Laptop Power Supply Problem Noise!!

[Mr Illusive]

It has already been mentioned but my response to this was to seek out a ground loop isolator. This is the best way to get rid of this noise which plagues every laptop that you plug into an audio rig of some sort. They work fine when powered by battery, but the second you connect them to a power suppl....nooooise.

The other method to getting round this, however a little more risky, is to remove the earth from the plug. It's the earth that causes this noise.

[rumsguy]

Don't have alot of info for you but I have never heard of a power supply making noise. That has to be defective so I would contact support for your laptop seller.

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[morgamusic]

Hello,

I have a similar problem with my old 2006 Toshiba M100 lap top work fine on batteries but audio from headphone jack and ASIO output is noisy - have assumed its a power supply problem or ground fault but suspect power supply. Info on this is either very technical or sparse. Support from Toshiba was not forthcoming as it was a supply problem. It not unheard of and noise is power supplies is a common problem.

I was wondering if you ever "fixed" the problem or if I should try a new power supply.

[AndyH]

I don't use a laptop so I can't speak with any authority but I've seen quite a few discussions of the problem and it is often (but maybe not always) solved one way or another. There does not seem to be any universal cure. One approach works with some laptops, another with others, etc. Possibly it is more the quality of the execution than the particular method, but that is just speculation.

There have been other threads in this forum that go into some detail.
There has been more than one thread here
http://www.audiomastersforum.net/amforum/index.php
discussing what works and doesn't work.
I'm pretty sure the topic has been discussed here too
http://www.hydrogenaudio.org/forums/...php?act=portal
but perhaps in less detail.

[morgamusic]

Thanks for your reply - I have tried many trial and error solutions over a couple of years - but only running on batteries works consistently. It's audio level seems to vary in DB from 70+ to 40 db but since i record some low level stuff it still and issue. I have also used recording the noise in Adobe audition and then filtering it out post tracking but that I still a work around. Some days I pine for my OLD 4 track reel to reel. Seems it may have something to do with power supply design and switching but I'm not sure ATM

[AndyH]

The problem is indeed the laptop power supply design and how it is grounded, vis a vis the whole system. There is almost always a significant noise and interference difference between having that power supply active and just running off the battery. I recall reading about a complete speciality power supply change-out but I think that is one of the more expensive solution. A few professionals who make some use of laptops for recording have constructed their own power supplies of automobile batteries (with appropriate electronic controls) to provide enough power to do a full recording session, but that is also one of the more extreme approaches.

[serkybaby]

Thanks to AndyH for his suggestion ... the "Radio Shack" piece works fine for me.

I just opened the plug and cut the earth wire wallah no noise. I asked an electrician it's safe to do if the equipment aint made of metal...

[DAS]

Thanks to AndyH for his suggestion ... the "Radio Shack" piece works fine for me.

That RS piece may work in many applications. Be advised, however, that (I think, it's hard to tell for sure) it's a capacitor based device, which is cheaper than a transformer. The way it works is different. It literally filters out low frequencies. The ground loop hum is often caused by direct connections in a loop. Filtering the DC component breaks those loops. The capacitor will often work, but it also has a tendency to filter low frequencies of your audio (unlike a transformer). The response as noted on that link is listed as going down to 40Hz. Not sure whether that's the -3 dB point or what. Just be mindful that you may lose some low end.

Not the greatest explanation...sorry. If anyone needs more background on this let me know...