New amp now a hum.

Skynut

First off peep out the new sig. Sherbourn 7/2100 is a new addition, I also switched the R/L centers I was using for the rt2000p's

Now for the question.

The new amp hums when hooked up to the Rcvr. It has hummed with two different types of cables from the same manufacturer. (one set is belden wires while the other is silver plated ofc.) When I hook it up to the DVD directly I did not hear a hum.

I also unhooked everything from the rcvr except the dvd and still a hum.

I plugged the amp into a wall instead of the power conditioner and still a hum.

With the rcvr only hooked up to the amp with one interconnect I get a hum.

With the rcvr turned all the way down to zero I get a hum and when I turn it up the hum goes up with it.

The hum also fluctuates alittle and changes it's tone a little. very little.

When I put sound through it I can drown the hum out with no problem but during soft passages I can still hear the hum from the seating possition.

I really can not afford a new pre/pro since I just bought the amp so I need sugestions from you experts as to what to do.

The Onkyo rcvr did not have a hum before the new amp even when turned all the way up with cd's paused.

HELP.

Thanks.

RuSsMaN

Cheater plugs, try some.

Skynut

What are cheater plugs?

hoosier21

here is one

Skynut

I just did a search and read bunches of articles about this hum.

My rcvr is not grounded so I am wondering if I can run a chassis ground to my power conditioner externally.

Does this sound like a bad idea?

steveinaz

Did you try a cheater plug and reverse directions yet?

Skynut

Not yet.

Skynut

I will try that later if it might work.

Skynut

steveinaz wrote:

Did you try a cheater plug and reverse directions yet?

This is to reverse the polarity?
Everything is going through the power conditioner and is still humming. Might this work in that instance also?

thehaens@cox.net

I have had the same problem with my parasound amp, I used a jensen transformer to take the "ground loop" hum out.

I also stumbled upon this article in Stereo Times when a reviewer had a problem with a Conrad Johnson MF2500 amplifier. Here is the link

He claims he used a Shakti Stone on the amp and the hum went away.

Perhaps snake oil, perhaps not.

Try running a wire between the chasis on the amp and receiver on a screw and see if the problem goes away.

Scott

cfrizz

I got an annoying hum when I got my Parasound amp. I went into Radio Shack & told them I had an annoying hum & they gave me a TV AM/FM AC line Interference Filter for 19.00. It took the hum away!!!

McLoki

I had a bad hum with my cinepro and was able to call a service facility and the solution was to cut one of the cables inside the amp. (it was a documented issue with the amp) Just reminding you to not forget to call the manufacturer and talk to their tech support.

It may be an easy fix if you have the know how needed. (btw - 9 times out of 10 a cheater plug will fix your issue.)

Michael

thehaens@cox.net

^^^Did that cable recommendation happen to be the wire that goes from the input ground to the chasis?

I guess if you cut that wire, then it would be the same as using a cheater plug...

Scott

McLoki

thehaens@cox.ne wrote:

^^^Did that cable recommendation happen to be the wire that goes from the input ground to the chasis?

I guess if you cut that wire, then it would be the same as using a cheater plug...

Scott

Actually it was one strand (luckly the outside strand) of a ribbon cable going from a main board to one of the amplifier boards. I am not sure what it did, but it dropped the hum.

Michael

pearsall001

Cheater plugs worked great for me. I've also been told that this a dangerous thing to do. How true is that?

polkatese

not very true unless you live in thunderstorm-alley..

SKsolutions

Cheater plug- "Ground buster" up here in Boston should work if the hum is coming in on the ground wire. You may need to put them on the Receiver and the Amp. There really is no polarity in an A/C system including speakers, but there is phase. I don't know if the Panamax reverses phase to try to isolate nuetral ground noise, but that is a possible cause. Minimal risk. Try it first. Cost: about 4 bucks.

Don't laugh- the unit from Radio shack that (Cfrizz) mentioned actually works, as I've used it. It's a ground loop isolator. Cheap too. Try second.

If you still have a hum, check the amp. Does it have balanced XLR's? Is the amp chasiss neutral grounded? Is there a grounding lug on the rear panel? You'll have to do some digging to find out your Amp's specs, and since that is the new piece of the system, why it's getting noise. Try a different manufacturer's IC's maybe. There may be something wrong with the input impedance load at the amp.....like putting your finger on one end of an RCA when you're plugging it in....maybe. Also, look at your impedance output and input specs: Rec out to Amp in?
Hope the cheater plugs work. You can switch phase with those usually too -try each combination.

Skynut

I did not get a chance to do anything last night but tonight I will be into it.

Thanks for all the suggestions.

Skynut

Ok. last night I plugged the amp in using cheater plugs and the hum is gone.

Problem now is I have a small hiss comming out of most of my tweeters.
This is a very small hiss that can only be heard when I get close to the speakers.
Is this something that I can do nothing about?

I said most tweeters because I realized one of my RT3000 tweets is blown.

Now what?
Is there a way to get rid of the hiss or is it going to be there just because I am using a 200 wpc amp?

Are the factory tweeters in my speakers worth replacing or should I take this opportunity to upgrade?

Currently I am using the RT5000 system with RT2000's as additional centers.

I will start searching for these and many more answers right now.

McLoki

If it is a hiss that is hard to hear more than 1 foot from the speakers, it is normal. At least it seems common.

Michael

adam2434

Agree, a small amount of hiss is very common. It was probably there all the time, but the hum drowned it out.

I wouldn't be surprised if a lot of the hiss is from the receiver, and that it will vary depending on whether it's set for surround, stereo, direct, etc. On mine, the surround modes are a little noisier than stereo direct. Quietest is when the receiver is bypassed altogether and I use my separate preamp.

SKsolutions

It's the foor noise.
You could measure the noise SPL and extrapolate the Signal:Noise to some degree. It would be something you could actually do to check the real world and the maker's specs. It's not an exact measure of the actual ratio, but you could come close.

You know. . if you are bored. . or the spousal unit is . . . ahhh.. . . malfunctioning.

Skynut

Here is what I did this weekend.

I put an external chassis ground on all components in the rack.
All was going good till I fired it all back up and the hum moved to the T.V. speaker.
So I figured out that the cable input is not grounded.(thanks to what I learned here)
I ran all cable/sat/fm antenna coax through the power conditioner and viola no more hum.

So now with everything on, a cd paused, I can hear no hum standing in front of the audio rack even with the pre/pro at reference level.

I am still going to ground all the cable/sat stuff closer to where it comes into the house but for now I am pleased.

So I watched 4 movies this weekend to celebrate.

cfrizz

Congrats! Enjoy.

Skynut

It is definatly a new system now.

SKsolutions

Very cool. I hate ghosts in the machine.