Greetings Readers,

Recently assembled a new power amplifier with an STK-4141 Kit, the amp seems to be working with excellence, except three things that seems to be bothering me a lot.

1) Click sound in speakers whenever an electrical appliance is switched on or off (lights, Fans, Juicers etc)

2) Buzz sounds when a ceiling fan in the same room is not operating in full speed.

3) A loud, short duration buzz (1sec) whenever the amp is switched "on".

In addition i would like to mention that. I also use another Pioneer built amp which doesn't show the above mentioned symptoms, so i dont think there is something wrong with my electricity line.

I'll deeply appreciate Any recommendation or advises.

Best Regards,
Lubnan.S

 

Hello,

Is there a line filter build in the amplifier?
Is the amplifier build in a plastic housing?
Are there decoupling capacitors on the power lines near each IC?

Bertus

 

bad/missing grounding

 

Hello,

Is there a line filter build in the amplifier?
Is the amplifier build in a plastic housing?
Are there decoupling capacitors on the power lines near each IC?

Bertus

Hello Bertus, Thank you for showing interest.
The amp is built in Metallic housing, the amp board consists of only one monster IC (stereo), please check the picture, the quantity of capacitors are not in great number.

The two big caps belong to the power-supply unit (2200uf 35v each).
The small (black) ones are six in number, three caps for each channel i suppose (100uf 100v all six of them).
One orange (10uf 100v)
Two small blue ones 35uf 50v both of them.
Finally two smaller blue ones i.e 4.7uf 63v both of them soldered at the input point (input, 1k resistor, then the cap's cathode, then anode direct to the IC).
These were all electrolytic caps, as for ceramic caps the board shows presence of only four of them.
two of which are 560pf (these are after the 1k resistor at input, grounding signal). The other two are 1uf.

 

bad/missing grounding

If it is Bad or missing ground, the output would have been disastrous I suppose.
In my case the Output is crystal clear except the unexpected clicks i encounter because of the the home appliances.

 

STK will have a muting function built in, are u using that.
Using the muting will eliminate turn on and turn off thumps from the speaker.

Another way is to use a speaker protection circuitry between the amp out and the speakers.

The noise is due to poor supply filtering...STK has a low CMRR. so supply noise tends to get in to the amp if not filtered properly

{ed}
One more problem for noise is not using common ground points. decoupling caps should be used from signal ground to power ground. And another point is to ground the heat sink too.

 

from the pictures I can see that ur signal cable does not have ground shields.
This is also another cause for noise pickups

 

STK will have a muting function built in, are u using that.
Using the muting will eliminate turn on and turn off thumps from the speaker.

Another way is to use a speaker protection circuitry between the amp out and the speakers.

The noise is due to poor supply filtering...STK has a low CMRR. so supply noise tends to get in to the amp if not filtered properly

{ed}
One more problem for noise is not using common ground points. decoupling caps should be used from signal ground to power ground. And another point is to ground the heat sink too.

Thanks for the useful Info.
Noted regarding the Muting function. I am not using the muting function currently as I was not aware of the same.

Regarding the signal cables, the picture you saw was of the other STK kit which i accidentally blew up, so that isn't the one i am using.
As for the one which i am using, I have soldered Shielded cables on the board.

About the grounding, i am using a common ground point. even the Heat sink is grounded at the same ground point.