Hum sound, what more do I need? power filter, conditioner,..

Loftprojection · « **on:** 31 Mar 2005, 03:28 pm »

Hello, sorry if this question as been answered before but I don't find the info I'm looking for. I'm not too good with all the technical audio stuff...

I have a 5x50w receiver and there was some low level "hum" sound in my speakers. So I bought a Monster Cable power bar (HTS800) with some kind of filter and it cured the problem. I have my CD, DVD and cable TV hooked up in this power bar. Now, I just added a small mono 80w amp to drive a sub and the hum is back when the mono amp is on.

Is it because my Monster Cable power bar filter is not strong enough for two amps or what? I'm tempted to go buy another one of these MC power bar but heck maybe there is a better solution. I hope you are not going to tell me I need one of those "power conditioner" boxes that cost >$1000... Is there a cost effective solution, I mean at least that is less then $300-400.

Thanks for your help.

Charles Calkins · « **Reply #1 on:** 31 Mar 2005, 03:42 pm »

Try disconnecting the FM antenna lead into the receiver. I had a similar problem and that's what it cured mine.

Cheers
Charlie

Loftprojection · « **Reply #2 on:** 31 Mar 2005, 03:51 pm »

Charles, I don't have an FM antenna, my receiver doesn't have a tuner!!! haha It's called a receiver but it's the first generation of "receivers" by Arcam and it's a pure analog machine, amp, pre-amp and Dolby Pro Logic processor not even DD or DTS...

skrivis · « **Reply #3 on:** 31 Mar 2005, 04:07 pm »

You could also try disconnecting the cable TV connection.

It sounds like a ground loop or similar grounding problem. They can be a pain.

I think would start in one of two places. Either the new amp, or the whole system.

If the whole system, don't use the Power Bar and try just the main amp. See if you get a hum. Then connect something else and try that. Keep adding things on until you get the hum. That should help pinpoint where the problem is. It could be a bad cable, or faulty ground, or even mis-wired equipment.

The other way to start is by changing things with the new amp. Have you tried plugging it directly into the wall rather than through the Power Bar? Are the cables good? Does it hum only when you've got a cable connected to the input, or does it hum by itself?

Have you checked your wall socket to make sure things are ok? They have cheap testers (probably $10 or less) that you can plug in and find problems.

I moved into a new house a few years ago and went around testing outlets before getting settled in. I'd say that 1/3 of them were mis-wired or otherwise faulty.

Another thing to check is whether you have power cables running parallel to signal cables. The low-level signal cables can pick up hum from the power cables. If they have to be close together or touch, it's best if they meet perpendicularly. (That's not always easy to do...)

Loftprojection · « **Reply #4 on:** 31 Mar 2005, 05:04 pm »

OK, at least I don't feel too idiot now, it seems like my problem is not something too obvious! haha

It is definitely coming from the new amp. When I disconnect it, no hum at all. I did try connecting it to another wall socket not the power bar where everything is plugged in and the hum is a bit less but still there.

I don't think it's related to the parallel wires picking up garbage because I took the amp power cable through a completely different path and it does not even run close to any other cables.

Now that you mention grounding, there is one thing that might be of interest. The power cable of this mono sub amp has only two pins, it is not a 3 pin adapter like all my other audio components. Could this explain the problem?

I'm now leaning towards the solution of buying another one of those MC power bar "filter" and plugging the sub amp alone in one of those! This is a bit stupid tough, I would prefer putting my money somewhere that could improve my sound quality, not just to eliminate a stupid hum!

Thanks much for your suggestions.

panderso · « **Reply #5 on:** 31 Mar 2005, 11:58 pm »

I recently went through ground loop grief, but the buzz/hum was rising and falling from the amp body, not through the speakers.

Did some troubleshooting and solved the problem; probably at least 3 solutions that may have been sufficient. I had an electrician install a dedicated line; a great investment for only about a hundred dollars.

The immediate cause was probably an improper hook-up between DVD and TV in the next room - but on the same line, until the new dedicated line was installed...I had the TV audio output going back into the DVD player.

Short term relief came from a $20 surge protector where the cable TV server hooked up to the TV - before figuring out what was really wrong.

Dedicated line, independent of all other electronics, AV, appliances etc. very worthwhile...

Good luck!