Topic: Digital Microphones and Their Advantages: Is This the Future?

[Scooter123]

The setup for sale in the yard sale, a Schoeps rig with a digital body, a CMD2 and a Sound Designs recorder made my mouth water, but more importantly, it left me to ponder whether this is the future of recording.  So I throw out this subject for general discussion, and offer these possible areas of banter:

--I assume no preamps are necessary
--Low phantom power requirements, only 10v, is there a battery box that might supply this?
--What recorders are currently available for the connection?
--What is the connection, I read it is an AES type connector?  What is that, like a SPDIF or Toslink? 
--I read this body can use regular Schoeps caps.  Does this include the mk4 and other caps?
--What are the advantages of digital mikes?
--Are the A/D converters as good as those in our typical bit boxes, Edirol/Rolland, Sound Designs, Tascam?
--Are there any other digital mikes out there that are being used, and with what rigs?

I'm fascinated by this apparent new leap in technology. 

[acidjack]

Interesting topic! 

I'll leave the more technical aspects to others, but I'd guess the main advantages are lower power requirements, and lower noise, as you pointed out. 

I think AES is an XLR-type digital connector, if I read my USBpre2 correctly.  I've never had anything that used it so haven't thought about it much. 

Neumann has a similar product line out there now, I believe.  Based on what BLee's rig came with cap-wise, the Schoeps one can use all existing Schoeps caps (he has 41s and 22s I believe)

My immediate view is that lots of people will be "against" this technology because it doesn't offer the natural, more analog sound we all know and love.  And I believe you're right that it would take away the ability we all have to "customize" the sound of our mics using different pres and A/D converters.  Of course, as with past technological leaps, these objections will likely be supplanted by a combination of convenience and by technological fixes that mimic what we liked about the old tech (for example, you can already mess around with tools in Izotope or Audition to mimic some of the sonic characteristics of different pres.  I know page has worked pretty hard, for example, to find software methods to mimic the sound of the Sax). 

At least insofar as BLee's rig is concerned, I think the most annoying thing would be having the bodies set to one sampling rate. But then, if you are running that type of rig, running out of disk space due to using 24/96 shouldn't be your main concern.

And while the iPad control is cool, not sure I want to add an $800, breakable, stealable iPad to an already high-cost mix.  OK, I mean, I would, but it is another thing to "carry around" if you go that route. 

I would imagine the transition will be slow as long as the cost differentials are high.  If anything, it might drive the price of analog bodies down a bit in the used market.

[hi and lo]

The AES type connection is a balanced, digital signal. It's better than unbalanced SPDIF connections for mostly the same reasons as analog balanced vs. unbalanced connections. Longer cables runs, better shielding, etc.
Neumann also makes a digital series of microphones and maybe others that I am unaware of.

You can use any Schoeps capsule intended for use with the Collette series including the MK4

Since I've never heard these mics in comparison to the standard analog versions, I couldn't possibly comment on their sound quality or really their advantages. I assume the main advantage is simply consistency in sonic quality, which could also be a disadvantage depending on how you look at it.

[hi and lo]

And while the iPad control is cool, not sure I want to add an $800, breakable, stealable iPad to an already high-cost mix.  OK, I mean, I would, but it is another thing to "carry around" if you go that route. 

It works with the iPhone too!

[acidjack]

And while the iPad control is cool, not sure I want to add an $800, breakable, stealable iPad to an already high-cost mix.  OK, I mean, I would, but it is another thing to "carry around" if you go that route. 

It works with the iPhone too!

Oh, good.  Now back to plotting that kidnapping I was planning so I can buy one of those rigs! 

[page]

--I assume no preamps are necessary

Correct, if you are staying digital post-body in the chain.

--Low phantom power requirements, only 10v, is there a battery box that might supply this?

I think they have a box if you're doing D>A for use with a system that won't accept the AES mic standard and it provides power (because your recorder/mixer doesn't).

--What recorders are currently available for the connection?

Nothing under $4k. This is all pimp stuff right now.

--What are the advantages of digital mikes?

Supposidly the noise floor of the mic>recorder is lower than mic>preamp>recorder and (paraphrasing the official schoeps blurb) "more low level-type details are preserved".

--Are the A/D converters as good as those in our typical bit boxes, Edirol/Rolland, Sound Designs, Tascam?

Supposidly they are optimized for these mics, as acidjack puts it;

My immediate view is that lots of people will be "against" this technology because it doesn't offer the natural, more analog sound we all know and love.  And I believe you're right that it would take away the ability we all have to "customize" the sound of our mics using different pres and A/D converters.  Of course, as with past technological leaps, these objections will likely be supplanted by a combination of convenience and by technological fixes that mimic what we liked about the old tech

correct, we see part of that now in the plugins for the neve1073 units that are being offered. While they are not exact, it's fairly close. Likewise, if you really have a good understanding of what a piece of gear does, you can work toward mimicing (and I use that term specifically instead of replicating) it's sound. Sometimes you can do well, sometimes you can't.

It will be different, not necessarily better or worse, but different. The optimized gain settings in terms of noise I think is one of the most intriguing things.

I think AES is an XLR-type digital connector

correct. This uses an offshoot of that technology, but the connector should be the same IIRC.

And while the iPad control is cool, not sure I want to add an $800, breakable, stealable iPad to an already high-cost mix.  OK, I mean, I would, but it is another thing to "carry around" if you go that route. 

It works with the iPhone too!

Oh, good.  Now back to plotting that kidnapping I was planning so I can buy one of those rigs! 

yep, that was the one thing I thought of. (iphone use). Some production companies might use it for wifi-control on a production set, but really, we would juse use teh ifons 

[H₂O]

The technology is not new and first appeared as early as the late 1980's - Go see:
http://www.hauptmikrofon.de/doc/WhitePaperE_AES42_v21_May2010.PDF


Their are different implementations of AES42 (mode 1 and mode 2) that have different requirements to make them work correctly.

Mode 1 mics - (i.e. the Schoeps CMD2's, Neumann (supports both 1 and 2)) you need an AD converter that resamples on the input.   No external control required.  Easier to adapt to AES3 connectors

Mode 2 mics - (i.e. Neumann, etc) Can sync to an external clock, but from what I have read may need some external control on the AES42. Need a processor/controller between the mics and a recorder (i.e. Neumann DMI-2 Portable)
http://www.neumann.com/?lang=en&id=current_microphones&cid=kmd_dmi-2portable

Other items that make using digital mics a challenge:
 - single channel mics (i.e. Schoeps CMD, Neumann, etc) only one of the two   channels on the AES42 connection will have signal - so to do stereo you   need 2 AES42 connectors, or 4 channel you need 4 AES42 connectors
 - 10V Phantom requires 250ma of power or is rated at up to 2.5 W whereas 48V phantom is rate at 10mA or 0.48W - so digital mics may require up to 5 times the amount of power (obviously with less in the chain then the power is taken out of those components)

Two recorders that support AES42 Mode 1 natively with 10V Phantom - SD 788t (4 AES3/42 connectors and Aeta 4Minx (2 AES3/42 connectors) - both retail in the $6K range

[hi and lo]

Mode 1 mics - (i.e. the Schoeps CMD2's, Neumann (supports both 1 and 2)) you need an AD converter that resamples on the input.   No external control required.  Easier to adapt to AES3 connectors

Resampling on the digital input? How could this possibly be a good thing? I would have hoped each digital microphone would lock to the recorders sample rate.

[H₂O]

I don't think resampling is as much of an issue here as you are dealing with very high end gear.    Note that most all the ultra high end recorders (i.e. Zacomm, Nagra (don't know for sure), AATON, etc) all resample on there digital inputs.

If you don't resample you have to have 1 master clock and standard AES (that AES42 mode 1 is modeled after - assuming for compatibility sake) is one way so the mics would need a Word Clock in (or you could lock on to one digitial mic (if you where running just one digital mic)). 

Mode 2 AES42 is bi directional (one cable handles control and clock to the mic and digital signal back from the mic)

[H₂O]

Also note that running Active cables with a digital Mic (cmd2) as with tube mics (i.e. m222) although is supported by Schoeps slightly defeats the purpose of digital mics as it adds an Analog FET and attenuator into the signal path.

Berhnard gave me a hard time of running actives with my M222's.

[H₂O]

Probably the cheapest stereo setup is the Neumann KM184 D's and a Neumann DMI-2 Portable at about $4.2K total or so.

[Gutbucket]

Yeah, I've long thought a standard Ethernet jack and good old cat5 cabling with Power Over Ethernet would be the obvious way to go for digital mics(substitute hardened/industrialized versions of LAN cableling & jacks for more pro applications.. Neutrik makes some those I think, plenty of other manufacturers do for industral automation LANs).  It works for prosound PA applications with large numbers of channels using CobraNet for example, and there are other similar competing digital audio + control networks that use Ethernet hardware.

Substituting USB for Ethernet could work pretty much the same way I'd think.

In a similar vein, I wonder why we've been offered active digital input monitors and controllers for several years now that are digitally linked and controlled via an Ethernet link, but none I have seen distribute digital audio over the same cat 5 link. See the JBL stuff , Dynaudio, etc.  They always require an individual audio input to each speaker in the setup via analog inputs or AES/SPDIF connectors on every speaker, in addition to the control link of daisy chained cat5.  If the big PA guys can do 32 channels or more of digital audio over cat5, why not the studio monitor guys?

[H₂O]

I don't think USB is robust enough for this purpose.   I would think you would need some sort of networking topology to truely make this work (I am thinking something like VoIP enabled network to replace all the cables on stage for example)

I know mLAN was an idea by yamaha about 10 years ago so I don't know if this would ever catch on.

A network topology could add security, resiliency, error correction, etc with everything in the digital realm.

[rastasean]

Just please, please don't put the microphones online and/or make them wireless... some genius decided it would be a good idea to make insulin pumps be wireless and its been hacked.
http://www.technewsworld.com/story/73020.html
http://blog.mhhealthsearch.com/2011/09/can-wireless-medical-devices-be-hacked/

[Gutbucket]

Wireless would be cool.  Or completely independant all-in-one mics that sync and SRC reclock when uploaded.  Scatter them around and collect them all afterwards.

[Brian Skalinder]

some genius decided it would be a good idea to make insulin pumps be wireless and its been hacked.

I suspect the benefits of wireless personal medical devices vastly outweight the miniscule risk of someone actually hacking the devices.

And wireless mics would be cool.

[John Willett]

The setup for sale in the yard sale, a Schoeps rig with a digital body, a CMD2 and a Sound Designs recorder made my mouth water, but more importantly, it left me to ponder whether this is the future of recording.  So I throw out this subject for general discussion, and offer these possible areas of banter:

--I assume no preamps are necessary
--Low phantom power requirements, only 10v, is there a battery box that might supply this?
--What recorders are currently available for the connection?
--What is the connection, I read it is an AES type connector?  What is that, like a SPDIF or Toslink? 
--I read this body can use regular Schoeps caps.  Does this include the mk4 and other caps?
--What are the advantages of digital mikes?
--Are the A/D converters as good as those in our typical bit boxes, Edirol/Rolland, Sound Designs, Tascam?
--Are there any other digital mikes out there that are being used, and with what rigs?

I'm fascinated by this apparent new leap in technology.

--I assume no pre-amps are necessary
Correct

--Low phantom power requirements, only 10v, is there a battery box that might supply this?
Low voltage but 250mA (48V phantom only specs 10mA)
Both Neumann and Schoeps provide connection kits / power adaptors that convert AES42 into AES3 and provide power for the mic.

--What recorders are currently available for the connection?
Sound Devices 788T and AETA 4MinX
You can use other recorders with the Neumann DMI-2 or DMI-2P interfaces, or the Connection Kits from Neumann or Schoeps
I use a Nagra VI and Neumann DMI-2P

--What is the connection, I read it is an AES type connector?  What is that, like a SPDIF or Toslink?
The standard is AES42 - basically AES3 with extras.
The connector is a standard 3-pin XLR - NB: NOT S-PDIF or Toslink
 
--I read this body can use regular Schoeps caps.  Does this include the mk4 and other caps?
It can use all the Schoeps heads and accessories - over 100 items

--What are the advantages of digital mikes?
Send me a PM with your e-mail address and I'll send you pdfs of my two AES papers and a few other things - far too much to write here.

--Are the A/D converters as good as those in our typical bit boxes, Edirol/Rolland, Sound Designs, Tascam?
Better than those you mention

--Are there any other digital mikes out there that are being used, and with what rigs?
There are over 40 different digital mic. options.  Neumann, Sennheiser and Gefell all make AES42 digital microphones as well as Schoeps (Neumann were the first).

I have several digital mics. - I have a pair of Neumann KM-D that I can use with either KK183-D or KK131-D heads.  I also have a Sennheiser MZD8000 that I can use with an MKH 8020 or MKH 8040 stereo pair.

I have two Neumann DMI-2P interfaces that I use with my Nagra VI for recording 4 digital  mics at once.

I have been using and recording with digital mics since 2006.

[OOK]

Here is the portable unit from Neumann....looks pretty straight forward...it operates on 10-18volts....

http://www.neumann.com/?lang=en&id=current_accessories&cid=db_current_accessories&dbid=193

[John Willett]

The technology is not new and first appeared as early as the late 1980's - Go see:
http://www.hauptmikrofon.de/doc/WhitePaperE_AES42_v21_May2010.PDF


Their are different implementations of AES42 (mode 1 and mode 2) that have different requirements to make them work correctly.

Mode 1 mics - (i.e. the Schoeps CMD2's, Neumann (supports both 1 and 2)) you need an AD converter that resamples on the input.   No external control required.  Easier to adapt to AES3 connectors

Mode 2 mics - (i.e. Neumann, etc) Can sync to an external clock, but from what I have read may need some external control on the AES42. Need a processor/controller between the mics and a recorder (i.e. Neumann DMI-2 Portable)
http://www.neumann.com/?lang=en&id=current_microphones&cid=kmd_dmi-2portable

Other items that make using digital mics a challenge:
 - single channel mics (i.e. Schoeps CMD, Neumann, etc) only one of the two   channels on the AES42 connection will have signal - so to do stereo you   need 2 AES42 connectors, or 4 channel you need 4 AES42 connectors
 - 10V Phantom requires 250ma of power or is rated at up to 2.5 W whereas 48V phantom is rate at 10mA or 0.48W - so digital mics may require up to 5 times the amount of power (obviously with less in the chain then the power is taken out of those components)

Two recorders that support AES42 Mode 1 natively with 10V Phantom - SD 788t (4 AES3/42 connectors and Aeta 4Minx (2 AES3/42 connectors) - both retail in the $6K range

Mostly correct - but I would say Mode-2 is better than Mode-1.

With Mode-1 you have to have a sample rate converter to clock.  You say "no external control required" - wrong - a SRC is external control - plus - lots of connection kits and an SRC is far more expensive than a Neumann or RME interface that will clock all the Mode-2 mics.

Mode-2 can work Mode-1 or Mode-2.

If you only have a single mic. (or a stereo pair if you use the Sennheiser MZD800 - which you forgot to mention), all you need is a simple connection kit and no SRC.

I have been using AES42 digital mics for 5 years now and have also written two AES papers on the subject (which I am happy to e-mail to anyone who sends me a PM with an e-mail address).  I also have a copy of an article that describes a recording at Abbey Road where all the mics were digital.

In addition, I wrote up my first recording sessions with digital mics HERE.

I hope this helps.

[John Willett]

Probably the cheapest stereo setup is the Neumann KM184 D's and a Neumann DMI-2 Portable at about $4.2K total or so.

No - I think the cheapest stereo set-up is a Sennheiser MZD 8000 + MKH 8040 (or 8020) Stereoset + Neumann Connection Kit

This is my rig with the MKH 8020 stereoset:



Click the picture for full size

[John Willett]

This is my rig - Nagra VI with two Neumann DMI-2P:



Click the picture for full size

Both the DMI-2P are powered via the Hirose connectors of the Nagra VI.

[H₂O]

I was not aware of the Senheiser mic

Can the DMI-2 support Mode 1 mics?

[bryonsos]

John - those are some sexy rig pics! You might have convinced me to start saving my pennies for a digital rig    Just wondering, how would you rate the battery life of your digital Neumanns vs. analogue ones?

BTW- I've been patiently monitoring this thread, waiting for you to chime in. Great input and insights!

Cheers

[John Willett]

I was not aware of the Senheiser mic

Can the DMI-2 support Mode 1 mics?

Yes - but using Mode-1 you will also need a SRC after the DMI-2.

But using the DMI-2 gives access to the Neumann RCS software control.

The RME unit has built-in SRC as well as Mode-2 control, so you can mix Mode-1 and Mode-2 mics if you wish.

[John Willett]

John - those are some sexy rig pics! You might have convinced me to start saving my pennies for a digital rig    Just wondering, how would you rate the battery life of your digital Neumanns vs. analogue ones?

BTW- I've been patiently monitoring this thread, waiting for you to chime in. Great input and insights!

Cheers

I get about 15 hours from a fully charged battery on my Nagra VI - I guess that powering two DMI-2P it will probably go down to about 7 or 8 hours.  I have never had to test it to destruction yet.

As I said earlier - I'm happy to send PDFs of my papers and a couple of other things I have on AES42 mics to anyone who PMs me with an e-mail address.

[hi and lo]

--Are the A/D converters as good as those in our typical bit boxes, Edirol/Rolland, Sound Designs, Tascam?
Better than those you mention

Forgive me if this is covered in your AES articles, but I would love it if you could elaborate more on this.

[H₂O]

Maybe Schoeps will come out with a VSTD someday

[bryonsos]

John - those are some sexy rig pics! You might have convinced me to start saving my pennies for a digital rig    Just wondering, how would you rate the battery life of your digital Neumanns vs. analogue ones?

BTW- I've been patiently monitoring this thread, waiting for you to chime in. Great input and insights!

Cheers

I get about 15 hours from a fully charged battery on my Nagra VI - I guess that powering two DMI-2P it will probably go down to about 7 or 8 hours.  I have never had to test it to destruction yet.

As I said earlier - I'm happy to send PDFs of my papers and a couple of other things I have on AES42 mics to anyone who PMs me with an e-mail address.

Damn! 15 OR 7 hours sounds pretty good to me. [sound of bryonsos counting pennies] One, two, three...

[page]

--Are there any other digital mikes out there that are being used, and with what rigs?

There are over 40 different digital mic. options.  Neumann, Sennheiser and Gefell all make AES42 digital microphones as well as Schoeps (Neumann were the first).

Have any literature on that? Their site has traditionally been tough for me (as someone who has trouble with just english, let alone other languages), so it may be there and I've just missed it in the German language section/materials.

[John Willett]

--Are the A/D converters as good as those in our typical bit boxes, Edirol/Rolland, Sound Designs, Tascam?
Better than those you mention

Forgive me if this is covered in your AES articles, but I would love it if you could elaborate more on this.

The ADC is matched to the microphone capsule.

The Neumann one is 28-bits (NB: not 24) that uses two converters in a patented way to get true 28-bits.  AES42 specifies 24-bits, but the Neumann is 28-bit in the mic.

The Sennheiser one was compared to the best ADCs on the market and the consensus of opinion was that it came out equal.

[John Willett]

John - those are some sexy rig pics! You might have convinced me to start saving my pennies for a digital rig    Just wondering, how would you rate the battery life of your digital Neumanns vs. analogue ones?

BTW- I've been patiently monitoring this thread, waiting for you to chime in. Great input and insights!

Cheers

I get about 15 hours from a fully charged battery on my Nagra VI - I guess that powering two DMI-2P it will probably go down to about 7 or 8 hours.  I have never had to test it to destruction yet.

As I said earlier - I'm happy to send PDFs of my papers and a couple of other things I have on AES42 mics to anyone who PMs me with an e-mail address.

Damn! 15 OR 7 hours sounds pretty good to me. [sound of bryonsos counting pennies] One, two, three...

I should say that I have the high capacity battery option with my Nagra VI, not the standard one.

[John Willett]

--Are there any other digital mikes out there that are being used, and with what rigs?

There are over 40 different digital mic. options.  Neumann, Sennheiser and Gefell all make AES42 digital microphones as well as Schoeps (Neumann were the first).

Have any literature on that? Their site has traditionally been tough for me (as someone who has trouble with just english, let alone other languages), so it may be there and I've just missed it in the German language section/materials.

The Gefell is the MV230 measurement mic. with interchangeable heads.

PDF info is HERE.

[John Willett]

The Neumann one is 28-bits (NB: not 24) that uses two converters in a patented way to get true 28-bits.  AES42 specifies 24-bits, but the Neumann is 28-bit in the mic.

What mic has >160dB unweighted dynamic range?  And as you noted, AES is only a 24-bit protocol, but I still don't think 138dB dynamic range is achieved by a mic.  Maybe 130dB if we allow for some additional headroom above the max SPL spec.

TI markets a DAC with 32 bit output, never mind that it only has 120dB dynamic range . . .

It is nice to have dynamic range in the ADC wider than the mic because then the gain into the ADC may be fixed.  That still fits pretty comfortably inside 24 bit.

I think Neumann work on the premise of 130dB dynamic range.

[John Willett]

Have a link to the patent?  I'm curious what they did.

The easiest way to increase dynamic range is preemphasis/deemphasis, which you could implement the de-emphasis in DSP in the microphone so it's transparent to the user.  You can stack multiple converters to realize a 3dB improvement each time you double the channel count, but that doesn't work unless the dominant noise source in each channel is independent.  If the dominant noise source in two channels is common-mode you can feed them a differential signal.  I don't think either of the latter would be the case in a quality converter though.

ah, I see they used compansion by sampling the control voltage.  Clever enough I suppose although emphasis is a lot simpler, saving the need for a second converter channel.

It's in a paper by Stephan Peus - you can download the pdf HERE.

[DSatz]

All currently available digital condenser microphones are hybrids: They have the same kind of analog front-end circuitry as analog condenser microphones, but this is then followed by an A/D converter rather than a traditional analog output stage. If people would get that basic fact straight in their minds, it would immediately dispel two common, incorrect assumptions:

• that digital recordings made with digital microphones have any cause to sound different from digital recordings made with analog microphones, and:
• that recordings made with digital microphones will have wider dynamic range than recordings made with analog microphones.

Of course the analog first stage and the input of the A/D can (and should) be designed together and optimized for one another. But even with theoretically "perfect" matching, their combined performance would only equal, and could not surpass, that of an analog microphone that is optimally matched to an external preamp and A/D converter.

There's no special exemption from the laws of physics, in other words, and this fact is borne out by the noise figures of the available "digital" microphones from Neumann, Schoeps and others. The noise floor is still set by the 1/f noise of the capsule at low frequencies, and by the first analog stage at mid and high frequencies--exactly as in the analog microphones of the same manufacturers. And then the built-in A/D adds a little of its own noise, as it must. Don't be fooled by the number of "marketing bits"--look at the distance from the noise floor to the maximum level, i.e. the actual total dynamic range. It's no greater than the best analog microphone / preamp / A-to-D converter combinations already offer.

The main advantages of "digital" microphones are of two kinds: operational (simplicity of connection, plus the sound quality isn't subject to RFI or analog cable losses), or else they are useful features based on digital signal processing, e.g. the Schoeps "SuperCMIT" shotgun microphone, which uses a rear-facing second capsule and DSP to achieve a narrower, more even pickup pattern than any other shotgun microphone and to maintain that narrow pattern down to far lower frequencies than any other shotgun.

--best regards

[page]

The Gefell is the MV230 measurement mic. with interchangeable heads.

PDF info is HERE.

sexy

thanks!

[notlance]

The main advantages of "digital" microphones are of two kinds: operational (simplicity of connection, plus the sound quality isn't subject to RFI or analog cable losses)....

That is why I could never get too excited about "digital" mics; they only solve problems I don't have since I seldom encounter RFI or analog cable losses.  And old fashioned analog mics are simple enough to connect, I figure.  A "digital" mic at the current state of the art just seems to be moving the ADC from one end of the cable to the other.

[DSatz]

notlance, that is well put and a thoroughly understandable viewpoint. It's not too far from my own opinion, although I have to admit that all other things being equal, from an engineering standpoint the A/D converter does belong as close to the microphone capsule as possible.

Someone earlier in this thread hoped that Schoeps would come out with a two-channel digital amplifier that would allow a pair of their Colette capsules to be connected. That would be my preferred approach as well, since it would eliminate the synchronization problem and obviate the need for sampling rate conversion at the recorder's inputs (not that I'm afraid of a good, modern SRC, but I just don't happen to own one!). I've certainly suggested it to them.

However, even if that were available, I wouldn't spring for it unless it had greater capabilities than existing, analog microphones have. And I just don't see that yet, at least for the kinds of recording I am usually involved in. I think that we are only in the early days of DSP for audio, though, and am hoping to be pleasantly surprised some day.

--best regards

[John Willett]

The main advantages of "digital" microphones are of two kinds: operational (simplicity of connection, plus the sound quality isn't subject to RFI or analog cable losses)....

That is why I could never get too excited about "digital" mics; they only solve problems I don't have since I seldom encounter RFI or analog cable losses.  And old fashioned analog mics are simple enough to connect, I figure.  A "digital" mic at the current state of the art just seems to be moving the ADC from one end of the cable to the other.

This is what I thought until I started to use digital microphones.

Although what DSatz says is correct there are things that he did not say.

With an analogue mic. the signal travels along a cable that can pick up RF interference and noise - it then goes into a mic. pre. that adds noise of its own and amplifies the signal.  You have to allow headroom for peaks, so you back off a bit to allow for this.  It comes out of here on another cable and goes to the ADC.  Again, you have to back-off the ADC to allow headroom for peaks.

The advantages of digital mics are not in the specs compared to an analogue mic., but the fact that you get a much better s/n ratio because you don't have to all the backing off you have to do with analogue and having it in digits from the mic. keeps the signal immune from RF interference and the other noise added by an analogue system.

RF interference may not be obvious, but can be there as an increase in the noise floor.

This is explained better in the paper by Stephan Peus and in my AES papers (send me a PM with an e-mail address if you want to read them - I'll send them by return).

When I first started recording with digital mics I kept thinking we had not recorded anything - until the music started - because the noise floor was so low.

What I have been sending to those who asked are: my two AES papers, an article I wrote for LineUp magazine on my first recording session with AES42 mics, another article from LineUp (not by me) on the Abbey Road digital sessions and the White Paper that has been mentioned.  Stephan Peus's paper is downloadable from the Neumann website, but I can include this as well - so, 6 x PDFs in all, if you want them.

[DSatz]

John, this comes down to elementary issues of logic and of making fair comparisons. If a certain headroom must be allowed for peaks, then use the same yardstick (or metre stick if you will) for the digital microphone as for the chain consisting of analog microphone + preamp + A/D converter. It is misleading to compare only the worst-case analog microphone / preamp / converter arrangements with only the best-case digital microphone arrangements, e.g. by setting the digital microphone's gain for the particular SPL of the event which one is recording, while pretending that similar adjustments somehow cannot be made in a recording with analog microphones.

Say a digital microphone is designed so that full-scale digital output occurs at the onset of audible distortion in its analog first stage (e.g. somewhat above 130 dB SPL perhaps). If one never adjusts that microphone's gain via its interface/controller, its signals will probably fail to use the uppermost 15 or even 20 dB in many of the recordings that one makes with it. Thus one would prefer to increase the gain of the digital microphone somewhat, via its interface/controller. But doing so has exactly the same effects on dynamic range as raising the gain of the analog mike preamp or the input to an outboard A/D controller. Digital gain is not noise-free, nor does it magically evade headroom limits.

--best regards

[F.O.Bean]

I don't know the tech aspects of digi mics, but I don't see them becoming the "standard" for MANY YEARS TO COME Besides, we can customize a sound we want w/ analog preamps and ADC's/Recorders

[John Willett]

John, this comes down to elementary issues of logic and of making fair comparisons. If a certain headroom must be allowed for peaks, then use the same yardstick (or metre stick if you will) for the digital microphone as for the chain consisting of analog microphone + preamp + A/D converter. It is misleading to compare only the worst-case analog microphone / preamp / converter arrangements with only the best-case digital microphone arrangements, e.g. by setting the digital microphone's gain for the particular SPL of the event which one is recording, while pretending that similar adjustments somehow cannot be made in a recording with analog microphones.

Say a digital microphone is designed so that full-scale digital output occurs at the onset of audible distortion in its analog first stage (e.g. somewhat above 130 dB SPL perhaps). If one never adjusts that microphone's gain via its interface/controller, its signals will probably fail to use the uppermost 15 or even 20 dB in many of the recordings that one makes with it. Thus one would prefer to increase the gain of the digital microphone somewhat, via its interface/controller. But doing so has exactly the same effects on dynamic range as raising the gain of the analog mike preamp or the input to an outboard A/D controller. Digital gain is not noise-free, nor does it magically evade headroom limits.

--best regards

An AES42 digital mic. has very little analogue in it at all - basically the capsule and an fet and not much else.  This is then fed directly into the DAC.

There is no need to adjust the gain at all as it it digital gain and will not affect the quality; though I do adjust the gain as it makes monitoring easier.

But, every bit of analogue circuitry adds its own little bit of noise and the more there is in the analogue path the more noise there is - OK, on a good system this can be very small, but it's still there.

I am not saying that digital mics are perfect and analogue mics are rubbish - there is room for both and will be for many years.

But digital microphones have great advantages and the more I use them the more I like them.

I have been using AES42 digital microphones in anger for 5 years now, so I am speaking as someone who uses them, has read up on them, had long discussions with the designers of them (Neumann, Schoeps, Sennheiser and Gefell) and written papers on them (and before my papers were published they were sent to Schoeps, Neumann, Sennheiser and Gefell for review so they could make comments/corrections before I presented them).

People tend to forget all the little bits in the analogue chain that slowly decrease the specs of an analogue mic. that does not happen with an AES42 mic.

And, yes, I know it was you who translated the White Paper that has been mentioned previously - it's a good paper, though I don't agree with all that is said in it.

[John Willett]

I don't know the tech aspects of digi mics, but I don't see them becoming the "standard" for MANY YEARS TO COME Besides, we can customize a sound we want w/ analog preamps and ADC's/Recorders

Probably quite right.

But there are many advantages in digital microphones over analogue ones that, for some applications, make them a better choice.

And you can customise a sound in a DAW if you want to.

Personally I see AES42 digital mics will probably mainly be used in the classical arena where you are attempting to capture a performance as perfectly as possible.

Though there is a PA company in France that is all digital from the mics to the power amplifiers.  They find that the sound-check time is drastically reduced and the hiss and noise out of the loudspeakers is so quiet that they forget the system is on; which happened when they went for a pre-show meal at the café round the corner and left the system on.  Someone started up a motorbike by the stage and there was a very loud rendering of this sound through the system.

[SmokinJoe]

Correct me if I'm wrong... a 24bit A/D can basically break an analog signal into 2^24 increments across it's full range.  With the A/D in the mic, if full scale is 130db and you are recording quiet acoustic material than only goes to 80db, you are failing to optimize a big portion of your bandwidth.  Digital gain is like digital zoom on a camera... it makes it seem closer (louder) but it doesn't enhance resolution.  If you recording is all at -50 on the meter and you have to add that all in post, that's digital gain too.  With an analog preamp chain you can better optimize the full range coming into your A/D.

Now if you can set something back at the control box/recorder to tell the FET front-end to increase analog gain before the mic's A/D, that's completely different, but I didn't get the impression it works that way.

If you tell me that resolution issue is peanuts compared to the overall increase in signal accuracy of a much shorter analog chain, I can't argue with you on that point.

[John Willett]

Correct me if I'm wrong... a 24bit A/D can basically break an analog signal into 2^24 increments across it's full range.  With the A/D in the mic, if full scale is 130db and you are recording quiet acoustic material than only goes to 80db, you are failing to optimize a big portion of your bandwidth.  Digital gain is like digital zoom on a camera... it makes it seem closer (louder) but it doesn't enhance resolution.  If you recording is all at -50 on the meter and you have to add that all in post, that's digital gain too.  With an analog preamp chain you can better optimize the full range coming into your A/D.

Now if you can set something back at the control box/recorder to tell the FET front-end to increase analog gain before the mic's A/D, that's completely different, but I didn't get the impression it works that way.

If you tell me that resolution issue is peanuts compared to the overall increase in signal accuracy of a much shorter analog chain, I can't argue with you on that point.

There is virtually no analogue at all in an AES42 digital mic.  -  you have the capsule and the FET ad very little else.  This is fed directly to a dedicated ADC that is matched to the capsule.  The capsule is, in effect, driving the ADC directly.

There is no line driver stage in the mic..  Everything is taken away and the capsule goes directly to an ADC that is designed and matched to the capsule - in the case of Neumann it's a 28-bit ADC.

I know it can be difficult to get your head around, but you need to stop thinking like it's a normal analogue microphone.

As I said, I am very happy to send PDFs of info I have to anyone here who sends me a PM with an e-mail address - and most of these PDFs are very readable and not filled with difficult to understand technical stuff.

[Gutbucket]

New applied technology often starts with the top end and works its way to the mainstream, which reflects the current crop of digital mics.  Yet what I'm hopeing to see is a different emphasis, with development focusing on operational simplification and cost reduction for mid-range users.   Perhaps sacrificing some of the potential gain in ultimate sound quality for the top dog users, but probably not sacrificing any 'real world' quality for most users while making usage simple and much of the gear commodity computer type stuff.

We have cheap digital USB mics at the bottom end, and we have no compromize digital solutions like those discussed in this thread. But I'm talking about targeting the vast market of mid range gear users. 

Run some cat-5 to the mics, plug that into a standard ethernet switch along with a bit-bucket.  Substitute wireless LANs for cat-5 if you want.  Control it with smart phone apps, a tablet, computer, dedicated recorder or whatever you like.  Multichanel as simple as substituting a bigger switch.  Same for running a snake- its a simple star topograpy network. Fix the dynamic range of the mics at something reasonable that encompases 90% of what most people record with reasonable quality gear and optimize the useful bits of the 24bit ADC to take best advantage of that.  Buffer the output of the mic ADCs with memory and SRC as required.  Throw away the unused bits and don't worry about it (we already throw them away anyway, either from the top or the bottom).  If that is too simplified or dynamically compromized, put a single high/low gain switch on the mics (or in the app).  Users that need to optimize super high or low SPL capability or the absolute ulitmate quallity can stay analog or buy the current digital mics that use more specialized, adjustable and costly gear, but for most users cost goes way down by using commodity digital network gear except the control sofware, probably a specialized network layer and the most important part- the mic/ADCs themselves.

I have unintentionally made recordings of classical material which peaked 30dB below FS and did not suffer from raising the level afterwards.  Noise floor of the room was still above that of my analog chain.  I'd be more than happy selecting between a single high/low gain range for everything I record and never have to worry about further optimizing levels.  Fancy audio gear is cool in itself and we all dig it, but when it comes down to making recordings, I'm more than happy to give that up to simply concentrate on mic placement and arrangement which none of this changes. 

This will not satisfy a truely professional user and I don't mean it to.  A vast amount of audio gear is marketed to a 'prosumer' level where this applies perfectly.  Like many here at TS I'm no pro, although I greatly respect those who are.

[John Willett]

New applied technology often starts with the top end and works its way to the mainstream, which reflects the current crop of digital mics.  Yet what I'm hopeing to see is a different emphasis, with development focusing on operational simplification and cost reduction for mid-range users.   Perhaps sacrificing some of the potential gain in ultimate sound quality for the top dog users, but probably not sacrificing any 'real world' quality for most users while making usage simple and much of the gear commodity computer type stuff.

We have cheap digital USB mics at the bottom end, and we have no compromize digital solutions like those discussed in this thread. But I'm talking about targeting the vast market of mid range gear users. 

The first AES42 mic. was the Neumann D-01 which incorporated almost everything in the spec. and was certainly not cheap.

However, Schoeps quickly came out with their module that you could use with any of their collette series and Neumann came out later with the KM-D series.  Both these are mid range.

You can certainly run an AES42 mic. down CAT5 and I have seen the adaptors tp do this - but you have to convert it back to XLR at the other end.

Yes, it would be nice if more equipment would have AES42 inputs as standard, so you would not have to have an interface.  Only the SD 788T and AETA 4MinX do this at the moment; but mixers are starting to include them and there is a PC card with AES42 available.

Yes, I wish more microphone manufacturers would do an AES42 mic. - Gefell have already done one, lets hope they do more.  And now DPA have their new series with interchangeable heads and modules I am hoping that they will do an AES42 module as well.  After all, a mic. manufacturer only has to do a single module with detachable heads to make a whole series of microphones.

Digital mics are not difficult, and in fact can be cheaper as you don't have to purchase an analogue mic.pre-amp.

[rastasean]

Digital mics are not difficult, and in fact can be cheaper as you don't have to purchase an analogue mic.pre-amp.

Digital mics may not be expensive when factoring in pre-amps but if you're a recording studio with $50,000 or more in equipment and already very high end analogue microphones, you probably won't be switching until there is a need.
Now if you're some Hollywood big shot, going all digital is worth every penny then you would be able to afford the migration.

How are digital microphones matched with one another, in the same manner of analogue?

[John Willett]

Digital mics are not difficult, and in fact can be cheaper as you don't have to purchase an analogue mic.pre-amp.

Digital mics may not be expensive when factoring in pre-amps but if you're a recording studio with $50,000 or more in equipment and already very high end analogue microphones, you probably won't be switching until there is a need.
Now if you're some Hollywood big shot, going all digital is worth every penny then you would be able to afford the migration.

Agreed - though you would not necessarily need to switch, you can just add AES42 microphones to the mic. store and use as needed; just like any other mics.

How are digital microphones matched with one another, in the same manner of analogue?

I would assume the capsules would be matched in the same manner.

[hi and lo]

Digital mics are a big factor in that but I continue to be unimpressed with AES as a standard--at least as a sole solution.  It still requires a special box at the other end and allows use of too much power.  Gimme a mic that automatically switches between AES and analog and I might get a bit more interested . . . actually, maybe I should go and do that . . . make it automatically switch between AES, analog, USB, and wireless . . . mmmmm, now we are talking 

Yes. You should do this!

Sorry AKG/Gefell active folks.. I know you probably just a minor heart attack. 

[John Willett]

I continue to be unimpressed with AES as a standard--at least as a sole solution.  It still requires a special box at the other end and allows use of too much power. 

A special box is not necessarily required - this is only an interim solution until more manufacturers include it as standard.

I list all the products that are currently available - microphones and receiving equipment - in my papers.

It does not allow "too much power" at all.  The power requirements in AES42 were a compromise as to what the microphone manufacturers wanted and the console manufacturers were prepared to send.  After all, the power is for digital circuitry in the microphone that requires more power than a simple circuit in an analogue mic..

[Gutbucket]

What happens when your mic automatically goes looking to join your wi-fi network..

This big picture view is an extension of exactly what I'm getting at.  Eliminating all the special boxes, including AES standardized hardware mixers and recorders.  Not a solution for everyone, but for certainly a good fit for many.   Once it's digital (and synced/resynced) the downstream equipment need be nothing more than commodity networking and storage gear.  Bits is bits (+ sync).  Only the mics and software need to be 'audio specific' gear.

I'm looking forward to reading your papers when I get a chance John, thanks.  Still, I'm personally intersted in approaching the whole thing from Jon's (Mshillarious) perspective, rather than from a traditional 'installed base of pro customers and gear' angle.  More revolutionary than evolutionary.

I'll be at a music festival next weekend that includes a 'silent DJ' tent, with no PA where everyone wears wireless headphones (and in some incarnations can select between two different yet simultaneous live broadcast streams).  I've read about this and will stick my head in at some point to check it out.  It is only a few steps removed from the future live performance scenario Jon paints above.

[Brian E.]

this thread is sexy.

[F.O.Bean]

know you probably just a minor heart attack. 

They have already died waiting . . . 

With the low rate of implementation of AES42 I doubt I'd move many.  People will ask for SPDIF instead, or try it with an AES3 input, and then I'd have to explain why that won't work.  So I will probably stick with USB.


Re: power for an ADC, no way 2.5W is required.  Let's say PCM4202 + DIT4096 for a solution; that's 160mW plus we need an analog front-end, say AD8606 for another 10mW, plus capsule FET at another 10mW.   Plus an oscillator, another 100mW.  Total power budget, 280mW.  Use a charge pump to drop to 5V so there are no losses from linear regulation; I lose 85mW in the supply resistors for 365mW total.  So I still have a system that is only 77% efficient, which bothers me because with a dedicated power pin that would be better than 90%.  And as the power consumption of the system increases the efficiency drops further.

So I'm sorry, but 2.5W is an enormous amount of power in the digital portable world.  TI posts Youtubes of their MCUs running on batteries made from fruit (I'm not making this up), but AES thinks we need digital mics consuming enough power to heat a tube.  I don't get it.  Heck, P48 is too much power and it's time somebody recognized that.  The better brands often run on 11V-52V at low (and constant) current so this is hardly a great technical barrier.  Scrap it and mandate P12.

But I digress . . .

And AES42 does requires a special box, whether that box is a dedicated outboard receiver or an interface with an AES42 input.  My point is all boxes are going away except for the box that is the data storage and processing tool, and those aren't likely to support unique digital audio connectors especially if they require 10V.  As DSatz argues, it's a bit underwhelming because nothing physical has changed:  mic, cable, box, recorder.  It's a bit technically better, yes, but not dramatically improved enough to make it mandatory.

The audio industry ought to be looking at methods to make existing common protocols and connectors functional for professional audio.  I would guess fewer manufacturers will support AES42, not more, as more universal solutions replace it.

Thanks for the great read! I couldnt agree with yoiu anymore

[H₂O]

I do not think USB is suited for professional use outside of a simple audio interface.  USB is much larger platform then just audio and is design simply as a way to interface most anything to a single computer - although it supports isochronous traffic it is not designed to handle many streams from different sources (USB devices) and is a flat bus (it is not switched).  I don't see it feasible to run a recording studio off a USB hub.  Some limitations of USB:
 - non-locking connector
 - No way to get sample level synchronization (clock sync)
 - limited prioritization
 - requires external control (i.e. CPU intensive)
 - does not scale very well (although it supports 127 or more devices the bus will get congested quickly the more devices you add)

I would think for a multichannel audio you would need a more robust networked protocol that supports prioritization, with a queueing switched infrastructure (such as QoS enabled IP network) - regardless I think this is a big leap from the discussion of digital microphones.

Diaphragm > FET > AD > Digital Audio IO Bus (I2S is an example) > (optional: AES/SPDIF) > Digital Audio IO Bus > Processor (CPU/DSP) > (Recording Device/USB bus/Network Interface)

The digital mic portion is the first 5 parts in this chain - with some of the DSP affects moving into the Processor portion.   There are some USB (SOCs) that have Processor built in but the idea is still the same.

Two topics here are:
 - getting the audio into the digital realm (and at what stage does that take place)  - digital microphones
 - interfacing digital audio with a computer or recording device - USB

I don't know if AES42 is the future or not as technology moves fast. 

In fact I bet in the next 10 years there will be software that can take in a bunch of YouTube feeds of a single event and mix the different videos in to a virtual representation of the event with a 3d like sound and video experience (i.e. a bunch or people with iphones at a concert for example).  They can already do this with still pictures.  Will it have the dynamic range if all the mics where professional - no - but most people would be happy with the results.

[rastasean]

If youtube is still around in a decade, it will be much worse than it already is.

The main issue I have with audio technology getting better and better is that fewer and fewer people will care. The popular music of today really involves untalented people singing with synthesizers and auto tune.

Soulja Boy Tell'em - Crank That (Soulja Boy)
http://www.youtube.com/watch?v=8UFIYGkROII
 total number of views: 111,703,899

How many digital mics were used to produce this video?

[Gutbucket]

How about a microphone body with ADC, small memory card (like XD size) for storing the audio, small rechargable battery supply, and a wireless transmiter that sends/recieves only control and clock data.  Add capsule of choice. 

No seperate recorder, no wires, simple wireless requirements, multiple mics as you like.  Recharge and off-load afterwards.

[blee421]

What monster have I created here!!!Peeps...when I got this setup it was mainly to be able to record 4 channels and not have to carry a shitload of gear with me to make it happen.Slimming the bag was the main goal.I was more into DPA microphones at the time and figured I would give this Schoeps setup a try.So,I sold my DPA 4021,4027 and 4011 combo I had going and went with this.I also sold a Mini MP and a V3 to make it all happen.Man was it worth it!!!I frickin loved being able to just show up,clamp,turn on the 788T and hit record.The first thing I noticed was that my levels were L,R close together and not all over the place.They seemed very precise.Anyways,I'm very glad this thread took off.Maybe a TEAM DIGITAL MICROPHONES should happen down the road if some more folks move that way.Here is a recording that I think came out really good considering I was in the back of the TS at Bill Graham Civic.The acoustic set in the beginning is a little iffy,but the electric sets sound pretty damm good IMHO.Take a listen! 

http://www.archive.org/details/furthur2010-03-12.schoeps-mk41.lee.106719.flac24 

SBD
http://www.archive.org/details/furthur2010-03-12.sbd.official.112973.flac16

[John Willett]

Re: power for an ADC, no way 2.5W is required.  Let's say PCM4202 + DIT4096 for a solution; that's 160mW plus we need an analog front-end, say AD8606 for another 10mW, plus capsule FET at another 10mW.   Plus an oscillator, another 100mW.  Total power budget, 280mW.  Use a charge pump to drop to 5V so there are no losses from linear regulation; I lose 85mW in the supply resistors for 365mW total.  So I still have a system that is only 77% efficient, which bothers me because with a dedicated power pin that would be better than 90%.  And as the power consumption of the system increases the efficiency drops further.

So I'm sorry, but 2.5W is an enormous amount of power in the digital portable world.  TI posts Youtubes of their MCUs running on batteries made from fruit (I'm not making this up), but AES thinks we need digital mics consuming enough power to heat a tube.  I don't get it.  Heck, P48 is too much power and it's time somebody recognized that.  The better brands often run on 11V-52V at low (and constant) current so this is hardly a great technical barrier.  Scrap it and mandate P12.

Where do you get 2.5W from?

The spec. is 250mW.

And AES42 does requires a special box, whether that box is a dedicated outboard receiver or an interface with an AES42 input.  My point is all boxes are going away except for the box that is the data storage and processing tool, and those aren't likely to support unique digital audio connectors especially if they require 10V.  As DSatz argues, it's a bit underwhelming because nothing physical has changed:  mic, cable, box, recorder.  It's a bit technically better, yes, but not dramatically improved enough to make it mandatory.

The audio industry ought to be looking at methods to make existing common protocols and connectors functional for professional audio.  I would guess fewer manufacturers will support AES42, not more, as more universal solutions replace it.

No - AES42 only requires a special box where it is not already built in to the equipment.

AES42 is basically the same as AES3 with a few extras - so it's not that difficult to do.

[MIQ]

How about a microphone body with ADC, small memory card (like XD size) for storing the audio, small rechargable battery supply, and a wireless transmiter that sends/recieves only control and clock data.  Add capsule of choice. 

No seperate recorder, no wires, simple wireless requirements, multiple mics as you like.  Recharge and off-load afterwards.

That is killer Gutbucket!!  This has been a cool thread with some eye opening thoughts.  Thanks

-MIQ

[H₂O]

Hhb has had a memory card recording microphone for 3 years or so called flashmic

[MIQ]

Sure I can see that being a product already.  The really inventive part, that I'd look forward to, is that all the mics in use are wirelessly sync'ed and you are left with capsule choice, placement, and what you want to do in post.

-MIQ

[rastasean]

Hhb has had a memory card recording microphone for 3 years or so called flashmic

Yeah, I remember seeing that in the b&h catalogue/website and thought it was rather expensive but I don't recall the actual price.

[kleiner Rainer]

hi all,

there are two objections to use WLAN technology to link digital mics and recorders:

- security
- capacity

Security: a venue operator could shut down stealth taping with a simple jammer. Ever thought of that?

Capacity: there are limited numbers of WLAN channels available, with a limited channel capacity. Imagine arriving late at a venue only to find out that all "channel capacity" is used up by fellow tapers using 24/96. What now?

This cannot happen with a wire connection. As long as there is still space to squeeze in a cable, you have your own secure channel with nearly unlimited capacity.

Think about it.

Greetings,

Rainer

[Gutbucket]

Capacity: there are limited numbers of WLAN channels available, with a limited channel capacity. Imagine arriving late at a venue only to find out that all "channel capacity" is used up by fellow tapers using 24/96. What now?

Wireless bandwith for sync & control only is minimal if the high resolution audio data is stored locally.  This is a taper specific solution though, since the live feed is unavailable.

Since I'm digital dreaming and Jon has mentioned DSP, another thing I've invisioned in my George Jetson recording future is independant and selectable convolution for each mic capsule-  Used to match less than perfect capsules and adjust them to the desired response.  Use a little management app to select a basic set of mic convolutions that correct and match each of a set of capsules, and combine those with secondary sets of convolutions that adjust for specific applications: degrees of free field vs diffuse EQ, boundary mounting, adjusting for mounting my miniature omnis in small spheres (or big head sized ones), and odd user-specific setups like adjusting response for body mounted configurations.  Select the desired convolutions, combine them for each microphone and load the results into the DSP.

[John Willett]

The one thing that is being forgotten is latency.

An AES42 digital microphone has a latency so short that it's about the equivalent of, I think, about 13" of the speed of sound in air.

This means that it is not noticeable and the microphones can be used in a live situation.

As soon as the latency gets above about 2.5 to 3ms then it becomes noticeable.

[SmokinJoe]

I'm still interested what people think of the following... let's say we have a digital mic...  Your diaphragm/capsule can tolerate some loud SPL before it's sonic accuracy really goes to hell.  For the sake of argument lets say it's 150db, and we balance things so our A/D is 1111 1111 1111 1111 1111 1111 (24 bit digital max) at that point.  If you are recording audio at 75db, you are utilizing only about 1/5000th of your A/D's bandwidth.  Is that a big deal? I don't know.  I would think people would be freaking about that.

Here are a couple analogies:
- If someone on here ran Analog condenser Mics > phantom power supply > high end A/D (with no preamp) and added 75db of gain in post everyone would tell him he's nuts.
- If someone had a high-end digital camera with a bazillion pixels, and only used a 28mm lens, when things were far away you just digital zoom and crop in post.

How is this digital mic situation different from my analogies?

[Hypnocracy]

Smokin...I find I prefer the results of running my analog Preamp HOT and bumping along with peaks on the digital side close to cliping too...doing so it is almost like compression...

The days of running everything at low 12db peak because it is 24 bit...is somewhat hollow to me...I'd almost rather run closer to the edge and have 16bit...

for example...I had ran a string band that needed some boosting to just be in the 12db 24bit range...then the next band came on stage and rocked a sound check...I was distracted at first and came over to check the levels and saw I would be turning it down for the set...

Once I got home and heard the results....IT BLEW ME AWAY...I'm almost sure I ran right up against the V2's clip point...and I know where to set the FR2LE to match the max V2 signal with a level that approaches the digital clip point...

http://soundcloud.com/hypnocracy/preston-frank-with-donna-the

[SmokinJoe]

Hypno, that is probably largely a change in flavor. I'm talking about resolution, and quantization noise.

To make the math cleaner I'll use 60db instead of 75. suppose full scale on ADC happens at 140 and quiet studio recording at 80db. With 60db below max the voltage is 1/1000th of max. 10bits is a factor of 1024, which is close enough to 1000. This means we are only using about 14 bits out of 24 and the rest is zeros. I recorded good sounding tapes at 16 bit, and I do record at -12 at times because I'd rather let it ride than clean up my gain adjustments in post, so I can't say that 14bit resolution is crap, but I think the whole thing is worthy of consideration.

 The trade off is that this quantization noise is pretty much the only noise anywhere in the system, no chance of noise from ground loops, preamps, cell phones, or any of that stuff.  Probably the overall system is improved, but I'd really want to understand the tradeoffs before I dropped big bucks on a digital mic rig.

[SmokinJoe]

I'm sure you're right Jon, you have more experience than I do with that kind of thing in audio.

I work with A/D's on industrial equipment, much of which is 12bit.   If you have a 0-10VDC = 0-4095 A/D and if we have a sensor that only puts out a tiny portion of full scale, you get digital readings that are clearly visible in discrete steps and they are coarse enough to matter.  The solution is to match the sensor's output span to the A/D span, more so than buying a new A/D with greater bit depth.  Anyway I take that experience and apply it to audio A/D's, and I think "if you are using less than 1% of the A/D input range, that's got to act the same way."  Maybe our eyes are a lot more fussy than our ears.

[John Willett]

The Neumann ADC in an AES42 mic. is 28-bit (although the final output is 24-bit).

With the ADC right by the capsule you have done away with all the analogue circuitry.  The line driver amplifier in the mic. has gone, the analogue mic. cable has gone, Rf interference has gone, etc..  You have lost a lot of circuitry that all adds noise and problems and you can hear the difference.

All I would say is just try it for yourself and make up your own mind.

I find AES42 mics great and they are obviously quieter compared to analogue.

[dream]

I find AES42 mics great and they are obviously quieter compared to analogue.

I really like my (Neumann) AES42 mics ... rarely use something else now. But I would like to add some experiences concerning noise. Neumann asked me to do a
comparison between an analog TLM103 and the digital TLM103D (I own one). For this test I recorded a very quiet watch. The analog 103 went into a Grace Design Lunatec V3 and the
digital 103 was used with a DMI-2p (as if that matters). On the V3 I added full 70dB gain. I level matched the two recordings and the noise floor and the sound was practically the same.
But generally I would agree that digital microphones are quieter in most applications. In this special case the analog 103 and the V3 are very low noise devices anyway.

[DSatz]

SmokinJoe, you're right that microphone capsules can generally handle sound pressure levels far greater than what we find in live music recording, such as 150 dB. But the electronics of most microphones can't handle such high levels without some form of technical intervention--either the use of a capacitive attenuator, or decreasing the polarization voltage on the capsule. In general modern condenser microphones tend to have something more like 130 dB SPL as the upper limit of their dynamic range. In most live situations that seems to work out well enough, especially since that's well into the range where hearing damage becomes a serious issue withing a relatively short time of exposure. And the range from there down to the noise level of the quietest microphones available corresponds to 20 bits and change, not quite 21 bits. So that is really not a problem for a 24-bit AES/EBU data channel.

Of course the quality of the analog electronics and A/D converters in microphones is just as much an issue as it is with traditional analog microphones and outboard A/D converters. Just because those stages are built in to the microphones doesn't earn them automatic exemption from criticism.

The situation that you describe with industrial A/D converters is NOT applicable to audio recording. In audio applications the analog signal is always dithered prior to (or as part of) conversion--and when properly done, this completely eliminates the stairstepping that you refer to. That problem was solved back in the 1980s! Were that not the case, the THD of a tone would increase sharply if you lowered its recorded level to a point just above the noise floor. But that does not occur, as both measurements and listening tests make clear.

--best regards

[John Willett]

I find AES42 mics great and they are obviously quieter compared to analogue.

I really like my (Neumann) AES42 mics ... rarely use something else now. But I would like to add some experiences concerning noise. Neumann asked me to do a
comparison between an analog TLM103 and the digital TLM103D (I own one). For this test I recorded a very quiet watch. The analog 103 went into a Grace Design Lunatec V3 and the
digital 103 was used with a DMI-2p (as if that matters). On the V3 I added full 70dB gain. I level matched the two recordings and the noise floor and the sound was practically the same.
But generally I would agree that digital microphones are quieter in most applications. In this special case the analog 103 and the V3 are very low noise devices anyway.

Good test and is what I would expect - a minimalistic approach with a single mic., short cables, high quality mic. pre. going into a single line in; the noise difference would be extremely small.

The advantages in AES42 are in eliminating the analogue stage at the earliest possible moment - multiple mics, long cables, analogue mixers, etc. all add their little bit of noise and in a big sound system where the sound remains fully digital from the mics right up until the ADC which outputs directly to the power amplifier can be very large.