1. Home
  2. tech-talk
  3. 123000-70554

Help With 60Hz Hum PLEASE

Greetings,

I am having some issues with noise coming through my speakers at low volume. The noise sounds like a 60hz cycle hum, and can be heard clearly when the volume is all the way down. I have tried several things to quiet down this noise, but nothing has worked so far.

Before I give details of action items I have tried, let me inform you of the components I am running.

My system consist of:

·     AV PRE/PRO MARANTZ 8801

·     AMP ADCOM GFA-7805

·     SONY 300 DISC CD CHANGER

·     SPEAKERS B&W CDM9NT/CDM CNT/CDM1NT

·     SUB VELODYNE SPL1000 SERIES II (NOT HOOKED UP AT THIS TIME)

·     USING XLR INTERCONNECTS BETWEEN PRE-AMP AND AMP (MONO PRICE)

·     DEDICATED OUTLET CONNECTED TO 20AMP CIRCUIT BREAKER

·     FURMAN POWER CONDITIONER (EVERYTHING PLUGS INTO THIS)

·     I SEGREGATE OUT THE AC POWER LINES FROM THE SIGNAL AND SPEAKER CABLES


So this is what I have done to check the system so far.

1.   First off I separated all of the components power sources, plugging each component into its own outlet with the amp plugged into the dedicated outlet. (NO CHANGE, NOISE PRESENT)

2.   Unplugged any no essential item leaving just the pre-amp and amp plugged in (NO CHANGE, NOISE PRESENT)

3.   Removed the amp from the system, plugged in single source and speaker set (NOISE IS COMPLETELY GONE!!!)

a.   FOR ABOVE TEST I USED MY IPHONE WITH A SET OF RCA INTERCONNECTS STRAIGHT TO THE AMP.

                                              i.   I really suspected the amp at first because about a year ago I had the unit repaired for a standby condition. The repair center I used also repaired the CENTER CHANNEL BOARD while they had the unit. I noticed that the center channel has almost no noise coming through, but after the previous findings I decided this might be a symptom not the cause of the noise.

4.   Hooked back up system and tested (CRAP, THE NOISE IS BACK)

5.   Unplugged all of the XLR interconnects from pre-amp side (NOISE IS GONE, YEAH!)

6.   Plugged in one interconnect into pre-amp (noise comes through that channel)

7.   Switched between XLR and UNBALANCED (THE UNBALANCED CONNECTION WAS A BIT WORSE)


My conclusion is that something is happening between my pre-amp and amp that is allowing this 60hz signal though. I am wondering if it could be the interconnects themselves because I am not using a high quality interconnect. All I am using is Mono Price XLR cables. Although, why would there be no noise when the cable is plugged into the amp and not the pre-amp? Might the Marantz 8801 be the culprit due to the fact that when I plug in the cable into the pre-amp is when the noise comes through? Or maybe my first instinct was correct in that the amp is the problem?

Any help figuring this out is appreciated.

Thank You Kindly,

Joe

jo3533
jea48
2,944 posts
 

2.   Unplugged any non essential item leaving just the pre-amp and amp plugged in (NO CHANGE, NOISE PRESENT)

To be clear, you had nothing connected to any of the line inputs on the Marantz A/V preamp? (All the input jacks were empty of Interconnect cables?) Volume control set to minimum.

The only interconnects connections were from the outputs of the Marantz to the Adcom power amp. Is that correct? 


Do you have Cable TV, or a Dish, connected to the MARANTZ 8801? 

dweller's avatar
dweller
2,152 posts
 

If you have a cable TV connection to your audio system, it is probably this. I've had hum problems with my phono preamp that was corrected by re-orienting the equipment to a different location.

lowrider57's avatar
lowrider57
3,018 posts
 
Try using a "cheater plug" (2 prong plug) on your preamp. You may have a ground-loop coming thru the interconnect.
This test will make the amp the grounded component, and isolate the preamp.

As you said, you're using cheap XLR cables, so they may not be properly grounded.
tls49's avatar
tls49
1,318 posts
 

"Try using a "cheater plug" (2 prong plug) on your preamp. You may have a ground-loop coming thru the interconnect.
This test will make the amp the grounded component, and isolate the preamp."


I believe the preamp is already using a 2 prong plug. So, if the amp has a 3 prong plug, then try the cheater plug on the amp. IMHO, it is best when both the preamp and the amp are the same. Hopefully, someone else will respond to this.


jo3533 OP
18 posts
 
Wow a lot of feed back here. Thanks.

So currently the only components I have hooked up are listed in the original post. I have no TV, cable, satellite hooked up.

UNBALANCED CONNECTIONS are RCA connections. When I hooked them up the noise was worse.

Since this post I have tried using a cheater plug (no grounding pin) and there was no change.

Please read through my original post carefully as it has listed everything that is hooked up in the system, and I have not left anything out. If I have it, its listed

Any comments about the amp and amp repair? Might my fist thoughts been correct? What about a higher quality XLR cable? 

Thanks.
More to discover