[ddots-l] Re: Recording with laptop

  • From: Bryan Smart <bryansmart@xxxxxxxxxxxxxx>
  • To: "ddots-l@xxxxxxxxxxxxx" <ddots-l@xxxxxxxxxxxxx>
  • Date: Tue, 20 Oct 2009 02:10:50 -0400

Lifting the ground pin will only eliminate a 50hz or 60hz hum caused by 
equipment that is out of alternating phase with another piece of equipment that 
you're monitoring. Besides, its dangerous, and I can't believe how many people 
keep suggesting this to people on lists, as if grounding pins are silly 
unnecessary annoyances on high voltage equipment. When you hear hum, it means 
that you have an electrical problem. You can ignore the problem, and live with 
the hum, but defeating the safety features in order to remove the hum is 
foolish. Odds are that your electrical problem, now without the silly safeties 
to get in your way, could end up hurting or killing you if you accidentally 
touch the right combination of equipment and create a fatal circuit with your 
body. Those ground plug lifting adaptors are no problem on little devices that 
pull fractional amounts of power, but laptops, towers, audio gear, etc can pull 
between 100 to 1000 watts or more, and it is just not safe to do that!

Having said that, you probably don't have a hum. You probably have a digital 
chirping sound. If you listen closely, you'll notice that the sound of the 
chirping changes when the computer is doing something like loading web pages 
and opening programs.

A lot of laptops do this. It is a combination of poor electrical circuitry and 
a cheap USB sound card. The digital chirp that you're hearing is cross-talk 
from a poorly shielded electrical bus inside the laptop. Some USB sound devices 
have canceling circuitry that partially eliminates this chirp, but the only 
real way to get rid of it is to not run the sound card off of the laptop's 
power. That means buying a higher quality interface with better canceling 
circuitry, or, better still, buying an interface with its own power cord. An 
interface with its own power cord has its own internal transformer and power 
bus, and won't be as affected by the cross-talk from the laptop's leaky power 
bus.

If it turns out that you do have a power problem, then get a power conditioner. 
If you can't afford a power conditioner, then get an uninterruptable power 
supply from an office supply place. UPSes are cheap, and do a fairly good job 
at cleaning up the alternating current's waveform for the price that you pay.

Bryan

-----Original Message-----
From: ddots-l-bounce@xxxxxxxxxxxxx [mailto:ddots-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Mark Dew
Sent: Monday, October 19, 2009 8:11 PM
To: ddots-l@xxxxxxxxxxxxx
Subject: [ddots-l] Re: Recording with laptop

Steve, here's the deal.
We figured out if she unplugs the wall power supply from the laptop, the static 
sound is gone.
Clear as a bell.
When she plugs the power supply back in, the sound returns.
So maybe that ground loop you spoke of a few days ago might be the answer.

Mark

At 05:17 PM 10/19/2009 +0100, you wrote:
>Hi Mark,
>
>Have you tried charging up the laptop and recording without the mains 
>adapter plugged in?
>
>I use a laptop for my Studio computer and it works better without the 
>mains adapter.
>This maybe worth a try.
>
>Steve W
>----- Original Message -----
>From: "Mark Dew" <jmkeybd1@xxxxxxxxxxx>
>To: <ddots-l@xxxxxxxxxxxxx>
>Sent: Monday, October 19, 2009 12:45 AM
>Subject: [ddots-l] Re: Recording with laptop
>
>
>>
>> Gord, I'll check with her and let you know.
>> She just said it's a usb sound card.
>> Steve, it's hard to tell, I think it's just a frying sound.
>> I think maybe the sound card is just bad.
>> What would you folks recamend for the laptop?
>> She's using a Mackie mixer, with a sm-58 shure mic.
>> She's just doing simple work, recording vocals along with an audio 
>> file.
>>
>> Mark
>>
>>
>> At 04:28 PM 10/18/2009 -0400, you wrote:
>>>The mic in may be only mono.  Also, you really don't want to use the 
>>>laptop's onboard sound for recording audio.  What usb interface does 
>>>she have?
>>>Gord
>>>----- Original Message -----
>>>From: "Mark Dew" <jmkeybd1@xxxxxxxxxxx>
>>>To: <ddots-l@xxxxxxxxxxxxx>
>>>Sent: Saturday, October 17, 2009 12:55 PM
>>>Subject: [ddots-l] Recording with laptop
>>>
>>>
>>>> Hello folks.
>>>> Here's the problem.
>>>> I have a friend who has just a laptop and a mackie 8 channel mixer.
>>>> She has only a mic input on the laptop.
>>>> The audio siggnel is too hot.
>>>> She did perchased a u s b sound card that has a line in jack.
>>>> When she records using the line in there is a static sound she 
>>>> can't get rid of.
>>>> I believe the sound card is bad.
>>>> The mic input on the laptop itself is ok, except too hot.
>>>> My question is, is there such a thing as an audio cable that would 
>>>> restrict the audio level?
>>>> I had her to turn down the mic input on the laptop but with no results.
>>>> Any ideas would be welcome.
>>>>
>>>> Cheers!
>>>>
>>>> Mark
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> PLEASE READ THIS FOOTER AT LEAST ONCE!
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>>>>
>>>
>>>PLEASE READ THIS FOOTER AT LEAST ONCE!
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>>>
>> PLEASE READ THIS FOOTER AT LEAST ONCE!
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>> 
>
>
>PLEASE READ THIS FOOTER AT LEAST ONCE!
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>following link:
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>
>
PLEASE READ THIS FOOTER AT LEAST ONCE!
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