Buzz noise through Macbook Pro built-in output

[icedsushi]

When I plug my Macbook Pro headphones jack into a powered speaker, I'm getting some medium volume electrical buzz noise, definitely noticeable. I'm using the laptop's battery, not the power adapter so it can't be a ground loop I don't think. And when I plug my iPhone into the same powered speakers with the same cable I don't get the buzz noise. Using headphones with the laptop I don't get a buzz either.

So it's not the speaker, the cable or the headphones. Must be some other factor from the combination of the laptop & the speaker...

Any way to correct this?

[YILA]

it's a ground loop even if it's running off battery, does plugging in the power lead kill it?

some speaker combinations do it yes, that's why for example my Avantones have a ground switch to sort it out.

Are your speakers balanced? Maybe you need to make a pseudo balanced cable

ETC

[fishmonkey]

it's a ground loop even if it's running off battery, does plugging in the power lead kill it?

make sure you try this with the 3-prong grounded mains lead, not just the ungrounded 2-prong duck-head thingy...

[icedsushi]

Tried plugging in the 2-prong power adapter & unplugging. Didn't attenuate the buzzing noise either way. I don't have the 3-prong with me right now, will try that in a day or two. Is that one of the reasons they give you the longer cable for the adapter? I thought it mostly served as an extension cord, so I normally never bother with it. Perhaps it's a good idea to always use it because of the 3-prong end to keep any noise down?

The powered speaker is my bass amp, so I'm using the laptop to run my bass through some amp sims. The bass amp has an 1/8" aux that's intended for drum machines, ipod input, etc in so I'm running a stereo 1/8" cable from the Macbook headphones jack to aux in of the bass amp.

The bass amp also has a ground lift switch on the back. That also hasn't made a difference either way.

[icedsushi]

OK, now I tried the 3-prong cable with the adapter & flipped the ground lift both ways on the bass amp. It didn't make any difference. Any other ideas? I did notice that there was less noise when I tried the amp from an outlet at another location.

[YILA]

Less noise?

Normally ground problems are either there or there not, is it a rhythmical sound or just buzzing?

[icedsushi]

It's a high pitched whine or buzz, similar to that of radio station noise & loud consistent static. It's not quite like a 60 cycle hum.

Yeah the noise level is more or less depending on the location. I guess this has something to do with how well the mains are grounded in that building?

[8TROW8]

I had a similar problem, HTFR sell a ground loop buzz killer it's only £4 but they never have them in stock,

Best solution maybe not ideal cost but is to purchase and audio interface.

[icedsushi]

Actually I have an Audio Kontrol interface & it seems fine with that. I just thought it might be nice to use the built-in outputs now & then while on the go, less to hook up or carry. I'm not familiar with HTFR. "Hard To Find Records" website?

[8TROW8]

Ah suppose if your on the go you may want another solution.

Hard to find records ye, sorry should have explained, I'm not sure if they post to USA, I'm sure you could find a similar product on amazon though.