Help needed with disturbance coming from amp into speaker

[sachinchavan 15865]

Hi all,

I am finding a disturbance coming in one of my speakers. It’s intermittent, without any clue to what triggers it. Sometimes I feel it starts if there’s no audio signal (if source put on pause for example), but it also gets triggered at times when audio is playing.

Now, I have already tried exchanging the L/R speaker cables. The disturbance moved to the other speaker, indicating the problem is upstream of the speakers. Then I interchanged the RCA L/R going into the amp. The disturbance stays in the same speaker. That leads me to the conclusion that the source of the problem is in the amplifier (or its binding post).

I have uploaded a video in the following link where you can hear this disturbance in the first few seconds. Kindly help me troubleshoot this.

2024-09-04 15-29-50.mov - Shared with pCloud

Store videos in pCloud. Share them with just the right people. Access them on any device. Create a free account now!

u.pcloud.link

 

[Manoj Nair]

Hi all,

I am finding a disturbance coming in one of my speakers. It’s intermittent, without any clue to what triggers it. Sometimes I feel it starts if there’s no audio signal (if source put on pause for example), but it also gets triggered at times when audio is playing.

Now, I have already tried exchanging the L/R speaker cables. The disturbance moved to the other speaker, indicating the problem is upstream of the speakers. Then I interchanged the RCA L/R going into the amp. The disturbance stays in the same speaker. That leads me to the conclusion that the source of the problem is in the amplifier (or its binding post).

I have uploaded a video in the following link where you can hear this disturbance in the first few seconds. Kindly help me troubleshoot this.

2024-09-04 15-29-50.mov - Shared with pCloud

Store videos in pCloud. Share them with just the right people. Access them on any device. Create a free account now!

u.pcloud.link

Hi
Try using Deoxit Red .
Apply it on the amplifier RCA connections .
It works like Magic.
I use this regularly to remove oxides and get a sound connection .
Attached a photograph for reference please.
Thanks
Manoj

 

[sachinchavan 15865]

Hi
Try using Deoxit Red .
Apply it on the amplifier RCA connections .
It works like Magic.
I use this regularly to remove oxides and get a sound connection .
Attached a photograph for reference please.
Thanks
Manoj

Thanks. Do you suggest using it also inside the binding posts (where the speaker cables’ banana plugs go in) on the amplifier?

 

[mbhangui]

Does your amp have a volume control. Rotate that back and forth and see if the sound dissappears. Also clean the binding post but I doubt the issue is there as mostly it is a tight connection.

 

[sachinchavan 15865]

Does your amp have a volume control. Rotate that back and forth and see if the sound dissappears. Also clean the binding post but I doubt the issue is there as mostly it is a tight connection.

Thanks Manavendra. It has.

 

[mbhangui]

Thanks Manavendra. It has.

rotate the volume control clockwise and counter-clockwise few times. If it goes away fine. Else you will have to clean it with a contact spray. Mumbai has a corrosive (salty) atmosphere. These things happen and hence require more frequent cleaning compared to other cities away away from the sea.

 

[sachinchavan 15865]

rotate the volume control clockwise and counter-clockwise few times. If it goes away fine. Else you will have to clean it with a contact spray. Mumbai has a corrosive (salty) atmosphere. These things happen and hence require more frequent cleaning compared to other cities away away from the sea.

But why should it create disturbance only in one channel?

 

[mbhangui]

But why should it create disturbance only in one channel?

The volume control that you see with a single knob is actually two separate volume controls rotated by a single knob. For stereo you require two separate volume controls, one for left channel and one for right channel. One is closer to the behind and the other is closer to the front where the rotating knob comes out. The probability of both going bad at exactly the same time is rare. Also the one behind is always more exposed to elements and starts giving scratching noise first.

e.g. is this (a cheap one) The costlier one will be inside a housing, but basically all of them are more or less the same. So actually you have two volume controls and one of them has carbon particle that has loosend a bit.

The brown bakelite thing has carbon coating on which a slider moves. Few of the carbon particles become loose and cause noise. The carbon strip can be cleaned using a spray.


Here is a youtube video showing the gory innards of a volume control

 

[sbg]

I think the noise is something related to RF Interference . The sound is similar to the one you can hear in some local made amps and radios.
- this could be like shielding is damaged or off the place or could be some caps starting to go bad.
- are there any tube lights nearby - the old fluorescent ones - these too at times interfere a bit .

 

[sachinchavan 15865]

The volume control that you see with a single knob is actually two separate volume controls rotated by a single knob. For stereo you require two separate volume controls, one for left channel and one for right channel. One is closer to the behind and the other is closer to the front where the rotating knob comes out. The probability of both going bad at exactly the same time is rare. Also the one behind is always more exposed to elements and starts giving scratching noise first.

e.g. is this (a cheap one) The costlier one will be inside a housing, but basically all of them are more or less the same. So actually you have two volume controls and one of them has carbon particle that has loosend a bit.

The brown bakelite thing has carbon coating on which a slider moves. Few of the carbon particles become loose and cause noise. The carbon strip can be cleaned using a spray.
View attachment 86432

Here is a youtube video showing the gory innards of a volume control

Thanks for explaining so clearly. I have done the suggested rotation of all the knobs on the amp. Let me now observe for a day or two to see if the disturbance returns.

I think the noise is something related to RF Interference . The sound is similar to the one you can hear in some local made amps and radios.
- this could be like shielding is damaged or off the place or could be some caps starting to go bad.
- are there any tube lights nearby - the old fluorescent ones - these too at times interfere a bit .

I shall keep that possibility in mind. No, there’s no tube light nearby, all my light fixtures are LED. And this is an intermittent occurrence, wouldn’t RF interference be constant (unless I move something)?

 

[sbg]

Will this be similar to the issue discussed in this diyaudio ?
bad transistor at differential stage

 

[IndianEars]

Will this be similar to the issue discussed in this diyaudio ?
bad transistor at differential stage

Yes, a Distinct possibility, but did not want to alarm him, untill relatively simpler possibilities like a scratchy volume control are ruled out.

May also be worth checking if the noise level is lowered when the volume control is lowered.

 

[Manoj Nair]

Thanks. Do you suggest using it also inside the binding posts (where the speaker cables’ banana plugs go in) on the amplifier?

Yes please
You need to apply the Deoxit on tip of Banana plug insert in amp where it fits and rotate it ......in all directions....then pull it out and wipe clean the banana plugs tip to clean oxides.
This way it does work .
It works very well for scratchy sounds etc and you get a clear connection and sound .
Hope it helps
Thanks

 

[sachinchavan 15865]

May also be worth checking if the noise level is lowered when the volume control is lowered

No, it doesn’t, stays the same irrespective of volume control (even if turned all the way down). But would like to repeat it’s not a constant noise.

(I haven’t heard it yet after trying @mbhangui’s suggestion. Let’s see)

 

[Manoj Nair]

Yes please
You need to apply the Deoxit on tip of Banana plug insert in amp where it fits and rotate it ......in all directions....then pull it out and wipe clean the banana plugs tip to clean oxides.
This way it does work .
It works very well for scratchy sounds etc and you get a clear connection and sound .
Hope it helps
Thanks

If you have any questions you can reach me at 8692911110 ....based out of Mumbai

 

[mbhangui]

No, it doesn’t, stays the same irrespective of volume control (even if turned all the way down). But would like to repeat it’s not a constant noise.

(I haven’t heard it yet after trying @mbhangui’s suggestion. Let’s see)

It if is constant, then the noise is not because of loose resistive material in the volume control

 

[arj]

No, it doesn’t, stays the same irrespective of volume control (even if turned all the way down). But would like to repeat it’s not a constant noise.

(I haven’t heard it yet after trying @mbhangui’s suggestion. Let’s see)

So it's after the volume pot.
This sounds like electronic and not dust but I am no expert. Better take it to someone who knows electronics.
I am petrified of some sound spike with DC Burning the tweeter coils

 

[sachinchavan 15865]

So it's after the volume pot.
This sounds like electronic and not dust but I am no expert. Better take it to someone who knows electronics.
I am petrified of some sound spike with DC Burning the tweeter coils

Well, as I said earlier, the noise remained after I rotated the volume pot. But after I rotated the other knobs (mode, input, record), it has ceased. Been a day now and hasn’t returned. Hopefully it been addressed. I shall update here if it returns. Thanks all.

 

[IndianEars]

Well, as I said earlier, the noise remained after I rotated the volume pot. But after I rotated the other knobs (mode, input, record), it has ceased. Been a day now and hasn’t returned. Hopefully it been addressed. I shall update here if it returns. Thanks all.

Seems odd.

The fact that the noise did not reduce with the Volume Controlled turned down, would indicate that its probably popcorn noise at the input stage of the Power amp section.

The source input switch, mode, etc are Before the volume control .... So may be its just a coincidence that the cracking has stopped with rotation of these knobs...

 

[sachinchavan 15865]

Seems odd.

The fact that the noise did not reduce with the Volume Controlled turned down, would indicate that its probably popcorn noise at the input stage of the Power amp section.

The source input switch, mode, etc are Before the volume control .... So may be its just a coincidence that the cracking has stopped with rotation of these knobs...

It could be. I don’t possess the knowledge to ascertain the reason. As long as the noise stays away, I’m happy.