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Author Topic: New Sound Devices MixPre II-series coming?  (Read 8400 times)

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Offline DSatz

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Re: New Sound Devices MixPre II-series coming?
« Reply #60 on: September 01, 2019, 03:45:53 PM »
borjam, you did a nice job of clarifying the issues, separating frequency response (as a function of sampling rate) vs. dynamic range (as a function of word length / bit depth). Many people confuse these two issues and/or lump them together as "resolution"--a term which is perfect for misuse, since it sounds as if it must mean something definite, but has no agreed-upon meaning in fact.

I have two notes which aren't disagreements, but I hope clarifications of what you wrote. One is that in a properly dithered system there are no "stairsteps". That issue goes away totally, completely, 100%. It isn't relative to the strength of the signal, or the number of bits per sample; it "isn't merely really dead, [it]'s really most sincerely dead." Anyone who still thinks in terms of "more bits = smaller stairsteps" (e.g. 80% or more of "audiophile" opinion, still, after all these years) should find themselves a different concept, because that one has fallen and it can't get up. You are exactly right to equate bit depth/word length with the noise floor and nothing else.

The other thing is that there's some strange hand-waving going on in this thread about low-level signals needing to have the same s/n ratio as high-level signals. That makes no sense at all, as a few people have pointed out--but the hand-waving continues.

Any real-world noise floor shifts in level on a moment-to-moment basis. That's what noise is. But it's imperative that the shifts be random, and not correlated with the signal levels. Otherwise the noise tends to merge audibly with the signal, becoming a form of distortion known as modulation noise (or the phenomenon in general may be called "noise modulation" because the noise is being modulated by the signal). Whatever you call it, it doesn't sound good. It's sometimes called "granular noise" or described as "gritty" or "dirty" or "sandpapery" sounding, especially at the lowest signal levels, e.g. the way that the last moments of reverberant sound die down in an otherwise quiet hall.

(Somewhere I think I still have a Columbia CD of a piano concerto in which you can hear a "frying" sound each time a note decays into silence if you turn the volume up. Someone evidently didn't adjust the A/D converters in their PCM-1610 before the session, or maybe they left the dither switched off, or maybe both.)

We could talk about the issues of floating point representation near the noise floor, but I think that would leave a lot of audio-only people out. Summary is that it's not worth arguing about--as long as you don't inadvertently create modulation of the noise floor by the desired signal.

But given the marketing-type claims that I've seen so far, it's not clear to me whether this principle is being observed or not. If it is, I wouldn't expect to see anyone touting the advantages of potentially having more bits in the mantissa (the magnitude portion of the floating point representation) at and around the level of the noise floor, because that just doesn't matter; the roundoff error is below audible significance in relation to that noise floor, and rescaling the exponent just to get more bits into the mantissa in such cases is an illusory pursuit at best.
« Last Edit: September 01, 2019, 04:05:17 PM by DSatz »
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Offline borjam

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Re: New Sound Devices MixPre II-series coming?
« Reply #61 on: September 01, 2019, 05:14:10 PM »
I have two notes which aren't disagreements, but I hope clarifications of what you wrote. One is that in a properly dithered system there are no "stairsteps". That issue goes away totally, completely, 100%. It isn't relative to the strength of the signal, or the number of bits per sample; it "isn't merely really dead, [it]'s really most sincerely dead." Anyone who still thinks in terms of "more bits = smaller stairsteps" (e.g. 80% or more of "audiophile" opinion, still, after all these years) should find themselves a different concept, because that one has fallen and it can't get up. You are exactly right to equate bit depth/word length with the noise floor and nothing else.
I used the stairsteps as a simplification. I think it's easier to imagine than a mysterious sort of correlated noise somewhat following the recorded signal. Of course dithering will eliminate the "stairsteps" but still dithering is noise, so one way or another you signal to noise is lower. I know, dithering is much less noticeable than plain quantization noise especially if you apply clever tricks like shaping it so that most of its energy falls on the regions of the spectrum for which our hearing is less sensitive.

Quote
The other thing is that there's some strange hand-waving going on in this thread about low-level signals needing to have the same s/n ratio as high-level signals. That makes no sense at all, as a few people have pointed out--but the hand-waving continues.
Well, when recording it's useful to have a lot of headroom so that unexpected transients won't ruin your day. We use to record on 24 bit formats because of that. With more resolution available to the low level signals you have more freedom.

Quote
Any real-world noise floor shifts in level on a moment-to-moment basis. That's what noise is. But it's imperative that the shifts be random, and not correlated with the signal levels. Otherwise the noise tends to merge audibly with the signal, becoming a form of distortion known as modulation noise (or the phenomenon in general may be called "noise modulation" because the noise is being modulated by the signal). Whatever you call it, it doesn't sound good. It's sometimes called "granular noise" or described as "gritty" or "dirty" or "sandpapery" sounding, especially at the lowest signal levels, e.g. the way that the last moments of reverberant sound die down in an otherwise quiet hall.
I own a CD player that can play SACD recordings. The only difference I *think* I noticed in a dual format recording was, the reverb tail was much clearer, much more pleasant and more natural. For example, in this recording.
https://www.amazon.com/Mozart-Requiem-Mozarts-Original-Manuscript/dp/B00022UO9I

Of course you can only notice that if you are in a very well conditioned and quiet room, or listening on headphones. Still, it sounds beautiful and I imagine that the extra bit depth helps.

Quote
(Somewhere I think I still have a Columbia CD of a piano concerto in which you can hear a "frying" sound each time a note decays into silence if you turn the volume up. Someone evidently didn't adjust the A/D converters in their PCM-1610 before the session, or maybe they left the dither switched off, or maybe both.)
That's a valuable example then! It's often difficult to find goofs in order to ilustrate some of these phenomena :)

Quote
We could talk about the issues of floating point representation near the noise floor, but I think that would leave a lot of audio-only people out. Summary is that it's not worth arguing about--as long as you don't inadvertently create modulation of the noise floor by the desired signal.

But given the marketing-type claims that I've seen so far, it's not clear to me whether this principle is being observed or not. If it is, I wouldn't expect to see anyone touting the advantages of potentially having more bits in the mantissa (the magnitude portion of the floating point representation) at and around the level of the noise floor, because that just doesn't matter; the roundoff error is below audible significance in relation to that noise floor, and rescaling the exponent just to get more bits into the mantissa in such cases is an illusory pursuit at best.
Well, modern analog electronics can be really quiet. Moreover very quiet equipment has become really affordable. If you happen to record at a very low level and you raise the volume in postproduction that extra resolution should help.

High sample rates? I never saw the point (although some old A/D converters had poor filters and having the filter cut off frequency far from our hearing limit was beneficial) except of course for sound design where the recording can be reproduced at a much lower sample rate.
« Last Edit: September 01, 2019, 05:15:44 PM by borjam »
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Offline justme

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Re: New Sound Devices MixPre II-series coming?
« Reply #62 on: September 02, 2019, 02:21:47 PM »
As the first generation MixPres are having a lot of buffer error when writing to many SD cards - I really hope SD could step up a bit and actually publish a true and verified list of confirmed cards working at highest rates and all channels and not put all burden on us buyers on an individual basis to invest in cards and do trial and error tests on our own.

I took as peek at their Approved Media which still only list 1 (one) card - their own which we have seen failing as well.
Nor have they updated their Audio Calculator for 32-bit fp.
https://www.sounddevices.com/mixpre-series-approved-media-list/

As the data rate for 32-bit FP will be some 30-ish percent higher than todays 24-bit fixed in the first gen recorders, the buffer errors and card problems might still be present in the II-series.
Unless they do have change their memory card management but then I really wish SD told us about it.
And also released a firmware upgrade for us with the first gen MixPres.


I'm a bit annoyed - SoundDevices are no slouch in the pro audio business but when it comes to memory card support and their listing of a single card when other competing manufacturers manage to list hundred of cards. I do feel they just don't care when they give us answers like this:



we’ve preemptively given customers the ability to choose with the guidance on what to look for in an SD card. Our approved media list has cards that we’ve tested in-house with our products. The SAM32 SD is the only one on the list as we’ve ensured that the card has been thoroughly tested. It has been optimized to work with the MixPre Series.

If they only manage to come up with ONE card that also needed to be optimised to work with the MixPre Series, they really should consider if they do need to change the approach.
« Last Edit: September 02, 2019, 02:29:47 PM by justme »

Offline goodcooker

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Re: New Sound Devices MixPre II-series coming?
« Reply #63 on: September 02, 2019, 03:03:43 PM »

not put all burden on us buyers on an individual basis to invest in cards and do trial and error tests on our own.

Many manufacturers of recorders have been guilty of this. Never thought someone like Sound Devices would let this be the case when their reputation is so highly regarded. They need to test some cards and get a list together.

I expect this kind of behavior out of some other manufacturers but not SD.
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Offline EmRR

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Re: New Sound Devices MixPre II-series coming?
« Reply #64 on: September 02, 2019, 03:26:20 PM »
Elsewhere, I've reported there are ways to overdrive the input circuitry of an F8n without hitting digital zero, in fact with line input trim set to -10, it squarewaves at about -5.5dBFS.

I don't know about the SD units.  A meaningful spec would be one that relates analog input headroom to 0dBFS, so one knows when 0dBFS is accidentally touched, how much headroom exists beyond it.  Theoretical 32 bit Float headroom is meaningless if the front end is clipped. 
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Offline Paul Isaacs

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Re: New Sound Devices MixPre II-series coming?
« Reply #65 on: September 02, 2019, 11:42:28 PM »
MixPre-II: maximum microphone input level before clipping is +12dBV.

Offline jerryfreak

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Re: New Sound Devices MixPre II-series coming?
« Reply #66 on: September 03, 2019, 12:38:48 AM »
specs on site say +14 dB on mic and +28 dB on line

Mic XLR: +14dBu (limiters on or off)
Line XLR: +28dBu (limiters on or off)
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Re: New Sound Devices MixPre II-series coming?
« Reply #67 on: September 03, 2019, 01:40:51 AM »
dBu is not dBV!


Thanks for the facts, Paul!
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Offline justink

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Re: New Sound Devices MixPre II-series coming?
« Reply #68 on: September 03, 2019, 05:40:19 AM »
MixPre-II: maximum microphone input level before clipping is +12dBV.

Can someone explain this like I’m 5?

Thanks.
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Offline jerryfreak

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Re: New Sound Devices MixPre II-series coming?
« Reply #69 on: September 03, 2019, 09:49:01 AM »
dBu is not dBV!


Thanks for the facts, Paul!
oops I missed that.
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Offline pohaku

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Re: New Sound Devices MixPre II-series coming?
« Reply #70 on: September 04, 2019, 11:47:27 AM »
Pricing of the new line is interesting.  The list price of the 3 is the same, but the 6 is $50 lower and the base 10 looks to be quite a bit lower than the first iteration 10t and a little less expensive than the 10m (but you can buy the musician add on if you want that functionality).

Of course all the first generation units are now on sale.
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Offline Amir

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Re: New Sound Devices MixPre II-series coming?
« Reply #71 on: September 04, 2019, 11:50:43 AM »
Pricing of the new line is interesting.  The list price of the 3 is the same, but the 6 is $50 lower and the base 10 looks to be quite a bit lower than the first iteration 10t and a little less expensive than the 10m (but you can buy the musician add on if you want that functionality).

Of course all the first generation units are now on sale.
And considering the fact that the 2nd-gen MixPre recorders come with the badly needed AC adapter, it indicates that SoundDevices really wants to be competitive.

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Re: New Sound Devices MixPre II-series coming?
« Reply #72 on: September 04, 2019, 12:49:36 PM »
Pricing of the new line is interesting.  The list price of the 3 is the same, but the 6 is $50 lower and the base 10 looks to be quite a bit lower than the first iteration 10t and a little less expensive than the 10m (but you can buy the musician add on if you want that functionality).

Of course all the first generation units are now on sale.
And considering the fact that the 2nd-gen MixPre recorders come with the badly needed AC adapter, it indicates that SoundDevices really wants to be competitive.

badly needed? a usb-c to AC power adaptor can be had for $20....
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Offline WiFiJeff

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Re: New Sound Devices MixPre II-series coming?
« Reply #73 on: September 04, 2019, 01:42:23 PM »
Just got a shipping notice from B&H on the mixpre-6 II, supposed to arrive tomorrow.

Jeff

Offline mjwin

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Re: New Sound Devices MixPre II-series coming?
« Reply #74 on: September 04, 2019, 04:46:05 PM »
dBu and dBV measurements
-----------------------------------

Can someone explain this like I’m 5?

It can get a bit confusing when some measurements are quoted in dBu & some in dBV, but that's life! However, it's simple to convert between them.

dB in any measurement is always a ratio between two values, and so one of these needs to be your reference point:

dBV is referenced to 1.0 Volts
dBu is referenced to 0.775 Volts

When you have 2 signals, a & b,    the difference in dB  = 20*log(a/b)

So to convert a measurement in dBV to dBu, just add 2.21dB.

Paul quoted the MixPre's max mic input level  as 12dBV.
Just add 2.21dB to get to Jerryfreak's "official"  spec of 14dBu (more or less - don't lose sleep over fractions of a dB!)

This works out to be 3.88V.   (BTW, original & MkII are identical spec here)


 

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