Re: [ARSCLIST] Digital File Specs and StoryCorps

[Tom Fine <tflists@xxxxxxxxxxxxxxxxxxx>]

Hi Richard/All:

Richard, your list of bias frequencies inspired an hour-long trip into the service manuals files. 
Here are some more machines for your list, all bias frequencies listed in the service manuals:

Reel-to-reels:
Technics 1500/1506/1520 -- 120kHz
Tascam 32/44-OB -- 150kHz
(note -- I expect this would also be the bias frequency of the last-generation 8-track 1/2-inch 
Tascam, I believe the 48-OB)

Cassettes:
Tascam 122 -- 100kHz
Nakamichi MR-1 -- 105kHz

Also, 150kHz bias for the Ampex AG-440B and I am pretty sure the 440C given that part numbers and 
values on the bias/power boards appear to be the same around the oscillator.

-- Tom Fine



----- Original Message ----- 
From: "Richard L. Hess" <arclists@xxxxxxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxxxxxx>
Sent: Friday, February 01, 2008 7:42 PM
Subject: Re: [ARSCLIST] Digital File Specs and StoryCorps


> At 07:18 PM 2008-02-01, Tom Fine wrote:
>
> > What are the bias frequencies of cassettes? Did it vary by manufacturer or was there a standard? 
> > Did it vary by tape type? Sorry if these are ignorant questions. Richard will know where I'm going 
> > here ...
> >
> > Does any cassette playback system stand a chance of reproducing bias so Jamie Haworth's Plangent 
> > Process can be used on it?
>
> I think the likelihood of a standard deck (such as a Dragon) reproducing the bias from its output 
> jacks is highly unlikely.
>
> I posted the following to this list on 2006-07-04; 2008-02-01 revisions are marked *
>
> 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]
> Ampex ATR-100  144 kHz erase, 432 kHz bias  (1:3)  [manual]
>
> MCI JH-24 Multitrack 210 kHz bias, 105 kHz erase  [manual via Brian Roth]
>
> Otari MTR-10/12 II Bias 250 kHz (erase not spec'd) [manual]
> Otari MTR-90 (original) 246 kHz bias, 123 kHz erase [manual via Brian Roth]
>
> Sony APR-5000, APR-24  100 kHz erase, 400 kHz bias (1:4) [manual]
>
> Studer A80 80 kHz erase, 240 kHz bias (1:3) [Jay McKnight]
>    *This applies to the Studer A80 VU apparently
> *Studer A80 RC 150 kHz [manual]
> Studer A810 & A807 (and I think A820 2CH) 153.6 kHz  [manual]
>    *A820 2CH confirmed at 153.6 kHz
> ReVox A77  120 kHz [manual]
> *ReVox B67  150 kHz [manual]
> *ReVox B77  150 kHz [manual]
> *ReVox PR99  150 kHz [manual]
>
> 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: 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.