Bah Hum Buzz

[tunzzz]

CAUTION: An extreme newbie.

I am attempting to record out of my PA mixer via the monitor out by connecting it to the line in on an external Extigy sound card feeding a laptop (for portable recording). When I plug in the power transformer for the laptop, I get a very loud hum/buzz coming into the sound card/PC. I do not have this problem when running on the battery of the laptop. I have used this same hookup to record on my desktop PC without too much of a problem (very slight hum). Obviously it has to do something with the laptop's power transformer. I've tried plugging the transformer into the same power strip and even into a seperate power circuit (though I think that may enhance the problem from what I've read). But, no luck.

Sorry, my apologies for not being more technically savvy about line voltage, ground loops, etc... I think I am safely connnected. I am thinking "ground loop" based on my novice research. Would a ground loop isolator solve my problem?

Here are the specs on the monitor out channel in case my connections aren't as safe as I thought:
Load Impedance: 1K Ohms or greater
Nominal Output: 0 dBV, 1V RMS
Maximum Output: + 18 dBV. 8V RMS into 50K Ohms load

 

[Kurt Foster]

tunzzz,
Yes, that is what came to mind for me. Try an EBTECH Hun eliminator. They are very inexpensive, about $25 I think. That or some kind of transformer in the signal path. Good luck and keep us posted as to the results. Kurt

 

[realdynamix]

Hey Tunzz, the EBTECH Hum eliminator is a good suggestion, also you may want to make sure that the input accepts the level of your PA mixer, there might be a level mismatch. In that case the EBTECH again would convert levels to what ever you need, as well as balanced to unbalanced connections, and visa versa.

Another thing, laptops have a lot of electronics packed into a small space. The location of internal power supply parts may radiate into the electronics of the Laptop's audio circuits. To keep things super quiet, make sure level is matched, using line not mic, so you don't have to gain up your sound card too much. Use the battery during record. At setup and monitoring, plug in the supply, at record go to battery.
Hope this helps,
--Rick

 

[Kurt Foster]

Gee! How did I know that Rick would chime in on this??? Oh yeah! We have requested some equipment from EBTECH for Rick to evaluate and Review ... yeah, that's it! That's the ticket, yeah, a review.. :tu: Kurt

 

[tunzzz]

That did the trick! Thanks tag team (Kurt/Rick).