Topic: R-09 & MT bits and pieces

[pool]

Hi all
I would like opinions regards the following queries.

According to reviews by Coresounds, the Microtrack (http://www.core-sound.com/microtrack_2496/7.php):
"Its mic pre-amp and A-to-D converter provide only 16- or 17-bit performance."..."Its mic pre-amp and A-to-D converter will never be able to provide more than 16-bits of dynamic range, so it's really a 16-bit recorder unless you add an external Mic Pre/A-to-D converter "

1) Should this read "its not a perfect 24 bit" or as stated it's not a true 24 bit recorder"?

2) If it really is only a 16 bit recorder, should one tape at 24 bit w/ the microtrack just the same?



According to Sonicstudios review re the Edirol (http://www.sonicstudios.com/r-09revw.htm):
"inputs are nearly impossible to overload".

3) Does this mean it's impossible to get distortion at the high ends/clippings??

4) Is the Edirol a true 24 bit recorder?

5) does the Edirol save more than 2GB files or have a seemless transition after saving 2 GB file?

I'm simple minded, please keep it simplest.

thank you
wishing all a best 2007.

[Brian Skalinder]

1) Should this read "its not a perfect 24 bit" or as stated it's not a true 24 bit recorder"?

No field recorder that I know of offers "true 24-bit" recording.  The recorder mechanism, i.e. the function that simply writes the 0s and 1s to media, could handle true 24-bit recording if passed the proper signal.  So what we're talking about is the capability of the recorder's analog inputs / preamp / ADC to produce a true 24-bit signal for the recording mechanism to...well, record.

True 24-bit recording would provide dynamic range of 144 dB (1-bit = 6 dB; 24-bits * 6 dB = 144 dB of dynamic range).  The dynamic range of most 24-bit preamps / ADCs falls in the 17- to 19-bit range (dynamic range of 102 - 114 dB).

For example, two of the best spec'd preamps/ADCs people use here on TS:  Sound Devices 7xx offers 114 dB dynamic range, the Grace Design Lunatec V3 offers 110 dB dynamic range.  That means that they're offering 19-bit and 18.3-bit resolution recording, respectively.  (Far from true 24-bit!)

The MT2496, when running analog-in to the recorder, offers 98 dB of dynamic range (~16.3-bit ) through the 1/8" inputs and 100 dB of dynamic range through the 1/4" inputs (16.7-bit).

By recording with the MT 24-bit analog-in, you're gaining a small amount of extra resolution (16.3-bit via 1/8" inputs, 16.7-bit via 1/4").  My ears hear a significant difference between 16-bit recording, and the 18.3-bit recording of the V3 (a preamp/ADC I used for quite a while).  So IMO, every little bit (no pun intended) counts.  The extra dynamic range also allows one to run more conversvative levels when recording.

2) If it really is only a 16 bit recorder, should one tape at 24 bit w/ the microtrack just the same?

Really up to you.  You'll gain a bit more resolution, and/or be able to run your levels slightly lower while still maintaining 16-bit quality.  It's more work on the back-end, though:  dithering properly from 24-bit to 16-bit if you're burning to CDs, or want to seed 16-bit for others, etc.  I'd record both ways, and decide which you like best.

According to Sonicstudios review re the Edirol (http://www.sonicstudios.com/r-09revw.htm):
"inputs are nearly impossible to overload".

3) Does this mean it's impossible to get distortion at the high ends/clippings??

It means one may record a very "hot" (strong, or loud) signal before overloading the R-09's analog inputs.  It's still possible to <1> overload the mic's input (not likely, depending on the mics and source you're recording), or <2> set your levels too high and clip during the analog-to-digital conversion.  Since the R-09 can accept a hot signal, it's easier to run a preamp between the mics and the R-09 without causing problems.

4) Is the Edirol a true 24 bit recorder?

Nope.  I can't find a dynamic range spec on Roland/Edirol's site, so...I don't know at what resolution it actually records.  But when recording in 24-bit mode, it's probably capturing resolution of 16- to 19-bit range, like the others.

5) does the Edirol save more than 2GB files or have a seemless transition after saving 2 GB file?

I'll have to defer to others on this one, as I don't have an R-09 nor know for certain.  I bet the answer's in TS somewhere, though - maybe try searching the Recording Gear forum.

[Javier Cinakowski]

UA5 info (stock)

Dynamic Range: 99 dB (A-to-D converter), 108 dB (D-to-A converter)
Noise Level: -95 dBu or less (analog output)
Max mic input level: 0 dBu
Mic input gain range: 50 dB
Line level output: -10 dBu
Variable level headphone output
Power Requirement: 9 VDC at 450 milliAmps
Size: 8-5/8(W)x 5-7/16(D)x 1-7/8(H) inches [218(W)x 137(D)x 46.5(H) mm]
Weight: 1 pound 10 ounces [.71 kg]

[guysonic]

Using an external preamplifier into Microtrack's TRS analog LINE input does seem to increase the usefulness of this deck without necessarily adding much to the overall size.

Below is a spectrum showing noise floor with REC gain set at maximum for LINE level input with the three gains settings available from the preamplifier applied to the MT's input.  Recording mode is 24bit/88.2K WAV sample, and preamp input loaded with 1000 ohms. Spectrum generated using CEP operating on saved from flash audio file. 



Although not perfect 24 bit, this looks quite good to me.  Microtrack review at: www.sonicstudios.com/mt2496rv.htm

[divamum]

The original firmware would record over 2g but not always reliably; it is my understanding that the most recent firmware update for the R09 will split files seamlessly at the 2g mark.   (note to self: upgrade firmware this week!)

[gewwang]

The original firmware didn't attempt to split the file at the 2GB mark. It would record files from 2GB to 4GB, but the only issue was playing a recording over 2GB back on the R-09. You could transfer the 2GB+ sized file over to a PC without losing any of the recording though which was the functionality that absolutely had to work reliably.

[rodeen]

The extra dynamic range also allows one to run more conservative levels when recording.

Can you explain how added dynamic range allows you to run levels more conservative?  I'm not questioning the statement, I'm just trying to learn. 

Thanks Brian!

[Brian Skalinder]

Can you explain how added dynamic range allows you to run levels more conservative?  I'm not questioning the statement, I'm just trying to learn.

I'll try.    Although as I think through it again, it no longer makes sense.  At least not for 24-bit listening.  It may still make sense for 16-bit listening.  Here we go...


In an ideal world, we use all 24-bits of resolution, a full 144 dB of dynamic range.  Since 1 bit = 6 dBFS, the relationship between dBFS (our levels) and resolution (our bit-depth) looks like below, where S = signal and N = noise.  In this ideal case, if we set our levels to peak basically at 0 dBFS, we use all 24-bits of resolution, the full 144 dB of dynamic range.  The data is pure signal (no noise):

| -144 | -132 | -120 | -108 |  -96 |  -84 |  -72 |  -60 |  -48 |  -36 |  -24 |  -12 |   00 |  dBFS
--------------------------------------------------------------------------------------------
|   24 |   22 |   20 |   18 |   16 |   14 |   12 |   10 |   08 |   06 |   04 |   02 |   00 |  Bit-Depth
============================================================================================
|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|  Noise / Signal


However, none of our preamps and ADCs achieve full 24-bits of resolution - too much self-noise.  For the sake of discussion, let's assume that our preamp and ADC provides 108 dB of dynamic range, which equates to 18-bits of resolution.  Everything below -108 dBFS is noise, i.e. all the data in the least significant 6-bits is noise.  The new graph - again assuming our levels are effectively peaking at 0 dBFS - looks like the following, where S = signal and N = noise:

| -144 | -132 | -120 | -108 |  -96 |  -84 |  -72 |  -60 |  -48 |  -36 |  -24 |  -12 |   00 |  dBFS
--------------------------------------------------------------------------------------------
|   24 |   22 |   20 |   18 |   16 |   14 |   12 |   10 |   08 |   06 |   04 |   02 |   00 |  Bit-Depth
============================================================================================
|NNNNNN|NNNNNN|NNNNNN|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|  Noise / Signal


Now let's assume we change our levels to peak at -6 dBFS.  Since the noise-floor hasn't changed, we've now effectively reduced our resolution by 1-bit.  The new graph looks thus:

| -144 | -132 | -120 | -108 |  -96 |  -84 |  -72 |  -60 |  -48 |  -36 |  -24 |  -12 |   00 |  dBFS
--------------------------------------------------------------------------------------------
|   24 |   22 |   20 |   18 |   16 |   14 |   12 |   10 |   08 |   06 |   04 |   02 |   00 |  Bit-Depth
============================================================================================
|NNNNNN|NNNNNN|NNNNNN|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSSSSS|SSS...|  Noise / Signal


In this light, let's examine two qualifications of my previous statement (and one I've seen repeated often by others):

If our target listening resolution is 16-bit, we're in good shape - we're still capturing 17-bits of resolution, i.e. > 16-bits of resolution.  This assumes, though, that 17-bit resolution dithered down to 16-bit sounds the same as 18-bit resolution dithered down to 16-bit.  It also assumes any editing we perform does not benefit audibly from the extra 1-bit of resolution 18-bit provides v. 17-bit, prior to dithering down to 16-bit (or if there is an audible benefit, dithering down to 16-bit negates it).

If our target listening resolution is 24-bit (meaning an actual bit-depth of 18-bit), we're actually reducing our resolution from 18- to 17-bits.  Given that I hear a significant audible difference between 18- and 16-bit resolution, I'm inclined to say there's a significant audible difference between 17-bit and 16-bit (half of the difference between 18- and 16-bit).  I have not performed any specific testing of this suggestion, however.

Anyway...all this leads me to believe my previous conceptions were incorrect, and that we should run our levels as close to 0 dBFS as possible regardless of the final target resolution, but especially if our final target resolution is "24-bit". 

But I'm not 100% certain my understanding above is correct.  Anyone with more detailed technical knowledge able to chime in?


FWIW, two posts with lots more info regarding levels, other reasons why one may or may not want to run them hot (mixing with other channels, finding the sweetspot in your analog gear), etc.:

http://taperssection.com/index.php/topic,58384.msg906769.html#msg906769
http://taperssection.com/index.php/topic,58384.msg898317.html#msg898317

[pool]

Very good information from good posters indeed. Thank you for sharing.

[Brian Skalinder]

More discussion on 24-bit (well...~18-bit) v. 16-bit here:

http://taperssection.com/index.php/topic,77804.0.html

The most relevant section of which is:

The more I think about it, the more I believe we do, in fact, only have 18-bits of resolution (if we continue to use my example as a basis for discussion), due to limitations in our preamps and ADCs.  This means we can only utilize 108 dB of dynamic range, per my previous post.

But I think the piece that I was missing before is the fact that 18-bit audio provides a huge increase in precision on the Y-axis of the waveform, independently of the dynamic range.  The math:

• 16-bit audio = 2¹⁶ = 65,536 increments with which we may describe the audio in the Y-axis
  
• 18-bit audio = 2¹⁸ = 262,144 increments with which we may describe the audio in the Y-axis
  
  

In other words, while the extra 2-bits of resolution at our actual 18-bit resolution provide only 12 dB more dynamic range than 16-bit, the precision of our vertical axis has quadrupled relative to 16-bit.  So even when we're not capturing a broad dynamic range, the precision with which we capture -any- dynamic range has still quadrupled.

[sml42]

According to reviews by Coresounds, the Microtrack (http://www.core-sound.com/microtrack_2496/7.php):
"Its mic pre-amp and A-to-D converter provide only 16- or 17-bit performance."..."Its mic pre-amp and A-to-D converter will never be able to provide more than 16-bits of dynamic range, so it's really a 16-bit recorder unless you add an external Mic Pre/A-to-D converter "

1) Should this read "its not a perfect 24 bit" or as stated it's not a true 24 bit recorder"?

Not a great deal I can add to what's already been said, but a few comments...

1) yes the microtrack is a true 24-bit recorder, just that at the very lowest bits you're only capturing noise (hiss). Note that this is true of ALL 24 bit recorders, not just the microtrack. The amount of noise (hiss) is determined by the design of the electronics (broadly speaking, the quality of the preamp and a-to-d). People have measured the performance of the microtrack and found that the noise takes up (approx) 6 bits of your 24, leaving (approx) 18 bits which can really capture the signal. I say "approx" because it varies depending on what gain settings you're running the microtrack at. But 18 useable bits is a good rule of thumb. (and it's not too shabby... much better than say a jb3).

2) Obviously Core Sound want to sell you a Mic2496. Don't do it! I bought a Mic2496 from coresound and was never really happy with it. In particular I had issues with coresound customer support (or lack thereof) and Len's attitude. I'm not alone in this regards. I've ranted about this before, search for the 'critique your rig' thread if you care for details.

best regards,
stephen