Now I'm Really Confused. What MRL Tape Do I Need?

Now I'm Really Confused. What MRL Tape Do I Need?

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.
       Step 2:  What kind of tape are you recording on? There's three common "operating levels" (see below for definitions) of recording tape our MRL tapes will cover: +3 dB, +6 dB, and +9 dB. Ampex/Q 406, 407, 408, 480, and 478 are +3dB and use 250 nWb/m calibration tapes. 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 like 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.

Operating Levels: (See also "What Tape Should I Use?" in our archives section

Open reel recorders record at different "operating" levels depending on the deck's design and the tape you are recording on. The "maximum" operating level means this is the setting that will read "0 VU" on your meters with respect to .776 V or NAB 0 VU. AMPEX/Q 407 is a +3 dB tape for instance which means that when your deck is calibrated for a +3 dB tape that "0" on your VU meters is actually +3 dB with reference to the NAB "0".

What do you gain with elevated levels? By being able to record "louder" or "hotter" on the tape the residual noise level on the tape drops with respect to where your recording levels are set. To explain this, think of it this way. If your recordings are recorded hotter you will have to turn down your sound system's volume control compared to a recording not recorded at a hotter level. By turning down the volume control you will get the same music sound volume but the noise floor is reduced.

The noise floor becomes very critical in multi track situations where all the tracks of music and residual tape hiss are mixed together. In this situation, the noise floor becomes much more of a critical issue than simply copying a two track master tape, for instance.

Most consumer decks are set to a specific operating level. There were no +9 dB tapes around at the time, and these decks mostly can not take advantage of the increased recording volume. But you can gain even more headroom with these tapes. RMGI Emtec SM900 saturates at roughly +18.5 dB over a +9 dB operating level. If your deck is set to a +3 dB operating level like many consumer decks are, you'll gain an additional 6dB headroom by not recording as hot.

Just because a tape has a +9 dB or +6 dB operating level doesn't mean you have to record at that level. It's a recommended setting, not a must. When buying a calibration tape, buy one according to your deck's settings. You might be able to boost your settings by +3 dB but +6 dB would be a stretch unless you have a studio quality recorder.

What's an Azimuth?
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.

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