Hum problem

[PATRIOT2006]

When I turn up my Alesis RA100 monitor power amp I get a hum even though nothing is turned on. With the equipment on and the volume level at the monitor send at zero or cranked, nothing changes in regards to the volume level of the hum. I tried an experiment and disconnected the 1/4 cables going into the power amp with it up at full volume and no other equipment turned on and the hum dissappeared. My question is this? Will a hum eliminator work going into the input of the power amp or do I need something coming from the output to the speakers?

[c7sus]

MY SBLive card hums like a bitch through my 1402.

The Lynx2A is dead quiet.

Depends what gear is going through the amp.

[Robert D]

Hey, the best hum eliminator is to find the source of the hum and eliminate it. So, you found that the power amp with no cables connected is quiet. What are those cables connected to at the other end? If that unit, whatever it is, is turned off and the cables are connected, do you get hum? What if the driving source is turned on, but all inputs and outputs are at zero? Got hum? Are the cables to the Power Amp balanced or un-balanced? Are the power amp and whatever is driving it connected to the same AC outlet, all properly grounded (three terminal plug)? You may have a ground loop, you may have induced EMF, or the driving source may have a problem. Turn off everything else except those two units, coming from the same outlet, properly grounded, all inputs muted or attenuated, power amp volume up at normal level. Let us know what happens.

[Robert D]

Originally Posted by c7sus

MY SBLive card hums like a bitch through my 1402.

The Lynx2A is dead quiet.

Depends what gear is going through the amp.

I LOVE my Lynx card. Dead quiet, ruler flat, doesn't get much better than that.

[PATRIOT2006]

I have done all of that already. The monitor out of my digital recorder to the power amp. With both units on I get the hum. With just the power amp on I get the hum as well. If I disconnect the cables to the power amp inputs it stops. Both are in the same properly grounded outlet which is only a few years old. New room with new wiring on it's own circuit breaker. All power cables are separated from audio cables as well.

[c7sus]

Do you have dimmer switches or flourescent lighting on while the hum is happening???

[PATRIOT2006]

No, There is not any dimmers or flourescent lights.

[xiaorong]

Is there anything new in the equation? New gear? New cables? Moved your stuff to a different room, or to a different part of the room? You wrote "new room with new wiring" and that the outlet is only a few years old. Does this mean that the room, wiring, and outlet are a few years old, or does it mean that you're re-using an outlet from elsewhere in a newly built room?

When you disconnect the speaker, are you doing that at the speaker end of the cable or at the power amp end?

[PATRIOT2006]

Completely new room built almost three years ago with same results as in old room. I disconnect the audio cables coming from the digital recorder at the power amp inputs.

[PATRIOT2006]

Update, I purchased a two channel hum eliminator and the hum got worse. When I pick it up and move it around it increases and decreases but it is never better than what I heard initially. Going back to return it.

[Robert D]

Originally Posted by PATRIOT2006

I have done all of that already. The monitor out of my digital recorder to the power amp. With both units on I get the hum. With just the power amp on I get the hum as well. If I disconnect the cables to the power amp inputs it stops. Both are in the same properly grounded outlet which is only a few years old. New room with new wiring on it's own circuit breaker. All power cables are separated from audio cables as well.

I'm guessing the hum is the same in both channels? You didn't mention whether this is a balanced circuit (recorder outs, cables, pwr amp ins)?
With everything you've described, EMI induced into the cables is the prime suspect, especially if it's an unbalanced connection. What are the cables?

[xiaorong]

Originally Posted by PATRIOT2006

Update, I purchased a two channel hum eliminator and the hum got worse. When I pick it up and move it around it increases and decreases but it is never better than what I heard initially. Going back to return it.

In my experience with hum eliminators that use transformers to separate gear in the audio chain, this happens when the hum is not caused by a ground loop but when the hum is inducted via the cabling. It sounds, as though, by isolating the speaker end of the chain you ended up with an ungrounded antenna. Hence the increase in hum. When you walked around with the unit your were, essentially, repositioning an antenna.

How well do you know the location of the wiring in your house, including where your electrical service enters the building?

Do you have similar problems with dynamic mics or guitars?

[PATRIOT2006]

Unblanced outputs on Tascam digital recorder to inputs of monitor power amp.
I am not having trouble with other equipment. In fact, my old stereo which is now upstairs no longer has the 60 cycle hum it had for years before the dormer was added. I don't believe there is a wiring problem, at least up stairs where I am. I disconnected everything and re-connected it yesterday. Seems the buzzing I was getting along with the hum dissappeared and the hum decreased in volume. Most likely induced hum in the audio cables somewhere as you suggested. I also tried a gruondlift plug for the hell of it and this did nothing further indicating it's not the house wiring. I think I am correct about that.

[c7sus]

How long is that unbalanced cord? The general rule-of-thumb as I understand it is to stay under 10-feet.

Less is better.

[MOFO Pro]

Try disconnecting the cables at the recorder side... still have hum? It's induced...

You wouldn't happen to have a high voltage secondary arial in the street on that side of the house...

And an electric guitar is a great tool to locate the source of EMI... the pickups null when you're perpendicular to the source... just strap it on (that doesn't sound right), take a spin around the room, and whatever is right in front of you when the hum from the guitar amp is at is peak, is the source. though not nessesarily in the same room.

[soundchaser59]

Originally Posted by MOFO Pro

Try disconnecting the cables at the recorder side... still have hum? It's induced...

You wouldn't happen to have a high voltage secondary arial in the street on that side of the house...

And an electric guitar is a great tool to locate the source of EMI... the pickups null when you're perpendicular to the source... just strap it on (that doesn't sound right), take a spin around the room, and whatever is right in front of you when the hum from the guitar amp is at is peak, is the source. though not nessesarily in the same room.

MoFo is right......try it with just the amp on and the cables plugged into the amp, but with nothing conected tot he other end of the cables. Just amp and cables. If you still have hum then, it's induced in the cables. That's what I thought of when you said the hum stays there even if you turn the recorder off.

If it's anything like a guitar, you might try getting the best quality super shielded super everything cables you can afford (I'm guessing these are just like 1/4 inch guitar cables??) and get a couple of ferrite chokes from radio shuck. This is how I eliminated hum in my guitar, I bet your problem is similar. The cables are acting as an antenna for some EMI in the atmosphere.....

[PATRIOT2006]

I tried what you suggested. The hum almost dissapeared but a buzz was introduced when the cables were disconnected. I have to admit, ever since I disconnected and reconnected all the cables a few days ago the situation has improved. The hum at this point is at a fairly low volume now. I don't know if this is something that can typically be eliminated 100% or is it something that all studios have at some low level due to the nature of electronics and audio.

[soundchaser59]

Originally Posted by PATRIOT2006

or is it something that all studios have at some low level due to the nature of electronics and audio.

That would be a very solid "NO!"

Real studios that are built to be studios have all kinds of shielding, special wiring, all kinds of tricks and gimmicks built into the design just to prevent things like hum and interference.

Try the super duper shielded cables and the ferrite chokes trick first, that is the cheapest experiment you can do to eliminate the problem.