[JimmyDean]

Would it be feasible to use a laptop power supply as a power supply for a PIMETA? One like this for instance

http://cgi.ebay.com/ws/eBayISAPI.dll...ory=41993&rd=1

 

[phugger]

I use a dell laptop power supply my pimeta; works fine.

 

[JimmyDean]

The reason I ask is because I was reading on audiologica that most wall warts are really crappy power, and its best to get linear regulated supplies. Are laptop power supplies linear regulated?

 

[Voodoochile]

Most of them are pretty noisy (switching PSU). But there may be exceptions. I have tried two different laptop PSUs, mainly because I like the standard plug and seperate box over the "wart". In both cases they were just too noisy for my taste.

Some amps are more sensitive to noise, some switchers may be particularly quiet, so YMMV, which doesn't help much.

 

[mono]

Laptop power supplies are regulated but switchers. They are relatively noisey and definitely not good for audio. Because a Pimeta has a ground channel it will hide much noise but it is still not a good option.

However, it could be implemented better by simply following the switcing supply with a linear regulator. The switching supply has fair output capacitance already so if you took a 01.uF cermaic cap across the output, followed by an LM317 and a 10uf Tan or 100uF 'lytic cap, that should be sufficient. I left out the description of the LM317 adjustment circuit, if that is more complex than you want to do it then you could just use an LM7815, since most laptop supplies are in the 18V neighborhood (the one linked on ebay is odd, probably old, you'd do better to get an 18V version).

However, typically switching supplies are used for their greater efficiency. A Pimeta only uses ~120mA at most, there is no real benefit to using a switcher on a Pimeta, only more issues to deal with.

 

[MaxW]

I tried it and got a high pitch whine with my PIMETA. I'd say dont bother.

 

[chillysalsa]

The quality of these laptop supplies varies greatly, you may or may not get noise.

I know my Dell laptop supply emits a high pitch buzzing sound when it's connected.

Most laptops have further regulation inside of them, so the power supply noise can be tolerated. They ARE however very high current in most cases, but that's not really need for a PiMeta which has such little draw.

 

[BlazerFRS]

If you could get one on the cheap (or had an extra) you could always throw a tread in front of it to clean it up.

TREAD

 

[Voodoochile]

I think the main issue is not regulation, but switching noise.

 

[mono]

Quote:

Originally Posted by Voodoochile I think the main issue is not regulation, but switching noise.

I agree but a linear after a switcher can tend to reject a lot of it.

 

[Garbz]

It also depends on the circuitry. High freqency switchers like the kind used in cheap dvd players may be audibly fine. It also depends on the amp. Tubes have horrible PSRR but opamps will fair much better.