Topic: Sound Devices MixPre-3 and 6, Part 7

[Gordon]

I’m experiencing some unexpected behavior with my MixPre6. It’s probably my fault but I can’t make sense of it -

When I have two or more ISOs connected, ISO 1 and 2 always save as a stereo track, and I’ve triple checked that these channels are not linked. It’s making me paranoid that it’s a stereo mix down of all the connected ISOs (it’s not but I’m still paranoid about it). I would feel much more comfortable if these would save down as discrete tracks, but other than unlinking channels 1 and 2 there doesn’t seem to be much I can do about it.

Followup question - is it possible to save a stereo mix down in addition to the discrete ISO lines? That seems like something many would want to do, even though I don’t want to use it that way. I struggle to find anything in the settings that suggests I can.

When there are only 2 channels armed and the l/r mix is turned off you will get a stereo file.  When you have more than 2 channels armed you get a poly wave.  The answer to the follow up is yes, turn on the l/r mix though for me it is worthless as I want to mix the channels in post.

[vantheman]

Same, the stereo mix is useless to me too. I am definitely getting a stereo file with more than 2 ISOs, and all other stereo features turned off. Maybe it’s a bug in the way Audacity is handling them. As long as I can just split it and get ISOs 1-2 back as separate tracks, I guess it’s fine, it just seems like weird unexpected behavior on a device that otherwise is pretty intuitive to use.

[GLouie]

You record 3-4 ISOs and Audacity plays back a 2 track file of only 1 & 2? Which version of Audacity?

[checht]

I use Audacity 3.0 Mac and don't have the stereo file issue, usually record 4 or 6 tracks.

Wondering if it's possible to adjust the stereo mix, I haven't seen that in the manual. Anybody?

[dallman]

Same, the stereo mix is useless to me too. I am definitely getting a stereo file with more than 2 ISOs, and all other stereo features turned off. Maybe it’s a bug in the way Audacity is handling them. As long as I can just split it and get ISOs 1-2 back as separate tracks, I guess it’s fine, it just seems like weird unexpected behavior on a device that otherwise is pretty intuitive to use.

If I am understanding your comment above and you say you are getting what looks like a stereo file with more than 2 ISO's but are splitting to 2 ISO's, then you are getting a polywave file. Otherwise you would have 4 files assuming 4 mics or lines in as your ISO's.
Soundforge is great for Polywave Files offering each iso in a different color. I think Sound Devices offers a program too, but I have never tried it. I like the poly files as less files means less confusion for me. With the Zoom F6, you have a choice between Poly or separate ISO's, but with the MixPre6 which is my SD rig, you do not have a choice when using more than 2 ISO's I too have shut off my stereo mix as it serves no function for me other than taking up space in my SD card.

[Ronmac]

The MixPre 6 can be setup to operate in 3 different "feature modes": basic, advanced and custom. The differences in operation is explained on pages 20-21 of the owner manual.

If you are set to basic mode the record options are: Sample Rate fixed at 48 kHz - Bit Depth fixed at 24 bit - Records only the Left/Right mix

If you are set to advance mode the record options are: Sample Rate Options 44.1 - 192 kHz - Bit Depth options 16, 24, 32 (float) - Record Isolated channels and mix tracks - Individual control of Left and Right gain - Individual control of Left and Right record arming

Custom mode will allow you to select each feature to either mode.

[vantheman]

Same, the stereo mix is useless to me too. I am definitely getting a stereo file with more than 2 ISOs, and all other stereo features turned off. Maybe it’s a bug in the way Audacity is handling them. As long as I can just split it and get ISOs 1-2 back as separate tracks, I guess it’s fine, it just seems like weird unexpected behavior on a device that otherwise is pretty intuitive to use.

If I am understanding your comment above and you say you are getting what looks like a stereo file with more than 2 ISO's but are splitting to 2 ISO's, then you are getting a polywave file. Otherwise you would have 4 files assuming 4 mics or lines in as your ISO's.
Soundforge is great for Polywave Files offering each iso in a different color. I think Sound Devices offers a program too, but I have never tried it. I like the poly files as less files means less confusion for me. With the Zoom F6, you have a choice between Poly or separate ISO's, but with the MixPre6 which is my SD rig, you do not have a choice when using more than 2 ISO's I too have shut off my stereo mix as it serves no function for me other than taking up space in my SD card.

Yes, here's what Audacity looks like when I bring in a file with all 4 ISOs recording. ISOs 1-2 come in a stereo track, even though Linking is set to Off. I'm definitely in Advanced mode, because I'm recording in 32 bit float.

[GLouie]

This must be an Audacity problem, as the MixPre has no way of marking parts of its polywav as stereo to my knowledge. I use Reaper and it's never done that.

[dallman]

Same, the stereo mix is useless to me too. I am definitely getting a stereo file with more than 2 ISOs, and all other stereo features turned off. Maybe it’s a bug in the way Audacity is handling them. As long as I can just split it and get ISOs 1-2 back as separate tracks, I guess it’s fine, it just seems like weird unexpected behavior on a device that otherwise is pretty intuitive to use.

If I am understanding your comment above and you say you are getting what looks like a stereo file with more than 2 ISO's but are splitting to 2 ISO's, then you are getting a polywave file. Otherwise you would have 4 files assuming 4 mics or lines in as your ISO's.
Soundforge is great for Polywave Files offering each iso in a different color. I think Sound Devices offers a program too, but I have never tried it. I like the poly files as less files means less confusion for me. With the Zoom F6, you have a choice between Poly or separate ISO's, but with the MixPre6 which is my SD rig, you do not have a choice when using more than 2 ISO's I too have shut off my stereo mix as it serves no function for me other than taking up space in my SD card.

Yes, here's what Audacity looks like when I bring in a file with all 4 ISOs recording. ISOs 1-2 come in a stereo track, even though Linking is set to Off. I'm definitely in Advanced mode, because I'm recording in 32 bit float.

My assumption was that you were in advanced mode as you are.
 What you get is confusing/interesting. I for sure cannot say what you are getting, but it is at least possible you are getting first a stereo mix of all 4 ISO's and then a Left mix and a Right mix of the 2 left and 2right ISO's. I hate to even suggest that as it is pure speculation from a soundforge user, but it might be safe to say, you are not getting 4 separate ISO's.

Have you tried looking at 6 channels to see what happens. Maybe it would give some sort of clue as to what you are actually seeing.

[vantheman]

My assumption was that you were in advanced mode as you are.
 What you get is confusing/interesting. I for sure cannot say what you are getting, but it is at least possible you are getting first a stereo mix of all 4 ISO's and then a Left mix and a Right mix of the 2 left and 2right ISO's. I hate to even suggest that as it is pure speculation from a soundforge user, but it might be safe to say, you are not getting 4 separate ISO's.

Have you tried looking at 6 channels to see what happens. Maybe it would give some sort of clue as to what you are actually seeing.

Haven’t tried all 6. The initial test I ran suggests that the stereo track is ISOs one and too, but I’m not sure it was conclusive. I had just turned down the gain on ISO1 way down to create an obvious difference in the mix, and I had the balance for all ISOs centered. I’ll have to run some more tests. First I’ll download a trial of Reaper to see how it interprets the polywave.

[morst]

Yes, here's what Audacity looks like when I bring in a file with all 4 ISOs recording. ISOs 1-2 come in a stereo track, even though Linking is set to Off. I'm definitely in Advanced mode, because I'm recording in 32 bit float.

I realize it's a little annoying to have the inconsistency, but it doesn't really matter because audacity can make or split stereo files very easily.
That downward pointing black triangle next to the track name is the SECRET MENU! #UserHostile
PS audacity versions after 3.0 "phone home" so a lot of folks are still using 2.4.2... I am using 2.4.2.

[vantheman]

Agreed, now that I've seemingly confirmed that nothing else is getting mixed into the "stereo" track of ISOs 1-2, it's a minor annoyance I can live with. Wasn't sure if others had experienced the same thing too, which would have been more of a reason to worry. I appreciate the help in trying to run this issue down.

[Ronmac]

A mentor of mine once told me "If something doesn't make sense you likely don't have enough information".

The MixPre in Advanced mode will always create a single Polywave file when you record more than 1 track. A Polywave file is an ordered and interleaved channel recording of each armed track in a single container.

The Channel order in a Polywave file is constant, beginning with the Mixed L -R recording (if you chose to record the mix) and followed by the individually armed tracks.

You are recording 4 individual tracks and the Mix LR track:
The Polywave channel will contain the following tracks, in order: Mix L - Mix R - Track 1 - Track 2 - Track 3 -Track 4
When the Polywave file is exploded for editing within most DAW/Editors the Mix L-R are shown as a single stereo file, with the Tracks shown as individual mono files.

If you chose not to record the Mix L-R most DAW/Editors will explode the Polywave file to individual mono tracks. Some (I have not tried this in Audacity) may assume the first two tracks should be treated as a stereo file.

My workflow is to process the Polywave files in Sound Devices Wave Agent utility and then import to my DAW/Editor. nb. Wave Agent has not been updated to process files recorded in 32bit format.

I hope this helps explain

[vantheman]

Except I’m not recording the Mix LR track, and most DAWs apparently does not not include Audacity -

I did just run a test by downloading Wave Agent and putting two polywave files into it - one with and one without the Mix LR track. This seems to confirm that the issue is just the way that Audacity is interpreting the file. When I put the file containing Mix LR into Audacity then I get ISOs 1-2 as separate mono tracks. So, case closed, I guess.

[Ronmac]

Glad you confirmed that the MixPre is working as designed.

Cheers,
Ron