MAGNETIC REFERENCE LABORATORY, INC.
165 Wyandotte Dr, San Jose, CA 95123 USA
Phone and FAX +1.408.227.8631
Send orders, comments, and questions to us at MRL ( ).
Welcome to the
Magnetic Reference Laboratory
[Last updated 2014-05-05
Blank tape prices went up again in 2008, so
all MRL prices were increased after 2008-Apr-01.
(Part Numbers and Prices)
To Place an Order
MRL Technical Papers Available
More Information on Analog Magnetic Tape Recording
Magnetic Reference Laboratory
makes and sells Calibration Tapes (what is a
"Calibration Tape"?) for analog audio magnetic tape reproducers in
the Open Reel format. We no longer make Calibration Tapes in the Broadcast Cartridge format. Other people do cassettes
This page will lead you to all of our literature, which we have put
into the Adobe Acrobat (PDF) format.
You can download
the free Acrobat reader from Adobe's website. If you are not able
to download these publications, please email, call, or fax us, and we
will mail or fax them to you.
Catalog Pages (Part Numbers and Prices):
- We make
many different sets
signals, and each is described in one of our "Publications". Within
each publication you will find the test signal descriptions, part
numbers and prices for various tape widths, speeds, standard
equalizations, and lengths.
- Here are
same examples of the
catalog pages describing Calibration Tapes with the more
popular test signals:
purpose, for setting reproducer gain,
azimuth, and frequency
response from 32 Hz to 20 kHz);
- Two-speeds with
many different selections of frequencies; and
Complete List of MRL Publications gives all of the other test
we can record for you, including Polarity Calibration, special signals
for Sound Technology or for Audio Precision measurement systems, Fast
Swept-frequency for use with an oscilloscope, Slow Swept-frequency for
use with a plotter, single frequencies, Broadband Pink Noise, Broadband
White Noise, and Chromatic Sweep for use on your reproducer's vu meter. It also gives an explanation of the MRL Catalog Numbers.
MRL Calibration Tapes , a 12-page technical paper, gives a more advanced
discussion of general information that applies to all of our
calibration tapes. Topics covered
include a guide to choosing a Calibration Tape (standards, test signals
available, levels, reference
fluxivity, and fringing), tape reproducer adjusting techniques
(preliminaries, low-frequency response calibration, what to do in case
you don't have the
right calibration tape), some tape recorder adjusting techniques, and
our specifications and tolerances.
- Many other technical papers on
magnetic recording are also available online.
To place an order:
- You may order directly from MRL.
Contact us by e-mail at ,
or call or FAX our order desk at +1.408.227.8631 on weekdays
between 09:00 and 17:00 Pacific Time. Orders placed before noon Pacific
Time can usually be shipped that day.
- You may pay by major credit card
(VISA, Master Card, or American Express), or by guaranteed funds (money order or cashier's check).
For international monetary transfers (which are more expensive), call or email MRL for instructions.
Orders placed before noon Pacific Time can usually be shipped that day, but we can't guarantee it. We
have a very small staff (usually one person), and it may occasionally take up to a week to have your order ready to ship. So if
you require your order to be shipped by a deadline, place your order at least a week before that date. Don't wait
until the last day!
Please contact us if you need further information, or have questions that were not answered in this literature.
Sales tax of 8.75 % will be added to orders shipped to Santa Clara County,
CA; or 7.5 % to orders shipped elsewhere to California. (We are not required to
collect, and we do not collect, any other district taxes).
- You may place your order with one of our dealers --
this may be easiest for you if you have an account with them. See the list of MRL
USA Dealers or MRL International Dealers . If your favorite dealer's name is not
listed, ask him to contact us about becoming an MRL dealer.
MRL has been a Sustaining Member of the Audio Engineering Society since 1976
MRL Technical Papers Available
These papers answer many "frequently asked questions" on using analog
tape recorders. They discuss both theoretical and
practical matters, and supplement the information given in the manuals
for tape recorders. They are available for downloading from
The Standards (for instance
IEC Standard 60 094, Part 1), and the tape
recorder manuals, both say to set up your tape reproducer gain and
equalization from a "Calibration Tape" such as MRL makes. But you may
have wondered how MRL measures the response and fluxivity in the first
place. Well, we do it from first principles that are
explained in the technical paper "Flux
and Flux-Frequency Measurements and Standardization in Magnetic
Recording". Another paper, "Tape
Measurement Revisited ,
explains both an ac and a dc flux measurement in detail, with examples.
Tape Recording Equalization:
- "Head bumps" and Low-frequency response -- why the low-end
may not sound like what you thought you recorded:
in a Magnetic Tape Recorder (measurement methods and tolerances)
- Biasing in Magnetic Tape Recording
(what ac bias does; how it affects frequency response, distortion, and more)
- Demagnetizing A Tape Recorder
- Head Height Alignment Methods
- Is My Calibration Tape Still Accurate?
Strength for Partial Erasure of Magnetic Tape (how large a field
does it take to accidentally erase a tape?)
- Making and using Calibration Tapes, a pair of background papers from Ampex days:
Pitch, and Timing Errors in Tape Recording and Reproducing
Flutter" and Tape Compliance Bibliography
-- tape binder shedding,
and what to do about it -- MAJOR UPDATE 2008-01-30
- Tape Information Table , with a summary of coating thickness, coercivity, retentivity, and
remanance for 17 professional tapes from Ampex, 3M, and BASF, in consistent (SI) units
MRL President Jay McKnight has published over 70 papers on analog
magnetic recording and audio engineering. Topics include the design of
magnetic recording heads; the magnetic erasing, recording, and
reproducing processes; signal and noise considerations; frequency and
wavelength response, measurements, standardization, etc; audio systems
and practices; program level indicators; tape transport design, flutter
measurement, etc; and miscellany. Many of
these were published in the Journal of the Audio Engineering Society.
are listed in the Bibliography of
by J. McKnight, and many of the PDF files of the papers are linked there.
For information on RMGI blank tapes, including the technical specifications, see their website
- For information on ATR Magnetics blank tapes, including technical specifications, see their website .
- For information on the the
history of audio engineering (including
magnetic tape recording), see the website of the AES Historical Committee.
- For information on all
aspects of Ampex tape recorders, see the Ampex Virtual Museum and Mailing
List (not affiliated with Ampex Corp).
- For information on all
aspects of Studer tape recorders, subscribe to the Studer List (not affiliated with Studer Corp).
- For information on Sony/MCI tape recorders, see the Sony/MCI discussion
group (not affiliated with Sony Corp).
- For "Tips/Notes/Formats/Resources", see Richard Hess's Web pages .
- For Calibration Films (for 35-, 17.5-, and 16-mm motion-picture sound systems), see the Swiss company Sondor and the bottom of their product page (MRL does not make Calibration Films).
Updates for this home page
|Added links for motion-picture calibration films from Sondor.
|Deleted links to Pub644 and Pub673; added links to Pub070+LF and Pub 043+LF
|Link to Studer List restored -- still operating; CA state tax rates updated
|International Monetary Transfer information updated.
|Older updates moved to here
|The update of the home page from 2008-03-17 somehow got lost; reinstated here. Link to "Studer List" removed -- defunct.
|Major update of pubshed
|Updated "Azimuth in a Magnetic Tape Recorder"
|Added alternate email address firstname.lastname@example.org for anyone having difficulty contacting us at the comcast.net address.
|Price increase from 2008-04-01, PubPL2008 ; available on ATR Magnetics Tape; international dealers updated; prepay removed -- nobody does it
|Minor cleanup; added jm biography link.
||Added explanation of MRL Catalog Numbers to the "List of Publications"
| Bibliography of
by J. McKnight now includes links to PDF files of many of the papers.
|Ref to prices changed to
|Price increase, 10 $ per
item from 2006-11-03; new address & fone/fax.
|Added link to Jack Endino's measurements
of "head bumps"
|Added para "Delivery";
update "More Information..."