Amplifier with no speakers making sound

[Kermit100]

Ok heres the deal. When i turn of the speakers in both my Luxman l30 and new Marantz pm5004, and when i turn it up real loud (full way) while music is still playing through it i can actually hear the music from inside the amplifier. why is this?
Thanks in advance for your input

 

[peranders]

Magnetic forces....

 

[Kermit100]

please explain. p.s im actually studying electromagnetics at uni so do not hold back on the "slang"

 

[KatieandDad]

If you are studying electromagnetics at uni we should hardly have to explain why current or voltage through a wire can cause it to move and cause sound.

 

[Kermit100]

Im learning about motors mainly at this point in time, thats why i asked.

 

[Mooly]

Is it magnetic forces at work when its a transistor itself that is clearly audible and producing the sound ?

 

[Magnasanti]

What year? Well like others said I would guess its electromagnetic forces interfering with the signal that is being processed. My receiver also does this ( 100$ ).

 

[DF96]

Lorentz forces (i.e. normal electric motor action), magnetostriction, piezoelectricity - all methods by which electrical activity can produce sound.

If there is no output load then currents will be low so my guess is piezoelectricity.

 

[Kermit100]

i hope its not "cheap" ones they are a luxman l30 (around 1970 i think) while the other is a new marantz pm 5004 (bought it in 2012). but i do get what your saying.

 

[Magnasanti]

Well when I say "cheap" I mean not a mega buck go all out on "tweaks" such as shielding.

 

[Kermit100]

haha dont worry i dont take offence. tweaking is what i love! and
always sounds good!

 

[Nrik]

Quite interesting. What could be acting as transducer?
The output coil even though almost unloaded? (...except for the...)
The headphone-output voltage-divider?
The FL display picking up power supply 'noise'?

In my car the cabin airflow fan act as a speaker and 'plays' out the ignition-noise of the engine.

 

[Mooly]

Lorentz forces (i.e. normal electric motor action), magnetostriction, piezoelectricity - all methods by which electrical activity can produce sound.

If there is no output load then currents will be low so my guess is piezoelectricity.

Maybe. Its an effect I noted when I first started playing around with amps and semiconductors. A pair of T03 devices can be surprisingly loud.

 

[moschfet]

I once had an amplifier with TO3-transistors, who emitted heights at loud music.
You can very easily locate the place. Take a thin tube (Aquarium tube for example), one end in the ear and whit the other end you can locating the music.

 

[MarcelvdG]

Maybe. Its an effect I noted when I first started playing around with amps and semiconductors. A pair of T03 devices can be surprisingly loud.

I first noticed it on a high-voltage amp with bipolar transistors in the input stage and PL519 valves in the output stage. The PL519s seemed to produce the sound. I didn't dare to put my ear close to the PL519s, that was a bit too dangerous with 1100 V anode bias voltage.

 

[JMFahey]

Yes, I have also noticed it many times, when the speaker is not connected of course, because of masking.
I have heard output transistors/transformers/tubes/power resistor loads "sing".

 

[Mooly]

I first noticed it on a high-voltage amp with bipolar transistors in the input stage and PL519 valves in the output stage. The PL519s seemed to produce the sound. I didn't dare to put my ear close to the PL519s, that was a bit too dangerous with 1100 V anode bias voltage.

I remember those as TV line output valves You could draw quite an arc from the top cap of those with a (well insulated) screwdriver.

 

[KatieandDad]

I've never heard of Transistors "singing" due to the piezo effect. I'm not saying that speculation is wrong, I'd have thought it was something a bit bigger than a tiny silicon chip making the noise.

 

[DF96]

Could be magnetic coupling from bond wires? That would need some currents to flow.

 

[Rundmaus]

I had these effects only from inductors up to now. Interestingly, from series inductors in the PSU.

Rundmaus