Jump to content

Buzzing noise from amplifier


Bodgit
 Share

Recommended Posts

One of my mono blocks was make a buzzing/humming noise, sounded a lot like the pipe buzz I sometimes get around the boiler.

It first happened a week or two ago, my OH heard it and it lasted about 5 minutes, then silence.

It happened again this morning, the sound appeared to be coming from the left of one of the mono blocks, when I turned the amp off it went silent (so I know its not the heating!)

I wonder if its the coil inductor at the rear/left of the chassis (see below), when I tapped it, it does make a rattling sound so could be mechanical noise, perhaps due to soft vibrations coming from the toroidal? I've slightly stretched the inductor, its no longer making the noise. Time will tell.

Anyone have some thoughts on this, do toroidals vibrate ever so slighty? I tried calling John Sampson who upgraded these last year, but he's not picking up.

51211072019_7d09dd5817_c.jpg

Link to comment
Share on other sites

Toroidal transformers hum, the bigger the transformer the louder the hum. Apparently the UK Mains suffers more than other parts of europe. How acceptable the hum coming from the transformer is another thing. Personally speaking I think you should only pick up the hum when leaning over and putting your ear near/close to the amplifier... 

Link to comment
Share on other sites

4 hours ago, 2010*zuma said:

Toroidal transformers hum, the bigger the transformer the louder the hum. Apparently the UK Mains suffers more than other parts of europe. How acceptable the hum coming from the transformer is another thing. Personally speaking I think you should only pick up the hum when leaning over and putting your ear near/close to the amplifier... 

Its not the transformer I can hear, I think its the induction coil vibrating. Hence I'm wondering if the transformer also vibrates such that it would make the coil rattle slightly?

Link to comment
Share on other sites

Put a thin line of silicone across the top of the windings of the coil and see if that cures the problem. It won't affect the inductor value.

  • Like 2
  • Upvote 1
Link to comment
Share on other sites

I put the lid back on the amp and placed it back in the rack, yesterday morning the buzz returned briefly...it made the same sound for a short while, then reduced in volume before going silent. Its weird. I listened to a 50Hz sound from youtube, the buzz is at a slightly higher frequency.

I've got a mains power monitor close by now, so I can see what the voltage is doing the next time it buzzes, perhaps its caused by the voltage spiking? If it happens again I'll take the amp out and cover off...I only have the amps on at weekends.

Link to comment
Share on other sites

17 minutes ago, Bodgit said:

perhaps its caused by the voltage spiking?

Unfortunately "spike" is a technical term for a disturbance that lasts less than 3nS. Surges are typically less than 3mS. So it isn't either of them, It could be a shift in the absolute voltage caused by varying load in you area, or maybe a temporary DC offset on the mains. DC blockers have been disgust at length recently. :D

Link to comment
Share on other sites

Yes, a temporary shift in absolute voltage or DC offset were my thoughts, but both amps are identical so why would it only affect one of them?

I've had these amps in their current state since just before Xmas and its only now they're making this noise.

Link to comment
Share on other sites

Have you plugged in anything new on your mains circuit recently ....my balanced transformer setup that feeds my kit (contains a huge toroidal transformer) hums like mad when my wife plugs in her heating pad to ease a painful shoulder.

Link to comment
Share on other sites

2 hours ago, MF 1000 said:

Have you plugged in anything new on your mains circuit recently ....my balanced transformer setup that feeds my kit (contains a huge toroidal transformer) hums like mad when my wife plugs in her heating pad to ease a painful shoulder.

Not that I can think of generally, the hifi sockets (6 doubles) are on a circuit of their own anyway. Each time its buzzed (3 occasions) has been in the morning, which could be when loads are lighter so voltage is higher. The buzz doesn't seem to coincide with the sound I would think the induction coil would make as its quite low pitched.

I'm at a loss, need to hear the buzz again when I have the amp lid off and can poke around (very carefully!)

Link to comment
Share on other sites

4 hours ago, Bodgit said:

Not that I can think of generally, the hifi sockets (6 doubles) are on a circuit of their own anyway. Each time its buzzed (3 occasions) has been in the morning, which could be when loads are lighter so voltage is higher. The buzz doesn't seem to coincide with the sound I would think the induction coil would make as its quite low pitched.

I'm at a loss, need to hear the buzz again when I have the amp lid off and can poke around (very carefully!)

For ‘live poking’’ (ooer!) a wooden or plastic chopstick was suggested to me when my valve amp developed a loose connection.

  • Like 1
Link to comment
Share on other sites

17 hours ago, Bodgit said:

but both amps are identical so why would it only affect one of them?

Probably not that identical, especially a power transformer, that would require extreme quality control.

14 hours ago, Bodgit said:

Each time its buzzed (3 occasions) has been in the morning, which could be when loads are lighter so voltage is higher.

It could be caused by anyone(s) in your area sharing the same tap from the substation transformer, wherever that is.

14 hours ago, Bodgit said:

The buzz doesn't seem to coincide with the sound I would think the induction coil would make

 It is extremely unlikely to be that coil, unless it is physically loose and or being mechanically vibrated. Is the case steel? I fixed a steel case / toroidal buzz by fitting an aluminium plate under the toroid once.

Link to comment
Share on other sites

Thanks Dave, it certainly doesn't sound like its the coil, I would expect the buzz to be higher pitched and "lighter" in tone as the coil doesn't have much mass.

Will need to wait until it buzzes again and with the lid off so I can have a good poke around and see if I can hear exactly where its coming from!

Link to comment
Share on other sites

Had the amps on over the weekend just past, no buzzing. O.o

Link to comment
Share on other sites

29 minutes ago, Bodgit said:

Had the amps on over the weekend just past, no buzzing. O.o

That’s a relief.  Is it possible that you or a neighbouring property was using a device that put noise on the mains?  I think I read here about chokes on some kit causing problems.

You might’ve seen me report before that we had a coffee machine that set my MF Studio T amp buzzing when switched to the 1-4 cup setting.  Something about the mechanism in the coffee machine to reduce the power to the heating element. 

Link to comment
Share on other sites

Honestly no idea Nick, I haven't knowingly changed anything in the house so am at a complete loss at what is buzzing in the amp or what caused it.

All I can do is hope it doesn't return, and if it does, see if it will buzz with the amp top off so I can try to find out what its doing.

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...