[Vintage-Audio] Scotch Audio Tape Variations

[Duane B. Fischer, W8DBF]

Sheldon is correct. I found a note about it in the Sony seven inch reel marked
as SLH-7-550BL. The "SLH" meaning super low noise - high output. The box is not
cardboard, but a hard plastic with a top that is hinged. You push a button in to
open the top flip up door.  	
	
There is mention of not working with automatic functions that use metal foil put
on the tape to trip a sensor!	
	
I am still trying to determine if the Scotch 227 commercial/mil spec tape is
back coated or not. Does anyone know when MMM mad the type 227 for the US Navy?	

	Duane W8DBF	
	
P.S. I also find mention of back coating on Ampex ten inch and Maxell ten inch.

----------
From: Sheldon Daitch <sdaitch at ibb.gov>
To: Vintage home and professional audio equipment from 1975 back
<vintage-audio at mailman.qth.net>
Subject: Re: [Vintage-Audio] Scotch Audio Tape Variations
Date: Tuesday, February 22, 2005 11:55 AM

I never heard that the backcoating was to reduce print-through, although the
thicker the base stock, and the back coating would add to that, the lower the
print-through, in theory.

I always thought the back coating was to reduce static in fast forward and fast
rewind operations. and at least one site:

 http://www.videomaker.com/scripts/article.cfm?id=1540

seems to back that up:

"Many years ago, the 3M company added an extra layer to their audio and
videotapes. They applied a graphite compound to the base side of the tape, away
from the magnetic coating. Their reason for doing this was to lower static
electrical charges (which build up during fast wind/rewind) and improve the
durability of the tape--especially important for editing. Their studio-quality
audio tapes and broadcast videotapes were soon known by their dull black
backside appearance.

Today, some tapes are back-coated and some are not. While the advantages of
backcoating were (and still are) real, improvements in tape manufacturing have
made it a matter of choice for tape makers, and not so much a big deal to you,
the user."

I have a Teac A-7030 deck and I have problems with the back coated tapes, when I
leave the auto rewind mode on.  The rewind mode uses a split sensor in the
supply reel idler arm, the two pieces of the sensor are insulated, and when a
metallic section of tape shorts out the two pieces, it sends the deck into the
rewind mode.  SInce it relies on a small voltage across the two sensor points,
the voltage causes some "static" in the playback side, no doubt due to the
conductivity of the back coating.

Sheldon



Gerry Steffens wrote:

> Not sure of the difference between the two Scotch tapes but the back coating
> is there to reduce the level of print through.  When tapes are wound and
> remain that way for longer (or even shorter) periods of time the magnetism
> from one layer will "print through" to the next layer.  This is particularly
> true of loud passages.  Minimizing print through was one reason we left
> tapes tails out at the radio station when I was a DJ while in college a
> little over thirty-five years ago.
>
> Gerry
>
> Collecting & Restoring since 1959
> Gerald Steffens P.E.
> Oronoco, MN
>
> -----Original Message-----
> From: vintage-audio-bounces at mailman.qth.net
> [mailto:vintage-audio-bounces at mailman.qth.net] On Behalf Of Duane B.
> Fischer, W8DBF
> Sent: Saturday, February 19, 2005 5:57 PM
> To: vintage-audio at mailman.qth.net
> Subject: [Vintage-Audio] Scotch Audio Tape Variations
>
>
> Hi All,
>
> What is the 'real' difference between the seven inch reels of Scotch autio
> tape
> #207 and #227?
>
> I weighed each on a postal scale, as I thought the #227 felt heavier to me.
> The
> #207 weighed 13.5 ounces and the #227 was just under 14 ounces.
>
> Both appear to be very high quality, the #227 I am positive is commercial
> grade,
> as it has the black/gray oxide.
>
> Additionally, what was the thinking in the 'back coating" of audio tapes?
> The
> reddish oxide on one side and black on the other.
>
> Thank you.
>
> Duane W8DBF
>
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