STK402 muting speakers popping sound

jenom

Member
2013-02-10 3:02 pm
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!
 

jenom

Member
2013-02-10 3:02 pm
the pop coming from the stk402....even when I connect input to common ground
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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
 
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.
 

jenom

Member
2013-02-10 3:02 pm
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
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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.