Topic: co2>jb3

[bagtagsell]

ran this tonight w/ no problems at all. no clicks or dropped signals.  hmmm, interesting. sbm1 coax mod>co2>jb3

[F.O.Bean]

ran this tonight w/ no problems at all. no clicks or dropped signals. hmmm, interesting. sbm1 coax mod>co2>jb3

nice!

ive heard many times its flaky at best tho, and its not bit-perfect, you just cant hear the dropped samples

[hexyjones]

Im trying scare up the original tests that started this devices bad rep...stay tuned...

[hexyjones]

well - if you search DAT heads I can find only this

From: "Jamie Lutch" <jlutch@altairinc.com>
Subject: midiman co2 may not be bit-accurate/ jb3 progress
Date: Sat, 5 Oct 2002 23:17:28 -0700

in the neverending quest to test the nomad jb3, I picked up a midiman co2 to
test as the coax>optical converter I need before the unit. for those who
arent familiar with it, it is a 9vdc powered little box that can take coax
in and spit out both coax and optical. I did 3 tests with it, they were all
horrendous, causing  lierally 100's of short spikes of a few samples in the
recording, many of which were audible as pops and clicks. this happened on
both the coax out (to the vx) and the optical out (to the jb). I switched
back to my other coax>optical converters, both get me to 'near-bit
accuracy' (jb limited at this point) The performance was so bad with the
co2, I'm going to have to consider the possibility that the unit might be
defective. I'll try to get my hands on another unit to test (anyone have one
of these? I'll pay shipping both ways, and will only need it for a day or
so).

I know some people were considering purchasing these to use with the
jukebox. For now, I would hold off until more data becomes available. There
are other $20 that can convert coax>optical (tho they are dead-enders, and
dont allow for the continuation of a digi chain)

wrt the jukebox, a few other tapers have got them now, were going to pool
together and compile a database of transfer info to try and isolate the
problems of the jb3, which so far seem to be random and non-repeatable. so
again, for those considering purchasing a jukebox for recording, I'd hold
off a bit till more data becomes available

He also refers to this JL post
http://www.solorb.com/dat-heads/digests/V6.500/D577#Msg21

There is some claim about Lutch tests in the NJB3 tapers yahoo group...but I cant find them in their archives or files section.

From the taperssection JB3 FAQ: (- but no such files exist...)

Jamie Lutch has posted some testing results over on the NJB3Tapers Yahoo group Files section...


Anyone have these elusive testing results...

[Brian Skalinder]

Im trying scare up the original tests that started this devices bad rep...stay tuned...

FWIW, Jamie posted his test results in the NJB3Tapers Yahoo group, files section.  Not sure why you could'nt find 'em.  Unfortunately, I can't check right now as the proxy server at this office blocks my access.

[hexyjones]

I dont see them - not much there - am I missing something...?

[Brian Skalinder]

I dont see them - not much there - am I missing something...?

See attached...

[hexyjones]

Yeah found that - He never does test:

sinewave>V3>AES>canare 100-75 ohm transformer>greybox>sony poc15ab>nomad

Results 15-19 - The Thing before the CO2 is the variable...why point the finger at the CO2?

I just dont get it the logic here...

[Brian Skalinder]

The Thing before the CO2 is the variable...why point the finger at the CO2?

I just dont get it the logic here...

I suspect that Jamie varied the devices upstream in an attempt to isolate the CO2.  Which is more likely - that all three variables in the test (the components before the CO2 in the signal path) are independently bit-imperfect, or that the CO2 as the common thread is likely bit-perfect?  I would argue the latter is more likely.

I can't access the tests so I'm unable to see exactly what Jamie's tested.  But for me, it doesn't matter whether Jamie's proven conclusively that the CO2 is the problem.

Given:

[1]  anecdotal problems people have encountered with the CO2 in the signal path
[2]  no one has proven definitely some other device in the chain causes the problems
[3]  no one has proven the CO2 is truly bit-transparent

I don't see how we can make a determination one way or the other.  However, it seems reasonable to suspect the CO2 as the, or at least a culprit given the anecdotal experiences.  It's clear to me that sufficient doubt exists regarding the CO2s capabilities to operate bit-transparently.  I, for one, won't trust the CO2 unless/until someone demonstrates with definitive testing that it does, in fact, operate bit-transparently.  Bottom line:  no one has proven the CO2 is bit-transparent.

On a side note, I see you're running:

TASCAM PE-120x3 > Nakamichi Mx-100  > Midiman Flying Calf 24bit > Midiman CO2 > Creative Nomad Jukebox 3(x3)

Does the Flying Calf 24-bit ADC have an option to dither to 16-bit, or is the JB3 truncating your signal?

[hexyjones]

http://www.pennmar.net/new%20nomad%20testing-1.htm

I resaved the Excell file as html...not sure if that helps...

[Brian Skalinder]

http://www.pennmar.net/new%20nomad%20testing-1.htm

I resaved the Excell file as html...not sure if that helps...

Thanks, that helps.  Summarizing Jamie's tests:

FAIL    | V3 SPDIF > CO2 > POC15AB > JB3
FAIL    | V3 AES > transformer > CO2 > POC15AB > JB3 
SUCCEED | V3 AES > transformer > CO2 > POC15AB > JB3
FAIL    | V3 AES > transformer > CO2 > POC15AB > JB3 
SUCCEED | AD2K > CO2 > POC15AB > JB3
SUCCEED | AD2K > CO2 > POC15AB > JB3
FAIL    | R500 > CO2 > POC15AB > JB3
FAIL    | R500 > CO2 > POC15AB > JB3
FAIL    | R500 > CO2 > POC15AB > JB3

The only device with which it succeeded more than once is the AD2K.  And that's only 6 hrs of testing.  Given that some of the other tests indicated only a few dropped or misplaced samples, it's entirely possible - likely, even - the AD2K > CO2 combo may prove bit-imperfect with additional testing

My conclusion from the sample data:

the CO2 is not bit-transparent[/list]

Do you come to a different conclusion?

Also...still curious about your Flying Calf > CO2 > JB3 setup...

[hexyjones]

Also...still curious about your Flying Calf > CO2 > JB3 setup...

Truncated by the JB3 - anything I can do in post to improve what the JB3 records...? I always have used the 44.1 setting.

A/D Type: 24-bit, delta-sigma, 128 x oversampling.
Sample Rates: 48 kHz or 44.1 kHz.
Dynamic Range: 105 dB (A-weighted).
THD + Noise: .002%, -94 dB (A-weighted).
Nominal Input Signal: -10 dBV (standard input level setting).
-16 dBV (“+6” input level setting).
Full-scale Input Signal: +6 dBV (standard input level setting).
0 dBV (“+6” input level setting).
Frequency Response: 24 Hz to 22 kHz (+/- 0.2 dB).
Input Impedance: 10 K ohms minimum.
Analog In Connectors: 1/4” female TS-type, unbalanced.
Digital Out Connector: RCA, female.
Digital Out Format: S/PDIF, transformer-coupled.
S/PDIF SCMS: May be enabled or disabled.

[bluegrass_brad]

Truncated by the JB3

Ouch!  My understanding is that the Nomad does a major hack job on the truncation process.

[Brian Skalinder]

Truncated by the JB3 - anything I can do in post to improve what the JB3 records...? I always have used the 44.1 setting.

Not that I'm aware of, no.  I thought they made a 16-bit Flying Calf at some point...or something similar...maybe swap out the FC24 with a 16-bit ADC?

And still curious on this one, too:

My conclusion from the sample data:

the CO2 is not bit-transparent[/list]

Do you come to a different conclusion?

[hexyjones]

Truncated by the JB3

Ouch!  My understanding is that the Nomad does a major hack job on the truncation process.

How would this manifest itself? I certainly haven't picked up on any noticeable ugliness...

Maybe someday someone with a laptop will come along and I can get capture something in 24 bit -