Singing Leach amp while burning in

[murat]

When I was burning in my Leach amp at some high power (I don't think max power) with dummy load I was able to hear the amp clearly singing. I used caps recommended by Prof Leach and I think non of them were ceramics. So what was singing and do I need to worry about this? Thanks.

 

[traderbam]

How sweet. Which song did they sing?

 

[infinia]

Hi
Probably check your loads (wire wound resistor?)
You can use a larger dia. heatshrink tube to your ear to localize the source.
Use Elvis P.'s song "Are You Lonely Tonite" for source music. Tenn?

 

[traderbam]

Perhaps, "In the heat of the night" or "Smoke Gets In My Eyes"...?

IME this noise can emanate from the vibrations of either power transistors or resistors when they pump large ac currents. Nothing to worry about unless you've got a short somewhere you don't know about.

 

[murat]

Funny guys we have here

Was that song supposed to be "Are You Lonesome Tonight". I expect to get quite some improvement from it.

The loads were wire wound but they were not singing.

 

[bremen nacht]

Mine does that too. I suspect the big ceramic emitter resistors, or the output resistor/inductor.

 

[richie00boy]

I have experienced this too on a high power pro amp when I was in the r&d dept of a pro audio company.

 

[Eva]

Wirewound resistors and inductors are very likely to sing. Capacitors aren't. Mains transformers will also sing but in a different way.

 

[AKSA]

I've always preferred singing amps. The ones that hum aren't very musical, and obviously don't know the words......

Hugh

 

[Raka]

It happened alsto to me, I had a panic moment when I clearly heard the Rite of spring without speaker. I think there are two answers to this: Or the wirewounds are singing or Stravinsky is back.

 

[PMA]

Capacitors aren't.

You might be surprised. Try it, though I believe you have already tried.

Put a wound PP or PE capacitor as for stability test at amp speaker terminals and wobble sine tones at high output voltage level, or squares. I am sure that you will hear cap sing for some types.

 

[Eva]

You're right, high value wound foil film capacitors may produce sound when subject to strong voltage swings or overvoltage, but that's not a condition likely to happen in a class AB amplifier. Note that I'm currently working into high power class D and using that kind of capacitors for output filters, but the inductors and even the heatsink insulators produce far more sound...

 

[TonyTecson]

funny, my dummy loads are in a tub of watter, only bubbles can be heard when the water starts to boil...

 

[PMA]

Note that I'm currently working into high power class D and using that kind of capacitors for output filters, but the inductors and even the heatsink insulators produce far more sound...

I know you are, and I appreciate yourk work in the field of switched power supplies and class D amplifiers.