Loud Subwoofer Buzz. Help

A

ajhubble

Audiophyte
<font color='#000000'>Hi, I've recently purchased a new receiver (Sony STR DE595) and set of 5.1 speakers (Omni 898 - probably not much good from an audiophile point of view, but they were relatively inexpensive). I have the satellite speakers connected to the receiver and the subwoofer out from the receiver goes into the sub-in on the subwoofer (which is one of those with built-in amplifier and 5.1 analogue input with speaker outs to the satellites). I don't use the other 5 channels of line inputs on the subwoofer (I just need it as a subwoofer).

The receiver is connected to the TV, VCR and DVD units. All connections are with standard (I assume) RCA cables.

The problem is, the subwoofer exhibits a loud, annoying buzz &amp; hum, which seems to be very dependent on where the RCA input cable is positioned. If the cable isn't plugged in at all, the loud buzz is gone, but I can still here a faint buzz/hum coming from the subwoofer with the power on (when on standby, there is no buzz).

If I disconnect the cable from the receiver but still connected to the subwoofer, I still get a fairly loud buzz (also dependent on position). With the cable connected at both ends, if I grip the cable with my hands, then the buzz decreases to acceptable (for me) levels.

If the cable is connected to the receiver and subwoofer, the buzz decreases to acceptable levels when I place my hand over the unused RCA inputs on the back of the subwoofer unit. Covering one RCA input with my hand lessens the buzz somewhat, and covering more decreases the buzz even further.

The subwoofer also faintly picks up radio signals.

I don't have any of these problems with either the satellite speakers or the 2 speakers I was using before (either that, or it was less noticeable).

All my gear is connected to the same power socket, and they all have the 2-prong power plugs except for the subwoofer unit and an indoor TV signal gain amplifier antenna (we get shoddy TV reception in this apartment with all the high rises around - the outdoor antenna plugs into the indoor antenna and passes through to the TV), which both have 3-prong plugs.

From reading various sites, I'm getting the impression that I have a grounding problem (and a Radio transmitter that's too close to my area). These sites talk about balanced vs unbalanced inputs and outputs, but I'm still not sure what I can do to fix the problem given the various symptoms I described above.

Would a better shielded subwoofer RCA cable help (as opposed to a standard RCA cable)? Do I need a ground isolator or similar accessory (which is probably not going to be cheap)? Is my subwoofer defective?

Any help greatly appreciated! Thanks.</font>
 
Clint DeBoer

Clint DeBoer

Banned
<font color='#000080'>Do you have a well-shielded RCA cable going to the sub? If not, get one and see if the buzzing and RF intereference subsizes partially or altogether. Also check the shielding on the analogue cables going to your receiver from the cable TV box.</font>
 
A

ajhubble

Audiophyte
<font color='#000000'>The shielded RCA cable helps somewhat, but the buzz is still too loud. Unplugging all the other input &amp; output cables from the receiver and turning it off (as in unplugging it from the powerboard) didn't help either.

I'm going to test it out at a friend's place to see if it works any better. If not, then I'll claim on warranty for a replacement unit. Then I'll see how the new one goes.

I still can't understand why covering all the unused RCA speaker inputs with my hand reduces the buzz down to acceptable levels though. If all are unused, then the buzz is faint. If one is used (not necessarily the subwoofer input), then the buzz is loud. I actually haven't tried using up all the 5.1 inputs (nothing I have has 5.1 RCA output, it's just digital out from the DVD player).</font>
 
A

ajhubble

Audiophyte
<font color='#000000'>Tested out at friend's place and the problem still persisted. Now I've returned it for a replacement after they test it themselves. Hopefully it'll test faulty and they'll give me one that works better. Fingers crossed...</font>
 
A

ajhubble

Audiophyte
<font color='#000000'>Just replying to my monologue here. I've replaced the 5.1 speakers under warranty and the new subwoofer does exactly the same thing. It buzzes incessantly - particularly when a cable is connected to one of the RCA inputs, and decreases slightly when cables are connected to the other 5 RCA inputs with the other end plugged into the receiver (plugged into dummy RCA outputs as I don't use the RCA inputs for anything - only the subwoofer one). As stated before, the buzz also decreases when I cover the RCA inputs with my hand, and move the input cables around. The system also picks up radio station noise.

I've determined that this system just doesn't work in my area. We have 2 transmitter towers (TV/Radio) in close proximity and I don't think the speakers are adequately shielded against magnetic/EM/etc interference (cheap computer speakers in the same room also have a tendency to pick up radio stations and buzz). There could also be a grounding issue/transformer issue with this model, but I don't know for certain.

The upshot is, I don't think I can get away with a cheap speaker system. I'll have to go for one at least along the lines of the Sony SAVE345 stand-alone speakers.

I'm going to get a refund on my current system and try out the Sony...wish cheaper systems had the magnetic shielding though, because cost is a factor...</font>
 
A

ajhubble

Audiophyte
<font color='#000000'>Just to end the story, I'm going to get a refund on the Omni system. I've collected together a few speakers from various mini hifi systems to use as satellites. I now have matching pairs of 2-way Richter speakers (from a Teac mini-hifi system, both joined as center speakers), Voxson (front left and right) and Sony (rear surround left and right) speakers.

Since any one of these are better than all the mini-satellites from the Omni system put together (especially in the frequency range and bass), it all sounds great. I hardly need a subwoofer. In fact, a subwoofer will be overkill in my apartment.

But... I couldn't help it. I went out and got a Dome 10-inch subwoofer (140kw)...which doesn't buzz. It's great. It doesn't pick up the nearby TV/radio transmitter either. This system well and truly rocks now.

I couldn't be happier.
Signing off...</font>
 

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