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Motu converter extension not outputting the same level Audio Interfaces
Old 25th May 2018
  #1
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Jpastor's Avatar
 

Motu converter extension not outputting the same level

Hello everyone, i'm aligning my Studer 903 32 input console, i'm using a MOTU 16A (16 analog output TRS) and a 24AO extension (24 Analog output AES) connected together in AVB to send a 1khz / 6dBu signal to each channel, in order to aligne the output level of each module.

i've done the first 16 mono inputs, which are cabled to the MOTU 16A, i check the 1,55V on the output of the 16A before aligning the modules, all went well.

now i'm going for the 8 stereo inputs, connected to the MOTU 24AO, the problem is that it is not outputting 1,55V but 1,22V.


On my DAW, if i output from output 1 to 16, i've got the 1,55V, but anything that comes out of the 24AO is 1,22V. i've checked in the MOTU interface, and nothing seems to indicate a difference in level.

Any thoughts ? i guess i could align these modules with what i input into them, and it would be ok, but it really bothers me to have that difference of a few DB.
Old 25th May 2018
  #2
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crosscutred's Avatar
If you are sending the tone into a single mono input then back out through a stereo channel this can happen.

There is potential for much confusion with software monitoring.
Old 25th May 2018
  #3
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Hello

Technicality both converter can output +20dBu<=>0dBfs
check your ref level is set up the same for both converter (IIRC it's software trimable), DAW (dBfs) meter won't change.

Also as already stated this is certainly a pan law result.
Can you try sending your mono test tone to chn 17 ONLY, (24AO chn1, Studer stereo 1 Left). What do you read at DMM ?

side note: +6dBu studio line level is over conservative if ADDA can do +20dBu...

Best
Zam
Old 25th May 2018
  #4
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emrr's Avatar
These units do not have unity throughput, and they differ in output level. I can confirm this from measurements of actual units, and I've posted about it in the big MOTU AVB thread.
Old 25th May 2018
  #5
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Hi Doug

Quote:
Originally Posted by emrr View Post
These units do not have unity throughput, and they differ in output level. I can confirm this from measurements of actual units, and I've posted about it in the big MOTU AVB thread.
data spec show no unity out and in (which is not that smart...), 20dBu vs 24dBu but it should be trimable for unity ?
you mean with proper trim setting you still have 2dB offset/unaccuracy from different output ?

Best
Zam
Old 26th May 2018
  #6
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emrr's Avatar
Quote:
Originally Posted by zamproject View Post
Hi Doug



data spec show no unity out and in (which is not that smart...), 20dBu vs 24dBu but it should be trimable for unity ?
you mean with proper trim setting you still have 2dB offset/unaccuracy from different output ?

Best
Zam

The differences are fractional parts of a dB, and the trim is in 1 dB increments, thus impossible to resolve completely. I've said before, they could write correct code to fix this....
Old 26th May 2018
  #7
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Jpastor's Avatar
 

Quote:
Originally Posted by crosscutred View Post
If you are sending the tone into a single mono input then back out through a stereo channel this can happen.

There is potential for much confusion with software monitoring.
Hi, actually i'm not refering to the measure in or after the console, the measure is on the output of the converter.




Quote:
Originally Posted by zamproject View Post
Hello

Technicality both converter can output +20dBu<=>0dBfs
check your ref level is set up the same for both converter (IIRC it's software trimable), DAW (dBfs) meter won't change.

Also as already stated this is certainly a pan law result.
Can you try sending your mono test tone to chn 17 ONLY, (24AO chn1, Studer stereo 1 Left). What do you read at DMM ?

side note: +6dBu studio line level is over conservative if ADDA can do +20dBu...

Best
Zam
i did verify 17 only, when i align the console i treat each input like it's a mono input. the problem occurs just on the output of the converters itself. The whole 16A, when i output the same signal, gives me 1.55V accuratly, but the whole 24AO give me 1.22V, for the exact same signal. it's like for the same signal i've got 16 outputs giving me 1,55V and 16 output giving me 1,22V.

i did check the software and trims, and they are all maxed out, and these are not priceise enough trim anyway, on my DAW i had to use 0.01 increment to reach 1.55V on output.

it's really wierd that the extension isn't giving me the same level.

i use 6dBu because it's what the manuel requests in the line up procedure,then i can set the Vu so that the zero on my masters output will be at -6dBu into the AD converter, the console is from mid 1980.


Quote:
Originally Posted by emrr View Post
The differences are fractional parts of a dB, and the trim is in 1 dB increments, thus impossible to resolve completely. I've said before, they could write correct code to fix this....
What really bothers me about this situation is that if i have a ITB mix, and i output it into the console, then all the 17+ channels will be at about 2dB lower than the 1-16 channels. It's not really a huge deal, and i always mix OTB anyway, but it just drives me nuts, althought i'm an engineer with OCD so it doesn't help much :D
Old 26th May 2018
  #8
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crosscutred's Avatar
Quote:
Originally Posted by Jpastor View Post
Hi, actually i'm not refering to the measure in or after the console, the measure is on the output of the converter.
I meant within the software monitoring environment, the drivers of the motu soundcard.
Simply panning the channels in their pairs - 1left, 2right, 3left.... etc in the motu drivers may fix this issue.
Or not have them in pairs and only as mono outs individually, but I don't think from memory that the motu drivers allow this.

I have had the same issue in brief wrangle with a motu 828mk11
Old 26th May 2018
  #9
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Jpastor's Avatar
 

Quote:
Originally Posted by crosscutred View Post
I meant within the software monitoring environment, the drivers of the motu soundcard.
Simply panning the channels in their pairs - 1left, 2right, 3left.... etc in the motu drivers may fix this issue.
Or not have them in pairs and only as mono outs individually, but I don't think from memory that the motu drivers allow this.

I have had the same issue in brief wrangle with a motu 828mk11
Ahhhh ok i didn't get it, i'll try it tomorrow morning and tell you the result. thanks for that
Old 27th May 2018
  #10
Gear Addict
 

Hi

Quote:
Originally Posted by Jpastor View Post
i use 6dBu because it's what the manuel requests in the line up procedure,then i can set the Vu so that the zero on my masters output will be at -6dBu into the AD converter, the console is from mid 1980.
Studer desk offer variable line level setup you'r not locked at +6dBu, you have the choice of your studio line level.

If you chose +6dBu line level, 0Vu (if it's a Vu console) need alignment at -2dBu which is 22dB below AD full scale (0dBfs)
0PPM (if it's a PPM console) need alignment at +6dBu (then room is then 14dB over PPM before hitting 0dBfs)
It's definitely conservative side, but if it work for you that's fine.

About those 2dB difference, I talk about pan law but in the mean time it's little low, it's usually 3dB or more.

Maybe the published spec are wrong? and the 24AO can only output +18dBu max...
In this case if you need matching for all output (which is the common sens) you'll better trim the 16A to align at +18dBu<=>0dBfs

Best
Zam
Old 27th May 2018
  #11
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emrr's Avatar
Quote:
Originally Posted by crosscutred View Post
I meant within the software monitoring environment, the drivers of the motu soundcard.
Simply panning the channels in their pairs - 1left, 2right, 3left.... etc in the motu drivers may fix this issue.
Or not have them in pairs and only as mono outs individually, but I don't think from memory that the motu drivers allow this.

This is not a panning issue. It is a situation of different design standards for individual pieces within a product line, and an inaccurate simplified quoted spec.

I've taken measurements with test tones, nothing connected to the converter other than the test equipment, and the max output levels differ unit to unit.

There's also some variation to be found channel to channel in the same unit, which could be poor quality control in parts selection, roughly 0.1-0.2 dB. I've looked at a couple of different 16A's and Monitor 8's, and each has had it's own signature. Do other companies converters also display this? Probably, not many people look for differences that small.

Then there's the inability to make input match output in a hardwire loop situation.

Here's one screen capture I find; 17-24 are Monitor 8 channels which are trimmed -5dB relative to the 16A channels. Identical static test tone signals on all outputs, and input loop results. This particular capture could suggest gain errors on both input and output.
Attached Thumbnails
Motu converter extension not outputting the same level-2016-11-22_16a-4_mon8-9_test-tone-send-return.jpg  
Old 27th May 2018
  #12
Gear Addict
 

Hey Doug

You'r right those figures look little off limit (.5dB) even if we have out-to-in cumulative gain error (you have half a dB mismatch between 7-8 and 18-19).
let say with tolerance +/-0.1 dB per AD and DA chn, Out to In worst comparative situation is .4dB

IIRC my old 24IO have way better unity accuracy with loop test...
Annoying those AVB interface don't have a matched (IO) and fixed level for the whole product line...

Interesting notice is that you have perfect matching by pair except 18 to 20 which is mirroring, guess it follow a PCB layout design at the 8A ?

Best
Zam
Old 27th May 2018
  #13
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crosscutred's Avatar
Quote:
Originally Posted by emrr View Post
This is not a panning issue. It is a situation of different design standards for individual pieces within a product line, and an inaccurate simplified quoted spec.

I've taken measurements with test tones, nothing connected to the converter other than the test equipment, and the max output levels differ unit to unit.

There's also some variation to be found channel to channel in the same unit, which could be poor quality control in parts selection, roughly 0.1-0.2 dB. I've looked at a couple of different 16A's and Monitor 8's, and each has had it's own signature. Do other companies converters also display this? Probably, not many people look for differences that small.

Then there's the inability to make input match output in a hardwire loop situation.

Here's one screen capture I find; 17-24 are Monitor 8 channels which are trimmed -5dB relative to the 16A channels. Identical static test tone signals on all outputs, and input loop results. This particular capture could suggest gain errors on both input and output.
This is a difference of 2db, I don't think the issue is simply a manufacturing tolerances one.

It is also a difference between 2 different interfaces, which would indicate a setup discrepancy.

If you were to have a mono channel in the daw, drag in a +6 tone, send it out one mono output on the interface you should get +6 out (give or take 0.1db or so caused buy manufacturing tolerances)

If you create a stereo channel in the daw then drag the same +6 tone, pressing play would result in about +4 from each side, left and right.

With that in mind, investigating the motu software monitoring environment which sits between the daw and converters and has the facility to pan and group into pairs, would be the first place I would look.

2db is more than simply poor quality gear.
Old 27th May 2018
  #14
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emrr's Avatar
Quote:
Originally Posted by crosscutred View Post
This is a difference of 2db, I don't think the issue is simply a manufacturing tolerances one.

It is also a difference between 2 different interfaces, which would indicate a setup discrepancy.

If you were to have a mono channel in the daw, drag in a +6 tone, send it out one mono output on the interface you should get +6 out (give or take 0.1db or so caused buy manufacturing tolerances)

If you create a stereo channel in the daw then drag the same +6 tone, pressing play would result in about +4 from each side, left and right.

With that in mind, investigating the motu software monitoring environment which sits between the daw and converters and has the facility to pan and group into pairs, would be the first place I would look.

2db is more than simply poor quality gear.

You are confusing several issues.

The MOTU interface line does not have a consistent max output level standard, and if you mix multiple types, and change assignments, you will experience mix changes. The literature suggests the output standard is the same (+20dBu) for the interfaces in question, and it is in fact not. This is the primary problem Jpastor is experiencing. In my case, the difference between 16A and Mon8 should be 2dB, and it is not, and it cannot be trimmed out within a reasonable fraction of a dB for discrete analog output mixing use.

Rereading what I said, within any 1 unit, there are differences channel to channel of 0.1-0.2 dB output level, which could certainly be trimmed out in production and will affect any stereo signals side to side skewing. You can see clearly that 10 of 16 channels in the 16A example are exactly the same, and there are 3 other pairs which differ in level. In the Mon8, 6 of 8 are exactly the same, and one odd numbered pair live at a different standard.

My tests are all with mono outputs, no stereo in the AVB routing. I've been using these products for almost 4 years now, and have experimented with a lot of various AVB routing templates for various purposes. I've measured these devices a lot of different ways, including an Audio Precision test set.

The closest I can trim a 16A channel to a Mon8 channel is 0.27dB difference, the largest discrepancy is 0.41dB.
Old 27th May 2018
  #15
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crosscutred's Avatar
Quote:
Originally Posted by emrr View Post
You are confusing several issues.

The MOTU interface line does not have a consistent max output level standard, and if you mix multiple types, and change assignments, you will experience mix changes. The literature suggests the output standard is the same (+20dBu) for the interfaces in question, and it is in fact not. This is the primary problem Jpastor is experiencing. In my case, the difference between 16A and Mon8 should be 2dB, and it is not, and it cannot be trimmed out within a reasonable fraction of a dB for discrete analog output mixing use.

Rereading what I said, within any 1 unit, there are differences channel to channel of 0.1-0.2 dB output level, which could certainly be trimmed out in production and will affect any stereo signals side to side skewing. You can see clearly that 10 of 16 channels in the 16A example are exactly the same, and there are 3 other pairs which differ in level. In the Mon8, 6 of 8 are exactly the same, and one odd numbered pair live at a different standard.

My tests are all with mono outputs, no stereo in the AVB routing. I've been using these products for almost 4 years now, and have experimented with a lot of various AVB routing templates for various purposes. I've measured these devices a lot of different ways, including an Audio Precision test set.

The closest I can trim a 16A channel to a Mon8 channel is 0.27dB difference, the largest discrepancy is 0.41dB.
I'm not confusing the issues, there is only one issue as far as I can make out.

I'm only talking about the original post. There is a discrepancy of 2db between units. You may be correct about other issues, you keep referring to 0.1-0.2db. This I have not even tried to resolve, or care to try.
You appear to have different issues to the op, I am confused what your problem is. I can't see the badly labelled graphic, I'm on a mobile device and can't zoom without downloading the image and messing round with other apps.
There is nothing to do with max output that relates to the op's problem.
I think you are confusing the issue with your own experience of other aspects of these devices.

What does the op actually want to know?
I interpreted it as" why is one unit putting out 1.55vac and one 1.22vac?" I could see a possible solution, it may not be" the" solution.

Anyway have fun, I don't think I can be of further help here.
Old 27th May 2018
  #16
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Jpastor's Avatar
 

Hey guys, thank you for taking interest in my "problem". i've tried to pan on the interface, but i cannot seem to do so, i really can't stand the "web browser interface", it's very limited. i used to be with totalmix and RME and it would have been easy to check every setting, but beside trimming outputs and inputs in the interface tab, there is nothing in the "mixing" tab (i don't use it).

i'm done lining up the console 100%, for the 17 to 32 inputs, i've used the signal from the 16A, so that the console itself is all aligned from the same signal.

it won't be a huge problem for me because when i mix OTB i don't care much about the levels ITB, but it just bothers me that the outputs are different between the two modules, it's just not right. few years ago i use to work with a custom made 32inputs neumann V475 summing mixer, it would have been a problem for me to have 2db difference because the ITB mix would translate direclty into the summing mixer without any level compensation. It's a bit disapointing, the converters sound pretty good, and the amount of analog I/O is good for the price, but the user interface and this level problem on top of the reboot i have to do at the begining of each session so that the DAW will read the input is a bummer.
Old 27th May 2018
  #17
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crosscutred's Avatar
Quote:
Originally Posted by Jpastor View Post
Hey guys, thank you for taking interest in my "problem". i've tried to pan on the interface, but i cannot seem to do so, i really can't stand the "web browser interface", it's very limited. i used to be with totalmix and RME and it would have been easy to check every setting, but beside trimming outputs and inputs in the interface tab, there is nothing in the "mixing" tab (i don't use it).

i'm done lining up the console 100%, for the 17 to 32 inputs, i've used the signal from the 16A, so that the console itself is all aligned from the same signal.

it won't be a huge problem for me because when i mix OTB i don't care much about the levels ITB, but it just bothers me that the outputs are different between the two modules, it's just not right. few years ago i use to work with a custom made 32inputs neumann V475 summing mixer, it would have been a problem for me to have 2db difference because the ITB mix would translate direclty into the summing mixer without any level compensation. It's a bit disapointing, the converters sound pretty good, and the amount of analog I/O is good for the price, but the user interface and this level problem on top of the reboot i have to do at the begining of each session so that the DAW will read the input is a bummer.
Happy to help, or try to.

I think it may be worth persevering with the "web browser interface" it sounds like that's where the solution lies.

Cheers
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