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Is there a way to recover recording from M20d (powered off before pressing stop)?

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I just used my M20d with 2 L2t speakers for the very first time with my bluegrass band. It did great and I think it has a great future with us. We played two sets and I tried to record both directly to an SD card.


The first set recorded fine because I pressed stop, but the second set I forgot to press the stop button before powering it off. I recorded main outs and every input. I can see large files on the SD card for the second set. The main out file is 783 MB in size, but every one of them appear to somehow be corrupted and won't open in any sound player/editor.


Does anyone know of a way to recover them? Perhaps there's something that should have been written to the end of the .wav files that wasn't? Any ideas? Our second set was much better and I was really hoping to get some good recordings of us.

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I managed to do this a few weeks ago... or rather, the person I'd left in charge of control hadn't stopped the recording and I flipped the power off.


2 options:


I use mixcraft 6 as my DAW. I was able to drag and drop the files direct off the SD card and mixcraft imported them without issue, ie all audio was present. It is possible that other DAW software might be able to import the files, despite the header data being missing. This option is great if all you want to do is to import the tracks into a DAW.


BUT the above didn't allow me to play back the recordings as standalone files. A quick bit of research on this forum pointed me to a small piece of software called "Format Factory"

Use it to export the files as WAV (to a different location) and the missing header data is set into the new versions of the files. Worked a treat, and I was then able to put the copies back onto the SD card and play them back.

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I'm on a Mac so I had to improvise. I followed the WAV file format here (, opened up the files in a HEX editor, and set the two length fields. They work great now. Whew! I'm glad they weren't lost forever. Now I just need to remember to press STOP before powering off. :)

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  • 4 years later...

I am gonna bump this thread. I have been using M20d for years; and finally made the mistake of turning off the mixer while recording; with out stopping the recording. DOH!!


Anyway; I can't 100% confirm; but it seems I figured out how to rescue the files. I'll write the details out after I make sure it's all good; but I was able to import the repaired wav into ProTools after; so: fingers crossed!!


Basic summary:

I was unable to import them into ProTools; but the files were about 400mb each. Tested in the M20d; and confirmed can't load that session.


So; I opened the files in VLC; and they play fine! This part is worth repeating: I knew the audio data was there because I was able to listen to it with VLC.


So; this is a corrupted data header issue.


I attempted to use Audacity to import as raw PCM; but just got static noise with all the various settings.


What DID work; came from using MS Visual Studio (it's free) and using the binary editor.


I had to find a previous M20d session with file length longer than the corrupted file. IE; my corrupted file is about 52mins; so I found a session we did from about 2 weeks ago that was a little longer.


I did have some issues with the larger files requiring me to increase virtual memory available in windows system settings.


Basically; I copied the first 48bytes of the good file header data and pasted it into the bad file data header. 


For example: due to the virtual memory issue had to open the good file; copy the data, close it, and paste it into the bad file; then did save as from the binary editor.


Got the idea from this web article:


I need to do that process; for the rest of the files then make sure they all align and play before I get too excited; but I already did the MainMixOut.wav and worked fine.


Essentially; the new header data is longer than the corrupted file header data; so it just puts blank audio at the end of the file.


Note; the good file must be longer than the corrupt file. I tried it with a shorter also good session; it worked- but it truncated the corrupt wav to the length of the good file header data length.


It was a horrible feeling; I was Googling this at 4am last night after the gig when I realized it.  I was able to make that work this morning; and wanted to share in case anyone else has done the same thing.



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Yeah; it 100% definitely worked!


I was able to fully recover the whole batch of tracks; 49 mins music of about 12 tracks; 2nd half of extended set! I will try to put together a concise summary of what to do...


Tracks are Kick, snare, hi hat over, tom over, bass DI, amp 1 sm57, amp 1 e609, amp 2 beta57, amp 2 e609, vocal, trumpet, sax..

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