RT2000p / cs1000p amp problem?

[frodaddy]

It's wierd, but when I swapped receivers my amps on the RT2000p's and CS1000p are humming. I have all 3 speakers hooked up via speaker inputs only, and here is what's happening:

All three - the amps will auto-turn on when they receive audio, and will auto-turn off after a few minutes of no audio with one exception... read below
Left RT2000p - low hum, not audible unless you put your ear to the woofers
CS1000p - higher pitched buzz, not audible from my seating position 9' away
Right RT2000p - loud hum, very audible anywhere in the room and it's quite annoying. will auto-turn on sometimes even when the receiver is powered off and no signal is being sent

Also, please note that I have a power conditioner and the passive section of the speakers are dead silent. It's only the amplifier portion that's causing my troubles.

Here's what I've done to troubleshoot:
- I bought a 2nd receiver (for other reasons) and I'm having the same exact symptoms on my L/C/R amps. Both new receivers are 7.1 powered, so I have a couple of extra long wire runs to the extra surround speakers
- Unplugged the amps from the power conditioner and plugged them into a different 20amp circuit than my home theater is plugged into. I can't use a "ground lifter" since the ends are already 2 prong.

My troubleshooting is leading me to the amps being the problem since no matter if I plug it into a clean or dirty source they buzz/hum. But how can that make sense if they all began to have this problem when I was using a different receiver that does 7.1 instead of 5.1? Any help to fix this problem is appreciated!

[tonyb]

Chances of all the amps in your powered speakers going on the fritz at the same time....not likely.More so a good old fashioned ground loop.Cable box??These tend to give people headaches.With your system on,unplug one componant at a time and see if you hear a difference.Then,being carefull,unplug each interconnect one at a time,without touching another post.This will help narrow it down.Basically,sounds like you have too many componants being ground from a single source.Try what I said and we'll take it from there.

[frodaddy]

Chances of all the amps in your powered speakers going on the fritz at the same time....not likely.More so a good old fashioned ground loop.Cable box??These tend to give people headaches.With your system on,unplug one componant at a time and see if you hear a difference.Then,being carefull,unplug each interconnect one at a time,without touching another post.This will help narrow it down.Basically,sounds like you have too many componants being ground from a single source.Try what I said and we'll take it from there.

I went ahead and unplugged all my components except for the receiver and the speaker to troubleshoot the right RT2000p. When the receiver and RT2000p amp are on, the hum is 73dB with either line level or speaker level inputs. Taking the receiver out of the equation yields 68dB.

This is wierd:

- With the line level input connected between the receiver and RT2000p and I touch the back of the RT2000p's amp, the hum gets LOUDER.
- With the line level input disconnected and using the speaker level inputs, I can touch the RT2000p's amp anywhere on the back where there's metal and the HUM GOES AWAY!!

I hooked everything back up, and touching the RT2000p's amp only decreased it to 70dB. However, if I grabbed the either of the line level connectors, the hum went away again!

The connectors aren't loose, so do I need a grounding strap? If so, how do I hook it up and what components would I hook together?

Now it's time to test my center channel :(

[frodaddy]

I fixed the center channel! I had a cheap power strip plugged into the power conditioner to have more outlets, and the center channel was plugged in to the strip. I moved it directly to the power conditioner and now it's dead silent!

I decided to try something with the right RT2000p; I attached a picture of what I've done. I took a paint can opener and positioned it so it made enough contact between the two RCA connectors so I wouldn't have to hold them while watching a movie ;)

On my left RT2000p I quickly did the same things as I've done to the right RT2000p, but nothing I did made a difference. So now I'm thinking that maybe the amp I've been troubleshooting is on the fritz. Since this fixes the problem, does this mean this particular amp is having trouble? I'm going to rig up a more graceful looking solution based off what I've done with the paint can opener. It's free and it fixes it!

I measured the left RT2000p, and it's hum is around 52dB. I can't really hear it in my seating position, so it's not a problem for me.

Case closed! :)

[tonyb]

Personally,I would not do that,as you run the risk of doing some damage to the amp.What do you have it plugged into?The amps on the speaks that is.
Y ou didn't complete the process.....you need to disconnect one thing at a time....includeing cable box and all associated interconnects with all your gear,starting with the receiver.You could just have one bad I/C.Have you tried a cheater plug on any of the power cords for your speaks or the receiver?Cost 1.99 at anywhere USA.What you have there in the picture is disaster waiting to happen.

[frodaddy]

Y ou didn't complete the process.....you need to disconnect one thing at a time....including cable box and all associated interconnects with all your gear, starting with the receiver.You could just have one bad I/C.

Perhaps I wasn't explicit enough in my post. I decided to do the same troubleshooting but from a different viewpoint. I took the viewpoint of unplugging EVERYTHING and then plugging in a device one at a time to see which one would cause the hum, including the receiver. I'm glad I did it this way because I immediately discovered the problem. With EVERYTHING unplugged (the receiver, too) the RT2000p hums all by itself at 68dB, no matter what outlet I have it plugged into: The power conditioner, the same outlet that the power conditioner was plugged into (with the conditioner unplugged), and two different outlets that are on a different fuses in my fuse box. Plugging in the receiver has no effect on hum; BUT when a connection is made with either the line level or speaker level inputs between the receiver and the speaker, the hum gets louder going up to 73dB. All this is proving is the receiver adds to the problem slightly, but the true problem lies with the RT2000p's amp since it's humming at 68dB all by itself with nothing else plugged in. So, there is definitely something wrong with the left RT2000p's amp from what I can see.

Have you tried a cheater plug on any of the power cords for your speaks or the receiver?Cost 1.99 at anywhere USA.

The speaker's power cord is terminated with a 2 prong plug already (as is my receiver), so I can't use a cheater plug. Nevertheless, I still used it on the other devices when I plugged them back in one at a time. No change in hum.

What you have there in the picture is disaster waiting to happen.

How come?
My opinion on what I did to fix the amp's hum is that my troubleshooting has already proven there is something wrong with the right RT2000p's amp. My options are to: 1) pay to get a working amp, 2) pay to have it fixed, or 3) "rig" it for free to work as advertised until it dies. I'm going with option 3 because the rig just grounds a low voltage input/output together. Yes, the user manual warns not to use the speaker and line level inputs at the same time, but the amp doesn't "see" that I'm trying to use the line level inputs since the positive portion of the RCA isn't there (I tested this before I did my fix, btw). So unless there is a risk to my home like fire hazzard I'll continue to do it this way. Personally I'm more worried about the cheater plug I'm using on my subwoofer's Behringer EP1500 amp than my fix for my right RT2000p.

Anyway, I do appreciate the help. I had to choose whether to type an essay about every troubleshooting step I took, or just type a quick summary; so I chose to post the summary. It seems like I missed some key steps, why I came to certain conclusions about the troubleshooting, and what motivated my actions for the "fix".

I was going to post that my center channel is buzzing again. It seems to be intermittent, but I haven't done thorough troubleshooting on it yet. When I get a chance I'll post my results for it.

[beardog03]

maybe a set of shorting plugs on the line levels ?