Re: [ARSCLIST] Slow tape speed equalization time constants (was Repairing (or purchasing) a Uher)

["Richard L. Hess" <arclists@xxxxxxxxxxxxxxx>]

At 05:02 AM 6/14/2006, Prentice, Will wrote:
> Richard L Hess wrote:
> "I think at 15/16 all bets are off as Jay doesn't
> even sell a tape for that speed (I don't think), and I'm not even
> sure there is a standard curve for 15/16 nor 15/32."
>
> IASA TC-04 describes eq curves in terms of time constants, but lists
> 15/16ips as "undefined". Earlier this year however, Dietrich Schuller
> told me that the Phonogrammarchiv had obtained figures for the Uher
> curve at 15/16ips, I think from Uher themselves. They are: 3180
> microseconds and 159 microseconds.


That is indeed good to know, but considering that 3180 and 3150 have 
been used interchangeably for the low end EQ, I think perhaps saying 
160 microseconds for the 15/16 EQ would be reasonable. The 159 
microseconds implies a precision that would not have been included in 
the Uher portable recorders.

Has anyone unearthed the time constants for the Nakamichi cassette 
recorders that ran at 15/16? The microcassette dictation recorders at 
both 15/16 and 15/32 in/s? And the logging recorders that ran at 15/32?

I have a spreadsheet that I should clean up, double check, and post 
on my Web site that gives the curves that you have to use to offset 
playback at one EQ/speed for a tape recorded at another EQ/speed.

Jay McKnight has a DOS program and it should be here (according to 
his post from three years ago:

> I have put both files on our website: download
> http://www.flash.net/~mrltapes/magtapeq.seq and
> http://www.flash.net/~mrltapes/magtapeq.exe .
>
> The source code ".seq" file is plain text -- you can read it in
> "notepad". It gives general instructions for using magtapeq.exe .
>
> The magtapeq.exe is the complete F-PC forth, with software floating
> point and some other functions compiled on top, then magtapeq.seq
> compiled on top of that. So you have the complete "works" in
> magtapeq.exe , and the 3/4 baked instructions in the .seq file.
> Contact me when you have problems.



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.