LM1971 switching noise

Jaison Joy

Other Parts Discussed in Thread: LM1971, LF353

We have a tone generator sysetm, in which I have added LM1971 to control the volume level according to the requirement from a microcontroller. Volume Up and Down are working fine, but during the process, an audible switching noise is heard.

Is there any solution to avoid this switching noise? Or is there any other alternative part, which can ensure a clear volume transition?

Thanks,

Jaison

over 9 years ago

0 Andy Liu (BMS) over 9 years ago

TI__Guru 52115 points

Hi Jaison,

I will take a look at this issue and get back to you soon.

Andy

0 Andy Liu (BMS) over 9 years ago

TI__Guru 52115 points

Hi Jaison,

Here are some comments I got from my colleague:

"If the customer uses normal op-amps like Bip input type op-amp, when customer changes the volume, pop sound will occur due to the input bias current of op-amp. If so, the customer has to use MOSFET input type op-amp or JFET input type op-amp. Then the customer will not have the pop sound during volume level change."

Andy

0 Jaison Joy over 9 years ago in reply to Andy Liu (BMS)

Prodigy 185 points

Hello Andy,

I have the JFET input type Op-amp(LF353) in my circuit, as suggested in page-10 of LM1971 datasheet.

Attached the schematic where I have the small tick sound(not a big pop sound) during volume transition.

Jaison

Audio

Audio forum

LM1971 switching noise