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Old 20th November 2004, 09:01 AM   #1
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Default Noise from amp, appeared once, now gone??

Hi!

Yesterday and today I experienced something weird - at least in my eyes

Yesterday I turned on my P3a (without changing, let alone moving anything in my signal chain), and out of my speakers came some noise (like main line distortion), not very loud, and not hearable during music playback. But definitely it was not there when I used the amp before.

But after turning the amp off for the night, and then switching it back on this saturday morning (and again without changing anything in the signal chain), the noise was gone

Any ideas on what could be the cause for this behavior?

Bye,

Arndt
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Old 20th November 2004, 09:11 AM   #2
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Could be a bad solder joint, oscillation... who knows. A mobile phone too close?
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Old 20th November 2004, 07:36 PM   #3
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Hi!

Well, like I said, quite mysterious... The noise stayed there constantly for over three hours of listening, even after turning the amp off and on again.

Only after leaving it turned off for the night, and switching it back on this morning, the noise was gone.

And it worked flawlessly for almost two years now... and today it foes so, as well...

Maybe it was a case of "Friday the nineteenth..."


But just to be sure I will measure & set quiescent current again...

Bye,

Arndt
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Old 21st November 2004, 09:42 AM   #4
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Default Yes!, can be quiescent current trimpot.... sometimes openned can create problems..

Depends on the bias circuit design.... sometimes opening can reduce bias, sometimes can increase to many amperes....supply hum appear, and normally overheat smell are perceive...sometimes using high power, when well calculated fuses are used, they blow.

Check bias and make some vibration on the amplifier board...give them small hits...and check again.

Maybe another appliance under can create low frequency magnetic field....if your noise is hum....if another noise is heard...hehe.... Citizen Band Radios can be the guilty, in this case, put 270 pf shorting the input.

Carlos
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Old 22nd November 2004, 07:40 AM   #5
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Default Re: Yes!, can be quiescent current trimpot.... sometimes openned can create problems.

Hi!

Quote:
Originally posted by destroyer X

Maybe another appliance under can create low frequency magnetic field....if your noise is hum....if another noise is heard...hehe.... Citizen Band Radios can be the guilty, in this case, put 270 pf shorting the input.

Carlos

Well, could be... Someone across the street has a 4m long Citizen Band antenna on his roof, on the same level as my living room...

I would say that from a hifi-enthusiast view the air is getting more and more polluted by waveforms of all kind of frequencies...

Not much to do about it, except at least avoid using internet over powerline...

Bye,

Arndt
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Old 22nd November 2004, 11:14 AM   #6
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Default Yes Arndt, some sacrifice for freedom

I am a CBer too, this way i disturb people sometimes...they have some tollerance with me, and i do not stay too long, as sometimes they can hear my voice when hearing old long Play vinil recordings....transmitting in Amplitude Modulation, my voice is there, clear and with deep echo.

My freedom, sometimes disturb your freedom.

When you play loud, your amplifiers under test, you may disturb their freedom too...afecting his rigth for silence.

When those crazy Cbers (I am too!) produces Radio Frequecy Interferences (RFI), they will disturb your rigth of silence too, producing some annoyng noises.

That's freedom my friend.... the rigth to do what they want, till the moment you ask him to stop.

regards,

Carlos
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