Sign in with
Sign up | Sign in
Your question

Sound out from computer to receiver - hum is heard!

Last response: in Home Audio
Share
Anonymous
a b D Laptop
February 8, 2005 11:11:52 PM

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

This is a repost with some new developements. Hope someone has a
suggestion. I'm trying to run sound out from a PC and laptop to my
receiver. I'm using the 1/8 inch stereo cable from line out from computer
(marked with light green) with Y-adapter to two rca cables which are plugged
into receiver. The volume is low so receiver volume needs to be turned up
pretty high, unfortunately - even with computer volume turned to max.

When I do this with 2 PC's and laptop there's a bad hum with all three!
However I can get rid of hum by unplugging laptop from AC and using it's
internal battery. So I tried buying a AC line interference filter ($20 at
radio shack) but it won't prevent hum. So what is the best solution? Do I
try to ground the 3 computers better with a wire from ground to computer
casing or is there some other solution? I can't believe it's so difficult
to get decent sound out of a computer to a receiver - but I guess it is!
Anonymous
a b D Laptop
February 9, 2005 4:36:42 AM

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

"LarryLOOK" <anonlmp@yahoo.com> wrote in message
news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
....
> However I can get rid of hum by unplugging laptop from AC and using it's
> internal battery.
....
My Sony VAIO laptop has a similar problem with the microphone.

> So what is the best solution?

PC's provide an incredible hostile environment for analog audio. More
expensive sound cards do a good job at shielding . USB and Firewire
(preferred) external solutions will also provide acceptable (to great)
results. There is probably NOTHING you can do if you are trying to make use
of the standard built-in audio provided by most manufacturers.
Anonymous
a b D Laptop
February 9, 2005 4:36:43 AM

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

"Jerohm" <jDrEmLoEhTrE@snet.net> wrote in message
news:KOdOd.1611$he5.273@newssvr31.news.prodigy.com...
>
> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
> ...
> > However I can get rid of hum by unplugging laptop from AC and using it's
> > internal battery.
> ...
> My Sony VAIO laptop has a similar problem with the microphone.
>
> > So what is the best solution?
>
> PC's provide an incredible hostile environment for analog audio. More
> expensive sound cards do a good job at shielding . USB and Firewire
> (preferred) external solutions will also provide acceptable (to great)
> results. There is probably NOTHING you can do if you are trying to make
use
> of the standard built-in audio provided by most manufacturers.

Thanks for reply. It's not exactly what I hoped to hear, but I suppose it's
probably the truth. Can you or anyone make any suggestions about an
external solution (preferably USB)? What terms should I search for using
Amazon?
Related resources
Anonymous
a b D Laptop
February 9, 2005 4:36:44 AM

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

"larrylook" <LarryLOOK@noemail.com> wrote in message
news:m_6dnWlMZ_8J7pTfRVn-vw@comcast.com...
>
> "Jerohm" <jDrEmLoEhTrE@snet.net> wrote in message
> news:KOdOd.1611$he5.273@newssvr31.news.prodigy.com...
>>
>> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
>> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
>> ...
>> > However I can get rid of hum by unplugging laptop from AC and using
>> > it's
>> > internal battery.
>> ...
>> My Sony VAIO laptop has a similar problem with the microphone.
>>
>> > So what is the best solution?
>>
>> PC's provide an incredible hostile environment for analog audio. More
>> expensive sound cards do a good job at shielding . USB and Firewire
>> (preferred) external solutions will also provide acceptable (to great)
>> results. There is probably NOTHING you can do if you are trying to make
> use
>> of the standard built-in audio provided by most manufacturers.
>
> Thanks for reply. It's not exactly what I hoped to hear, but I suppose
> it's
> probably the truth. Can you or anyone make any suggestions about an
> external solution (preferably USB)? What terms should I search for using
> Amazon?

Is this the kind of thing I need? Can anyone recommend a device (prefer
usb)? I don't see any advertised as ideal for connecting pc to receiver and
eliminating hum. Remember I really don't need more than stereo:

http://shop.store.yahoo.com/directron/zmrssc.html
http://www.cwol.com/usb/sound-blaster-audigy-2-nx.htm
http://www.globetechnology.com/servlet/story/RTGAM.2003...
http://shopping.msn.com/search/detail.aspx?pcId=662&pro...
Anonymous
a b D Laptop
February 9, 2005 6:35:23 AM

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

>> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
>> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...

>
> Thanks for reply. It's not exactly what I hoped to hear, but I suppose
> it's
> probably the truth. Can you or anyone make any suggestions about an
> external solution (preferably USB)? What terms should I search for using
> Amazon?
>
>
The M-Audio Transit will give you both analog and optical digital
Inputs/Outputs. Edirol also makes various devices. The Xitel Analog HiFi
Link is probably the cheapest (analog out Only). Check around (eBay too)
because the prices can vary quite a bit. There may be others also (Google:
USB Audio). There are MANY USB audio devices, so find the one that provides
the features you are after. The M-Audio Transit @ $79.00 is pretty tough
to beat (and even though you may not need digital I/O now, it is nice to
have!). I am using the M-Audio Firewire Audiophile and am very pleased wih
it (but it is probably MORE than you are looking for). I have never used a
USB audio interface, but so much stuff is out there, that it MUST work okay.
Search around for reviews. Good Luck.
Anonymous
a b D Laptop
February 9, 2005 6:35:24 AM

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

"Jerohm" <jDrEmLoEhTrE@snet.net> wrote in message
news:%xfOd.3693$hU7.656@newssvr33.news.prodigy.com...
>
> >> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
> >> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
>
> >
> > Thanks for reply. It's not exactly what I hoped to hear, but I suppose
> > it's
> > probably the truth. Can you or anyone make any suggestions about an
> > external solution (preferably USB)? What terms should I search for
using
> > Amazon?
> >
> >
> The M-Audio Transit will give you both analog and optical digital
> Inputs/Outputs. Edirol also makes various devices. The Xitel Analog HiFi
> Link is probably the cheapest (analog out Only). Check around (eBay too)
> because the prices can vary quite a bit. There may be others also
(Google:
> USB Audio). There are MANY USB audio devices, so find the one that
provides
> the features you are after. The M-Audio Transit @ $79.00 is pretty tough
> to beat (and even though you may not need digital I/O now, it is nice to
> have!). I am using the M-Audio Firewire Audiophile and am very pleased
wih
> it (but it is probably MORE than you are looking for). I have never used
a
> USB audio interface, but so much stuff is out there, that it MUST work
okay.
> Search around for reviews. Good Luck.

Thanks so much! I may buy this:
http://tinyurl.com/4j967

http://www.amazon.com/gp/product/customer-reviews/B0000...
Unless anyone has any other good suggestions. I don't need a long cord at
all. Don't need more than stereo and analog is ok. Just want to get rid of
loud hum and have decent sound.
Anonymous
a b D Laptop
February 9, 2005 7:07:54 AM

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

Some links to ponder:

http://reviews.cnet.com/Xitel_HiFi_Link__Analog_/4505-6...
http://www.minidiscaccess.com/generic.html?pid=36

http://www.powerbookcentral.com/columns/kravitz/transit...
http://www.ramelectronics.net/html/transit-usb.html

http://www.zzounds.com/item--EDIUA1X

and don't forget to check out eBay... A lot of retailers of these type of
devices also sell on eBay, but you can also order directly from their Web
sites.... many times with FREE SHIPPING!
Anonymous
a b D Laptop
February 9, 2005 1:40:12 PM

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

Larry,

> The volume is low so receiver volume needs to be turned up pretty high,
unfortunately - even with computer volume turned to max. <

Keep looking for other software volume controls. Most sound cards can put
out a decent "consumer line level" signal, to adequately drive a typical
receiver.

> I can get rid of hum by unplugging laptop from AC and using it's internal
battery. <

That means you have a simple ground loop. The solution is simple too, but
not cheap. You need an audio isolation transformer. Two, actually, with one
each for the left and right channels. The least expensive audio transformer
I know of is the Ebtech Hum Eliminator (about $60 for a stereo pair). Good
transformers cost more like $100 per channel. I have a Jensen transformer on
the subwoofer in my home theater to solve this same problem, and it cost me
$115.

--Ethan
Anonymous
a b D Laptop
February 9, 2005 1:40:13 PM

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

On Wed, 9 Feb 2005 10:40:12 -0500, Ethan Winer <> wrote:
>Larry,

>> The volume is low so receiver volume needs to be turned up pretty high,
>unfortunately - even with computer volume turned to max. <

>Keep looking for other software volume controls. Most sound cards can put
>out a decent "consumer line level" signal, to adequately drive a typical
>receiver.

>> I can get rid of hum by unplugging laptop from AC and using it's internal
>battery. <

>That means you have a simple ground loop. The solution is simple too, but

Not likely that the laptop is getting grounded to the mains through the
charger.

What is much more likely is that the laptop has poor voltage regulation or
none at all on one of the voltages used by the sound hardware. When the
charger is connected, there's ripple on the supply line.

Try opening the ground on the charger if you think there's a ground fault.
As long as you don't routinely take the laptop to the bath, it won't harm
anybody or anything.
Anonymous
a b D Laptop
February 9, 2005 2:49:39 PM

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

On Wed, 09 Feb 2005 01:36:42 GMT, "Jerohm" <jDrEmLoEhTrE@snet.net>
wrote:

>> However I can get rid of hum by unplugging laptop from AC and using it's
>> internal battery.
>...
>My Sony VAIO laptop has a similar problem with the microphone.
>
>> So what is the best solution?
>
>PC's provide an incredible hostile environment for analog audio. More
>expensive sound cards do a good job at shielding . USB and Firewire
>(preferred) external solutions will also provide acceptable (to great)
>results. There is probably NOTHING you can do if you are trying to make use
>of the standard built-in audio provided by most manufacturers.

Well yes. But today's computers manage pretty good "multimedia"
output from onboard sound. Unfortunately laptops are often an
exception. Their sound systems are consistently lousy, and many have
electrically noisy power supplies. You may spend money on a USB or
Firewire audio interface only to find you still get noise when running
on the mains adaptor.
Anonymous
a b D Laptop
February 9, 2005 3:07:32 PM

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

"Jerohm" <jDrEmLoEhTrE@snet.net> wrote in message
news:KOdOd.1611$he5.273@newssvr31.news.prodigy.com
> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
> ...
>> However I can get rid of hum by unplugging laptop from AC and using
>> it's internal battery.
> ...
> My Sony VAIO laptop has a similar problem with the microphone.
>
>> So what is the best solution?
>
> PC's provide an incredible hostile environment for analog audio. More
> expensive sound cards do a good job at shielding . USB and Firewire
> (preferred) external solutions will also provide acceptable (to great)
> results. There is probably NOTHING you can do if you are trying to
> make use of the standard built-in audio provided by most
> manufacturers.

This "PC's provide an incredible hostile environment" stuff is totally
irreelvant.

You've got ground loops pure and simple. You'd have the same problems if you
interconnected similar but pure analog equipment.

Here's some info about ground loops:

http://www.smr-home-theatre.org/Ground-Loops/

http://www.epanorama.net/documents/groundloop/index.htm...
Anonymous
a b D Laptop
February 9, 2005 3:08:41 PM

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

"TCS" <The-Central-Scrutinizer@p.o.b.o.x.com> wrote in message
news:slrnd0kc05.546.The-Central-Scrutinizer@linux.client.comcast.net
> On Wed, 9 Feb 2005 10:40:12 -0500, Ethan Winer <> wrote:
>> Larry,
>
>>> The volume is low so receiver volume needs to be turned up pretty
>>> high,
>> unfortunately - even with computer volume turned to max. <
>
>> Keep looking for other software volume controls. Most sound cards
>> can put out a decent "consumer line level" signal, to adequately
>> drive a typical receiver.
>
>>> I can get rid of hum by unplugging laptop from AC and using it's
>>> internal battery. <
>
>> That means you have a simple ground loop. The solution is simple
>> too, but
>
> Not likely that the laptop is getting grounded to the mains through
> the charger.

Actually very likely. There is no rule, some are some aren't.
Anonymous
a b D Laptop
February 10, 2005 12:11:55 AM

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

"Jerohm" <jDrEmLoEhTrE@snet.net> writes:

> >> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
> >> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
>
> >
> > Thanks for reply. It's not exactly what I hoped to hear, but I suppose
> > it's
> > probably the truth. Can you or anyone make any suggestions about an
> > external solution (preferably USB)? What terms should I search for using
> > Amazon?
> >
> >
> The M-Audio Transit will give you both analog and optical digital
> Inputs/Outputs. Edirol also makes various devices. The Xitel Analog HiFi
> Link is probably the cheapest (analog out Only). Check around (eBay too)
> because the prices can vary quite a bit. There may be others also (Google:
> USB Audio). There are MANY USB audio devices, so find the one that provides
> the features you are after. The M-Audio Transit @ $79.00 is pretty tough
> to beat (and even though you may not need digital I/O now, it is nice to
> have!). I am using the M-Audio Firewire Audiophile and am very pleased wih
> it (but it is probably MORE than you are looking for). I have never used a
> USB audio interface, but so much stuff is out there, that it MUST work okay.
> Search around for reviews. Good Luck.

The original question had humming noise when computer was
connected to mains outlet. Most propably the problem is related
to ground loop problem.

If the ground loop problem is the reason, then generally the
problem does not go away by using external USB audio device
with line output. Both on the USB audio adapters and the PC
soundcards (all I know this type of devices) the audio
output ground is connected to PC case ground
(which gets connected to mains ground through power
lead ground pin). In this kind of connection both
internal sound card and USB device would make the noise.

Generally the best way to get rid of ground loop problem is to
isolate the audio signal using audio isolation transformer.
This gets rid of the grounding related noise.
Usually this is done using external audio isolator adapter
(theoretically this function could be built into USB audio
device or PC soundcards, but I don't know any product that does this).

If you can make the connection using optical digital
interface, that connection will carry sound as well
without noise.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
Anonymous
a b D Laptop
February 10, 2005 12:11:56 AM

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

"Tomi Holger Engdahl" <then@solarflare.cs.hut.fi> wrote in message
news:lajfz05wnt0.fsf@solarflare.cs.hut.fi...
> "Jerohm" <jDrEmLoEhTrE@snet.net> writes:
>
>> >> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
>> >> news:Zc2dnT7UJOXH_pTfRVn-sQ@comcast.com...
>>
>> >
>> > Thanks for reply. It's not exactly what I hoped to hear, but I suppose
>> > it's
>> > probably the truth. Can you or anyone make any suggestions about an
>> > external solution (preferably USB)? What terms should I search for
>> > using
>> > Amazon?
>> >
>> >
>> The M-Audio Transit will give you both analog and optical digital
>> Inputs/Outputs. Edirol also makes various devices. The Xitel Analog
>> HiFi
>> Link is probably the cheapest (analog out Only). Check around (eBay too)
>> because the prices can vary quite a bit. There may be others also
>> (Google:
>> USB Audio). There are MANY USB audio devices, so find the one that
>> provides
>> the features you are after. The M-Audio Transit @ $79.00 is pretty
>> tough
>> to beat (and even though you may not need digital I/O now, it is nice to
>> have!). I am using the M-Audio Firewire Audiophile and am very pleased
>> wih
>> it (but it is probably MORE than you are looking for). I have never used
>> a
>> USB audio interface, but so much stuff is out there, that it MUST work
>> okay.
>> Search around for reviews. Good Luck.
>
> The original question had humming noise when computer was
> connected to mains outlet. Most propably the problem is related
> to ground loop problem.
>
> If the ground loop problem is the reason, then generally the
> problem does not go away by using external USB audio device
> with line output. Both on the USB audio adapters and the PC
> soundcards (all I know this type of devices) the audio
> output ground is connected to PC case ground
> (which gets connected to mains ground through power
> lead ground pin). In this kind of connection both
> internal sound card and USB device would make the noise.
>
> Generally the best way to get rid of ground loop problem is to
> isolate the audio signal using audio isolation transformer.
> This gets rid of the grounding related noise.
> Usually this is done using external audio isolator adapter

Not sure how to buy or use an external audio isolater adapter. Is this
complex and/or expensive? I'd prefer not to have to go into the computer and
mess around if I don't have to - I'm afraid I'll do more harm than good.
Can you send me a link to this device?

> (theoretically this function could be built into USB audio
> device or PC soundcards, but I don't know any product that does this).
>
> If you can make the connection using optical digital
> interface, that connection will carry sound as well
> without noise.
>
> --
> Tomi Engdahl (http://www.iki.fi/then/)
> Take a look at my electronics web links and documents at
> http://www.epanorama.net/
Anonymous
a b D Laptop
February 10, 2005 12:19:25 PM

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

"Ethan Winer" <ethanw at ethanwiner dot com> writes:

> Larry,
>
> > The volume is low so receiver volume needs to be turned up pretty high,
> unfortunately - even with computer volume turned to max. <
>
> Keep looking for other software volume controls. Most sound cards can put
> out a decent "consumer line level" signal, to adequately drive a typical
> receiver.
>
> > I can get rid of hum by unplugging laptop from AC and using it's internal
> battery. <
>
> That means you have a simple ground loop. The solution is simple too, but
> not cheap. You need an audio isolation transformer. Two, actually, with one
> each for the left and right channels.

You are right on this.

> The least expensive audio transformer
> I know of is the Ebtech Hum Eliminator (about $60 for a stereo pair).

The least expensive transformer that work quite ecceptably is this:
http://www.biltema.fi/osteri/osteri.cgi?sivu=skriptisiv...
The price of it is 9.25 Euros

> Good transformers cost more like $100 per channel. I have a Jensen transformer on
> the subwoofer in my home theater to solve this same problem, and it cost me
> $115.

You are right on this.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
Anonymous
a b D Laptop
February 10, 2005 12:32:48 PM

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

"LarryLOOK" <anonlmp@yahoo.com> writes:

> > If the ground loop problem is the reason, then generally the
> > problem does not go away by using external USB audio device
> > with line output. Both on the USB audio adapters and the PC
> > soundcards (all I know this type of devices) the audio
> > output ground is connected to PC case ground
> > (which gets connected to mains ground through power
> > lead ground pin). In this kind of connection both
> > internal sound card and USB device would make the noise.
> >
> > Generally the best way to get rid of ground loop problem is to
> > isolate the audio signal using audio isolation transformer.
> > This gets rid of the grounding related noise.
> > Usually this is done using external audio isolator adapter
>
> Not sure how to buy or use an external audio isolater adapter. Is this
> complex and/or expensive? I'd prefer not to have to go into the computer and
> mess around if I don't have to - I'm afraid I'll do more harm than good.
> Can you send me a link to this device?

Audio isolator adapter is very simple to use device if you get
right kind of device. Those typically are just a small box
/made of plastic or metal). There are two cable pairs coming
out of it. One is terminated to two RCA make connectors and other
is terminated with two RCA female connectors.
Intallation is simple: Just put this device between your cable
coming form computer and your amplifier. So just diconnect computer
cable RCA connectors form amplifier, plug in RCA connectors from
audio isolator to amplifier inputs and plug the RCA connectors
from computer audio cable to free RCA male connectors on the isolator.
Now thigns should work nicely and without noise.
You can fidn picture of one device I have used at
http://www.biltema.fi/osteri/data/Kuvat/31_441iso.jpg

This product is sold in Finland for little less than 10 Euros
http://www.biltema.fi/osteri/osteri.cgi?sivu=skriptisiv...
I have used this successfully to solve this kind of ground
loop problems many times.

There are links to some other commecially available products at
the end of the web page at
http://www.epanorama.net/documents/groundloop/audio_iso...
(those links are for all kinds of isolators, one with RCA
connectors and also other ones with different connectors that
might not be directly suitable ot you).

> > (theoretically this function could be built into USB audio
> > device or PC soundcards, but I don't know any product that does this).
> > If you can make the connection using optical digital
> > interface, that connection will carry sound as well
> > without noise.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
Anonymous
a b D Laptop
February 10, 2005 12:49:37 PM

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

TC,

> Not likely that the laptop is getting grounded to the mains through the
charger. <

In my experience the charger is most definitely a potential ground
connection. In fact, Larry even said that when he unplugs the laptop from
the wall the hum goes away!

--Ethan
Anonymous
a b D Laptop
February 10, 2005 12:49:38 PM

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

On Thu, 10 Feb 2005 09:49:37 -0500, Ethan Winer <> wrote:
>TC,

>> Not likely that the laptop is getting grounded to the mains through the
>charger. <

>In my experience the charger is most definitely a potential ground
>connection. In fact, Larry even said that when he unplugs the laptop from
>the wall the hum goes away!

That doesn't mean it's a ground fault. The charger is most likely putting
a ripple onto the laptop's power supply.

Here's a drawing I grabbed off the web to give you an idea what power supply
ripple is:
http://www.tpub.com/neets/book7/0272.GIF
Anonymous
a b D Laptop
February 10, 2005 4:09:45 PM

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

"TCS" <The-Central-Scrutinizer@p.o.b.o.x.com> wrote in message
news:slrnd0mtj4.rd3.The-Central-Scrutinizer@linux.client.comcast.net
> On Thu, 10 Feb 2005 09:49:37 -0500, Ethan Winer <> wrote:

>>> Not likely that the laptop is getting grounded to the mains through
>>> the charger. <

>> In my experience the charger is most definitely a potential ground
>> connection. In fact, Larry even said that when he unplugs the laptop
>> from the wall the hum goes away!

Agreed.

doesn't mean it's a ground fault. The charger is most likely
> putting a ripple onto the laptop's power supply.

I doubt it. I've never seen a laptop with a charger. OTOH I've seen plenty
of laptops with external AC power supplies. Those external power supplies
were all switchmode supplies that happily switched away at some nicely
ultrasonic frequency. No audible hum from can be due to that!

Also, I've measured the outputs of several of them and they are really
pretty clean - under 1 mv ripple. It's pretty easy to make ripple go away
when its at 35 KHz or more.

> Here's a drawing I grabbed off the web to give you an idea what power
> supply ripple is: http://www.tpub.com/neets/book7/0272.GIF

Any resemblence between these circuits and a that of a laptop switchmode
external power supply would be less than coincidental.
Anonymous
a b D Laptop
February 10, 2005 4:09:46 PM

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

On Thu, 10 Feb 2005 13:09:45 -0500, Arny Krueger <arnyk@hotpop.com> wrote:
>"TCS" <The-Central-Scrutinizer@p.o.b.o.x.com> wrote in message
>news:slrnd0mtj4.rd3.The-Central-Scrutinizer@linux.client.comcast.net
>> On Thu, 10 Feb 2005 09:49:37 -0500, Ethan Winer <> wrote:

>>>> Not likely that the laptop is getting grounded to the mains through
>>>> the charger. <

>>> In my experience the charger is most definitely a potential ground
>>> connection. In fact, Larry even said that when he unplugs the laptop
>>> from the wall the hum goes away!

>Agreed.

> doesn't mean it's a ground fault. The charger is most likely
>> putting a ripple onto the laptop's power supply.

>I doubt it. I've never seen a laptop with a charger. OTOH I've seen plenty
>of laptops with external AC power supplies. Those external power supplies
>were all switchmode supplies that happily switched away at some nicely
>ultrasonic frequency. No audible hum from can be due to that!

>Also, I've measured the outputs of several of them and they are really
>pretty clean - under 1 mv ripple. It's pretty easy to make ripple go away
>when its at 35 KHz or more.

Under load?
Anonymous
a b D Laptop
February 10, 2005 5:16:26 PM

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

Tomi Holger Engdahl wrote:
> "LarryLOOK" <anonlmp@yahoo.com> writes:
>
> > > If the ground loop problem is the reason, then generally the
> > > problem does not go away by using external USB audio device
> > > with line output. Both on the USB audio adapters and the PC
> > > soundcards (all I know this type of devices) the audio
> > > output ground is connected to PC case ground
> > > (which gets connected to mains ground through power
> > > lead ground pin). In this kind of connection both
> > > internal sound card and USB device would make the noise.
> > >
> > > Generally the best way to get rid of ground loop problem is to
> > > isolate the audio signal using audio isolation transformer.
> > > This gets rid of the grounding related noise.
> > > Usually this is done using external audio isolator adapter
> >
> > Not sure how to buy or use an external audio isolater adapter. Is
this
> > complex and/or expensive? I'd prefer not to have to go into the
computer and
> > mess around if I don't have to - I'm afraid I'll do more harm than
good.
> > Can you send me a link to this device?
>
> Audio isolator adapter is very simple to use device if you get
> right kind of device. Those typically are just a small box
> /made of plastic or metal). There are two cable pairs coming
> out of it. One is terminated to two RCA make connectors and other
> is terminated with two RCA female connectors.
> Intallation is simple: Just put this device between your cable
> coming form computer and your amplifier. So just diconnect computer
> cable RCA connectors form amplifier, plug in RCA connectors from
> audio isolator to amplifier inputs and plug the RCA connectors
> from computer audio cable to free RCA male connectors on the
isolator.
> Now thigns should work nicely and without noise.
> You can fidn picture of one device I have used at
> http://www.biltema.fi/osteri/data/Kuvat/31_441iso.jpg
>
> This product is sold in Finland for little less than 10 Euros
>
http://www.biltema.fi/osteri/osteri.cgi?sivu=skriptisiv...
> I have used this successfully to solve this kind of ground
> loop problems many times.
>
> There are links to some other commecially available products at
> the end of the web page at
> http://www.epanorama.net/documents/groundloop/audio_iso...
> (those links are for all kinds of isolators, one with RCA
> connectors and also other ones with different connectors that
> might not be directly suitable ot you).
>

I think I may buy this item. What do you think? Not much to lose by
trying and not too expensive:
http://www.xitel.com/product_gli.htm
Thanks to you and others for trying to be helpful!

> > > (theoretically this function could be built into USB audio
> > > device or PC soundcards, but I don't know any product that does
this).
> > > If you can make the connection using optical digital
> > > interface, that connection will carry sound as well
> > > without noise.
>
> --
> Tomi Engdahl (http://www.iki.fi/then/)
> Take a look at my electronics web links and documents at
> http://www.epanorama.net/
Anonymous
a b D Laptop
February 10, 2005 8:16:48 PM

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

"TCS" <The-Central-Scrutinizer@p.o.b.o.x.com> wrote in message
news:slrnd0nb2p.a5j.The-Central-Scrutinizer@linux.client.comcast.net
> On Thu, 10 Feb 2005 13:09:45 -0500, Arny Krueger <arnyk@hotpop.com>
> wrote:
>> "TCS" <The-Central-Scrutinizer@p.o.b.o.x.com> wrote in message
>> news:slrnd0mtj4.rd3.The-Central-Scrutinizer@linux.client.comcast.net
>>> On Thu, 10 Feb 2005 09:49:37 -0500, Ethan Winer <> wrote:
>
>>>>> Not likely that the laptop is getting grounded to the mains
>>>>> through the charger. <
>
>>>> In my experience the charger is most definitely a potential ground
>>>> connection. In fact, Larry even said that when he unplugs the
>>>> laptop from the wall the hum goes away!
>
>> Agreed.
>
>> doesn't mean it's a ground fault. The charger is most likely
>>> putting a ripple onto the laptop's power supply.
>
>> I doubt it. I've never seen a laptop with a charger. OTOH I've seen
>> plenty of laptops with external AC power supplies. Those external
>> power supplies were all switchmode supplies that happily switched
>> away at some nicely ultrasonic frequency. No audible hum from can be
>> due to that!
>
>> Also, I've measured the outputs of several of them and they are
>> really pretty clean - under 1 mv ripple. It's pretty easy to make
>> ripple go away when its at 35 KHz or more.
>
> Under load?

Yes.
Anonymous
a b D Laptop
February 10, 2005 9:34:08 PM

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

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:o 6CdndrFEJz-PpbfRVn-3A@comcast.com...
> "TCS" <The-Central-Scrutinizer@p.o.b.o.x.com> wrote in message
> news:slrnd0mtj4.rd3.The-Central-Scrutinizer@linux.client.comcast.net

> Also, I've measured the outputs of several of them and they are really
> pretty clean - under 1 mv ripple. It's pretty easy to make ripple go away
> when its at 35 KHz or more.
>

My problem with the microphone input interference can be minimized by
coiling it's cable and reorienting it. Isn't it much more likely the Power
Supply is acting as a little transmitter (rather than a ground loop issue).
Anonymous
a b D Laptop
February 10, 2005 10:12:22 PM

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

On 10 Feb 2005 14:37:16 -0800, "larrylook" <lmpmd@yahoo.com> wrote:

>This is cheap:
>http://www.radioshack.com/product.asp?catalog%5Fname=CT...
>Do you think it might work?

After researching in this group, I went to the Shack last week and
bought one. Worked great here! Hope you find the same.

--

Woodsy,
Off the Grid, Off the Road, Off my Rocker...
Anonymous
a b D Laptop
February 10, 2005 11:23:58 PM

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

LarryLOOK wrote:
> This is a repost with some new developements. Hope someone has a
> suggestion. I'm trying to run sound out from a PC and laptop to my
> receiver. I'm using the 1/8 inch stereo cable from line out from computer
> (marked with light green) with Y-adapter to two rca cables which are plugged
> into receiver. The volume is low so receiver volume needs to be turned up
> pretty high, unfortunately - even with computer volume turned to max.
>
> When I do this with 2 PC's and laptop there's a bad hum with all three!
> However I can get rid of hum by unplugging laptop from AC and using it's
> internal battery. So I tried buying a AC line interference filter ($20 at
> radio shack) but it won't prevent hum.

Go back to radioshack and exchange teh AC interference filter for a
"ground loop isolator".. It looks like a black cylinder,with RCA leads
out of each end.
That should do it for ya. (assuming it's a ground loop.)

> So what is the best solution? Do I
> try to ground the 3 computers better with a wire from ground to computer
> casing or is there some other solution? I can't believe it's so difficult
> to get decent sound out of a computer to a receiver - but I guess it is!
>
>
Anonymous
a b D Laptop
February 10, 2005 11:28:39 PM

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

ptaylor wrote:

> LarryLOOK wrote:
>
>> This is a repost with some new developements. Hope someone has a
>> suggestion. I'm trying to run sound out from a PC and laptop to my
>> receiver. I'm using the 1/8 inch stereo cable from line out from
>> computer (marked with light green) with Y-adapter to two rca cables
>> which are plugged into receiver. The volume is low so receiver volume
>> needs to be turned up pretty high, unfortunately - even with computer
>> volume turned to max.
>>
>> When I do this with 2 PC's and laptop there's a bad hum with all
>> three! However I can get rid of hum by unplugging laptop from AC and
>> using it's internal battery. So I tried buying a AC line interference
>> filter ($20 at radio shack) but it won't prevent hum.
>
>
> Go back to radioshack and exchange teh AC interference filter for a
> "ground loop isolator".. It looks like a black cylinder,with RCA leads
> out of each end.
> That should do it for ya. (assuming it's a ground loop.)
>

Also,You *could* use an impedance matching/step-up transformer inplace
of the usual 1:1 ratio for isolation.
This way you could more closely match the lower impedance output of the
PC to the higher impedance of the input of the reciever *AND* get a
larger voltage swing out of it,thus getting more gain,and not having to
crank up the PC's volume. But,Decent quality transformers are not likely
to be cheap...I suppose you could try it with the 8ohm->1Kohm little
transformers radioshack sells,just to test/make sure it all works.They
are only like $2 each,instead of $50+ each for decent quality trannies..
Anyways,just a thought.
I actually built a 1 tube preamp for use between my PC and stereo
because the signal/volume was so low. 1/2 of a 12AX7 per channel,worked
great!



>> So what is the best solution? Do I try to ground the 3 computers
>> better with a wire from ground to computer casing or is there some
>> other solution? I can't believe it's so difficult to get decent sound
>> out of a computer to a receiver - but I guess it is!
>>
Anonymous
a b D Laptop
February 11, 2005 2:30:38 AM

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

"Woodsy" <Woods@ymadbbs.com> wrote in message
news:70un01lnmq05jrjv5tc9a3puqle1g4ntm4@4ax.com...
> On 10 Feb 2005 14:37:16 -0800, "larrylook" <lmpmd@yahoo.com> wrote:
>
>>This is cheap:
>>http://www.radioshack.com/product.asp?catalog%5Fname=CT...
>>Do you think it might work?
>
> After researching in this group, I went to the Shack last week and
> bought one. Worked great here! Hope you find the same.

How do you like that! Problem solved for me too with a $16.99 item! Never
thought it would turn out to be that easily solved. I'm listening to
Debussy now and sounds fine. Thanks to all. This item will turn out to be
a big seller as more and more will be trying this kind of set up.

>
> --
>
> Woodsy,
> Off the Grid, Off the Road, Off my Rocker...
Anonymous
a b D Laptop
February 11, 2005 10:32:24 AM

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

"LarryLOOK" <anonlmp@yahoo.com> wrote in message
news:o sednfKu6o5uqZHfRVn-vQ@comcast.com
> "Woodsy" <Woods@ymadbbs.com> wrote in message
> news:70un01lnmq05jrjv5tc9a3puqle1g4ntm4@4ax.com...
>> On 10 Feb 2005 14:37:16 -0800, "larrylook" <lmpmd@yahoo.com> wrote:
>>
>>> This is cheap:
>>> http://www.radioshack.com/product.asp?catalog%5Fname=CT...
>>> Do you think it might work?
>>
>> After researching in this group, I went to the Shack last week and
>> bought one. Worked great here! Hope you find the same.
>
> How do you like that! Problem solved for me too with a $16.99 item! Never
> thought it would turn out to be that easily solved. I'm
> listening to Debussy now and sounds fine. Thanks to all. This item
> will turn out to be a big seller as more and more will be trying this
> kind of set up.

I'm glad that this item worked for you. Its effectiveness clearly supports
the hypothesis that the problem was a ground loop.

You should be aware that there is a pretty fair possibility that this
device, because of its low cost and basic nature, may be causing an audible
sound quality loss. This may or not be important to you. I'm sure its great
to be free of the nasty humming sound.

Here's what a first rate version of a similar product involves:

http://www.jensentransformers.com/datashts/ci2rr.pdf
Anonymous
a b D Laptop
February 11, 2005 2:37:28 PM

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

LarryLOOK wrote:

> This is a repost with some new developements. Hope someone has a
> suggestion. I'm trying to run sound out from a PC and laptop to my
> receiver. I'm using the 1/8 inch stereo cable from line out from computer
> (marked with light green) with Y-adapter to two rca cables which are plugged
> into receiver. The volume is low so receiver volume needs to be turned up
> pretty high, unfortunately - even with computer volume turned to max.
>
> When I do this with 2 PC's and laptop there's a bad hum with all three!
> However I can get rid of hum by unplugging laptop from AC and using it's
> internal battery. So I tried buying a AC line interference filter ($20 at
> radio shack) but it won't prevent hum. So what is the best solution? Do I
> try to ground the 3 computers better with a wire from ground to computer
> casing or is there some other solution? I can't believe it's so difficult
> to get decent sound out of a computer to a receiver - but I guess it is!
>
>
The most elegant and ideal solution would be to have all your audio
equipment that is connected together to use the same ground. If that is
not physically possible, then the next best thing would be to use ground
loop isolators.

CD
Anonymous
a b D Laptop
February 11, 2005 10:49:59 PM

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

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:b-KdnfgRT_RLOJHfRVn-2g@comcast.com...
> "LarryLOOK" <anonlmp@yahoo.com> wrote in message
> news:o sednfKu6o5uqZHfRVn-vQ@comcast.com
> > "Woodsy" <Woods@ymadbbs.com> wrote in message
> > news:70un01lnmq05jrjv5tc9a3puqle1g4ntm4@4ax.com...
> >> On 10 Feb 2005 14:37:16 -0800, "larrylook" <lmpmd@yahoo.com> wrote:
> >>
> >>> This is cheap:
> >>>
http://www.radioshack.com/product.asp?catalog%5Fname=CT...
> >>> Do you think it might work?
> >>
> >> After researching in this group, I went to the Shack last week and
> >> bought one. Worked great here! Hope you find the same.
> >
> > How do you like that! Problem solved for me too with a $16.99 item!
Never
> > thought it would turn out to be that easily solved. I'm
> > listening to Debussy now and sounds fine. Thanks to all. This item
> > will turn out to be a big seller as more and more will be trying this
> > kind of set up.
>
> I'm glad that this item worked for you. Its effectiveness clearly supports
> the hypothesis that the problem was a ground loop.
>
> You should be aware that there is a pretty fair possibility that this
> device, because of its low cost and basic nature, may be causing an
audible
> sound quality loss. This may or not be important to you. I'm sure its
great
> to be free of the nasty humming sound.
>
> Here's what a first rate version of a similar product involves:
>
> http://www.jensentransformers.com/datashts/ci2rr.pdf

Thanks, and maybe I'll upgrade to something like this later. It's great
knowing there's a solution that's easily obtained because I was worried.

We did a home renovation that involved sound out from my study where there's
3 computers, to home theater 40-50 feet away in family room. There are
baluns to avoid signal degradation (sound guy did some of this). Home
theater takes sound to 3 rooms and the deck. I wanted this for the future
when all music is on hard drives (not cd's).
!