Buzz/Hum Hm?

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Re: Buzz/Hum Hm?

Post by Hugh Robjohns »

blinddrew wrote: Mon May 23, 2022 6:15 pm I have a similar situation with a valve mic. If it's plugged into the same socket as everything else I get hiss and hum.
Stick it in a socket on the other side of the room and it behaves itself perfectly.

Is the only difference the mains socket location, or do you locate the PSU in different places when using the different sockets?
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Re: Buzz/Hum Hm?

Post by blinddrew »

Nope, that's a good shout, the PSU is also in a completely different place. :thumbup:
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Re: Buzz/Hum Hm?

Post by Hugh Robjohns »

Hmmm... there could be an audio transformer within the PSU which is picking up the field radiating from a nearby mains transformer in the first location but not the second... or something along those lines. :ugeek:
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Re: Buzz/Hum Hm?

Post by blinddrew »

Absolutely, it was previously sitting on top of my minidisc player (don't laugh!) which doesn't have a hard off-switch just a standby.
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Re: Buzz/Hum Hm?

Post by awjoe »

Whatever the reality behind the symptoms is, it got me reading and learning (SOS and Wikipedia articles), and you've all been very helpful. And if it goes sideways again, I've got things to try out. Thanks, all.
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Re: Buzz/Hum Hm?

Post by Hugh Robjohns »

blinddrew wrote: Mon May 23, 2022 8:03 pm Absolutely, it was previously sitting on top of my minidisc player (don't laugh!) which doesn't have a hard off-switch just a standby.

Ah, that explains the hiss too.

Digital gear often radiates all manner of nasty RF stuff in the local area which can easily get demodulated into a hiss-like interference.
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Re: Buzz/Hum Hm?

Post by blinddrew »

Which is good to know, but I am now having some regrets about my last microphone purchase... :headbang:
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Re: Buzz/Hum Hm?

Post by awjoe »

Hugh Robjohns wrote: Mon May 23, 2022 9:05 pm
blinddrew wrote: Mon May 23, 2022 8:03 pm Absolutely, it was previously sitting on top of my minidisc player (don't laugh!) which doesn't have a hard off-switch just a standby.

Ah, that explains the hiss too.

Digital gear often radiates all manner of nasty RF stuff in the local area which can easily get demodulated into a hiss-like interference.

What about a wireless modem/router within two meters of the gear that is ostensibly the scene of the ground loop? Major culprit?
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Re: Buzz/Hum Hm?

Post by Mike Stranks »

Picking up on two previous posts...

Routers: I'm having some issues in one of 'my' church installs. They recently installed a digital recorder which is picking up all manner of chirps and whistles. There is a router and 'Ethernet via mains' gear about a metre away. Investigations continue...

CD and other digital players: I discovered many years ago that these do not make good bedfellows with radio-mic receivers...!
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Re: Buzz/Hum Hm?

Post by Hugh Robjohns »

Mike Stranks wrote: Tue May 24, 2022 8:52 amThey recently installed a digital recorder which is picking up all manner of chirps and whistles. There is a router and 'Ethernet via mains' gear about a metre away. Investigations continue...

The Ethernet via the mains would be the first thing to check out, I think. And then I'd look at the integrity of the unit's screening and those of cable connections. A powerful router within a metre could easily cause interference problems.

And yes, anything digital does not make good bedfellows with analogue radio mic receivers.
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Re: Buzz/Hum Hm?

Post by Hugh Robjohns »

awjoe wrote: Tue May 24, 2022 4:06 amWhat about a wireless modem/router within two meters of the gear that is ostensibly the scene of the ground loop? Major culprit?

Probably not, but certainly possible. Try depowering the modem/router and see if the audio system noise floor changes.
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Re: Buzz/Hum Hm?

Post by James Perrett »

Even LED lighting could be causing problems. I was telling our lad about short wave radio this morning and showing him on a Sony portable. We couldn't pick up anything until I switched off the LED lights that were near the aerial. They were supposed to be 12V DC but there was obviously noise from the switch mode power supply getting onto the cables.
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