DAT-Heads Digest #801, Volume #3                 Wed, 22 Oct 97 09:15:03 EDT
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From: alex@unisearchmm.com (Alexander W. Chin)
Subject: The D100 FAQ
Date: Wed, 22 Oct 1997 18:47:44 +1000

Hi all,

Alex is back! (now I hear groans.. and see rolling eyes)... Oh! And in case
anybody wanted to know, I think my exam went well! (The one with the video
signal processing). And yes, the line frequency of PAL is 15.625 kHz (got 3
marks for that one!).

Anyways, back to DAT talk, more specifically DAT tech talk. This may prove
interesting to everybody here, now, or in the future.

Reason for this post is twofold. Firstly, to celebrate the success of the
exam (yay!). Secondly, well, to inform DAT-Heads about what I can figure
out from information of the D100. After my exam, naturally I walked home
from Uni, half-asleep, full of coffee (previous night studying). I found
this card in my postbox, for an ordinary parcel.

Since I do not remember ordering anything, I was naturally curious as to
who would send me a parcel (possibly a secret admirer?). Sadly to say, no,
it wasn't a secret admirer (sigh)... it was from Klay Anderson. Opening the
package revealed a TCD-D100 Service Manual... So, thanks a million Klay, I
appreciate it.. (till of course he comes up to me with a bill of US$24.95 -
ok, ok... I was kidding).

So, everybody, send some stamps to his son (stamp collector), on my behalf,
especially those from overseas (not in the US).

Well, upon close inspection of the manual (the parts with the schematic
diagram), which only a four eyed, short sighted, messy haired engineer like
me can comprehend... I have some news!

Once upon a time, there was talk and argument about the digital I/O of the
D100. Well, it now comes to rest... let me clarify...

>>From what I can tell from the input circuitry, the D100 will accept any
signal from the 7 pin jack. That is the input. So if you have any passive
cables (passive meaning they have no electronics in them), they will work
fine for the input stage.

I cannot say that the POC-DA12M will work for the inputs, as I suspect that
the input stage of that cable is not passive. But if you have a RCA cable
to 7 pin cable, it will work for input.

So much for input, now the output. Not good. The output is really at a low
level. From what I can tell, it is approximately 3.5 Volts. Again, a
passive cable (RCA) output should work. Meaning if you go D100 -> DA-P1, it
will work with just a passive cable.

As for the POC-DA12M, I don't think it will work. Voltage too low.
Naturally I looked at the schematics to see if I could come up with a mod
to jack up the voltage. Sadly, I cannot see any easy way to do this. All
the voltages inside from the SMPS top out at 3.8 V. Too low. Would be too
much work to effect a mod to jack this up to 4.8 V.

Sad.

Next on the agenda. I noticed something different about the Signal
Processor IC. Attached to pin 46 (PLCO) is..... you guessed it.. a VCO (IC
511 TLC29321PW). What this means to the ordinary layman is the IC will sync
to external S/PDIF. He don't click... click.... click... click... when
coming in from a Digital Source. This means that it is safe to patch via
line-outs to another deck in the recording chain.

The D7 and D8 would click.. click.. if you patched them via line-outs with
a digital signal coming in. My comments on this are...

Boo, Hiss... boo, hiss... scratch... scratch, grumble... kick.. kick...

The D3 could do it. The next models up D7 and D8 click and buzz. And now
the D100 can do it too. Must be some form of progress that I am not aware
of..

Oh, by the way, if it really does click... click... click... don't shoot
me. I tell you what the manual tells me (which could very well be bloody
lies). They write service manuals to confuse technicians... but then again,
their own technicians can't understand, less make use of the service
manuals.. so two wrongs could very well effect a fix <grin>.

Next.

>>From what I can tell from the diagrams.. the back-tension system is
mechanical. Like the D7 and D8 (and D3). This is good news. Means that you
can safely use 90 Meter and 120 Meter tapes like on the D7 and D8.
Furthermore, I noticed that the D100 has an extra sensor pin (called THIN).
This pin is to sense THIN tapes (meaning 90 and 120 Meter). In the previous
models there was no such sensor.

This THIN sensor is mainly for computer data grade DAT backup drives. The
THIN sensor on computer drives is mandatory, but not for audio-DAT. So
there you go... maybe someone can do a test to see if this pin actually
works.

I suspect that the D100 will give correct 'Remaining Time' for 90 M tapes,
and also the tape position progress bar during FF/REW may *actually*
reflect the correct position for 90 M tapes. Anybody care to try that out?

On the D7 and D8, even though you can safely use 90 M, the remaining time
and progress bar are all wrong. It works, but the dumb deck starts to wind
slow thinking the tape is almost up (since he don't know that tapes can be
longer than 60 M).

Anyways.. lets move on..

Analog talk. If you thought the D7's headphone output was wimpy... oh yeah
baby, wait till you see that of the D100. Sissy. The scale goes ..

D100 (Sissy) < WMD-DT1 (Baby) < D7 (Wimpy)

You read right, the output stage of the puny play only WMD-DT1, is
marginally more powerful than that of the D100. So if you think the DT1 is
already too quiet... you are in for a surprise... again known as progress.
Maybe evolution is a better word.

In other words, if you expect the headphone outputs to blow away your 200
Watt speakers, you can forget about it. At least the line outs are not so
disappointing. They look reasonable.

One good thing I can say about the output stage of the D100 headphone is
that they take the full output from the D/A converter, then attenuate it.
This provides better resolution, rather than the D7 style. In the D7, the
output from the headphone is actually direct from the D/A converter. So at
low volume levels, you are actually listening to few bits. Ie, if your
volume setting is at 2 or 3, you are actually listening to (my guess) 8 bit
(or even less) resolution.

In the D100, you always have 16 bit (or more likely 18 bit) resolution at
all volumes, and it doesn't change with volume level.

Now, the hype. 'Thee mayeth overloadeth der mikrofone stage, and ye D100,
he not-th distorts'.

You can overload the mic amp. Can be done. Want me to show you?

The line in on the other hand is designed to take a lot more abuse than
that of the D7. For starters, it is impossible to overload via the manual
Rec-Level knob. Well, if you leave the Rec-Level at maximum and plug the
line ins into the mains of course you will overload it, but what I am
getting at here is that you do not have the restriction of the D7 and D8
where if your rec-level is less than '4.2, the magic number', you can
'brickwall'. I always hated the brickwall term, but it seems to have caught
on here. Brickwall actually does mean something else in Engineer speak, so
it is wrongly used here. But you all get the idea.

You cannot clip or otherwise distort the signal if you use manual
rec-levels, via line in. This don't apply to mic in.

If on the other hand, you have AGC or whatever automatic level limiting on
(I don't have a D100, so I don't know what it is called), you could
possibly clip the signal. It would have to be quite hot to clip though, but
it is possible. By quite hot, I mean about 8.2 Volts peak-to-peak. You
exceed that in AGC, then you distort.

Well, that is as much as I can deduce from the service manual. If you want
more information, feel free to send me an experimental D100 that you have
(or a spare one). Or better still, deposit USD$700 into bank account
123456789 in my name, then I can buy one to take apart.

Oh by the way, from the picture on the manual, it looks sexy. The D100 has
sex appeal - curves, bumps and two nipples at the front....ooohhh yeah... I
digress.... Hope I didn't offend anybody...

That's all for now folks... back to the normal program...

bzzt!

Cheers

Alex

==============================================================================
Alexander W. Chin                               Unisearch Multimedia

                                                Suite 232
Systems Manager                                 National Innovation Centre
E-mail : alex@unisearchmm.com                   Australian Technology Park
Phone  : (612) 9209 4066                        Garden Street, Eveleigh
Fax    : (612) 9209 4061                        NSW 1430
http://orion.unisearchmm.com/~alex              Australia