It sounds like digital clipping to me. What are you recording through?

Motu 828mk3 with a Shure SM58 in front of an amp. But I have tried to record it Line-In with Line6 POD too. There still was this sound..

I record it just like the way I record anything else so I don't know why this sound comes with the bass guitar...

Transients are fast enough that you might not even see it clip. If you hit 0dBfs at any point in time it will clip and sound bad. Turn down the gain. You don't need it to be that loud when you record. You can always boost after the fact.

It's signal dropout. Have a look in detail at the waveform between 40.9937 and 40.9947 seconds. This shows four drops in the direction towards zero about 0.25ms (10 samples) apart. The ringing visible is the response of the anti-aliasing filter in the ADC to these out-of-band signals, and this shows it's not due to missing samples after digitization.

Do all the channels in the MOTU behave in the same way?

Thanks for your reply.

And I have just recorded some acoustic guitars without these noises. They only come out in bass recordings.

I have zoomed to the location you said and saw them, those places are not curve like.

I will try other channels, but what does it mean if another channel records it normally? And isn't it weird it happens only with bass guitars?

Thanks again.

Boswell, post: 349813 wrote: It's signal dropout. Have a look in detail at the waveform between 40.9937 and 40.9947 seconds. This shows four drops in the direction towards zero about 0.25ms (10 samples) apart. The ringing visible is the response of the anti-aliasing filter in the ADC to these out-of-band signals, and this shows it's not due to missing samples after digitization.

Do all the channels in the MOTU behave in the same way?

Yikes. That's weird. Isn't this topic going on in another thread already?

And I have taken another recording today which was fine. I wonder what was the reason ruined that session and how did it get better in time?