LM386: Could you please tell me how to remove pop noise at powered up?

Hi Kazuya-san,

Is LM384 you mention the same as this one?: http://www.ti.com/product/LM384
This devices does not seem to be EOL, perhaps you can consider it if its pin-to-pin compatible.

Regarding LM386, you mention gain=50 but the default gain of the device, with no parts between pins 1 and 8 is 20, what would be the correct gain?
In order to reduce the pop noise, you can try the following options:

• Reduce input capacitor values, something like 0.1uF or 0.01uF could make it better
• Reduce the gain. Pop noise is the amplified transients that occur at the inputs, lower the gain lower the pop at the output.
• Use precision resistors, using 1% tolerance resistors would be the best option
• Use differential inputs, in case you're using single-ended

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

 Hi Ivan,

 Thank you for your reply and I'm sorry for my typo. What I'd like to ask about is LM386. http://www.ti.com/lit/ds/symlink/lm386.pdf

 I will inform these ways to the customer for pop-noise removing.

 Could I ask you an additional question as the follow?

  The customer uses 0.047uF + 10 ohm in series between Vout pin and GND. Their amp gain = 20 with no parts between No.1 and No.8.

In these conditions, TI LM386 output has a little osccilation just after LM386 was powered on. The osccilation was disapeared after some seconds.

 What is the cause of the osccilation and what is any countermeasure to remode the osccilatin? Should we change any parts?

 Thank you and best regards,

 Kazuya.

 Hi Ivan,

 The followings are additional information.

 Input signal = sine curve, 1kHz, Vp-p=100mV.

 Output signal = sine curve, 1kHz, Vp-p=2V.

 The high frequency(~100kHz, small Vp-p) oscillation waveform is superimposed on only lower side of the 1 kHz output sine curve.

  Could you give me your reply?

 Thank you and best regards,

 Kazuya.

Ivan Salazar said:

Hi Kazuya-san,

Is LM384 you mention the same as this one?:

Hi Kazuya-san,

Is LM384 you mention the same as this one?:

Hi Kazuya-san,

Is LM384 you mention the same as this one?: http://www.ti.com/product/LM38410.0.0.1
This devices does not seem to be EOL, perhaps you can consider it if its pin-to-pin compatible.

Regarding LM386, you mention gain=50 but the default gain of the device, with no parts between pins 1 and 8 is 20, what would be the correct gain?
In order to reduce the pop noise, you can try the following options:

• Reduce input capacitor values, something like 0.1uF or 0.01uF could make it better
• Reduce the gain. Pop noise is the amplified transients that occur at the inputs, lower the gain lower the pop at the output.
• Use precision resistors, using 1% tolerance resistors would be the best option
• Use differential inputs, in case you're using single-ended

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Regarding LM386, you mention gain=50 but the default gain of the device, with no parts between pins 1 and 8 is 20, what would be the correct gain?
In order to reduce the pop noise, you can try the following options:

• Reduce input capacitor values, something like 0.1uF or 0.01uF could make it better
• Reduce the gain. Pop noise is the amplified transients that occur at the inputs, lower the gain lower the pop at the output.
• Use precision resistors, using 1% tolerance resistors would be the best option
• Use differential inputs, in case you're using single-ended

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

[/quote]
This devices does not seem to be EOL, perhaps you can consider it if its pin-to-pin compatible.

Regarding LM386, you mention gain=50 but the default gain of the device, with no parts between pins 1 and 8 is 20, what would be the correct gain?
In order to reduce the pop noise, you can try the following options:

• Reduce input capacitor values, something like 0.1uF or 0.01uF could make it better
• Reduce the gain. Pop noise is the amplified transients that occur at the inputs, lower the gain lower the pop at the output.
• Use precision resistors, using 1% tolerance resistors would be the best option
• Use differential inputs, in case you're using single-ended

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

[/quote]

Thanks for the info.

Hi Kazuya-san,

Is Bypass capacitor placed on pin 7? If it is, have you tried to increase the value of this capacitor?
Sometimes oscillation is caused by capacitive load, you can try by placing a small value resistor in series with the output, before any other component at the output.
One last thing would be to check the supply voltage, is there any oscillation in the supply voltage?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

 Hi Ivan,

 Thank you for your reply.

 1. Any capacitor is not placed on pin 7 . How much capacitance should be placed on pin 7 as the evaluation starting?

 2. How much resistance shold be inserted between LM386 output (pin 5) and a couplling capacitor (Electrolytic capacitor, 100uF/16V) connected to a speaker?

 3. The supply voltage is 9V. Lower voltage than 9V is better for the oscillation removing?

 Thank you again and best regards,

 Kazuya.