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Old 10th February 2013, 02:21 PM   #1
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Default STK402 muting speakers popping sound

I have an amplifier using SANYO STK402-270 hybrid IC.
The power supply is just a bridge rectifier making +/- 40 V and filtered by two 4800 uF capacitor.
My problem is the popping sound when power turned on.
The datasheet for the STK says:

Supports the use of standby, muting, and load shorting
protection circuits


Here is the datasheet schematics, including pin outs and internal circuits:

STK402-270 datasheet(3/4 Pages) SANYO | Three-Channel Class AB Audio Power Amplifier IC 40 W + 40 W + 40 W


Unfortunately, the shown sample circuit does not shows any hint how to do it.
Any help will be appreciated .
Thanks!
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Old 10th February 2013, 05:01 PM   #2
DUG is offline DUG  Canada
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It look like the only pin you would get to play with is pin 5

Putting a cap on that (pin 5 to pin 12) will slow down the current throughout the amps.

When you first try it, put a resistor for a load...not your speakers.



Any one else?
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Old 10th February 2013, 05:12 PM   #3
jaycee is offline jaycee  United Kingdom
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depends whats making the pop. most amplifier circuits do that, which is one reason why there's a relay on the output that connects the speakers a few seconds after power on.
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Old 11th February 2013, 12:04 AM   #4
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the pop coming from the stk402....even when I connect input to common ground
---------------------------------------------------------------------------------------------------
yes, pin 5 is the BIAS, connected to common ground thru a 10 kohm resistor....when I disconnect resistor, (pin 5 open)..... no more popping sound
measured voltage on pin 5 without resistor, it is close to the negative supply voltage level
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Old 11th February 2013, 03:49 AM   #5
DUG is offline DUG  Canada
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Quote:
Originally Posted by jenom View Post
the pop coming from the stk402....even when I connect input to common ground
---------------------------------------------------------------------------------------------------
yes, pin 5 is the BIAS, connected to common ground thru a 10 kohm resistor....when I disconnect resistor, (pin 5 open)..... no more popping sound
measured voltage on pin 5 without resistor, it is close to the negative supply voltage level
That is why I suggested:

"Putting a cap on that (pin 5 to pin 12) will slow down the current throughout the amps."

Negative supply is pin 12.

If you put a cap from pin 5 to ground you WILL blow up the amp.
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Old 12th February 2013, 09:05 PM   #6
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Default STK402 popping sound

pin #5 work very well for a MUTE function
when pin #5 not connected (open)= MUTE ON
when pin #5 is connected to common (gnd) thru a 10 kOhm resistor=MUTE OFF
--------------------------------------------------------------------------------------
I have created a 1 pnp transistor, 1 zener diode (16 V) , 1 capacitor (100 uF, 1 resistor (33 kOhm) delay timer circuit (~ 4 sec delay) to have MUTE ON when power comes on ....still there is a popping sound !
Now I am thinking to use the same circuit to drive a DPST relay to have speakers connected with 4 sec delay.
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