does your amp "HMmmmmmmm"?? (1 Viewer)

[rodneyH]

I recently got a new amp (marsh a400s)and as I was playing tonight, I noticed that there is a "hmmmmmm" coming out of my speakers, I disconnected my interconnects that come from my pre/pro, and it is still there, I didn't notice it before, It doesn't happen with my other amp (rotel). My rotel is running off a rotel line conditioner and my Marsh is direct into the wall outlet (but I use a 12V dc trigger from my pre/pro, the Marsh will not work by way of the power conditioner, so I have to plug it direct, ALSO that particular outlet has an "on/off" switch, like the ones used for lights (if that makes a difference??). I immediately went and checked my dads system (he is using Mc and Rotel amps) and his Mc and Rotel do the SAME thing but at a slightly lower volume (they are both plugged into the exact same type of rotel power conditioner. Also, The Hmmm doesn't get louder as the volume is increased, I don't get it??

So is this even a problem?? (it is a very powerful 200WPC amp)

Is is possibly b/c

1.NO line conditioner?

2.plugged into outlet with a "on/off" switch on the wall?

3.just the nature of that amp?

4.the 12v dc trigger switch is causing some type of leakage?

5.any other opinions??

it really isn't bad, I just want to make sure it is OK, and will NOT cause any damage, even when I listen to music at very low volume it isn't even noticable. I seem to remember hearing similar sounds at a high end audio store (using very powerful amps).

thanx for the advice!! (in advance)

 

[John Kotches]

I suspect you've got either

• Transformer Hum from DC Offset -- this is caused by halogens and sometimes fluourescents on the same circuit as the power amp.
• A ground loop that the power conditioner doesn't have, as it resolves the ground loop internally.

Have you considered moving the Rotel to the unconditioned outlet, and putting the Marsh amp on the power conditioner to remove the hum?
Congrats, once you get this little problem fixed, you'll have a very good amplifier in the Marsh.
Regards,

 

[rodneyH]

john, interesting point about the light situation, the room does have a sliding dim switch that when you begin to dim it, there is a hum, the hum doesn't seem to come out of the speakers, but out of the lights, I suspect that even though the lights don't hum when they are turned all the way up and that it ONLY hums when the lights are dim, in some way this still seems like it could be a potential source of the problem. MAybe the fact that the "wall switch" that can turn on/off the outlet that the marsh is plugged into is RIGHT next to the diming switch, could have something to do with it as well. I will play around with the set up,

I can't have it hooked up to the power conditioner like the Rotel, b/c it uses a different typw of on/off switch that makes it impossible to turn on or off with a line conditioner trigger, and you can ONLY use the 12vDC trigger switch to turn it on, so it has to hooked up to a "unswitched" outlet, the rotel only has 1 of those and it is only good for 100w equiptment (in other words, NO amps) So I have to go direct somehow, perhaps I should get and extension cord and try another wall outlet further down the wall???

anyother ideas???

btw, I LOVE the amp!!.

 

[rodneyH]

JOhn, after playing around. I got some interesting results.

1.using a different outlet didN'T change a thing,

2.I just went down to listen for it, and I didn't even hear it at first (I thought it was gone), and I stand back and can't hear a thing unless my ear is right nest to the speaker, YET last night about 1:00am, the environment is so much quiter, that I could hear it a bit more, perhaps it was just that much quieter outside to make a difffernce

3.when the light switctch (dimmer) is "on" it the "humm" is slightly loader than when it is "off" (last night, I had the lights "on").

 

[rodneyH]

I need to clearify something, when I say that it is "louder" when I turn on the light, this isn't noticable to my hear, ONLY to my SPL meter when placed 2" away from the driver, so it is VERY small.

 

[John Kotches]

Rodney,

Is it a hum or a hiss?

Transformer hum has a mechanical quality to it, and hiss, well you know what that sounds like.

Can you beg/borrow a balanced power transformer, or maybe a Monster Cable Power Center (model 2500 or above) just for kicks and grins?

I suspect your dimmer switched light is the source of the noise.

Regards,

 

[jeff lam]

Hum in your audio system due to lights being on is a common problem in the PRO Audio market. Vince Maskeeper should know a lot about this as he has lot's of experience in Pro Audio.

What you're hearing is probably 60Hz hum comming from the elecrical wiring in your house.

 

[rodneyH]

it is a definate HUmmm, not a hissss

 

[ted a]

Humming problems I have had are related to ground loops. Try putting it on 3 prong to 2 prong adapter (getting rid of the ground connection) and see if the hum goes away. If it does then you have some sort of ground loop problem.

 

[Leo]

I've got the notorious "hummmmm" from my speakers also now that I'm using the Yamaha 995 as a pre/pro and Maranta MA-500 (4 of them) as the power amps for my system (the used store I bought them from only had 4 so I'm looking for another MA-500 to finish of the last channel). Any way, I also have halogen lights (2) with a Lutron Maestro dimmer, but my equipment is running off a dedicated 20amp circuit. I would assume this would be separate from the line the lights are on. Not being an electrician, will I need to replace the dimmer to eliminate this problem? I am currently using a VansEver Super Companion II as my line conditioner. I've checked all my connections this past weekend and even with only the single amp, interconnect to the Yamaha, I was getting the hum. Any thoughts?

 

[rodneyH]

ted, if that turns out to be the problem, could I safely run it like that???

 

[ted a]

If you search other forums you will find that the Parasounds are sensitive to ground loops. Most people just use the "cheater plug". It's just a safety thing. Without the ground if there is some kind of short to the chasis then the chasis will be "hot", with it connected any short will go straight to ground (and not through you).

I have an Parasound HXA 1000 and love it, I have to run a cheater plug too...

 

[rodneyH]

TED, that did the trick, I just did it, and the noise is bearly noticable, if at all. I just happen to have a couple of those sitting around the house and put it on, I couldn't believe the difference-WOW, thanx for your help. Another great reason to have this site, people helping each other out-THANX!!!!

 

[ted a]

GREAT, glad it worked

 

[RicP]

Rodney:
DO NOT leave a cheater plug on your amplifier.
You are bypassing the ground on the amp, and if there is ever an internal short and you touch the chassis...
well...it won't be pretty.
Now that you know it's a ground loop problem. Find the true source of it. Do you have CATV? If so, the problem most likely lies there.
Check out Link Removed for great information on removing hum from a system.
You are taking a chance lifting ground on your power amp. It should not be a long term solution by any means.

 

[John Kotches]

RicP,
That's a point so many people overlook. "Well a cheater plug fixed my problem", life is good.
The ground is a safety ground, provided to protect you from the internal short that you described.
I think (but I'm no electrical expert) that if the piece of equipment provides a ground lift switch, its another matter altogether, and is a safe alternative.
Regards,

 

[rodneyH]

john, can you expand on what you mean?

 

[Leo]

Ok, so help me understand. I'm running a Yamaha 995 using the pre-out to Marantz MA-500 and am getting a hum/crackling from the tweeters. The Marantz and Yamaha are all plugged into a VansEvers Super Companion II which is plugged into an outlet with a dedicated 20AMP circuit. The Marantz and Yamaha are 2-prong plugs. Are you saying not to use a 3-prong cheater plug because it would defeat the ground on the unit?

I've taken everything apart this weekend and the hum/crackling was most noticeable when I plugged the interconnect (a DH Labs Silversonic BL-1) between the amp and the Yamaha pre-out. I could stand about a foot from the speaker and clearly hear hiss, hum and a slight crackling. Any ideas?

 

[rodneyH]

leo, I think that it ONLY applys when going from a 3 prong to a 2 prong cheater plug, NOT 2 to 2.

 

[Leo]

Ok, so they don't make 2 prong to 3 prong cheaters that could solve my problem?