Live loop recording adds unwanted signal [INVESTIGATING]


An audible unwanted signal with very short duration (under 1 second) is added to the signal being recorded from analog input.

Steps to reproduce:

  1. Turn the power on S2400
  2. Set pattern length to 8
  3. Turn on live looping by holding down F4
  4. In input monitoring menu, enable analog inputs 1-2, set input to Left
  5. Connect synth out (mono) to input 1 of S2400
  6. Press shift+pad and set division to 2.
  7. Verify the BPM is set to 120.
  8. Arm the track for recording by hitting the pad. The pad turns yellow.
  9. Begin recording


  • The unwanted signal is audible during recording and playing back the recorded loop.
  • The waveform view of the recorded live loop confirms the unwanted signal.
  • The unwanted signal is not present during input monitoring.
  • Power cycling the unit does not resolve the issue.
  • The issue is random but fairly consistent. It happens about 60% of times.
  • The unwanted signal occurs at a random time during recording of the live loop.
  • The unwanted signal occurs either 0 or 1 times during recording of the live loop. Never more.
  • Can reproduce the issue when using input 1 or input 2. Have not verified other inputs.
  • Changing gain settings does not resolve the issue
  • Input signal is not clipping. Verified in Sample menu. Confirmed signal amplitude of the recorded live loop in waveform view too.
  • Latched/Immediate/Fixed length looping modes have no effect on the issue.

Additional information

Both videos below demonstrate the unwanted signal appear somewhere in Bar 4 of the live loop.

  1. Playing back recorded loop, waveform view IMG_0804.MOV - Google Drive
  2. Recording another live loop: IMG_0805.MOV - Google Drive

Signal source:

  • Akai AX73


Dec 24, 2021, release

1 Like

Can you upload the liveloop1.wav file?
And, let me know at what point in time the unwanted sound occurs

Hi Mickey,
Thanks for your reply!

I’m afraid I do not have the file anymore as I have been re-recording over and over again until that unwanted glitchy sound was not occurring and my hands played at the correct timing, haha.

I am going to have to live loop something else for you in about 20 minutes.

In the meantime, on the first video that I provided, you can hear it at 6-7 second mark. It’s at the bar 4.
See picture for clarification. The sound occurs exactly where the playhead is at.

Thank you for your patience.
You can find the files below!

Loop 1 @ 0:05:

Loop 2 @ 0:05:

Loop 3 @ 0:02:

Let me know if there’s anything else I can do to help you find the root cause.

This sounds very similar to the sound I got when using my first SD card, which was too slow for SD streaming (samples > 2MB). Could this be the cause?

Mind that you are playing back and recording at the same time, so the SD card gets a lot more taxed…

1 Like

I had this thought too. This happens regardless of the amount of audio loops/samples being played back/loaded. The loops I have posted have been recorded in an empty project on a power cycled unit as indicated in the steps in my first post.

The SD card that I am using is Sandisk Extreme Pro SDXC UHS-I card rated for 4K UHD video quality. To re-iterate, I do not see how the SD card is the problem in this case, given that the issue occurs when attempting to record the first 4 bar loop @ 120 bpm in the whole project without anything else in the project.

Could be totally not related to SD card speeds…

However, that 4K video rating does not tell you anything about how it performs in the 2400. The performance will depend more on access times than on bandwidth for one stream.

Every sample that is too large for memory will stream from the card. I don’t know how it is implemented, but Vlad spoke once about 2 audio streams for stereo samples… So, if you (worst case) use 8 long & sliced stereo samples and those slices are triggered often, you probably will have 16 streams constantly (re)loading from the card and you are writing at the same time to record it.

But that’s all theory. You are only recording an external synth, so it probably is not related to the SD card…

I have not yet had this problem with my current card. I will test it on my system (Sandisk Extreme Pro U3 - 170MB/s) and see if the latest firmware behaves differently. I have not used the livelooper in the lastest OS.

I followed your scenario, but with 1 difference:
Between step 2 and 3 I recorded one midi note on E1 with length of 3 measures. My synth sound release is a bit longer than 1 measure, so when recording the liveloop, sound is there for all 4 bars.

The sound is clear for the full liveloop of 4 measures and repeats perfect for the next 4 bars. So, I cannot reproduce it using the same firmware and almost the same SD card.

Have you checked the serial number on the card? I read on this forum that the fake ones miss that serial number…

Liveloops are recorded and played back from RAM, so not likely a card issue.

1 Like

Oh wow what a detailed response. Thank you for caring! I followed the instructions for verifying the authenticity of the card from sandisk website and mine seems legit. It totally has a serial on it, too.

I appreciate your effort, I really do but we shouldn’t be making assumptions unless we know something for sure. Our SD card conversation might be very misleading for the debugging process of a developer and we need to be very careful with the information we provide because system debugging can get insane too quickly. I suggest we sit and wait until the guys ask for more information.

1 Like

Hi, @Mickey !

Did you have a chance to look at my wave files that I provided earlier? Live looping is important for me and I would like to help to get it fixed.

I did look at your files. I can see and hear the extra sound. It seems like the same sound layered on top of itself.
However, we have not been able to reproduce this bug. So we still do not know what caused that to happen.

Yes, as if a portion of previously signal is being layered.

Fixed in dev. Fix will be in next firmware update.


Woo-hoo! Thanks so much for the update!

I had the issue happen to me a few times again since the update. I have reasons to believe it is related to inputs 1 and 2. Never had an issue since I started using inputs 3 and 4.

UPD: can reproduce the issue using outputs 3 or 4

Today I used the live looper again and the issue happened to me. I came back to a project from a few months ago with the bpm of 137, 8 bar pattern. It had 6 loops committed as well as about 6 tracks of sequenced 707 drums on bank A. When I wanted to add loop 7 the issue started happening again. Fairly randomly but still incredibly frequently. (about 60% of times)

Below are examples demonstrating the issue (this time I used casio VL-tone as source plugged into input 3 on the S2400):

at about 0:11:

at 0:04:

@rozz3r can you please re-open this issue?

Updated my previous message with important details.

Are you recording MIDI parts on the S2400 for your external synth, and then recording that as a live loop on another channel?

I don’t know if that would have anything to do with it but part of me could imagine that might create errors when recording the audio back into the machine?

Does it do this when you record an audio sample? Like from your computer or vinyl?

1 Like

Hi Scott!

Thanks for giving this topic a little bit of attention! I am hoping more people experiencing this bug will notice the topic and chime in. :stuck_out_tongue:

Good suggestions! No MIDI unfortunately, just plain audio signal. The steps in my bug report do not indicate recording MIDI in any way.

Originally, the issue was opened when I tried to record loops with my AX-73. It also happens when I record my Casio VL-Tone and/or my guitar as I mentioned a few posts before. Plugging in directly and in different inputs produces the same results.

Man, this issue drives me crazy! My timing is already horrible enough so I re-record everything dozens of times but then this issue also multiplies the number of attempts by 2.