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Re: [ARSCLIST] NAB vs. DIN recordings

At 08:43 PM 2007-03-25, Eric Jacobs wrote:
Hi Richard,

What's your favorite tool for measuring recorded track width on
a tape?  I use the Arnold B-1022 Magnetic Viewer, but it's not
the easiest tool on the planet to use - it's sometimes hard to
see the tracks.

Viewing the tracks is a headache no matter what. I use a 3M Plastiform (older) which is, I'm pretty sure) now the Arnold.


The spray can be seen in action here:

You won't see audio quite as nice because these are 50 mil FM IRIG tracks with a high-level FM carrier on them.

FYI, the 2.8mm track width works out to 110.2 mils.  Do the
standards for track widths specify them in millimeters or mils?

I think the German tracks are actually 2.75 mm which is about 108 mils. I think that's how they are standardized, at least that's how Studer discusses them. Jay rounded 2.75 to 2.8.

If I understand correctly from your email, mismatching track
widths (head vs recorded track) primarily influences noise
(fringing), but not EQ?

Correct. EQ is a function of the twiddly knobs and switches in the machine, while fringing and noise, which are two separate artifacts, are related to the track-width mismatch. Also, David's point about noise in the wider NAB guard band is a real one.

For the record:

I have a Studer A810 which originates from the Seattle area
which has DIN heads.  I need to check if it was originally a
CBC machine, but I don't think so.

It might have been. CBC probably had a thousand machines at one point.

I also have a Studer A810 from Universal Studios - in great
shape, low mileage, high serial number - with NAB TC.

Oddly, two of my A810s--in some respects my best two--are from a CBC TV facility and they are NAB TC as well (TC=SMPTE TimeCode on a centre track) Not surprisingly my two best APR-5003v machines came from a post facility in the DC area.

My other Studer A810, which is a CBC machine, has NAB (no TC).

Go figure. Maybe TV.

My Studer A820 is NAB TC.  It originates from Newfoundland
and has an Ontario power sticker on it.

The Ontario Power sticker had to be applied since the machines did not bear a UL/ULC/CSA label. It's the safety inspection. Since it was sold out of Toronto, I would think that might have been the reason, but it could have also been sold into Ontario and then resold to Newfoundland.

It's rumored that the DIN heads reduce the need to swap head
stacks when switching between full-track mono and half-track
stereo recordings.  If so, might this flexibility be a
potential explanation for the prevalence of the DIN heads?

Yes, and the only real reason is that it makes the stereo recordings playable on full-track mono machines with about a 1.3 dB loss on overall level vs. the 3.2 dB loss with 0.082 NAB track stereo tapes played on a FT player. The Ampex 0.075 tapes would be about 4 dB down on a full-track player.

Oddly, that may explain why the DIN head tone on one of the tapes was about a dB and a half above 250 nWb/m. That would provide perfect backwards compatibility, but not perfect forwards compatibility.

Might there be other performance advantages to the DIN heads
that made them popular?

The big deal is the S/N and a smaller deal is the butterfly implementation MAY have reduced head bumps--it appears so.



Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.

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