# DI Box and Computer noise



## rdagit (May 15, 2009)

Long story short, My laptop is nice in most respects, but it has a normal problem that it likes to spit out digital noice when it is connected to a board through 1/8" to 1/4" cable in the insert jacks. I know that one can buy one of the $150-$500 digital interface boxes that go through one's USB or Firewire port, but I"m on a student budget and can't quite afford that right now (wish I could). I was curous to know if anyone has tried to connect their laptop through a decent ($40-$50) DI box and if this is enough to get rid of the digital noise that picks up through the laptop's headphone jack.


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## avkid (May 15, 2009)

$150?
A cheap USB box will do the job.

This Edirol device works quite nicely and is plug and play.
EDIROL UA-1EX USB Audio Interface :: Overview

You should be able to find them for $80 shipped.


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## jkowtko (May 15, 2009)

Or, if your laptop battery is good enough to power you for the duration of the playing time, unplug the AC adapter whenever you have the faders up.


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## mnfreelancer (May 15, 2009)

I've always had good luck with proco direct boxes that accept stereo 1/8" or dual RCA inputs. They have a ground lift switch that takes care of the noisy Dell laptops (Dell is the only manufacturer I've encountered this problem with). I've seen toshibas however that have audio noise on their HDMI output when plugged in (grounded power supply).


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## BNEL (May 16, 2009)

More than likely the noise is coming from your power adapter. Instead of buying a DI box a friend suggested that I buy a ground loop isolator.

Ground Loop Isolator - RadioShack.com

After buying that with a additional stereo 1/8" plug to stereo RCA adapter that solved my problem with my computer noise.


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## museav (May 16, 2009)

rdagit said:


> Long story short, My laptop is nice in most respects, but it has a normal problem that it likes to spit out digital noice when it is connected to a board through 1/8" to 1/4" cable in the insert jacks.


Inserts are typically a 1/4" TRS with send on tip and return on ring that are used for outboard effects and processors. The 1/8" jacks on laptops are usually stereo inputs or outputs. What are you actually doing and how is it wired? An outboard interface or transformer may be a good idea, but there could easily be some wiring issues as well.


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## tech2000 (May 16, 2009)

I typically have this issue with HP laptops only and one great way to fix it is with a cheap ($25) DI box. I plugged in an adapter (1/8" to 1/4") to the DI box and an XLR from there to the mixer and problem solved!-for me anyways.


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## mbenonis (May 16, 2009)

Just get a DI box to go between your computer and the sound system. By doing this, you can electrically isolate the devices by magnetically coupling them - this will remove any RFI on the line caused by switching power supplies, computer chips, etc. They're not very cheap, but they do work.

Whirlwind pcDI


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## museav (May 16, 2009)

Just pointing out that DI boxes are typically used to provide a balanced, mic level input signal, so probably not the right device to use with an unbalanced, line level insert. Clarifying how and why the laptop is connected to an insert might be useful in trying to address the problem and determine a proper solution. If the situation is trying to use the laptop as an effects or processing device then that might require a different approach than if the situation is trying to 'Y' the laptop stereo output to mono and/or using the insert as a line level input.


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## firewater88 (May 17, 2009)

I use a Griffin iMic Griffin Technology: iMic - USB Audio Interface to use the output of my Mac Pro. It resides on the USB side and it really cleans up the audio out. I have tried the 1/8" out and you get a bit of a buzz.


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## TimmyP1955 (May 17, 2009)

The one and only time I allow or advocate the floating of an AC ground is on the power adapter of laptops. It will likely solve the problem. Just don't do it on anything else.


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## museav (May 18, 2009)

TimmyP1955 said:


> The one and only time I allow or advocate the floating of an AC ground is on the power adapter of laptops. It will likely solve the problem. Just don't do it on anything else.


I do not understand the logic to this, floating an AC ground is never an acceptable solution. DO NOT break the safety ground path as a soultion.


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## mbenonis (May 18, 2009)

Agreed. Use an isolation transformer instead (like the one I posted above). If you need line level inputs, there are 1:1 transformers as well.


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