Added a power amp, now HUM and BUZZ- HELP! (1 Viewer)

[Mike_Ch]

I acquired a new Rotel RB-993 3*200W power amp yesterday. I have it hooked up to a Denon 2801 receiver, and use a Pioneer DV535 DVD player as a transport. The sound has been great (I will post a review of it soon), but unfortunately I now have a very annoying hum/buzzing noise coming from all the speakers connected to the power amp.

I have tried unplugging/plugging all components in and out (btw, I don't have cable tv) trying to isolate the source. With the Rotel amp plugged in, I get a very slight hum from the speakers which I cannot hear from the listening position (nevertheless the Denon never had this problem). I assume it is just the transformer humming?

More disconcerting is the buzzing noise. If I hook up any interconnect to the DVD player and connect it to the TV (S-video) and receiver (coaxial) I get a buzzing noise which I can hear from the listening position. If I don't hook up the interconnects from the DVD player to the end components (that is, one end connected to the DVD player and another on the floor) I don't get the buzzing noise. Turning off its power-point switch (not the one on the player, but the one the mains socket is connected to) also eliminates the buzz. The TV and receiver alone do not cause the buzzing noise, it is only when the DVD player is connected to them. I have tried using different cables, but they all cause the same problem. What could be causing the buzzing noise, and how can I fix it? Plugging the DVD directly into the mains socket does not help either (it has a 2 prong cord if this helps).

The DVD player's warranty has just expired, and I don't want to buy another player after upgrading the amp (I'm still still a poor uni student!). Please help me, I have no idea what could be wrong!

Mike

 

[Henry W]

Try going here for help:
Link Removed
Best regards-Henry

 

[Luis A]

Mike, do a search on "amplfier hum". There have been a few threads on ths issue already with some solutions that may help. Good luck.
L

 

[Mike_Ch]

Thanks for the replies, I have indeed checked out a few threads on amp hum using the search engine before posting this thread. Where I live, it is apparently illegal to use a cheater plug, and even if I did want to use it, its nigh on impossible to find one. Also, do you think it is a problem with the amp, or is it a problem with the dvd player? The buzz is only present when the DVD player has a cable connected- if I take the DVD player out of the system, everything is fine. Will a power conditioner or using a new socket on the DVD player solve things? Do any Australians know where I can find a cheater plug, and does that mean I cannot touch the metal case of the amp without a ground?

Thanks,

Mike

 

[Henry W]

You probably need a CATV RF isolator. You can buy them at Radio Shack. This is the most common solution to ground loop hum generated by a cable system.

Best regards-Henry

 

[John Morris]

Here is what I use:Link Removed

 

[RicP]

Uh....Guys...
Did you totally miss the part of his post that said:

(btw, I don't have cable tv)

See if you can pick up an A/C isolator or cleaner, like PS Audio's products. Sometimes they can remove the DC from the line that's causing the hum.
Other option may be to have a separate 20amp line put in for the HT gear. Obviously this requires an electrician and some new wiring. Good Luck.

 

[HankM]

I use a Mondial MAGIC box. Mondial Antenna Ground Isolation Circuit. Retail is $100.00 but you can get one for around $70.00

 

[SamRoza]

Just because you don't have cable doesn't mean you can't have a ground loop.

First, Remove all motorized equipment from the circuit in which your HT is on. THen go and buy a Line conditioner. I've had good luck with those in the 50-70 dollar range, but I currently use a Monster Power HTs-5000.

Try the cheater plug first, it's the cheapest and easiest. If that works, then look into getting a line conditioner.

Sam

 

[Ken Bohn]

Mike, I had a similar problem with a hum which I concluded to be a result of grounding as explained in the Jensen Transformer link posted by Henry.

I was running for a while with a pre-amp with a two prong plug connected to an amp with a three prong plug. The amp was thus the path to ground for any current in the shield wiring of the interconnects between components. I was able to reduce the hum in my system by grounding the chassis of all components with a common wire. If a ground terminal wasn't provided I loosened a screw on the metal chassis of the component to connect my grounding wire. I went the extra bit by purchasing a male three prong plug and connecting my ground wire to the ground pin of this male plug and then inserting it in the same power bar that my amp was plugged into. Thus my grounding wire was connected as close to the same ground point as my amp via the three prong plug I used.

This method reduced the hum on my system by about 50% which could still be heard when everything was quite but quite acceptable. My problem went away when I upgraded my pre-amp to a unit with a three prong plug.

 

[Mike_Ch]

Many thanks for the help all, I do indeed have a ground loop problem (the denon and rotel both have a 3-prong plug). Went to an electronics store today and yes indeed the cheater plugs are illegal here. However, I snapped off the earth on a double-adaptor (which the guy in the store recommended, albeit saying it was illegal) and now the dreaded hum is gone. Now its back to enjoying the music
Mike

 

[Jim Korns]

Of course you know the cheater plug is a TEMPORARY solution, right? You are risking a potential hazardous condition using it for more than that.
I had a battle with the dreaded ground loop hum after
I added another amp but mine was coming in from the DSS
system.
For more info on ground loops check out:
http://www.epanorama.net/documents/groundloop/index.htm
and
http://www.smr-home-theatre.org/Interface.html
(look for "Ground Loops - or 'Let Me Hum A Few Bars')

 

[Mike_Ch]

Jim,
No I wasn't intending on using the cheater as a long-term solution. I have very little knowledge of EE (i'm studying medicine... probably the complete opposite ) , however, since the amp is connected to the Denon preamp, which itself has a ground (3 prong plug) does this mean that it would be safe to use the cheater plug? Also, the house I live in was built about 5 years ago, and I am wondering whether lifting the ground will disable the safety switch for the circuit the amp is connected to.
As for line conditioners, will this solve a ground loop problem? Can't get the Jensen (live in Australia), but can get something like the Monster power board. Are there any other alternatives?
Mike

 

[Wayne A. Pflughaupt]

Mike,

First, welcome to the Forum! Sorry to hear about your troubles.

Do you have the Rotel plugged into the same outlet as the Denon?

Happy Holidays,

Wayne A. Pflughaupt

 

[Richard_M]

Hello Mike,

First off welcome to the forum, and secondly where are you located, I am in the Frankston/Cranbourne area?.

I posted some details of my problems similar to yours earlier when I upgraded from my Yamaha to a Denon 3802.

I have a Rotel amp driving the front speakers, there is a very low hum coming from these that wasn't there with the Yamaha. I am now onto my third Denon 3802, and this one is the best of the bunch, as far as the hum is concerned. It appears that the Denons may have problems with noise from the pre outs, as I stated earlier I just replaced my Yamaha with the Denon i.e. same interconnects etc and the problem wasn't there with the Yamaha.

Another thing that I have done is used 2x power boards with filters one has the Denon only, the Rotel, Cd,DVD,Video etc are plugged into the other.

Do you have an amplifier on you TV antenna for country channels? this could also be a cause.

Anyway if you live not too far from me I might be able to offer some assistance, but those cheater plugs are not good if something develops a problem.

Regards,

Richard

 

[Jim Korns]

Mike,

Well the cheater plug has definitely identified the problem, but now you have to solve it. If you follow those links I sent earlier, there are some very good steps to follow to isolate the ground loop. Tying the chassis ground together of your various components may definitely help, but there may be better ways to solve it depending where the ground loop is being created. Obviously a ground loop exists because there are multiple paths to a ground potential and all grounds are not the same, so a reverse current flow is created and you get the dreaded ground loop hum.

I would start by plugging all your components into the same circuit if that is possible. A ground loop can exist because you are using different legs from you electrical service.

I know you mentioned that you do not have CATV which I do either. Not sure if you also mean that you do not have DSS, but just in case I will mention my experience. In my case it was my DSS that was my problem since it had a separate ground for lightning isolation. I determined mine by lifting the DSS coax from the back of the DSS receiver and checking that the ground loop hum disappeared. There are several overpriced products that can perform coax isolation from Mondial, Tributary, etc, but what finally worked for me was a power center with surge suppression (that I already had but was not running the DSS coax through). When I did connect it through the power center, the ground loop was gone.

Ground loops are frustrating to deal with, but when you finally track down the source, it is a great thing to listen to your system without that annoying hum.

 

[Jason Watson]

Mike,

It seems you have tracked down the humm, but what about the buzz? If you still have it with the DVD player connected,you might want to look at your interconnects. Unshielded or coax type interconnects can pick up noise. Try first to route all power cables and interconnects away from one another. If they must touch, try to keep them at right angles. If no help there, try some properly shielded interconnects where the shield is NOT used as a conductor. I built an unshielded, twisted pair of interconnects that sounded great in a friends system,but caused buzz in mine no matter how I routed them.

Jason

 

[Mike_Ch]

Richard,

I live in inner Melbourne, but I took the one hour drive to Frankston to buy the last RB993 in Victoria! I will try a filter board and see if it helps.

Jim,

I have no CATV, DSS or any other pay-tv service... Just plain old analogue TV. I do however have an indoor antenna with an amp connected to the same circuit as the amp, maybe this is a problem?

Jason,

The buzz went away along with the hum after adding the cheater. All interconnects I believe are shielded I believe(not sure if the shield is a conductor- how would I find this out?), and are well away from power cables.

Hopefully a powerboard with filter will solve my problem!

 

[Ben Salvemini]

Dear Mike ( fellow aussie)

Sorry to hear about your troubles with humm.

I can fully understand this problem as humming away and buzzing like a angry bee here in W.A

I was using a harman kardon avp1a. Went through two separate units here. Trying to sort the problem out I went through the similar processes you mentioned. I would advise against a cheater plug with my limited understanding. That the third pin underneather the two is for the earth. If this is taken out of the equasion, if you have a short in your equipment and if you touch a part of it that is metal you could get a nasty shock.

Getting back to your dilema I suggest do these things.

1. try another dvd player same as your one borrow it from a friend.

2. take your dvd payer into a shop and connect it up to some thing there(the shop you bought it from)

3. take your dennon to a friend and try it there.

it is a process of elimiation and you should find the source component that is causing the trouble.

A repairer here in W.A. regal electronics in nedlands (robert) said when he was trying to fix the humm in my set that he said he had to fix a few dennons re grounding problems and it was related with the tv set. That is the dennon had outputted its onscreen menu to the tv??

Anyway I PUSHED and PUSH with my unit and got a replacement.

With regards to your amp what is its operating voltage or I shpould say what is its rated voltage. A big amp will hum a very little when initially powered up.

With regards to your interconnects the sheilding depending on how good it is (may use braided copper and foil in layers) protects the inner core usually soilid copper from stray feilds and proximaty to other components. What type of interconnects are you using?

 

[Mike_Ch]

Ben,
I don't think its the Denon or the DVD player since I never had this problem until I added the amp. The amp has a bit of mechanical hum when I put my ear above the case, but I guess that is to be expected. Interconnects are Monster Video Cable (digital coax), Tara Lab Prism 500i interconnects between amp and receiver, the S-video cable's brand escapes me for the moment, but its shielded. Speakers cables are Monster MCX-1s bi-wire. Looks like the more things you add the more problems you can get. Maybe I will try for more KISS (keep it simple stupid) next time .