The No.1 Website for Pro Audio
MixPre-II 32-bit float USB audio interface
Old 3 days ago
  #1
Gear Nut
 

MixPre-II 32-bit float USB audio interface

MixPre-II's V6.00 firmware released today makes it the first available 32-bit float USB audio interface for your DAW... https://www.sounddevices.com/mixpre-...now-available/

Mac OS Catalina is the only OS that currently supports 32-bit float over USB properly. Also, you need a DAW that handles 32-bit float USB streaming properly ... https://www.sounddevices.com/32-bit-float-applications/
Old 3 days ago
  #2
Lives for gear
Nice release..

However I see it.. like they only managed to work at Catalina with their current software/hardware. Eg. it's current state of things.
But it's not entirely true, that Catalina is the only OS, which handles 32 float bit streaming properly.
Custom ASIO drivers on Windows can definitely support 32 bit float buffers (it can be even 64 bit doubles) and enable such path from and to a DAW.. It's then completely on particular vendor, how he handle streaming to his hardware.
Just as one example.. commonly used OEM drivers by Thesycon for class compliant USB interfaces fully supports 32 bit float format.
https://www.thesycon.de/eng/usb_audiodriver.shtml

Michal
Old 3 days ago
  #3
Gear Nut
 

Cool - I'll check Thesycon out.
Other than that, are you aware of any USB audio interface hardware other than the MixPre-II that can deliver true 32-bit float audio over USB. Its not just about the 32-bit float formatting of audio data over USB and USB driver but also about a wide enough dynamic range of the device preamps able to be handle max mic SPLs without overload and minimum mic noise floors without adding more noise.
Old 3 days ago
  #4
Gear Head
 

And the linux usb audio class driver supports 32 bit float format since 2002.
Old 3 days ago
  #5
Gear Nut
 

Quote:
Originally Posted by Drumfix View Post
And the linux usb audio class driver supports 32 bit float format since 2002.
Yes, but do you know of a 32-bit float USB interface that can take advantage of this (other than the MixPre-II)?
Old 3 days ago
  #6
Gear Guru
 
jwh1192's Avatar
people already record near Zero DBFS, not taking into account the Analog Front End that cannot handle all this HEat !!! .. will this make people push their analog gear harder to get an even higher Signal to DAW !!! at the moment there seems to be a Lack of People using Proper Gain Staging for 24 bit .. now everything will be out the window .. you can now record a fly pee'ing to a Falcon 9 taking off at 2 feet !!! just before the Microphone Melts .. Oh WAIT !! the microphones ... what real world, usable, not one million dollars, microphone can you use to get that kind of headroom, then how do you play it back !!! oh yeah, Down Convert to Mp3 !!! hahah

i will need to learn to turn up all my devices so they can be at +15 over Zero DBFS ... maybe i will just crank up my power from 120v to 160v ... should make everything sound warmer !!! and me and the room and the Wires !!! man, i love the idea of 32bit Front End !! BUT lets see the first time someone receives 32 bit Files from Someone and everything is +30 -+50 because they CAN do it .. so now we tun everything down with a Gain Trim PLugin so faders can stay at Zero ...

maybe i am crazy but some Education needs to come with this Gear .. or we are in for a Flood of new Threads ... IE: why do my Analog Meters not Move when i record .. they just stay all the way to the right all the time !!! hahahah

ADD: StageTech Consoles have 32 bit front end ... tons of headroom on input ... pretty expensive though
Old 3 days ago
  #7
Lives for gear
Quote:
Originally Posted by pauljisaacs View Post
Cool - I'll check Thesycon out.
Thesycon was just an example. It's actually what most vendors use as 3rd party driver for their class compliant interfaces at Windows. Of course this is not possible to buy as end user, it's meant for companies and developers. Often there is also some additional software and some customization at their side (say to provide control for proprietary low latency mixer, to switch some hardware specific features etc.).

So I'm positive, that ASIO itself support FP audio (it's included standard) and there are existing drivers, which supports that. For another example, I use special loopback ASIO driver, which enables streaming audio between applications (DAWs, players etc.) and you can modulate over digital zero without clipping.

Quote:
Other than that, are you aware of any USB audio interface hardware other than the MixPre-II that can deliver true 32-bit float audio over USB. Its not just about the 32-bit float formatting of audio data over USB and USB driver but also about a wide enough dynamic range of the device preamps able to be handle max mic SPLs without overload and minimum mic noise floors without adding more noise.
Nope, I'm not aware about other interface with this functionality.
AFAIK this architecture with dual ADCs (for low level and high level signals) combined to float stream is available only from Sound Devices and Zoom F series recorders. Something similar was/is made by company StageTec for mixers and recording gear, but they combined that to 28 bit fixed point.
However only Sound Devices makes that available via USB audio interface, as you've mentioned, Zoom can also work as audio interface, but with 24 bit sample format.

I can definitely see advantages of that for field recordists, where such functionality can salvage a take on location, you're recording unique moments and noisy sources (how noisy is sometimes hard to predict) and without that you likely employ analog limiters for such situations.
However honestly I would be so excited about having that feature for normal audio interface, where that's typically no so big issue. Of course, **** happens , but if you have at least some basic experience and keep reasonable headroom without unnecessarily pushing 24 bit converters to max (which is bad practice anyway, converters has higher distortion close to digital zero), you likely have no issues with that.
Or to put it in different words, that unique feature rather won't convince me to pick this interface over some conventional one, when I would be doing predominantly studio and home recordings. It's really intended for location with its feature set, which is on the other hand bit limited for use in studio with normal computer (like one stereo unbalanced output with pretty low level).
So for me it will be pretty much always secondary recorder, so it won't matter to much, if floating files will be recorded just to card.. and interface will be working in conventional fixed point mode (even if it will be just for some location editing on notebook, because I would still have access to all unclipped PCM date from previously transferred files).

Michal
Old 2 days ago
  #8
Gear Nut
 

Thx Michal.
Old 2 days ago
  #9
Gear Guru
 
jwh1192's Avatar
Quote:
Originally Posted by msmucr View Post
but if you have at least some basic experience and keep reasonable headroom without unnecessarily pushing 24 bit converters to max (which is bad practice anyway, converters has higher distortion close to digital zero)
"converters has higher distortion close to digital zero" please show some proof of this ... documents or something ... thank you john
Old 1 day ago
  #10
Gear Guru
FWIW this feature is for guys recording sfx not for music..... It won't work with the M series software......They feel 24 bit is plenty and actually 32 bit float is 24bit essentially......
Old 1 day ago
  #11
Gear Guru
 
jwh1192's Avatar
Quote:
Originally Posted by ardis View Post
FWIW this feature is for guys recording sfx not for music..... It won't work with the M series software......They feel 24 bit is plenty and actually 32 bit float is 24bit essentially......
makes sense for Gunshots, Huge Transients ... tame them later !!

but for the bedroom producer ... might help them not have those nasty overs they tend to get recording with No Front End - so no comp's limiters to help squeeze your source into Digtal world ...

we used to work very hard on Analog Boradcast Cameras to use all the Channels and get a good Sig to Noise Ratio ... world has changed, now you slap on a LAV and as long as you do not get a Boat Load of Noise because you tunred your Preamp down on the Transmitters to help with the EXPLOSION that will happen next to the Actor (stuntperson) ... super low recordings can now possibly be saved ... so there could be some possible uses for the rest of the Unwashed Masses !!!

i am thinking of super quiet to super loud things .. oh yeah !!! Music .. Classical wold love this !!! with a proper playback system Classical could sound larger than life - or more like being there .. more creaking chairs to RX out, more Coughing to RX out, more Paper Turning to RX out ...

just kidding .. progess is good !! Forward is the only Way !!!

thx !!!
Old 1 day ago
  #12
Gear Guru
Just to be clear the float 32 bit is NOT for music recording...... It is 24bit recording anyway optimized through float for sfx recording......
Old 1 day ago
  #13
Lives for gear
Quote:
Originally Posted by jwh1192 View Post
"converters has higher distortion close to digital zero" please show some proof of this ... documents or something ... thank you john
Hi John,

unfortunately I haven't found my own older measurement files from AP, which I made some years ago, when I had access to good analyzer for stepped sine measurements with high quality generator. So I just briefly looked to other sites and materials by vendors.

Some chip vendors also show that info (ideally plot) in product datasheets, others also specify it, but just few values (eg. -60, -20, -1 dBFS) without enough granularity.

For DACs you can find quite a lot sources of measurements over ASR website,
https://www.audiosciencereview.com/f...4/#post-202519
Open some review of desktop DACs.. like Grace Design Balanced DAC (just example)
and scroll down to IMD vs level measurement (which is present at almost every his review), there you can easily see distortion is decreasing with signal level up to point, where it starts to grow again towards digital zero.
That point varies between different converters, some has that at -10, some has that at -5 dBFS.

For ADCs there are not many similar measurements available, because lot of plots are made using loopback from audio interface, where you can't discriminate individual distortion of ADC and DAC.
However as I've mentioned, some vendors give you that plot.. TI come to my mind.
So for instance their PCM4220 (btw. very nice ADC chip IMHO).. scroll to page 9, where you find its THD+N vs level plot.
http://www.ti.com/lit/ds/symlink/pcm4220.pdf
AKM doesn't specify that in sheets for chips, but at sheets for evaluation kits.. in general, you can see THD+N also slightly deteriorate above -10 dBFS, but less than for previously mentioned TIs.
Benchmark has always very detailed measurements of their products, so for ADC-1 page 18.
https://cdn.shopify.com/s/files/1/03...Rev_C.pdf?1239

THD+N is composite value and deserves further explanation in context of some published graphs. It is level of measured signal without fundamental tone (which is basically notched out), so it contains both noise and distortion components.
The turning point, where THD+N line starts to rise or became flat, is typically level, where distortion dominates the composite figure.
To better show that on some practical example I've attached plot from quick test of DAC/ADC of RME audio interface using latest beta of REW software, which can do stepped tone measurements and show plots for levels of fist five harmonic components (that's THD), the rest (noise, remaining harmonic components) and composite THD+N.

To be continued with some resume..

Michal
Attached Thumbnails
MixPre-II 32-bit float USB audio interface-thd-n.png  
Old 1 day ago
  #14
Gear Guru
 
jwh1192's Avatar
Quote:
Originally Posted by msmucr View Post
Hi John,

unfortunately I haven't found my own older measurement files from AP, which I made some years ago, when I had access to good analyzer for stepped sine measurements with high quality generator. So I just briefly looked to other sites and materials by vendors.

Some chip vendors also show that info (ideally plot) in product datasheets, others also specify it, but just few values (eg. -60, -20, -1 dBFS) without enough granularity.

For DACs you can find quite a lot sources of measurements over ASR website,
https://www.audiosciencereview.com/f...4/#post-202519
Open some review of desktop DACs.. like Grace Design Balanced DAC (just example)
and scroll down to IMD vs level measurement (which is present at almost every his review), there you can easily see distortion is decreasing with signal level up to point, where it starts to grow again towards digital zero.
That point varies between different converters, some has that at -10, some has that at -5 dBFS.

For ADCs there are not many similar measurements available, because lot of plots are made using loopback from audio interface, where you can't discriminate individual distortion of ADC and DAC.
However as I've mentioned, some vendors give you that plot.. TI come to my mind.
So for instance their PCM4220 (btw. very nice ADC chip IMHO).. scroll to page 9, where you find its THD+N vs level plot.
http://www.ti.com/lit/ds/symlink/pcm4220.pdf
AKM doesn't specify that in sheets for chips, but at sheets for evaluation kits.. in general, you can see THD+N also slightly deteriorate above -10 dBFS, but less than for previously mentioned TIs.
Benchmark has always very detailed measurements of their products, so for ADC-1 page 18.
https://cdn.shopify.com/s/files/1/03...Rev_C.pdf?1239

THD+N is composite value and deserves further explanation in context of some published graphs. It is level of measured signal without fundamental tone (which is basically notched out), so it contains both noise and distortion components.
The turning point, where THD+N line starts to rise or became flat, is typically level, where distortion dominates the composite figure.
To better show that on some practical example I've attached plot from quick test of DAC/ADC of RME audio interface using latest beta of REW software, which can do stepped tone measurements and show plots for levels of fist five harmonic components (that's THD), the rest (noise, remaining harmonic components) and composite THD+N.

To be continued with some resume..

Michal
Hi Michal, thank you kindly for the awesome information.
since i own an RME interface i am interested in that info. i wonder, is this good distortion or bad distortion. i assume bad in the audio sense.

cheers john
Old 1 day ago
  #15
Lives for gear
part 2..

Of course, I realize scale of distortion increase. It's not that I want to tell you, that if you will modulate your gear to digital zero and there will be -100dB partials instead of -105 dBFS, it will make night and day difference It was just to illustrate you behavior of many converters or interfaces.
Although when playing at mastering rig, where I had several different converters for comparison in straight, level matched DA/AD loop, I perceived, that with most material it was definitely more transparent (eg. closer to source) if I attenuated source signal in digital domain, give it some headroom and apply corresponding makeup gain that after capture again in digital domain. Of course you'll going to lose some original dynamic range that way, but that's usually not so big issue.

Now back to original context, eg. mic capture. Because there's of course another element and that is mic preamplifier. If you would like to get higher level after ADC in digital domain, you have to apply more gain there. Almost universally gain increase there leads to higher distortion. So for instance going from peaks at -13 to -3 dBFS require 10 dB more of gain. Depending on actual needed gain and particular preamp.. that alone can add much more distortion than in converter.
Especially with preamps in some cheaper interfaces it can be really perceivable in character, when you go from say 40 to 50 dB.

So in sum I'd like to say, that there can be additional reasons to have headroom and avoid unnecessarily hot recording besides higher chance for unwanted clipping.

Michal
Old 23 hours ago
  #16
Lives for gear
Quote:
Originally Posted by jwh1192 View Post
Hi Michal, thank you kindly for the awesome information.
since i own an RME interface i am interested in that info. i wonder, is this good distortion or bad distortion. i assume bad in the audio sense.
You're welcome

Well, that's another aspect of course.. some distortion can be good and preferred. And yes, you're true, there might be certainly cases, when someone will like "sound signature" or whatever we'd call it of certain preamp or even converter when it will be pushed.
Except of some rare pieces (like Burl or UAD 2192 with input transformers) converters and chips are rather designed with transparency in mind and intend to preserve original signal without any "enhancement" or added distortion. So it's generally unwanted.
However again in practice there can be people, who might like it with particular material.

If you're interested and have application for line level I/O (say with some outboard), I can certainly recommend similar test with your interface like I described in previous post. So for example take some mixes and make several passes of analog loop capture with different output level. Then carefully level match that with source and compare, how that would be sounding to you and whether you spot some difference.
As an helper, I can wholeheartedly recommend free HOFA 4U Blindtest plugin.
https://hofa-plugins.de/en/plugins/4u/

Michal
Old 8 hours ago
  #17
Gear Guru
 
jwh1192's Avatar
Quote:
Originally Posted by msmucr View Post
You're welcome

Well, that's another aspect of course.. some distortion can be good and preferred. And yes, you're true, there might be certainly cases, when someone will like "sound signature" or whatever we'd call it of certain preamp or even converter when it will be pushed.
Except of some rare pieces (like Burl or UAD 2192 with input transformers) converters and chips are rather designed with transparency in mind and intend to preserve original signal without any "enhancement" or added distortion. So it's generally unwanted.
However again in practice there can be people, who might like it with particular material.

If you're interested and have application for line level I/O (say with some outboard), I can certainly recommend similar test with your interface like I described in previous post. So for example take some mixes and make several passes of analog loop capture with different output level. Then carefully level match that with source and compare, how that would be sounding to you and whether you spot some difference.
As an helper, I can wholeheartedly recommend free HOFA 4U Blindtest plugin.
https://hofa-plugins.de/en/plugins/4u/

Michal
thank you again .... interesting on the Graph what happens in that last 5 to 10db - the coming together of the Sig & THD !!!!
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump