Date:         Tue, 4 Jul 2006 12:13:08 -0400
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         "Richard L. Hess" <[log in to unmask]>
Subject:      Re: Bias Frequencies of tape recorders
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Rob wrote me off-list to enquire about the Revox B77 and B67. I don't 
know these, but the manuals are available at 
ftp://ftp.studer.ch/Public/Products/

They are huge files (100-200 MB each) but you can check out any 
non-currently supported Studer product there. (The A807 is still 
supported through 2010 and is not available there).

Cheers,

Richard

At 10:58 AM 7/4/2006, Richard L. Hess wrote:
>At 10:21 AM 7/4/2006, Rob Poretti wrote:
>>Hi guys and gals,
>>
>>I'm just curious if anyone has taken stock of what bias frequencies were
>>employed by the more common "professional" reel-to-reel tape recorders used
>>through history...
>
>Fortunately, this has been discussed elsewhere and I can provide 
>some of the information:
>
>In the early days, apparently wire recorders used bias as low as 
>30-40 kc, but Jay McKnight recalled in the pre-Ampex days, 60 kHz was common.
>The Ampex Standard was 100 kc up to the MR-70.
>With the MR-70, Ampex switched to 150 kHz bias frequency (and 
>adopted the Hz) [Larry Miller, ex Ampex]
>
>Other later machines used different bias and erase frequencies.
>Ampex AG-440 (A) stayed with 150 kHz [manual]
>Studer A80 80 kHz erase, 240 kHz bias (1:3) [Jay McKnight]
>ReVox A77  120 kHz [manual]
>Ampex ATR-100  144 kHz erase, 432 kHz bias  (1:3)  [manual]
>Studer A810 & A807 (and I think A820 2CH) 153.6 kHz  [manual]
>Otari MTR-10/12 II Bias 250 kHz (erase not spec'd) [manual]
>Sony APR-5000, APR-24  100 kHz erase, 400 kHz bias (1:4) [manual]
>
>MCI JH-24 Multitrack 210 kHz bias, 105 kHz erase  [manual via Brian Roth]
>Otari MTR-90 (original) 246 kHz bias, 123 kHz erase [manual via Brian Roth]
>
>Here is a quick sampling of published bias frequencies for two 
>top-of-the line cassette recorders, a better-than-average portable, 
>and an early compact portable.
>
>Nakamichi Dragon (perhaps the finest machine ever made for overall 
>audio quality) 105kHz (Service manual dated 1985 (scan) 1990 (Xerox))
>Studer A710 (a high-end cassette recorder, without the auto-azimuth 
>that makes the Dragon superior) 150kHz (no date, scan on Studer ftp site)
>Sony TC-D5M (a workhorse, good quality stereo portable) 85 kHz (Svc 
>Manual dated 1980)
>Sony TC-55 (an early compact -- jacket pocket -- mono portable) 
>41kHz (as low as I've ever seen) (Svc Manual dated 1972)
>
>Richard L. Hess                   email: [log in to unmask]
>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.

Richard L. Hess                   email: [log in to unmask]
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.