I have a good deal of experience with high speed duplication gear,
including bin-loop playback. Richard is quite correct. These devices are
more like RF recorders than anything else. Everything about them is
geared that way. I have spent many, many hours aligning high speed
pancake reel-to-reel cassette duplication equipment. (yes, pancake r-t-r
recording where the tape is then loaded automatically in cassette
shells). Properly done, decent response out past 15khz could be expected
on the dups... but the alignment process was VERY painful. The playback
circuits from the bin-loop playback machines and the record r-t-r
machines looked more like AM radio transmitting technology, but it
works. The bin-loop devices used high pressure air to support and move
the tape around with little friction and contact, sort of like a cushion
of air. The pinch rollers on the actual playback devices moved tape so
quickly that it was scary. Imagine the tape path issues. 

There were reel to reel video machines WITHOUT rotating heads that just
relied on stationary heads and very high tape speed, after all. 

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Richard L. Hess
Sent: Sunday, February 12, 2006 5:14 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] 1/4" audio tape digitizing

At 05:54 PM 2/12/2006, Michael Shoshani wrote:
>Jeffrey Kane <[log in to unmask]> wrote:
>How does that affect the frequency response, though?
>I mean, theoretically...let's say you have a machine whose high end
>tops out at 25 kHz.  You have a tape whose highest frequency is 22
>kHz. If you play that tape at twice its speed, I should think that the
>high frequency now tops out at 44 kHz while the machine itself is
>still limited to 25 kHz, rather destroying any nuances in that 22 kHz
>sound once it's been brought back down to normal playing speed.
>Or is my math severely off? (This is something I have wondered about
>for years concerning high-speed tape duplication...)

The original post was about spoken word recordings. I responded to 
that with what I do with normal audio tape machines--that go out to 
30-35 kHz at the higher speeds (a Sony APR-5000 test report that came 
in one of my manuals shows -1.5 dB at 27 kHz at 30 in/s).

An instrumentation recorder can go out to 100 kHz or more.

Duplicators were designed to work at the higher frequencies. They 
were not normal tape recorders. Sadly, most of them are now in 
landfills. Few have been preserved as they're mostly recorders and 
usually an oddball player (like a 1/2" tape or a bin loop.)

I was thinking of 2x reproduction to speed things along. For 
voice-grade oral-history type recordings, 2x is certainly fine using 
the machines we've been talking about, as there probably isn't much 
information past 10 kHz on the original. I just checked a couple of 
originals and there didn't seem to be much energy past 10 kHz and 
what's there is often noise and noise modulation.

I have done some work at 4x where I had a 15/16 in/s 4-track cassette 
and only a 3-3/4 in/s worked OK. The transfer process 
wasn't the worst that had already happened to the tape by a long shot.

Given good pro tape machines and oral-history content, you might be 
able to go up to 4x, but that would be the limit. I was thinking 2x. 
But if you ingest both sides in one pass, then that gains you another

An approach I'm working on is four transfers in real time for 
cassettes with monitoring each cassette for audible problems out four 
of the five identical speakers in my studio. I think this is 
preferable to speeding up the process...and who wants to modify Dragons.



Richard L. Hess                   email: [log in to unmask]
Vignettes Media                   web:
Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
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