Hi,

I've purchased my M60ti/VP100/QS8/EP350 system in 2005, and since about a year ago I started receiving my TV using Over the air broadcasts. There was a single channel I had trouble getting; this one was notoriously lower power, but channel 6 is also apparently more susceptible to impulse noise. I have a Delhi VIP 302SR antenna in my attic pointing at the transmitter tower.

This week-end: tested NAD T763 receiver coming out of the NAD repair shop. Oscillating buzz is still coming out of the speakers when the sub is connected. Tried changing the sub cable, moving the power cable of the receiver & sub (worse: gets high volume hum instead), as well as the cable outlet where the Monster HTPowerBar gets its power. I even connected a 14 gauge wire between the sub and receiver chassis and removed the ground lift screw on the sub. Buzz goes a lot quieter when the sub is disconnected from the receiver or powered off. My next step is trying an rca ground loop isolator i just ordered on amazon to go between the rca LFE output of the receiver and the sub. But this is now the least of my worries...

I checked the Global Ottawa CIII channel 6 levels today. We'd been lobbying Shaw to do something about it so I figured they may have upped the power. But nobody was reporting better reception. I went back and turned on my EP350 again. Boom, my channel 6 is gone. Aren't there specific guidelines for electronic equipment to stay out of certain broadcast frequencies ? Do you think this is the case with my EP350 at the moment ? Can I possibly get the EP350 shielded better to make sure it does not interfere with channel 6 anymore ?

I am now wondering if both issues have something in common now. The sub does sound like it is interfering with broadcast channel 6, can it also interfere with my NAD receiver ?

Thanks,
Francois

By the way, the FM band resides right above VHF channel 6.

I just saw the EP350 troubleshooting. I am using RG6 Quad shield for my antenna cabling.
==
http://www.axiomaudio.com/troubleshooting_ep350.html says
F.M. Noise Use fully shielded coax cable to the antenna - RG6 Quad Shielded recommended
Do not use a folded dipole antenna
==
I don't know if my OTA antenna has a dipole in it or not, but it is not connected to my receiver anyways, so I will discard that part. It is for TV reception.

Francois, the beginning of your second post answers the question you had at the end of the first. As channel 6 is right below the FM frequencies, any EMI(electromagnetic interference)which affects one will also affect the other.

Your description indicates that this isn't a ground loop problem, or at least that it isn't the major cause. Switching class D amplifiers which turn on and off several hundred thousand times a second generate enormous amounts of EMI and need careful design to minimize the effect of this. The EP350 trouble shooting page you link unfortunately seems to indicate that it's up to the user to try to do this, by using a heavily shielded coaxial cable to a distant antenna and by not using an indoor(e.g., folded dipole)antenna nearby.


Keeping the sub and its power cord as far as possible from the receiver and TV connections can help.

The sad part here is the EP350 kills my channel 6 when it's just idle, not connected to any AV receiver and not outputting any sound. How can you expect a class D amp to generate that much of EMI/RFI when it doesn't even receive an input...

So I actually have the heaviest shielded cable I could get already, a Quad shield RG6 all the way. The "problem" is my antenna is in my attic, so it must pick up the EMI/RFI generated from the EP350 on my 1st floor of my 2 story house. Getting the antenna outside would likely attenuate the noise generated in the house and increasing the signal gain because of less obstructions, thus increasing SNR. But i won't do that, WAF says I can only have 1 antenna on the roof, so this one stays in the attic. I'd rather change the sub or put it inside a Faraday cage.

I am definitely turning paranoid now, so i'll have to scrutinize everything. Compact Fluorescents, UPS for the HTPC, HTPC itself, maybe this will help figure out my receiver buzzing when connected to sub issue.