As to quarter-track 30 in/s playback, this is one of the reasons I have
invested so much time and effort into the Sony APR line. They officially
play 3.75 in/s to 30 in/s, although each head assembly is nominally only
three speeds, but there is a DIP switch in the head assembly that allows
you to select 3.75 to 15 or 7.5 to 30. That DIP switch also permits
assignment to 12 different memories (some parameters are preset to
certain memory locations, such as some are for half-inch tape, some are
for timecode, some are for mono).
In any event, I could capture some of the 30 in/s material with either a
quarter-track head if that was ideal or the 8-track, four-channel
elevator head if we have to look for remaining swaths less than 43 mils
As to B-wind, in instrumentation, the IRIG standard was written with
tracks counting up from the baseplate with the heads essentially in a
B-wind position due to a turn-around roller, although the tape is A-wind
on the reels. That conveniently corresponds to the normal topology in
audio of tracks being counted from the edge farthest from the baseplate
and increasing as you get to the baseplate.
In both instances, track 1 is the same edge of the tape! Of course, that
is really only useful in one instance, as the only common track format
between audio and instrumentation is 1/4-inch 4-track. Everything else
in instrumentation uses staggered heads (including 8-track 1/4-inch). In
these cases, the tracks are split between odd and even heads in order to
provide for greater shielding between tracks in the heads. This reduces
the need for wide guardbands to accommodate inter-track shields in the
head construction because, as far as the head is concerned, the adjacent
tracks can be used for inter-track shielding within the head.
For example, in audio, four-track 1/2-inch track width is about 70 mils
and in instrumentation, they put seven 50-mil tracks in the same real
estate. For audio, only 56 % of the tape width is actively recorded;
while for instrumentation, 70 % of the width is actively recorded. I
think the general practice was to put elements that were critically
related time-wise all on odd tracks or all on even tracks. The Mt. St.
Helens seismic tapes I had recorded WWVB on one track and a locally
generated IRIG code on another track and, if I recall correctly, one was
odd and one was even. The displacement between the odd and even gaps is
specified as 1.5000 inches and that is "baked in" to the machine
On 2013-02-26 3:12 AM, Tommy Sj÷berg wrote:
> Hi Henry (and Richard)
> I see a lot of re-used tapes that were never erased - just recorded over. Like Richard says, if the old recording is long enough to be intelligible, it can be saved. "Overwritten" and "Partially erased" would apply for the original program material, but I haven't heard any term for the material put "on top" of the original - perhaps "new recording"?
> I do come across half-track and full-track tapes that have been overwritten by quarter-track recordings. One of the worst cases, as far as playing back, are full-track 30 ips recordings overwritten by 1-7/8 ips quarter-track. That leaves, in essence, a 30 ips quarter-track recording, of which I know no suitable machines to play it with.
> Another thing I occasionally see are half-track recordings where the tracks are reversed, i.e. the left track is backwards and the right is forwards. I came across a possible clue the other day, where such a tape (from 1957) was wound oxide out. I suspect B-wind machines were "mirrored" as far as track placement goes?
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
Quality tape transfers -- even from hard-to-play tapes.