Ground loop hum? (1 Viewer)

[MikeTz]

Aaron:

Normally it's not the amp but you said that with the 9B on, and interconnects between the amp and premap installed but the preamp unplugged, you still get hum. If the amp picks up 60Hz from a ground loop, or through the interconnects (loose RCA plugs, speaker wire, etc.) then it will amplify the hum through the speakers. This is normal. However if the amp has a power supply issue the 60Hz could actually be coming from the 9B itself and this is not normal and can be easily checked by Bryston.

The test you did with the Parasound and Anthem is interesting. The Anthem has a two prong AC cord at the amp side if I remember correctly. Is the Parasound a three prong plug at the amp side?

 

[AaronG]

Mike,

I don't remember about the Anthem, but the Parasound had three prongs.

Can you think of a reason why I would have a hum, and the previous owner didn't?

Thanks,
Aaron

 

[MikeTz]

Aaron:

You've got a ground loop. The Anthem doesn't have the ground pin attached so no ground loop, and no hum. The Parasound does have a ground pin, and hum, even though it's not as bad as the Bryston. The previous owner didn't have a ground loop so no hum.

Put the cheater on the Bryston this time (humor me) and let me know if there is an audible difference in the hum. Do this with the interconnects connected and the Denon plugged in (and nothing else connected). Pull the plugs from everything else in the room and the powered sub if you have one(you don't have dimmer lights do you). I don't know much about using an external amp with the Denon so if you have another preamp that would be an interesting test. I assume using the Denon without the 9B results in no hum.

 

[AaronG]

Mike,

I'll give it a try. I can tell you that the hum was the same with the cheater and without, and, with the Denon plugged in and not plugged in.

Any ways, I'm beat and my head is spinning so I'll try out the other variations tomorrow.

thanks again for your help,

Aaron

 

[MikeTz]

Aaron:

I was bored at lunch today and thinking of your problem. I read the Denon owners manual (yes, I am an obsessed electrical engineer) and on page 4 it states the following:

"Noise or humming may be generated if a connected audio equipment is used independently without turning the power of this unit on. If this happens, turn on the power of this unit."

OK so technical writers at Denon flunked grammar but they do give us a clue about part of your problem. Now we can explain why you get the hum when the Denon is unplugged or plugged in but not turned on. Hate to say this but now you have to try the tests with tight interconnects between the Bryston and the Denon Pre-Out connectors, and with the Denon plugged in and turned on. With no souce components connected to the Denon try this:

1. No cheaters on the Denon or 9B, same outlet for both. Jiggle the interconnects at both ends, same for the speaker wires.

If hum then:

2. Same drill as #1 but cheater on the Denon power cord

If hum then:

3. Same drill as #2 but cheater on the 9B power cord

If hum then:

4. Everything else in the room unplugged

If hum then:

Let me know and I'll give you the name of an exorcist and recommend a couple hardware solutions that can fix this problem.

Good luck

MT

 

[Chu Gai]

maybe borrow a set of interconnects. no doubt you're starting to feel like you need an exorcist. I know she needed one!

 

[AaronG]

So Mike, have you got Max von Sydow's number?
Even with the room black I get the hum.
Should I be using candles instead of a flashlight?

Thanks,
Aaron

P.S. If I start throwing Holy Water at the amp should I make sure the cheater isn't attached?

 

[MikeTz]

Aaron:

Sounds like it's time for Bryston to check your amp. Or you could use the excorcist at www.ebtechaudio.com/he-2des.htm

Actually I'm your next door neighbor and I just wanted to see if you would really use the candles.

Good luck!

MT

 

[AaronG]

Thanks Mike,

I guess I'll try Bryston first (I just found out they're only 20 min. from my office).
If they can't help, the Denon is still under warranty so maybe I'll have to send it for a check-up.

I'll let you guys know what happens.

Thanks to everyone for their help!

Aaron

 

[JohnKings]

Aaron:


Just so you know, I have the exact same problem you have with my HT Steup which is based on an Outlaw 950 and Parasound Amps (1205A & 1500A) and I have tried everything identifed in this thread and all others on ground loops listed in this forum and others as well and I cannot get rid of it! There are just too many variables involved. The hum could possible be a result of one of your neighbors use of power on the same grid. It could be the result of dirty power. At some point you just have to make peace with it and get back to enjoying the HT. I have to admit I am as obssessive about these things as anyone, but I am trying to get over it. God must get a real kick out of watching us constantly unplugging AV gear, tweaking interconnects and turning out all the lights in the house to rid ourselves of a hum we couldn't hear from the listening position in a anechoic chamber (this is hyperbole of course)! I really have to get a new hobby! All that said, I really wish I could get rid of the hum so I could move on to obssessing about something else in my system.

Best of luck chasing the demons!

John

 

[AaronG]

Hi Guys,

Well, the amp is now at Bryston. They hooked it up while I was there and said that there was some noise (although it didn't seem nearly as loud a hum as when hooked up to my system).
The gentleman there told me they would open it up, take a look at it, and possibly redo the grounding (the sst's have a different grounding system).
I probably won't know till Friday but I'll let you know what happens.

Aaron

 

[MikeRP]

OK!

I have what I think is a grounding problem and have truied evrything I can think of.

I have a Pioneer 45TX hooked up with an Adcom 545.

I've disconnected everything and what I get is a slight pop when changing inputs on the receiver. I also get a barely audible hum when I'm using the remote with the ADCOM ON and the Pioneer OFF and I'm just watching cable (with the volume turned off on the TV).

I've rewired the system. Diconnected ALL interconnects one at a time. Changed the speakers which the ADCOM is running (like FL and FR to surrounds).

Nothing works except disconnecting the ADCOM.

I bought a Rat Shack ground loope isolator and instead of the pop I got a serious hum but no popping sound.

There is nothing on the circuit but some lighting that I turned off also. But, that wasn't the culprit cause I do have dedicated HT circuit in another room and I ran an extension cord to it and that didn't help.

I added a cheater plug last night on the moster power strip (2000) I have and got some sparking as I plugged it into the wall so I quit that FAST!

All my components have only two plugs bith the Pioneer and the ADCOM only have two plugs the only other thing that has three plugs in the Monster Power thingy.

Unless I get some help from you guys I'm selling the ADCOM and disconnnecting it tonight!

Thanks

Mike

 

[Chu Gai]

Mike, that's an absolutely frightening thing to happen! May I suggest that you go down to Home Depot and pick up a circuit tester. They're $4 and well worth it to diagnose any wiring issues that you may have. And btw, that EBtech post earlier is a very very good thing to investigate.
Got to love Bryston for their responsiveness and thoroughness. That warranty ain't half bad either.

 

[MikeRP]

I took the ADCOM out of the setup.

Last night I was flipping around and on a dark scene I notced a weird flash on my Tosh 57HDX82 like a bright flash on one crt.

I think its the amp.

$200 amp is now not in service - can't have that!

Mike

 

[JimmyK]

Last night I was flipping around and on a dark scene I notced a weird flash on my Tosh 57HDX82 like a bright flash on one crt.

That sounds like a known Tosh HDX problem described in this thread. I suggest you check it out.

http://www.hometheaterspot.com/htsth...b=5&o=&fpart=1


JimmyK

 

[MikeRP]

JimmyK:

I definitely been following the burst flicker issue.

But, I don't have that problem yet. I keep my set on all the time. When not in use we put it on the DVI input.

This burst was directly related to changing an input with the ADcom amp hooked up and made me think I might damage my CRT's.

I just watched Ghost ship tonight and the picture is really awesome. My set was calibrated about a month ago by Chad , wo frequents this forum and he did a great job.

Mike

 

[Shiu]

Mike, did you verify that all your power outlets are hooked up correctly in terms of polarity. That is,black-live, white-neutral... are connected correctly all the way through from the switchboard to each and every wall receptabcles, including the way you use to power the Adcom.
I have a GFA-555. It does not make any sound of noticeable hum except when you turned it off the capacitor discharge would be audible from the speakers a few seconds later.

 

[AaronG]

Hi Guys,

Just an update. I called today and they are still working on it. They wouldn't tell me much other than they were updating some of the circuitry.
I'll let you know more as I get more info.

Thanks,
Aaron

 

[AaronG]

Hi Guys,

I got the amp back from Bryston today.
My hum is gone !!!!
I had visions of the Techs standing over the unit saying "THE POWER OF BRYSTON COMPELS YOU!!", but what they did was rework the grounding on my unit to the new sst specs, and there is no hum even with the TV cable hooked up.
I am officially a happy camper.

Thanks everyone!

Aaron

 

[Chu Gai]

Well that is spectacular!! Any chance you can get Bryston to maybe get a bit more into the nitty gritty of what specifically was causing the hum and what the nature of the changes were that eliminated it? Makes one wonder a bit.

Have a beer!!