Narrowing the Choices:
Step 1: What is
the width of your tape? It's going to be 1/4", 1/2", 1", or 2".
Make sure you're looking at the right tape width when ordering. MRL
tapes are not
returnable unless defective.
What kind of tape are you recording on? There's three common
levels" (see below for definitions) of recording tape our MRL tapes
+3 dB, +6 dB, and +9 dB. Ampex/Q 406, 407, 408, 480, and 478 are +3dB
and use 250 nWb/m calibration
RMGI Emtec SM911, LPR35, & Ampex/Q 456 and 457 are +6 dB and use
355 nWb/m calibration tapes. Also, the very high output tapes
RMGI Emtec SM900, Ampex/Q GP9 are +9 dB tapes and can also use the 355
nWb/m tapes by
setting the operating level on playback to a -3 VU on the meters. Why
not have a +9 or a 520 nWb/m calibration tape? Most users of tape use
either RMGI Emtec SM911, RMGI Emtec SM900, AMPEX/Q 456 or AMPEX/Q GP9
(and soon the ATR Magnetics tapes).
The 350 nWb/m tapes will cover both with a -3VU output
adjustment for the +9 tapes.
Step 3: How many
adjustments to your deck are you going to do? Usually, the main adjustments are the
"operating level" and the azimuth adjustment to the heads. The next in
line adjustment would be the low frequency equalization. Beyond that,
MRL offers calibration tapes that offer complete octaves of frequencies
over the whole spectrum of hearing.
Levels: (See also "What Tape Should I Use?" in our archives section
Open reel recorders record at different "operating" levels depending on
deck's design and the tape you are recording on. The "maximum"
level means this is the setting that will read "0 VU" on your meters
respect to .776 V or NAB 0 VU. AMPEX/Q 407 is a +3 dB tape for
means that when your deck is calibrated for a +3 dB tape that "0" on
meters is actually +3 dB with reference to the NAB "0".
What do you gain with elevated levels? By being able to record "louder"
"hotter" on the tape the residual noise level on the tape drops with
to where your recording levels are set. To explain this, think of it
way. If your recordings are recorded hotter you will have to turn down
sound system's volume control compared to a recording not recorded at a
level. By turning down the volume control you will get the same music
volume but the noise floor is reduced.
The noise floor becomes very critical in multi track situations where
the tracks of music and residual tape hiss are mixed together. In this
the noise floor becomes much more of a critical issue than simply
a two track master tape, for instance.
Most consumer decks are set to a specific operating level. There were
+9 dB tapes around at the time, and these decks mostly can not take
of the increased recording volume. But you
even more headroom with these tapes. RMGI Emtec SM900 saturates at
a +9 dB operating level. If your deck is set to a +3 dB operating level
consumer decks are, you'll gain an additional 6dB headroom by not
Just because a tape has a +9 dB or +6 dB operating level doesn't mean
have to record at
level. It's a recommended setting, not a must. When buying a
calibration tape, buy
according to your deck's settings. You might be able to boost your
by +3 dB but +6 dB would be a stretch unless you have a studio quality
Azimuth is a rotational clockwise or
counterclockwise position of your tape heads. (Don't mess with this
unless you know what you're doing!) To visualize effect of azimuth,
hold up your right hand with your fingers together. Imagine your
fingers are the gap of a tape head. (The gap "reads" the tape, not the
whole head.) And then imagine there's a seven inch wide
roll of tape behind it and your hand has to read all the information
off of the tape. Imagine the information on the tape is in neat
vertical columns. You can see that if your hand is turned from
clockwise or counterclockwise from being perfectly vertical, you won't
be reading the "columns" of
information properly. These "columns" are associated with high
frequency information on the tape. MRL tapes have a perfect "vertical
alignment" of high frequency tones. The job for you is to adjust the
tape head playback "azimuth" or clock/anti clock wise position for the
maximum output with the precision high frequency tones.