Humming Sound from tube amp

[swlew]

Any idea what is the root cause of humming sound ? Both of my speakers have humming sound right after I power on my amp.

 

[funk1980]

What kind of amp? 50Hz? 100Hz? Does it alter over time? Schematics perhaps?? More info will give you a better and faster response.

 

[DF96]

The root cause of hum is the AC mains. I suspect you didn't mean to ask that.

Tell us more, and we may be able to help you.

 

[rmyauck]

If it's Old ( though if new and it didn't hum before bad cap(s) can cause it) be careful as PS caps & coupling caps can cause that leading to Failure of any of the Output or PS transformers.

 

[swlew]

The humming is soft. Only can hear it when you close the speaker. It act the same when I power on at my friend house. I don't have the schematic but is a Consonance M100-06 EL34 amp.

 

[DF96]

Has it recently started? Does it go away after a few minutes? What, if anything, has recently been changed in or around the amp? You haven't told us anything which will help with fault diagnosis.

 

[strawberry]

My amp hums too. I believe all three transformers hum and it is the same hum that is heard from the speakers. 50 Hz probably, but with angry over tones, a low sparkling sound. If this has to do with capacitors in the PS is it safe to remove them one at a time?

The hum is less when powered through a power back up supply, but still annoying.

Does a certain DC or AC reading show up on a bad PS capacitor?

 

[swlew]

Has it recently started? Does it go away after a few minutes? What, if anything, has recently been changed in or around the amp? You haven't told us anything which will help with fault diagnosis.

Hi DF96,

No. the humming doesn't goes off. The recent changed was the amp shared the same power source with my fridge. I don't think this is the reason as I have tried different power source.

 

[funk1980]

@swlew: Before we venture into any possible fault finding, could you elaborate on your level of expertise? Available test equipment perhaps??

 

[Vincent77]

Does it still hum with the audio input cables unplugged?

edit: you say it hums right after you power on the amp, you mean even while the tubes are cold and non conducting (while the amp cannot reproduce music)? Or it starts humming when the tubes are hot enough?

 

[swlew]

@swlew: Before we venture into any possible fault finding, could you elaborate on your level of expertise? Available test equipment perhaps??

Hi, I don't have electronic backup and test equipment. But if you can share with what need to be test, I can ask help from my friend.

 

[swlew]

Does it still hum with the audio input cables unplugged?

edit: you say it hums right after you power on the amp, you mean even while the tubes are cold and non conducting (while the amp cannot reproduce music)? Or it starts humming when the tubes are hot enough?

The hum started after about 30 secs power on.

 

[DF96]

If a previously non-humming amp starts humming then two possible causes are a faulty (low value) smoothing capacitor or a faulty (heater-cathode leakage) valve. An oscilloscope would help. Is the hum 50/60Hz or 100/120Hz? Does it sound like a pure hum or a buzz?

 

[swlew]

If a previously non-humming amp starts humming then two possible causes are a faulty (low value) smoothing capacitor or a faulty (heater-cathode leakage) valve. An oscilloscope would help. Is the hum 50/60Hz or 100/120Hz? Does it sound like a pure hum or a buzz?

The hum is 50Hz. I think is a buzz. I have recorded the hum using iphone. Attached here the file.

 

[Junk Audio]

Hum in both channels is usually the power supply capacitors.