15 Sep
2004
15 Sep
'04
7:12 a.m.
On Sat, 11 Sep 2004, Tom Jennings wrote:
> I was assuming PC audio cards would not be fast
enough.
On Sat, 2004-09-11 at 19:24, John Lawson wrote:
What can the actual drum clock be... I dunno... another reason to slow
the drum; see below further...
It's 80KHz. So you think that slowing the motor speed say 4X will not
affect the head outputs more than proportionately? I'm a bit wary of
this, partly out of ignorance (relatively speaking; I know the physics
involved, and I know electronics, but I know enough now that I know I
don't know more than I do know -- now). IOTW, there's always Another
Factor, like relying on the slope of the signal off the head, etc etc.
> The disk has one (or a few) timing tracks. I
assumed I would record the
> timing track plus a data track; hence all recordings would have a
> reference.
If you could trigger a simple pulse to SMPTE
converter, and if the data
rate of the "index" pulse is slow enough, then your synce problems get
solved...
Well I was an idiot writing before I went back and re-read it all.
There's three timing tracks, one of them though is the sector address,
and the timing pulses are all derived.
[Aside: I always wanted to have a manual entitles:
"The Book of
Armaments"]
(It could never be big enough! :-)
>> if you
>> could get a 'whole drum after this pulse' (sort of like capturing one
>> video frame) sync set up, then you could record each track onto a similar
>> parallel track in the DAW....
Physical geometry is 32 heads * 128 sectors, logically juggled to
re-create the LGP-30's 64 * 64. There are six spare tracks with spare
heads over them.
THe simplest thing (sic) would be to brute-force record 32 tracks at
once. Assuming the data isn't totally awful, sync could be derived
easily from the captured data set.
Another choice
is to simply disable writing electrically, and use the
computer itself. The biggest worry (at this point) is head/platter
issues. THe heads contact at rest, then lift. The mechanical issues
exist no matter the data-recovery method.
Yeah. I'd intercept the 'lift' line and do that manually. before spin-up,
if this is at all possible. Well the
problem as I see it is deterioration of the magnetic
surface/circuit, and changing motor speed won't improve that (probably).
Lost data is secondary to a lost timing track! That would be ruinous, I
have no idea how I'd re-create that. Certainly, I need a copy of that.
On a system this old, with (relatively) large data tracks, I think that
there would probably be recognizable pulses at slower speeds...