Buzz coming from new amplifier (1 Viewer)

[Robb Roy]

I purchased a new Parasound 1500A this weekend, and immediately noticed a buzzing noise coming from the speakers. Unhooked the cable, dss, etc. (all the gear attached to the HTS2500), with no change in the buzz. I did find a lamp in the same room (our main source of light, actually) that is halogen with dimmers, and the buzz goes up and down in volume with the brightness of the lamp. With the lamp unplugged, there is still a slight buzz.

Now it gets interesting, I think. Sounds like a ground loop problem, so I buy a cheater plug to test the theory (I know this is only a short term solution). I have everything hooked up to a Monster HTS2500. When I plug the amp into the other socket of the same outlet as the HTS2500 (with the cheater plug), there is absolutely no buzz, no matter what I do with the lamp. If I plug into that same socket without the cheater it behaves exactly the same as I had it in the HTS2500. If I plug in the amp with the cheater into the HTS2500, the buzz is back, but is not affected by the lamp!

So, I guess this long explanation comes down to 2 questions: 1) Do people think getting a dedicated circuit to my system will help? 2) Any other ideas/theories I'm missing?

Thank you all in advance for any ideas you have!

-Robb Roy

 

[JackS]

I think you may have discovered the answer. Don't connect the amp to a surge supressor. Years ago, the mfg. would have probably given the same advise, but in todays litigious society when someone can win a law suit because their coffee is too hot, no more mention of anything that might open up the amp company to something that may be proven in court to be dangerous. You might call Parasound and see if they have any recommended unit to try.

 

[Robb Roy]

JackS,

Thanks! While I do like the idea of protecting the equipment (or at least making Monster pay for it if something happens to it under their warranty) I'd be willing to plug the unit directly into a wall outlet. I am still concerned, however, about leaving on the cheater plug to eliminate the buzz. Any ideas? (My wife is, without question, much more enamored with the lamp than the amp, so let's assume I'm stuck with the lamp.) Thanks!

 

[Bill Kane]

Robb, a headscratcher...

1.So ok, you got a BUZZ prob, since there's no probable ground loop hum by disconnecting the coax.
2. The cleanest signal path is cheaterplug to wall outlet. This indicates lifting a ground, but in any case you're not gonna leave it in cheaterland, right?
3. Monster HTS2500 is another animal, a middle-of-the-road unit now updated by Monster perhaps by their new outside designer, Richard Marsh, to higher level of filtering. Your HTS may be filtering some of the floorlamp induced EMI. But trying the cheater plug on/off on the Monster gives you no solution, as you note. And yet with the lamp unplugged, there's still a buzz(?!)

So it's pretty obvious the floorlamp is to some degree a player here and this may IN ADDN to the Buzz. Think globally, there may be several things going, because you have introduced A Change in the previous equilibrium.

It's too bad the Parasound cannot perform plugged bareback into the wall outlet without downstream Buzz. Surge protector aside, many of us separate 5-chl amps owners, after consulting with the makers' techs, have concluded the amps have SO much redundant protection they are not vulnerable to anything except a calamitous electrical strike. Otherwise, a two-outlet Brickwall.com Series Mode surge protector would cover even lightning in close proximity as AR is known for.

I hate to throw more hardware $$$ fixes on top of a problem that can be trouble-shot to its source, but I cant figure yours.

There is a tester at the hardware store to check the outlets to see if you have an open ground; that's a cheapie step to take.

Checking your mainservice breakers, find a little used household circuit that does not serve any kitchen appliances, your computer station or other such loads. Get a heavyduty extension cord and plug the amp into one of the outlets to see if you get "cleaner" power. This may be an indicator that a dedicated circuit could work for you.

Other big box fixes might include a $999 Balanced Power unit to eliminate Common Mode noise (b-p-t.com)and achieve a much lower noise floor.

Just brainstorming here for ya, bro. I'm no electrician.

bill

 

[Robb Roy]

Bill,

Thanks! I've got a heavy duty extension cord for things like power tools and so on I can use (finding an outlet with little power drain could be hard -- I make my living with computers and have them all over the place). Yeah, it's a bit of a stumper. I haven't had my neighbor over yet (he's an electrician and EE instructor), but my brief description to him of what I was dealing with puzzled him off the top of his head as well. At this point I appreciate any ideas. Thanks again!

-Robb Roy

P.S. No, leaving the thing in cheated is not an option without some REALLY good argument -- it's just making the sytem tolerable for a few days (weeks max) until I find a more lasting solution.

 

[Bill Kane]

Nice to have that neighbor
I picked up the tester idea on another forum where a guy had the same problem, and discovered an open ground. Course your Monster plugged in at that outlet may still have an LED that glows for "Grounded" or "Wires OK" but you never know. Perhaps someone upgraded that wall out duplex to an industrial or spec grade some time ago and the ground wire has loosened.

 

[Robb Roy]

Did some more experimenting, and I think I found the problem -- I need to have the Denon 3802, which is the pre for the Parasound, and the lamp unplugged at the same time. There is still a slight buzz, but we're talking so little that it can't be heard from more than five inches.

The amp isn't happy with the lamp by itself, but the Denon becomes very unhappy about the lamp. It does not affect any speakers hooked directly to the 3802 very much, but the RCA outs carry a very strong buzz (tried multiple cables of varying quality to no avail). If I set these up without the HTS2500, it is even much worse and clearly audible from the speakers hooked directly to the 3802 (so at least I know the HTS2500 is actually doing something for my money).

Since the 3802 does not have a grounded plug, I can't hook a cheater to it. So, I'm going to have the dedicated circuit installed anyway, keep the cheater on the amp until then so the buzz is very minor, and eventually replace the 3802.

 

[Matt]

I just encountered a similar problem Robb. I just purchased a Parasound HCA-2205A (thanks Mark ) and it had a buzz. It didn't appear to come from the speakers, but from the Amp itself. Well, I finally remembered that the lamp I had in the room was a Halogen lamp (with a 3 position switch, off, low, high). It was causing the buzz. I then remembered that the lamp also caused my computer speakers subwoofer a problem. I had an old set of Altec Lansing's that the sub would buzz and the newer set of Logitech Z-560's also buzzed. I had moved my computer to a different room a while ago, so I forgot about that problem.
Now, the buzz was only really loud when the lamp was on low. If it was on high, you could barely hear the buzz. If the lamp was off, there was no problem. I would have to say Halogen lamps and speaker amps do not mix well.
Matt

 

[Robb Roy]

The 2250A is next on my list (don't tell my wife!) to get seperate amps for all 7 channels. I'm still a little bit away from doing that, but feel free to PM of where you got a good deal on it. Thanks!

-Robb Roy

 

[Chu Gai]

halogen lamps, especially those with dimmer switches (in fact most dimmer switches that are installed by contractors) are notorius for dumping hash or EMI either into the airspace and the power lines. This EMI can travel down any one or more legs of the power line. Consider getting rid of the offending unit or going down to your local electric supply store and asking for recommendations for higher quality dimmers. While you're there, and assuming you've got a good person, have them give you the lowdown on what makes dimmers bad and why you're going to pay more for a quality one. Those damned dimmable halogen lamps, the torchiere ones especially, are all out there for something like 10 or 20 bucks.

 

[Robb Roy]

It finally cooled down enough here in AZ to get up in the attic and install the dedicated circuit yesterday (woo hoo! Hot wires and cold beer -- what a great combination!!). The problem is officially gone. Between that and the SVS arriving Friday, I think I'll spend the rest of the weekend on the couch watching movies! Thanks for all your help.

-Robb

 

[DaveLenhert]

Robb-

Glad you could fix the problem, I also have a simular problem. I have a Denon 3801 attached to a Monster 5100. I have two sources of buzzing. The first source is the the Samson amp for SVS sub. When it is plugged into the Monster (w/o the cheater plug), i get a buzz that I can hear from over 5 ft away. If I use a cheater plug, I still get the buzz (Its actually a tad worse with the cheater plug). To completely remove the buzz, I have to remove the RCA interconnect. So when I sit down to listen to some classical music, I remove unplug the RCA interconnect, so i get rid of that buzz. Its a pain in the arse....but better then the noise.

-dbl

PS:
Just for the record, I have tried to hunt down every other source of noise, Cable TV, lights, wallwarts, etc...and the ground noise level is about as quiet as I can get it, and actually they make very little difference in the ground noise with the Monster 5100 (i can't hear the difference, perhaps if i used a SPL meter, I might be able to "see" a small difference of the ground noise with a SPL meter between with and without the wallwarts, lights, cabletv, etc)

 

[Robb Roy]

DaveLenhert,

What kind of RCA cable are you running? Have you tried a better quality cable?

 

[Mike_P]

Two things to try:

1. Check the outlet wiring. The GREEN wire should be ground. No current should run on this wire. The black wire should be the hot wire, carrying 120 volts. The white wire is neutral, and it should be carrying the current back from the hot wire. It's common for the neutral and ground wires to be reversed in the electrical panel or somewhere downstream. If your outlet tester finds a problem, it may be time to call an electrician, because it can be really "shocking" if you rewire it incorrectly.

2. Try a shielded cable for your sub. A lot of the time the shield is grounded on only 1 end to avoid ground loops. The grounded end should be connected to the receiver. On Monster cables, there is a little tag with an arrow on it that shows which way the cable should be connected.


Hope this helps,

Mike P

 

[DaveLenhert]

Robb-

Its a BetterCable cable that came with the SVS Sub.

Mike-
I think you might be mistaken or i'm really confused.... Yes, a "real" shielded cable provides a shielded (foil or braid) that is grounded at each end. (In my experience, a double grounded shield keeps signal noise at a minimium.) However, alot of companies tout that they use shielded RCA audio cables, which is technically not correct. A standard RCA cable does have a foil or braided shielded, BUT the RCA connector uses the shield as a return signal line. Hence its not truely a shield, its a signal wire. There are a few designs which use RCA connectors and try to overcome this inherent flaw. BUT, if the cable does not have a wire with say a gator clip to ground the shield, then its not really shield or shilded properly.

I think what the problem with my system might be is that the two different filters in the HTS5100 (the Receiver Filter & the Sub Filter) cause a slight imbalance in the ground, and with klipsch speakers, this imbalance is quite noticible. I do have a ground strap attachment point that I might try to connect to the Samson Amp to se if that might fix the problem.

-Dave

 

[Robb Roy]

Dave,

What happens when you plug the Samson into an outlet not related to the 5100?

-Robb

 

[DaveLenhert]

Robb-

To be honest, I haven't tried. Prior to the 5100, I had a Triplite surge protector and when I plugged in the Samson into the wall outlet, I got a LOUD ground loop humm from the sub. This was easily fixable with a cheater plug, but the triplite was OLD and didn't have nearly the filters as the 5100 so when it was added, the ground level noise (not including this ground loop humm/buzz) was significantly lower. The second reason for adding the 5100 was the switched power so i didn't have to independently turn on the Samson.

-Dave

 

[DaveLenhert]

Robb-

To be honest, I haven't tried. Prior to the 5100, I had a Triplite surge protector and when I plugged in the Samson into the wall outlet, I got a LOUD ground loop humm from the sub. This was easily fixable with a cheater plug, but the triplite was OLD and didn't have nearly the filters as the 5100 so when it was added, the ground level noise (not including this ground loop humm/buzz) was significantly lower. The second reason for adding the 5100 was the switched power so i didn't have to independently turn on the Samson.

-Dave

 

[Robb Roy]

Trying the Samson in another outlet should let you know if it's the 5100's filters. It's a little odd that you get the buzz with or without the cheater plug...

As long as I'm in this thread -- I had a 20 amp dedicated circuit installed. Should I have made that a 15? (Dammit Jim, I'm a programmer, not an electrical engineer!)

 

[Bill Kane]

Robb, what's the perceived problem? 20A is fine, especially when you get that 2505A power amp. What type of duplex outlet was installed? A 15-amp Industrial Grade spec duplex wud be work well.

A 20amp circuit is rated for 2400 watts at maximum current, and applying the code-approved 80 percent safety factor gives you 1920-watt capacity. This allows a multitude of connected components and a cushion for high-current ones. Remember that nearly all the consumer HT gear we use is rated/designed for 15A 1800-watt max. Any overloads should cause the connected component fuses to give before the 20amp circuit breaker.