Horrible sound from PC

[Hi Ho]

What kind of laptop is it? I have never seen a grounded laptop either.

 

[tgoyette]

It's an HP dv6000. I thought that most laptops are grounded, but when I checked my old one it was just a two prong plug.

 

[linda o keeffe]

hissing problem

I have an external sound card, presonus digital audio connected to a laptop via a fireiwire cable, this is then connected to Yamaha MSp5's, with the plug in on the laptop the his and static is incredible. I have unplugged it and placed it in various boards, no difference, the only thing I can recommend is a cabling suggestion.
If your computer audio device has unbalanced I/O, but you want to plug it into an analogue mixer or other device with balanced I/O, you can make up special pseudo-balanced leads that safely break the ground loop. Over the years I've soldered up lots of these to lower the noise floor of my external MIDI synths, and I've also used them to completely cure background noise problems when connecting the multiple audio channels of devices such as M Audio's Firewire 410 to my other gear.
You just buy twin-core screened (mic) cable instead of single-core screened, and then solder an unbalanced TS plug on one end (the soundcard end) and a balanced TRS jack one to the other (the mixer end). The 'tip' connections are made as normal using one cable core, while the 'sleeve' of the unbalanced end is connected to the 'ring' connection at the balanced end using the other cable core, and the 'sleeve' of the balanced end is either left unconnected, or preferably connected via a series eighth-Watt metal-oxide resistor of between 50(omega) and 500(omega) (I normally use 100(omega)) to the 'sleeve' connector at the unbalanced end. Such an approach will completely cure most soundcard ground-loop problems, and if you're going to solder up your own leads anyway it will only cost you a few pence more.

this might help

Thanks guys. I'm pretty sure it's not a ground loop as I have all my components as well as my computer (which is three pronged) plugged into the same power conditioner.
I am using the headphone out (stereo mini jack) on my laptop with the volume set to max on both the windows control as well as the particular program like Rhapsody. To connect to the pre I have to use a 1/8" stereo to RCA or "Y" adapter. Seeing as this is an unshielded cable, would looking for a shielded one help with the possible interference, or is it just an internal problem with sound card placement that needs to be taken out of the computer case?
Interestingly, the sound started when I began using the Emoitva as a pre as opposed to my old stereo Yamaha receiver which was silent (but didn't sound nearly as good as the current setup).

 

[TLS Guy]

I have an external sound card, presonus digital audio connected to a laptop via a fireiwire cable, this is then connected to Yamaha MSp5's, with the plug in on the laptop the his and static is incredible. I have unplugged it and placed it in various boards, no difference, the only thing I can recommend is a cabling suggestion.
If your computer audio device has unbalanced I/O, but you want to plug it into an analogue mixer or other device with balanced I/O, you can make up special pseudo-balanced leads that safely break the ground loop. Over the years I've soldered up lots of these to lower the noise floor of my external MIDI synths, and I've also used them to completely cure background noise problems when connecting the multiple audio channels of devices such as M Audio's Firewire 410 to my other gear.
You just buy twin-core screened (mic) cable instead of single-core screened, and then solder an unbalanced TS plug on one end (the soundcard end) and a balanced TRS jack one to the other (the mixer end). The 'tip' connections are made as normal using one cable core, while the 'sleeve' of the unbalanced end is connected to the 'ring' connection at the balanced end using the other cable core, and the 'sleeve' of the balanced end is either left unconnected, or preferably connected via a series eighth-Watt metal-oxide resistor of between 50(omega) and 500(omega) (I normally use 100(omega)) to the 'sleeve' connector at the unbalanced end. Such an approach will completely cure most soundcard ground-loop problems, and if you're going to solder up your own leads anyway it will only cost you a few pence more.

this might help

I have to provide some corrective education, so other members will not be misled.

What you have described is going from a high impedance (Hz) unbalanced output to a balanced low impedance input (Lz). You have concocted a reverse "floating line. This is not good practice, as the Hz output is adversely loaded, which is likely to affect quality.

Correct engineering practice in this situation is to use a line transformer to convert the Hz output to 600 ohm (not omega) balanced line. A device like this is what is required.

http://www.radioshack.com/product/index.jsp?productId=2062443&cp=2032058.2032231.2032280&pg=16&parentPage=family

Now there are also line transformers that go the other way Lz to Hz.

http://www.radioshack.com/product/index.jsp?productId=2062444&cp=2032058.2032231.2032280&pg=16&parentPage=family

This is the best solution. However when going from Lz balanced to Hz unbalanced it is a acceptable to use a floating line.

You come out with the signal on pins 2 and 1 and 3 is ground (shield). Connect 2 to tip of the phone jack, and at the phone jack connect the cable from pin 1 and shield to the ground side of the phone jack. It is important pin 2 goes to tip or phase will be reversed. That will upset a lot of mixes.

You use of those is not acceptable practice.

I'm a stickler for correct practice, otherwise we spread confusion.

 

[TLS Guy]

I have to provide some corrective education, so other members will not be misled.

What you have described is going from a high impedance (Hz) unbalanced output to a balanced low impedance input (Lz). You have concocted a reverse "floating line. This is not good practice, as the Hz output is adversely loaded, which is likely to affect quality.

Correct engineering practice in this situation is to use a line transformer to convert the Hz output to 600 ohm (not omega) balanced line. A device like this is what is required.

http://www.radioshack.com/product/index.jsp?productId=2062443&cp=2032058.2032231.2032280&pg=16&parentPage=family

Now there are also line transformers that go the other way Lz to Hz.

http://www.radioshack.com/product/index.jsp?productId=2062444&cp=2032058.2032231.2032280&pg=16&parentPage=family

This is the best solution. However when going from Lz balanced to Hz unbalanced it is a acceptable to use a floating line.

You come out with the signal on pins 2 and 1 and 3 is ground (shield). Connect 2 to tip of the phone jack, and at the phone jack connect the cable from pin 1 and shield to the ground side of the phone jack. It is important pin 2 goes to tip or phase will be reversed. That will upset a lot of mixes.

You use of those is not acceptable practice.

I'm a stickler for correct practice, otherwise we spread confusion.

It was too early in the morning, and I made one error. It should be signal on 2, and 3, 1 is ground (shield). Sorry for the confusion.