mostlyharmless Posted September 1, 2006 Share Posted September 1, 2006 Hi there, I recently purchased some monitor speakers (active, Alesis M1 520s). Which I am running with a small mixer, and my laptop. This was fine, until I plugged the mains power supply into the laptop, at which point I got a load of 'buzzing and interference'. At first I had everything plugged into the same multi-extension lead (opps). But, moving them to seperate wall sockets still has this problem, although not as much. Is it just the cheap power supply/standard sound card on my laptop? Thanks, Chris. Link to comment Share on other sites More sharing options...
gareth Posted September 1, 2006 Share Posted September 1, 2006 Is it a Dell laptop, by any chance? Link to comment Share on other sites More sharing options...
Bobbsy Posted September 1, 2006 Share Posted September 1, 2006 Alas, this is an all-too-common problem, even with supposedly name-brand laptops. It's generally a classic ground loop issue, caused because the ground connected at the power supply is not connected through to the laptop, which in turn is connected to the mixer. Addition of an isolating transformer between the laptop and the mixer will usually sort this out. Bob Link to comment Share on other sites More sharing options...
gareth Posted September 1, 2006 Share Posted September 1, 2006 That's precisely why I asked the question - Dell laptops (like mine!) are apparently notorious for being the cause of ground loop scenarios due to the way their PSU is connected to earth. I bought a small isolating transformer (of the kind used in car audio installations) from a seller on Ebay for a few quid, and that's sorted the problem out nicely. Link to comment Share on other sites More sharing options...
timtheenchanteruk Posted September 1, 2006 Share Posted September 1, 2006 would an external sound-card solve this problem? I ask because I am in the process of getting a lappy for use in theatre work, but I am aiming on an external sound-card with balanced outputs on it Link to comment Share on other sites More sharing options...
Bobbsy Posted September 1, 2006 Share Posted September 1, 2006 As I mentioned in my previous post, this is a pretty common topic, so I've merged this one with a previous discussion that has most of the answers...I suggest people read back to the start now! Bob Link to comment Share on other sites More sharing options...
bruce Posted September 1, 2006 Share Posted September 1, 2006 there's also THIS THREAD which covers similar ground. As for the question about whether an external sound card will help - the answer is "maybe it will, maybe it won't". Some have reported success here, but when I tried it, it made no difference at all. A DI with ground lift, or a transformer, is the way forward. Link to comment Share on other sites More sharing options...
mostlyharmless Posted September 2, 2006 Share Posted September 2, 2006 Thanks guys.. Its an acer laptop. So I'm sure it'll be a cheap power supply in there then! I'm just about to attack google for these 1:1 transformers, but if anyone has a link it would be most helpful. Link to comment Share on other sites More sharing options...
bruce Posted September 2, 2006 Share Posted September 2, 2006 Its an acer laptop. So I'm sure it'll be a cheap power supply in there then!Actually, the cheapest/simplest power supplies are often the best. The ones I've had problems with include Dell, Toshiba and IBM. In the case of the Tosh, replacing the standard PSU with a cheap "universal laptop PSU" from CPC (I think - might have been Misco/Inmac) sorted it. Link to comment Share on other sites More sharing options...
mostlyharmless Posted September 2, 2006 Share Posted September 2, 2006 Actually, the cheapest/simplest power supplies are often the best. The ones I've had problems with include Dell, Toshiba and IBM. In the case of the Tosh, replacing the standard PSU with a cheap "universal laptop PSU" from CPC (I think - might have been Misco/Inmac) sorted it.It must be a problem that they don't really think through. I've run the laptop through some cheap JVC 'microsystem' and had no problems at all. So I'm assuming that the kind of set ups these companys test with don't notice it. Anyway, the challenge for today is to find something much cheaper and student like than http://www.studiospares.com/pd_325310_ART%...MERISOLATOR.htm Link to comment Share on other sites More sharing options...
bruce Posted September 2, 2006 Share Posted September 2, 2006 It must be a problem that they don't really think through. I've run the laptop through some cheap JVC 'microsystem' and had no problems at all. So I'm assuming that the kind of set ups these companys test with don't notice it. Probably because the JVC microsystem is double-insulated and the line input has no direct reference to an external ground. Anyway, the challenge for today is to find something much cheaper and student like than http://www.studiospares.com/pd_325310_ART%...MERISOLATOR.htm Plenty on Ebay for less than a tenner - search for "ground loop". Most intended for the in-car market. It's not exactly hi-fi quality, but neither is the audio output on your laptop... Link to comment Share on other sites More sharing options...
gareth Posted September 2, 2006 Share Posted September 2, 2006 I'm using one of these bought from Ebay (for considerably less than the price of that one, though - £3.49 inc P&P!! :P) and it does the job nicely. Link to comment Share on other sites More sharing options...
mostlyharmless Posted September 2, 2006 Share Posted September 2, 2006 Cheers for the responses guys. http://www.maplin.co.uk/Free_UK_Delivery/G...lator_33172.htm thats looking like the winner so far. Ebay seems to be the same price as online shops elsewhere. Although, I'm very tempted to spend a lot less money on one of these beasts:http://cpc.farnell.com/jsp/endecaSearch/pa...jsp?sku=AV08632http://cpc.farnell.com/jsp/endecaSearch/pa...jsp?sku=CP03283Just they get you on the £6 postage. Link to comment Share on other sites More sharing options...
bruce Posted September 2, 2006 Share Posted September 2, 2006 Just they get you on the £6 postage.That's one of the nice things about having a corporate account with them - as well as discount, we get free next day delivery, and no minimum order. So we tend to use them as an extension of our local stores. We have, on occasion, placed orders for a total of less than 50p... although typically we'd spend a little more :P Link to comment Share on other sites More sharing options...
jamesperrett Posted September 2, 2006 Share Posted September 2, 2006 Does the mixer have balanced line inputs? If so then there's no need for a transformer. Just connect the signal output from the laptop to the + side of the balanced input and the screen from the laptop to the - of the balanced input. Leave the earth/screen of the balanced input disconnected. Cheers James. Link to comment Share on other sites More sharing options...
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