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Speaker interference - advice please


BlueStringPudding

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16 hours ago, Boater Sam said:

Its the switched mode power supply in the brick connected to the TV putting hash back onto the 12v supply.

To prove it, connect the TV power lead to a seperate 12v battery that is connected to nothing else, the buzz will not be there.

How do I know this? Because I had exactly the same problem.

Sing it again Sam. :)

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First off I'd try popping some reasonable headphones in the TV and check that the hum isn't actually there in the signal to start with, maybe the small TV speaker doesn't go low enough in frequency to reproduce it but the big speakers do?

 

For any hummy audio interference, belt and braces is decent cables (prior to amplification, speaker cables can sometimes act as an antenna and bring crap back to an amp, unlikely though) with plenty of copper in the shielding, electrical isolation with a 1:1 transformer and harmonic suppression with inductors, your mileage will vary with all these things though.

 

This:

 

https://www.ebay.co.uk/itm/New-3-5mm-Jack-Ground-Loop-Isolator-Audio-Noise-Filter-Unwanted-Hum-Inductor/232000190447

 

with these clipped everywhere:

 

https://www.ebay.co.uk/itm/10-20Pcs-5mm-Ferrite-Bead-Clamp-Choke-Coil-EMI-RFI-Noise-Filter-Clip-Cable/372607193446

 

Stands a good chance of improving the problem, it's likely the TV that's the origin of the noise, though so much electronics these days makes use of solid state power conversion, often done poorly, hence the noise, square wave hell, the TV could be picking it up from something else, passing that to the amp...

 

Now, is that drip I can hear inside or outside my boat....?

 

bx

 

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  • 2 weeks later...

All hail the great Moomin!!!! ?

 

His ground isolator cable thingy plugged in directly between the amp and the tele and instantly there was no feedback at all! Not so much as a nonchalant hum at any volume.

 

So thank you everyone for your suggestions, the problem is now cured. I'm a very happy clanger. ?

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Nooooo!!!! What's just happened!?

 

Monkey and I had the tele on all last night wired through the amp with perfect sound. 

Half an hour ago I put the tele on again and had perfect sound. Then while I was on the other side of the room I heard several loud crackles through the speakers and then suddenly "huuumm!!!!" The bloody interference sound came back for no reason!!!! Checked the plugs were all tightly in place and they are. Turned everything off and on again but the hum is still there. What's going on? At first I wondered if the crackling sound might be related to the wind that's gusting outside. But I don't think it is and it doesn't explain the hum coming back all on its own.

Any ideas?

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That sounds like a cable or hardware fault (tv or inverter).

 

You've probably got a mobile phone, portable radio or other audio producing device with a headphone socket the same as your TV. Try plugging that in, that'll at least eliminate the TV as the source of the problem. If you've a battery device and one running off AC that's even better, if the battery is clean but the AC is buzzing it points to power issues from your inverter, maybe intermittent grounding?

 

bx

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11 minutes ago, cuthound said:

Try another ground isolating cable. It sounds as though the original has failed.

 

Then if it works send the original back for replacement and you will then have a spare.

Not sure moomin papa accepts returns :)

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  • Haha 1
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Well, a certain clever simian solved the problem from his own boat! I told him about the weird popping and crackling noises and he reckoned that because the speakers hadn't been used for a decade, the cone on one has probably split. I took a close look and he's right, there's a couple of little tears.  So I've unplugged that one speaker from the amp and turned everything back on and the hum has gone, the volume is properly controllable again and there's no crackling and popping anymore.

RIP not-very-trusty-speaker. ☠️? His brother must carry the burden for now. And long live the Great Moomin! ?

20190310_164945.jpg

Edited by BlueStringPudding
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I had a Maranz speaker once that also burst into tears, I was playing amazing Grace at the time.  If speakers arn't driven with a powerful enough amplifier their cone can become paralized and jamb.

Edited by bizzard
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If the speaker cones or drivers are to be suspect at all then the symptoms are going to be distortion and crackling during audio being present, especially bass notes. If the buzzing is there at fairly constant levels and with no audio (quiet or the TV is on but muted) then you should cross speaker issues off your list.

 

Just going back to the original post, you mention "12v speakers". Not sure what you mean by this....

 

bx

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Just now, BlueStringPudding said:

If I replace them I'll want to do so with something that fits in the same size cut out hole, really 

It looks a big speake,r is your amp powerful enough to drive it ? If you pull it out it should say what wattage it is. Get a modern speaker with synthetic cone. You could mount a smaller speaker on a board and screw that over the big hole. JBL are very good.

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7 hours ago, Boater Sam said:

You can buy re-coning kits for speakers.

Depends on the speaker of course. If it’s not a high-end make then a replacement speaker is probably going to be around the same price or even less than a recone kit. 

 

And an awful lot less hassle. 

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