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Amp noise from laptop

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Anonymous
a b D Laptop
January 23, 2005 9:30:03 PM

Archived from groups: rec.audio.tech (More info?)

Hello.

I'm trying to use a laptop to record my band. However, when I hook up a
shielded cable between the "tape out" on my mixer and the "microphone
in" on my laptop, I get a tremendous amount of noise from the laptop
through the amp via the mixer, apparently picked up by the cable. The
noise consists of a whine that seems to increase in intensity when the
hard drive is active, the mouse is moved, etc.

It seems wierd to me that hooking the laptop to an -output- on the
mixer introduces noise, I could understand it better were I hooking
output from the laptop to an input on the mixer, but so be it.

Anybody had this problem and know a solution? There seem to be many
noise suppressor products on the market, but mostly they are aiming
towards car audio (alternator noise). Not sure if my problem is the
same.

I'm tempted to think that a rectifier between the laptop and the mixer
could keep the noisy signals from travelling backwards, but maybe this
is nonsense?

Thanks in advance.

More about : amp noise laptop

Anonymous
a b D Laptop
January 24, 2005 5:22:24 PM

Archived from groups: rec.audio.tech (More info?)

On 23 Jan 2005 18:30:03 -0800, LongShotBuddy <greg@truckmaster.com> wrote:
>Hello.

>I'm trying to use a laptop to record my band. However, when I hook up a
>shielded cable between the "tape out" on my mixer and the "microphone
>in" on my laptop, I get a tremendous amount of noise from the laptop

You're connecting a 2-4 volt output into a .005 volt input!

Connect to the line input instead and don't surprised if you've
burned out the sound chip.
Anonymous
a b D Laptop
January 24, 2005 6:32:08 PM

Archived from groups: rec.audio.tech (More info?)

"LongShotBuddy" <greg@truckmaster.com> wrote in message
news:1106533803.154052.162540@c13g2000cwb.googlegroups.com
> Hello.
>
> I'm trying to use a laptop to record my band. However, when I hook up
> a shielded cable between the "tape out" on my mixer and the
> "microphone in" on my laptop, I get a tremendous amount of noise from
> the laptop through the amp via the mixer, apparently picked up by the
> cable. The noise consists of a whine that seems to increase in
> intensity when the hard drive is active, the mouse is moved, etc.

Try hooking into the other input, the blue jack. It might be called "line
in" or some such.
Related resources
Anonymous
a b D Laptop
January 24, 2005 7:45:04 PM

Archived from groups: rec.audio.tech (More info?)

Thanks TCS.. So you're saying that the "tape out" on my mixer (an
analog Mackie 12 channel) is 2-4 volts, and the "microphone in" on my
laptop (Dell Inspiron 1150) is expecting .005 volts..
So is the solution to somehow step down the voltage?
Anonymous
a b D Laptop
January 24, 2005 7:45:47 PM

Archived from groups: rec.audio.tech (More info?)

Thanks TCS.. So you're saying that the "tape out" on my mixer (an
analog Mackie 12 channel) is 2-4 volts, and the "microphone in" on my
laptop (Dell Inspiron 1150) is expecting .005 volts..
So is the solution to somehow step down the voltage?
Anonymous
a b D Laptop
January 24, 2005 7:46:42 PM

Archived from groups: rec.audio.tech (More info?)

Good suggestion Andrew, I should have thought of it myself :>/
Thanks a bunch.
Anonymous
a b D Laptop
January 24, 2005 7:48:29 PM

Archived from groups: rec.audio.tech (More info?)

My laptop (Dell Inspiron 1150) has no "line in" jack. It has a "speaker
out" and a "microphone in". There is an adjustable gain in the
software mixer, which I'm assuming "kicks in" the preamp..

Thanks Arny.
Anonymous
a b D Laptop
January 24, 2005 7:49:10 PM

Archived from groups: rec.audio.tech (More info?)

My laptop (Dell Inspiron 1150) has no "line in" jack. It has a "speaker
out" and a "microphone in". There is an adjustable gain in the
software mixer, which I'm assuming "kicks in" the preamp..

Thanks Arny.
Anonymous
a b D Laptop
January 24, 2005 11:01:41 PM

Archived from groups: rec.audio.tech (More info?)

LongShotBuddy wrote:
> Hello.
>
> I'm trying to use a laptop to record my band. However, when I hook up a
> shielded cable between the "tape out" on my mixer and the "microphone
> in" on my laptop, I get a tremendous amount of noise from the laptop
> through the amp via the mixer, apparently picked up by the cable. The
> noise consists of a whine that seems to increase in intensity when the
> hard drive is active, the mouse is moved, etc.
>
> It seems wierd to me that hooking the laptop to an -output- on the
> mixer introduces noise, I could understand it better were I hooking
> output from the laptop to an input on the mixer, but so be it.
>
> Anybody had this problem and know a solution? There seem to be many
> noise suppressor products on the market, but mostly they are aiming
> towards car audio (alternator noise). Not sure if my problem is the
> same.
>
> I'm tempted to think that a rectifier between the laptop and the mixer
> could keep the noisy signals from travelling backwards, but maybe this
> is nonsense?
>
> Thanks in advance.
>
A rectifier is a dead end. What you are trying to record is AC at
varying frequency.

It might be worth trying the set-up running on batteries. The power
supplys seem to be a problem on some laptops (not mine, so I've not got
direct experience) :-)

If this does fix it, sorry but I'm not really sure where that leaves
you, best of luck!!

Andrew
Anonymous
a b D Laptop
January 25, 2005 1:17:05 AM

Archived from groups: rec.audio.tech (More info?)

On 24 Jan 2005 16:45:04 -0800, LongShotBuddy <greg@truckmaster.com> wrote:
>Thanks TCS.. So you're saying that the "tape out" on my mixer (an
>analog Mackie 12 channel) is 2-4 volts, and the "microphone in" on my
>laptop (Dell Inspiron 1150) is expecting .005 volts..
>So is the solution to somehow step down the voltage?

I was going to say use the line-in, but I just visited the dell website and
learned the dell got cheap and left it out (to save about 3 pennies).

You could step it down with a resistor divider:

R1 R2
in ----/\/\/\/\/\/--+----/\/\/\/\/\/\/------ground
\
---out

Vout = Vin * R2 / (R1+R2)

make R1 33K ohms
make R2 100 ohms

http://www.hut.fi/Misc/Electronics/circuits/line_to_mic...

Radio shack might have an attenuator cable that do exactly this. Or maybe not.


Another solution would be to use an external sound device. It'll connect
to the USB and hopefully have a line-in input.

Or use a different computer.
Anonymous
a b D Laptop
January 25, 2005 5:05:21 AM

Archived from groups: rec.audio.tech (More info?)

On 24 Jan 2005 16:49:10 -0800, "LongShotBuddy" <greg@truckmaster.com>
wrote:

>My laptop (Dell Inspiron 1150) has no "line in" jack. It has a "speaker
>out" and a "microphone in". There is an adjustable gain in the
>software mixer, which I'm assuming "kicks in" the preamp..

If you want to do this properly, get an external USB or Firewire audio
interface for the laptop. If you want to try a bodge, attenuate the
signal going to Mic In.

Note that Mic In of domestic computers is lousy quality, even when
presented with an appropriate signal. And that the power supply of
many laptops introduces an unacceptable amount of noise. Try
recording when running on battery power, not with the mains adaptor.
!