# Long Aux cable run?

#### texmark

##### Member
I need to have my music director on front row with laptop controlling accompaniment track. Need to get that signal to board 80 ft away. Audio is mixed stereo so I need 2 channels. I can use 2 orch pit mic inputs, but how to convert aux out of laptop to that? Help.

#### jkowtko

##### Well-Known Member
... or use a DI Box. I do this regularly to run DVD projector audio output to my board on the other side of the room.

But yes, for audio playback from a computer, getting a USB I/O interface sounds most appropriate.

Last edited:
RonHebbard

#### DrewE

##### Well-Known Member
Long USB cables can be tricky. Using a USB audio interface to go to a balanced audio run is a perfectly fine idea and stands a good chance of having observably better audio quality than the headphone output of a laptop.

DI boxes work well; connect to a pair of microphone inputs on the mixer.

I have also used a line level unbalanced to balanced converter box much like this. For feeding a line level rather than a microphone input on a mixer, it or an equivalent box is the right tool.

Last edited:

#### macsound

##### Well-Known Member
Depending on how long the show run is and if it's worth the investment, the headphone jack is a terrible thing to break since it's a small pin, I always try to use USB whenever possible.

#### TimMc

The Peavey USB device mentioned above will have much, much better audio quality than the 29 cent headphone amp chip in the laptop. The output of the Peavey device is transformer balanced, too, and has a "mono" option switch. I paid <$60 for mine from a local Peavey dealer. #### Ben Stiegler ##### Well-Known Member Alternatively, analog or USB to Dante "digital DI" can be useful if - your console can accept Dante directly, or - in tx/rx pairs if not. But ... simpler, perhaps ... have you considered putting the laptop at the console position and giving the music director remote control of the laptop, either with freeware like VNC, or with a Bluetooth or IR remote often seen for doing PPT slide advancing? Remote the control, not the audio! #### Malabaristo ##### Well-Known Member I keep a Whirlwind pcDI around for this sort of thing since I'm often using it to connect someone else's device and can't count on being able to add a USB interface. It's passive, stereo or mono with the flip of a switch, has a couple connector options, and is solidly built. Not only is converting to a balanced signal important for the longer distance, but transformer isolation and a ground lift can often cut down on some of the noise you get with mediocre sound cards. A real audio interface like the Peavey mentioned above is definitely a better choice for overall sound quality if you have the option, but a good DI can make a big difference too. #### BCAP ##### Active Member I use a Radial USB Pro. It's a bit more expensive at$229 but here's what I like about it:

1). Adjustable output level on the box. Sometimes this is helpful if I fire off the wrong cue accidentally I can quickly turn down the volume on the box while I get to the right one.
2). Headphones output jack on the box
3). Solid USB driver performance (I have used the Peavey box too and had occasional issues with the USB driver on some computers)
4). Good quality D/A converters 24 bit 96kHz (won't make much of a difference for 16 bit material or MP3 tho..)
5). Mono sum button
6). Ground lift button

Using either a DI box, or a "PC" USB type DI box you may still experience a ground loop between your console and the laptop when running a balanced XLR line, depending on whether there's a difference in AC ground potential. The obvious solution is to use the ground lift button in that case but if you can find a way to run an AC extension cord out to the computer you might be able to solve it that way too.

All of the Radial stuff is built like a brick sh*thouse and more often than not they put excellent components into their gear.

#### FMEng

##### Well-Known Member
Fight Leukemia
Add Mackie and On-Stage to the USB DI box crowd, with identical features to the Radial.

#### DrewE

##### Well-Known Member
Using either a DI box, or a "PC" USB type DI box you may still experience a ground loop between your console and the laptop when running a balanced XLR line, depending on whether there's a difference in AC ground potential. The obvious solution is to use the ground lift button in that case but if you can find a way to run an AC extension cord out to the computer you might be able to solve it that way too.
When was the last time you used a laptop with a grounded (or even polarized) AC power supply? It seems to me it's hard to have a ground loop with no ground line to loop through. Laptop power supplies can be pretty noisy (electrically) in their own right, though, so I don't at all disagree with the several real advantages of using a good outboard DAC of some sort.

#### FMEng

##### Well-Known Member
Fight Leukemia
Switching power supplies are not always floating. Even a bypass capacitor to the neutral can cause noise by leakage current. When the laptop is connected to a screen or projector, it often gets ground referenced that way. Isolation is your friend, a reliable way to prevents noises.

#### TimMc

##### Well-Known Member
When was the last time you used a laptop with a grounded (or even polarized) AC power supply? It seems to me it's hard to have a ground loop with no ground line to loop through. Laptop power supplies can be pretty noisy (electrically) in their own right, though, so I don't at all disagree with the several real advantages of using a good outboard DAC of some sort.
EVERY Dell laptop has a 3 prong AC cord, and many aftermarket laptop replacement PSUs have them, too. They can hum like a mofo.

Last edited:

#### RonHebbard

##### Well-Known Member
I use a Radial USB Pro. It's a bit more expensive at \$229 but here's what I like about it:

1). Adjustable output level on the box. Sometimes this is helpful if I fire off the wrong cue accidentally I can quickly turn down the volume on the box while I get to the right one.
2). Headphones output jack on the box
3). Solid USB driver performance (I have used the Peavey box too and had occasional issues with the USB driver on some computers)
4). Good quality D/A converters 24 bit 96kHz (won't make much of a difference for 16 bit material or MP3 tho..)
5). Mono sum button
6). Ground lift button

Using either a DI box, or a "PC" USB type DI box you may still experience a ground loop between your console and the laptop when running a balanced XLR line, depending on whether there's a difference in AC ground potential. The obvious solution is to use the ground lift button in that case but if you can find a way to run an AC extension cord out to the computer you might be able to solve it that way too.

All of the Radial stuff is built like a brick excrement house and more often than not they put excellent components into their gear.
Most of us think that way up here North of Donnie's walls. ( Go NANCY!!! You go girl!! )
Toodleoo!
Ron Hebbard

#### macsound

##### Well-Known Member
When was the last time you used a laptop with a grounded (or even polarized) AC power supply? It seems to me it's hard to have a ground loop with no ground line to loop through. Laptop power supplies can be pretty noisy (electrically) in their own right, though, so I don't at all disagree with the several real advantages of using a good outboard DAC of some sort.
On some older MacBooks, using the extension to the white brick caused audio noise because it was grounded. So we always used the ducks foot and plugged directly into the outlet.