Amp and speaker hiss - do I go back an AVR?

[alucard]

Jul 8, 2017 10:59:03 GMT -5 DYohn said:

Jul 8, 2017 10:44:07 GMT -5 alucard said:

Thanks for the response. I'm using the Emo XMC-1.

OK so this is home theater we are talking about and not 2-channel, yes? Does the XMC-1 use a three-prong power cable or two-prong? First try disconnecting all interconnects from pre/pro to amp and see if the hum is in the amp by itself. You can then try unplugging all inputs to the XMC-1 (especially HDMI) and see if the issue changes. And lastly if none of those things change the issue, try taking a piece of speaker wire and touch one end to the metal case of the pre/pro and the other end to the metal case of the amp. If none of those things has any effect then the issue is coming from the power system in your house and we are back to probable DC offset.

Yes, it is an HT setup.
Yes, the XMC-1 has 3-prong plug.
Most/all of the equipment is different than the previous house.
I'll test again with unplugging everything and going one by one, and the speaker wire test.

[DYohn]

I'm just making suggestions based on my experience. I hope you can track it down.

[novisnick]

Wish you best of luck. I once owned a prepro and a two channel pre with HT bypass, they never did like each other! Never could get rid of the buzz! Tried for two months and finally gave up. I don't usually quit !! Im sure your frustration level is NOT helping. Hope you get it fixed. 👍👍🎶🎶

[Axis]

I lived one place that I had to turn all the breakers off except for the wall outlet to not get noise in my gear. Most of the time I have had ground issues that caused hum it was a interconnect of some kind or bad connection internally in the gear. Very seldom has it been because of a power connection but I know it happens a lot.

Emotiva makes the CMX-2, one of the only good cures for power supply noise I have seen.

Here is what they say about it in the Overview :

'The CMX-2 offers a solution to a less-familiar, common problem - DC offset on the AC power line. DC offset is usually the result of unbalanced loads or by flaws in the power distribution system itself. It can cause DC current flow in the transformers that power your audio equipment, making them run hotter, produce more mechanical hum, and, in extreme cases, even potentially causing permanent damage.'

Many people have reported back that this has eliminated noise in there system. It normally was when nothing else worked, but it has worked good for many since I have been here.

emotiva.com/products/accessories/cmx-2

[novisnick]

Does the circuit have dimmer switches on it? Another culprit!

[alucard]

Jul 8, 2017 13:21:00 GMT -5 novisnick said:

Does the circuit have dimmer switches on it? Another culprit!

There was a dimmer in the dining room but took that out a couple years ago - that switch made the lights and the switch itself have that electric hum. Replaced it with a normal on/off switch. No hum from switch or lights now.

There is a ceiling light in one of the bedroom that uses a remote control instead of a switch, but does have dimmer feature.

[bluemeanies]

Like I said in prior post.
Have patience and tear your system apart, clean everything and start from scratch.
One unit at a time turning each on one at a time as you go on but make sure all connections are tight.
Also shielded cable helps if you are not already using it.
Invest in one or two manual ground fault protectors...FIRST THING.
You could have D.C. signal on a AC line.
If you do there is a device for that also but I think there is a better chance that you have a ground loop that you can figure out. The ground fault protection is preventive maintenance in case of a surge but can also help with your ground loop if done correctly.
It is a time consuming project.

[alucard]

I had fun this afternoon. I unplugged every HT item from one another and from wall outlets, and unplugged every single item in the house except for the washer&dryer, oven, and the HVAC system. At the circuit breaker I turned off everything except the room my HT is in. I plugged the amp and the preamp directly to the wall and same outlet. I connected a single RCA interconnect from preamp to amp, and speaker cable from amp to speaker. And there was hum. The hum went away after disconnecting the RCA. Does this mean there is a ground loop between the amp and preamp?

[hemster]

Is the RCA cable near (parallel to) a power cable? If so, you're hearing an induced hum. If they must be in close proximity, cross them at right angles.

Also can you test plugging the pre and amp into different outlets?

[alucard]

Jul 8, 2017 16:05:37 GMT -5 hemster said:

Is the RCA cable near (parallel to) a power cable? If so, you're hearing an induced hum. If they must be in close proximity, cross them at right angles.

Also can you test plugging the pre and amp into different outlets?

Here's a top-down view. I have 1 XLR from Monoprice on order just to see.


Testing another outlet is possible. Probably won't get to that until next weekend as it is a bit of work - though I could have done it earlier when I had everything apart. Or buy extension cables.

[DYohn]

That means the hum, whether it is coming from your house or from a system ground loop, is being picked up in your preamp not in your amp. Try the speaker wire star-ground trick and see if it changes anything. Also try lifting the ground on the preamp using a 3-to-2 prong adapter.

[hemster]

Yes, lifting the ground would do the trick. I did have to do that in my last place.

Just pick up one of these:

[alucard]

I tried the speaker cable trick - I taped the bare wire on top of each case but it did not change anything. Perhaps that is because of the coating on the case is preventing a good contact.

THE GROUND LIFT PLUG DID WORK! Wow. So after all this time it was the preamp. Hmmm. Does that mean the ground in the preamp needs to be looked at or that the house ground could be the culprit? I took out the ground lift - read that was dangerous to keep in. What are my options here?

Thanks everything helping me track this down it bit further. Almost there.

[socketman]

I plugged my stuff into a surge protector and used a ground lift. No lighting to worry about here and i dont shower in my bedroom. I have plenty of stereo equipment that only has 2 prong. Some people worry 2 much LOL

[alucard]

Jul 8, 2017 20:01:12 GMT -5 socketman said:

I plugged my stuff into a surge protector and used a ground lift. No lighting to worry about here and i dont shower in my bedroom. I have plenty of stereo equipment that only has 2 prong. Some people worry 2 much LOL

I'll probably use the lift for now and let the electrician know of these findings. Maybe they can fix it and I can take out the lift. In any case, if the preamp is connected to the amp via RCA, and the amp is grounded, does that mean the preamp is grounded through the amp?

[hemster]

Jul 8, 2017 20:31:05 GMT -5 alucard said:

Jul 8, 2017 20:01:12 GMT -5 socketman said:

I plugged my stuff into a surge protector and used a ground lift. No lighting to worry about here and i dont shower in my bedroom. I have plenty of stereo equipment that only has 2 prong. Some people worry 2 much LOL

I'll probably use the lift for now and let the electrician know of these findings. Maybe they can fix it and I can take out the lift. In any case, if the preamp is connected to the amp via RCA, and the amp is grounded, does that mean the preamp is grounded through the amp?

Yes, but... There can be multiple paths to ground and these can lead to voltage differentials that can cause hum. This is why a star topology is preferred for grounding wherein all devices are tied to a common ground.

The electrician should be able to help.

[westom]

Jul 8, 2017 9:46:09 GMT -5 alucard said:

I will start with having the electrician check for earth ground, etc. I'll also test using a ground fault protector.

A ground loop creates a hum. Earth ground (which is not a receptacle safety ground)does nothing for amp noise. Buzzing indicates an internal failure. Even temperature (a diagnostic tool) might change behavior of that defect.

Nothing attached to signal or power wires will avert or cause a fault that typically causes buzzing.

[DYohn]

Jul 8, 2017 19:27:46 GMT -5 alucard said:

I tried the speaker cable trick - I taped the bare wire on top of each case but it did not change anything. Perhaps that is because of the coating on the case is preventing a good contact.

THE GROUND LIFT PLUG DID WORK! Wow. So after all this time it was the preamp. Hmmm. Does that mean the ground in the preamp needs to be looked at or that the house ground could be the culprit? I took out the ground lift - read that was dangerous to keep in. What are my options here?

Thanks everything helping me track this down it bit further. Almost there.

The house ground is the culprit and no it is not really dangerous to leave the ground lifted. If it works, leave it. Or better yet, plug the XMC-1 into a CM2.

[bluemeanies]

Also try that manual ground fault protector from Home Depot...you can always return it if it does not work. A surge protector is not sufficient...I still had the ground loop. A surge protector was not designed to safe guard against ground loops.
Also there is a product called HUM-X that some people claim got rid of their ground loop issue.

[leonski]

Something like THIS should be part of everyones kit.

www.homedepot.com/p/Power-Gear-3-Wire-Receptacle-Tester-50542/206212329?gclid=CIihitP4_NQCFQxrfgodo30I-g&gclsrc=aw.ds

This is the easy way to find out if a fundamental flault is in your house wiring. Common fault might be a ground / neutral reverse, which this device will indicate.
Cost is a trivial 7$ but you might be able to find same thing for less $$

If / When you get an electrician out there, see if he has a 'Megger' to check ground resistance.

www.megger.com/eu/products/ProductDetailsBySubGroup.php?PSGC=T104&BS=