Hi Eli.  Thanks for the update!

So, just to clarify, you used the built-in S/PDIF optical input on the G5?
And the data was already re-linearized (there was some conjecture that the
data might need to be processed using a lookup table to remove the
non-linear encoding).  If the audio was re-linearized, then I assume it was
16 bit and you captured at 16 bit and not 12 bit?

Did you find a method for 16 bit recordings that works reliably using a DDS
drive?

Thanks,

Ellis Burman
www.audiomechanics.com

On Mon, Jun 5, 2017 at 11:01 AM, Eli Bildirici <
[log in to unmask]> wrote:

> Hey all,
>
> Last week I managed to do a 32kHz cap via S/PDIF using our PowerMac G5
> almost without issue - hurray! Thanks to everyone who chimed in, esp re the
> clarifications about what '12-bit' meant in the context of DAT LP
> recording, and to John Gledhill, who graciously called me and discussed
> SPDIF capture issues at length and provided a test signal. Two small notes
> - on older versions of OS X (10.3), apparently the optical input had to be
> set to use the external SPDIF clock, using the Audio MIDI Setup
> application. On 10.4 Tiger on these machines, this option is greyed out,
> and the external clock is used by default. Also, if you are trying to
> capture a mixed frequency DAT, Audacity will crash on the freq changeover.
> Upon recovering Audacity though, it should have your entire cap before the
> changeover (it did for me). Still, if you'd like to avoid this, don't leave
> your cap unattended (which I should not have done; moment of weakness).
>
> Separately, we ended up getting one of the CM6206-based USB sound cards I
> mentioned in my initial posting (quoted below), which reputedly had the
> ability to capture 32kHz input via its SPDIF in, in the hopes that we could
> use our other, less-obsolete computers to do caps. Sadly, a) even without
> any input at all, all that's coming out of its S/PDIF input is a wall of
> loud noise and b) in OS X Audio MIDI Setup, it does not offer the option of
> recording at 32kHz at all, only at 44.1kHz or 48kHz. This happens on both
> the G5 and on our other Macs, so my guess is that the card is shoddy
> (surprise!) and the 32kHz functionality is disabled on the card or in the
> driver, if it's there at all. (According to the datasheets, even for the
> newer version of this chipset, it should, but how knows). Even if it's just
> disabled in the driver, it is probably not worth trying to edit the kext to
> get it to work. So, this route appears to be out, on the off-chance anybody
> was considering it. A real shame.
>
> However, I'm realizing now that our other office workstations (if you
> could call them that), late-2009 model Mac Minis (aka MacMini 3,1) have
> mini-TOSLINK/3.5mm TRS jacks for both input and out. I had previously
> missed this because the Sound preference pane made no mention of a Digital
> Input, and have comparatively little experience with actual Macs. I
> stumbled across this by opening up System Information. My guess is,
> plugging in a mini-TOSLINK cable to the line-in port will 'activate' the
> input in OS X (I've observed similar behavior when plugging in and
> disconnecting headphones). Can anybody confirm this? Does anybody here have
> experience using this input?
> Aside from that - from what I can tell, unfortunately, this Mac probably -
> no datasheet to this effect, just some Googling and guessing - uses a
> Realtek ALC88x chipset (which is listed in system information as 'Intel
> High Definition Audio' - this is a standard akin to AC97, not an Intel
> chipset per se), and of these, only the highest-end ALC889 supports 32kHz
> input. I will be testing to confirm my suspicions as soon as I can but am
> not too hopeful.
>
> Again, all ears. If this doesn't work out, we can use the PowerMac G5 for
> these caps, but that is not ideal for the long-term - obviously the
> computer is obsolete, somewhat slow, and something of a power-hog, and if
> it breaks, repairing it is probably a dubious proposition. So - if anybody
> knows of any SPDIF capture card or box that can do 32kHz caps and doesn't
> cost too much - say, $50 maximum - please chime in. Otherwise, probably the
> most economical solution (as well as the least, er, technically janky) to
> capturing 32kHz or mixed freq DATs, without an analogue intermediary, for
> those who have not already invested in SPDIF capture equipment and
> otherwise have no use for such, is using a SCSI DDS drive. But I was hoping
> to discover a cheaper, reliable alternative that still worked, and would
> still love to find it.
>
> Thanks everyone for your time!
> Eli
>
> May 2 2017 1:56 PM, "Eli Bildirici"  wrote:
> Hey ARSClisters,
>
> I'm an intern in the archives department at Democracy Now! and have come
> across a couple hundred mixed-frequency DAT tapes, many of which have
> 12-bit/32kHz content on them. (And yes, this is the same issue an archivist
> from DN! posted about nearly ten years ago, here (
> http://www.cool.conservation-us.org/byform/mailing-lists/
> arsclist/2007/07/msg00380.html).) We'd like to make bit-perfect digital
> copies, but don't have a SCSI DDS drive at the moment, and in any case
> would like to know if there's a reliable alternative path to digitally
> copying DATs, especially those recorded at a bit-depth of 12, via S/PDIF
> and capture cards. I attempted to copy a portion of a tape recorded at
> Redbook rates using our main deck - a Sony PCM-R500 - with an M-Audio
> FireWire Solo and Audacity to record, but this was full of pops and clicks
> that, I assume, are the result of the M-Audio failing to lock onto the tape
> deck's clock. (The pops and clicks only show up during recording and are
> not on the tape itself. Actually, I suspect Audacity may in part be to
> blame, since the pops and clicks are absent when monitoring via the M-Audio
> control panel app on OS X...but I digress.) I've also found that external
> sound cards based on the C-Media CM6206 chipset - cheap and plentiful on
> eBay - reportedly support 16-bit/32kHz input, as does the S/PDIF input of
> our aging PowerMac G5. But that doesn't help us with 12-bit content, and
> nor do we know whether clock syncing will pose an issue and how to deal
> with it if it does. My suspicion is that, while there might be an
> economical and reliable solution to recording DAT tapes with 16-bit content
> (at least at 44.1 or 48 kHz sample rates) without a DDS drive, that we're
> out of luck for 12-bit content - but, any advice/confirmation/refutation
> would be most welcome.
>
> Thanks,
> Eli
>
> Eli Bildirici
> (347) 837-8337
>



-- 
Ellis
[log in to unmask]
818-846-5525