A Power Supply Story

[Primalsea]

Just something interesting that happened.

Just for an experiment I made a tube buffer using some 6/30L2 valves. Why? Well I had all the bits (mostly) in my scrap box and I have loads of 6/30L2 valves, enough to last several lifetimes.

The buffer uses a step up inverter to get 175VDC and is powered by a 12V SMPS wallwart. I plugged it all in and it seemed to work very well but the internet and WIFI stopped working. Turned it off and the internet and WIFI came back. Turned it on and the internet and WIFI stopped again.

I used a mains filter on the SMPS wallwart and it solved the problem. Just shows you how SMPS supplies can effect other equipment.

Time to get a linear 12V supply I think.

[Jazid]

Sounds like a super crappy wall wart, driving an oscillating buffer stage throwing out emi/rfi all over the place.
Did you put a scope across it to see what was going on?
Funnily enough when I plug in my 'scope it takes out the USB connection to my sounds and I have to reboot the computer.. . Doesn't affect any other USB lines.

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[Macca]

If it affects the wi-fi does that automatically mean it will affect the sound coming from your hi-fi system? They aren't the same thing.


Not saying it won't affect the sound but seems that without further evidence a conclusion is being jumped to.


Go to a show and you've got rooms with a poor sound and maybe a few with a good sound - but they are all using the same electricity supply. And how many SMPS will be operating in the typical hotel? I don't know but you've got to figure it's a lot. Yes, some demonstrators use regenerators but IME that doesn't seem to match up with who is getting a good sound and who isn't.


I've only got 2 things in the house using SMPS that are on all the time (in standby): the TV and the cable box. I can't detect any improvement if I unplug them while listening.

[Primalsea]

Until I buy something better it’s just a very cheap, small multi-voltage SMPS that most likely has very poor filtering. Once a heavy load is imposed on it the internet goes down unless I use the additional high quality filter. Like a lot of Chinese made electronic goods that are not specifically made for the European market they do not meet the EMI/RFI emission standards and many SMPS units have very generous current ratings on their specifications compared to what they should really have.

To effect the wifi and broadbrand it must be kicking out some fairly high frequency noise!

[Macca]

Might be faulty?

[Jazid]

More likely just stressed. It probably wasn't designed to run a voltage doubler which delivers an odd and heavily capacitive load. That will generate its own emi, and that can also feed back through to the mains.

Funnily enough most mains regeneraters use switching PSUs. Principally they purify what comes out of them, not what supplies them, although decent ones shouldn't make the mains worse.

Re sounds any halfway decent hifi should be able to reject such mains rubbish and it shouldn't affect the music. Oscillators and freaking out SMPUs nearby are another matter!

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[Primalsea]

Cheers for the sugestions. The PSU is a cheap crappy thing and I am just using as a stop gap until I get something better. It really was a cheap Amazon special, so never expected it to be good.

I was just interesting how it polluted the mains to the extent that it did, not that I could tell if it was effecting how the hfi sounded.