I troubleshot my noise problem...now what?

[EJD]

For the last couple days I have been tracking down a noise problem in my new LPA-1 amp which I have connected to a Sony DA5ES receiver serving as a pre/pro. The noise is a slight but noticeable buzz that is heard from all speakers when there is no sound coming through. If the TV is connected to the receiver, the noise increases fairly dramatically when the TV is turned on - but I think that is more of a symptom than a cause.

After lots of plugging, unplugging, swapping of cables, and general moving of stuff, I can report the following:

• Putting the amp on a separate circuit = still noise
• Running the amp through a Tripp Lite Isobar = still noise
• Cable completely disconnected from TV = still noise
• Only the amp on with nothing else plugged in to the outlet = still noise
• Only the amp on but removing the signal cables = noise gone

So it appears that somehow the problem lies in the noise being transmitted through the signal cables, even though there is no signal and the recevier is not even plugged in. Thinking maybe the cables were to blame, I tried three different types of cables with no effect.

So what does this all tell me, or what could I do to make my current combo work and the noise disappear? The fact that noise is present when the pre/pro is not even plugged in has me totally confused. Any insights would be appreciated (other than Sony sucks )

 

[mtrycrafts]

For the last couple days I have been tracking down a noise problem in my new LPA-1 amp which I have connected to a Sony DA5ES receiver serving as a pre/pro. The noise is a slight but noticeable buzz that is heard from all speakers when there is no sound coming through. If the TV is connected to the receiver, the noise increases fairly dramatically when the TV is turned on - but I think that is more of a symptom than a cause.

After lots of plugging, unplugging, swapping of cables, and general moving of stuff, I can report the following:

• Putting the amp on a separate circuit = still noise
• Running the amp through a Tripp Lite Isobar = still noise
• Cable completely disconnected from TV = still noise
• Only the amp on with nothing else plugged in to the outlet = still noise
• Only the amp on but removing the signal cables = noise gone

So it appears that somehow the problem lies in the noise being transmitted through the signal cables, even though there is no signal and the recevier is not even plugged in. Thinking maybe the cables were to blame, I tried three different types of cables with no effect.

So what does this all tell me, or what could I do to make my current combo work and the noise disappear? The fact that noise is present when the pre/pro is not even plugged in has me totally confused. Any insights would be appreciated (other than Sony sucks )

Well, you are on the right track by your testing and eliminating process.
It does seem to be a ground loop issue.
I think the easiest to try first is to disconnect the cable TV cable at the wall or cable box, totally, not just turning that device off.

I would add a few more tests. If you have some single conductor copper wire and see if you can wire the case or all those components together, grounding together, if that helps.

Since the noise is not there with just the amp, disconnect everything into the Sony pre/processor, all inputs, and connect it to the amp. Then each input to that processor. It should point to the one that causes or through it delivers the ground loop. In the past, a cable TV ground isolator has helped.

 

[EJD]

Thanks for the suggestions, here is an update:

I think the easiest to try first is to disconnect the cable TV cable at the wall or cable box, totally, not just turning that device off.

Done = Still noise

If you have some single conductor copper wire and see if you can wire the case or all those components together, grounding together, if that helps.

Done = still noise.
I used 18gauge copper automotive type wire to connect the amp and pre/pro at two chassis screws, although maybe this wasn't the type of wire you mean. There are no other components plugged in so I didn't ground them.

Since the noise is not there with just the amp, disconnect everything into the Sony pre/processor, all inputs, and connect it to the amp. Then each input to that processor. It should point to the one that causes or through it delivers the ground loop.

Yep = still noise.
Even with only the signal cables running from the pre/pro to the amp and no other inputs plugged into the pre/pro, the noise is there. Once you disconnect a pre-out cable to the amp, the noise is gone from that speaker.

Somehow noise seems to be entering the signal cables from the pre/pro without the unit being on or any inputs connected.

In my digging for solutions, I did find two recommendations that I am not familar with:
1) an isolation transformer - not sure if my Tripp Lite is one or if this is something else
2) shorting the plugs on all unused analog inputs on the receiver - I think this means somehow modifying an RCA plug and attaching it to the input without the cable??

Any idea on those two things or other possible ideas?

 

[markw]

Well, if all else fails...

http://www.impactacoustics.com/product.asp?cat_id=1009&sku=41163

 

[jcPanny]

Amp noise

EJD,
Is there noise when the receiver AND the amp are on with no source playing?

If not then setup the power trigger on the amp and you wont have to worry about the amp being on when other gear is off.

If so, then you have a ground loop problem or possibly a bad amp. Try to determine is the noise is an issue on a single channel or all channels and call Emotiva for further assistance.

 

[EJD]

Yes, the noise is still there when both amp and pre/pro are on. Turning the pre/pro on or off doesn't have an affect on the level of noise. The noise is coming from all channels, although it doesn't sound exactly the same through each speaker. For example, it is more pronounced through the center and left surround - less so through the left front.

I had considered the fact that there might be a problem with the amp, so I tried a couple different things:

1) Plugging an analog out of the DVD player directly into the amp (not turning the DVD player on) - this reduced the noise somewhat, but did not eliminate it completely.

2) Plugging the CD player directly into the amp (not turning the CD player on) - this seemed to eliminate the noise.

So looking at what the output specs of the different devices are - the pre/pro has an output voltage of 2v with an impedance of 1 kilohm, and the CD player also has an output voltage of 2v but with an impedance of over 10 kilhoms. Maybe that means something, but it's over my head....

Thanks for the continued help

 

[jcPanny]

Amp problem?

EJD,
Also try swapping the cables to verify that they are not the problem.

 

[EJD]

Yep - tried Monoprice RG59, Monoprice RG6, and Blue Jeans LC-1 with no effect

 

[mtrycrafts]

Yep - tried Monoprice RG59, Monoprice RG6, and Blue Jeans LC-1 with no effect

If you have a cheater plug, try that but only as an experiment, not as a solution.
Yours seems to be a brute of a problem.

 

[EJD]

OK, the cheater plug had no effect on the noise - it's still there.

So if I understand the ground loop issue correctly - the cheater plug should have broken any ground loop and eliminated the noise. Since it that did not happen, does logic seem to dictate that there is a problem with the amp itself?

I am thinking one of two things:

1) There is a problem with the power supply or a ground point in the LPA-1 as suggested in post #11 here
(This is entirely possible because the box arrived beat to h*ll)
2) Maybe the LPA-1 just has a high noise floor and this is as quiet as it's going to get.

Seem logical?

Maybe a call to Emotiva is in order....

 

[rmongiovi]

Might you have some of your components plugged into different outlets?

If you do, and the two outlets are on different electrical circuits, that could create a ground loop....

 

[mtrycrafts]

OK, the cheater plug had no effect on the noise - it's still there.

So if I understand the ground loop issue correctly - the cheater plug should have broken any ground loop and eliminated the noise. Since it that did not happen, does logic seem to dictate that there is a problem with the amp itself?

I am thinking one of two things:

1) There is a problem with the power supply or a ground point in the LPA-1 as suggested in post #11 here
(This is entirely possible because the box arrived beat to h*ll)
2) Maybe the LPA-1 just has a high noise floor and this is as quiet as it's going to get.

Seem logical?

Maybe a call to Emotiva is in order....

Well, since the only time the noise is eliminated is when nothing is connected to the amp, that would be the only cause of the source of the noise.

 

[Stealth X]

your noise is definately different than my noise, but this may be worth a look - maybe its something else in the house creating interference...

http://www.remotecentral.com/cgi-bin/mboard/rc-custom/thread.cgi?12231,1

it seems my new reciever is more "sensitive" or something as i didnt have this issue with my yammy amp....