nick, off the cuff...
have you tried an smps into the 5v power socket?
I only ask because ime pi doesn't always play nice with usb dac when powered through usb data socket.
I discovered this with my steinberg ur22 and my behringer.

just a thought