As many of you know, I spent my "formative" recording years working in the wonderful world of analog tape. One of the first tasks I had to learn was how to align a tape machine. And one of the tasks I was to get thoroughly familiar with was that of aligning the machine before every session. Consequently, one of the things I don't miss about not recording analog anymore is aligning a tape machine before every session.

As a result of doing this darn near every day for seven or eight years, I became pretty good at it. And later on, when I had occasion to teach recording classes, I had to teach alignment. So I created a teaching supplement that broke the alignment down into 17 simple steps, most of which had to be completed 24 times - one time each for all 24 tracks on the machine.

Then I quit teaching, moved to Nashville and watched analog recording gradually fade out of practice (at least in Nashville). And for the last fifteen years or so, I haven't done any analog multi-track recording to speak of.

Interestingly, the subject of machine alignment has come up several times in the past few months. Each time I've gone back to my old teaching notebook and pulled out the supplement I wrote and ran copies. So I thought it might be nice if I just posted the instructions on the website and save the wear and tear on my copy machine, not to mention the paper (trying to think "green", you know).

So here it is:

                                                           TAPE MACHINES: ROUTINE MAINTENANCE AND ALIGNMENT

  1. Clean machine. Clean heads, idlers, flutter filters, guides, capstan and pinch roller. Use cotton swabs with denatured alcohol or freon. These are safe for heads, guides and rubber pinch roller. Do Not Use isopropyl (rubbing) alcohol on pinch roller.

  2. Demagnetize machine. First TURN MACHINE OFF!!!!! Remove all tapes from the vicinity of the machine. Plug in HAN-D-MAG demagnetizer as far from machine as power cord will allow. Approach one of the tape heads slowly with the HAN-D-MAG, drawing to within a half-inch of the head and, using an up-and-down motion, slowly demagnetize it. Then SLOWLY draw the HAN-D-MAG away from the head. Repeat this procedure with each head and the capstan. When finished, pull the HAN-D-MAG as far away from the machine as possible before unplugging.

                                                                                                                  ALIGNMENT

  1. Carefully load alignment tape (Magnetic Reference Laboratories Reproducer Calibration Tape) and rewind it to the 1000 Hz tone near the beginning of the tape.

  2. On machine's autolocator, select MASTER REPRO to assure that the tape will play back off the repro head. Also push the MASTER SAFE switch. This will prevent the machine from accidentally being put into record mode and erasing your expensive alignment tape. Grab your small screwdriver (jeweler's) as you'll have to use it to do the alignment.

  3. Play alignment tape. As the 1000 Hz tone plays, look at the meter associated with Track #1 and adjust Track #1's REPRODUCE LEVEL potentiometer so that the meter reads "0". Do this on all 24 tracks. Note: machines have separate adjustments for fast speed (30 i.p.s) and slow speed (15 i.p.s.) . Make sure you are adjusting for the speed at which you are working.

  4. Fast forward the alignment tape to the 10,000 Hz tone. As you play the tone, adjust the REPRO HIGH FREQ EQ pot so that the meter reads "0" on each of the 24 tracks.

  5. Now you are ready to align the sync head. On machine's autolocator, select MASTER SYNC so that the machine will now playback off the sync head. The meters will also indicate levels coming from the sync head.

  6. Rewind the alignment tape back to the 1000 Hz tone. As the tone plays adjust the SYNC LEVEL pot so that the meter reads "0" on each of the 24 tracks.

  7. Fast-forward to the 10,000 Hz tone and as it plays adjust the SYNC HIGH FREQ EQ pot so that meter reads "0" on all 24 tracks.

  8. Now you are finished with the alignment tape. Fast-forward it off the machine, remove it and carefully return it to a safe place.

  9. Load the reel of tape on which you are going to record.

  10. Go to machine's autolocator and push MASTER REPRO switch. Also turn off the MASTER SAFE switch. Then push RECORD READY buttons for all 24 tracks. Now you're ready to set up your record electronics.

  11. Assign console's oscillator to the multi-track machine. Select 10,000 Hz at oscillator and use console meters to determine that you are sending "0 VU" to the multi-track.

  12. Put the multi-track machine in RECORD. All of the record adjustments will be made with the machine in RECORD. The first record adjustment in BIAS. To set bias, turn Track #1's Bias Level pot counterclockwise. The meter will likely swing to the right and then go back to the left as you continue turning. Once meter goes all the way down to the left (-20) side, turn pot clockwise slowly and observe the meter as it goes up . Eventually, the meter will reach a peak and start backing down as you continue turning the pot clockwise. Note the meter reading at its peak and continue turning clockwise until the meter drops 1-1/2 VU below the point at which it peaked. This is known as OVERBIASING and we are overbiasing 1-1/2 . This is the amount of overbias required for Ampex 456 tape on Studer tape machines. Other tape brands require different amounts of overbias for maximum performance. (See table at end of instructions.) Make the bias adjustment for all 24 tracks. Setting record level, which is the next step, is dependent upon bias being properly set.

  13. Change oscillator frequency to 1000 Hz and make sure you are sending "0 VU" to the multi-track machine. You will now set RECORD LEVEL. Put the machine in RECORD and adjust the RECORD LEVEL pot on Track #1 so that the meter reads "0". Do this on all 24 tracks.

  14. Change oscillator frequency to 10,000 Hz and make sure you are sending a level of 0 VU to the multi-track machine. You will now set up RECORD HIGH FREQUENCY EQ. Put the machine in RECORD and adjust Track #1's RECORD HI FREQ EQ pot so that the machine meter reads"0". Do this on all 24 tracks.

  15. Change oscillator frequency to 100 Hz. You will now set up LOW FREQUNCY REPRO. Put the machine in RECORD and adjust Track #1's REPRO LO FREQ EQ pot so that the machine's meter reads "0". Do this on all 24 tracks. (NOTE: We don't set up repro low frequency eq using the alignment tape because of a phenomenon known as FRINGING*. We have to wait and set it up AFTER we set the record levels.)

  16. At autolocator select MASTER SYNC switch. Now rewind tape to the beginning of the 100 Hz tone you just recorded. DO NOT record, but play back that tone and adjust Track #1's SYNC LO FREQ EQ pot so that the machine's meter reads "0". Do this on all 24 tracks.

  17. Your machine is now aligned. Now, you must print your tones.** Record about a minute of 1000 Hz, a minute of 10,000 Hz and a minute of 100 Hz. You should not adjust any pots on the tape machine while you print these tones. When the tones are recorded place some tail leader in the tape to mark the end of the tones. Then fast forward through about a minute of blank tape and place another piece of leader. This one minute of blank tape is your RECORD PAD and will be used by you or another engineer who might work on this recording project and has to align the tape machine to the tones you printed. In that case, the tones you printed would be treated as the alignment tape and would serve to set up REPRO and SYNC adjustments. The record pad would be used to set up the RECORD adjustments.

                                                                                                                                  ELEVATING RECORD LEVEL

Elevating record level is the practice of setting the tape machine so that it records at a level that's hotter than that of the alignment tape. Alignment tapes have been produced at different levels over the years. The first one I ever used was 185 nanoWebers per meter (nW/m). Later I used a tape that was made with a reference level of 250 nW/m. More nanoWebers translates to more level and the 250 nW/m tape was about 3 dB hotter than the 185 nW/m tape. But, in order to maximize the signal to noise performance of the multi-track machine, many studios elevated the record level to anywhere from 1 to 6 dB over the level of the alignment tape. Let's say we wanted to elevate our level to 3 dB hotter than our 250 nW/m alignment tape. Here's how we would do that: Follow the above alignment instructions, but in steps 3, 4, 6 and 7, set the repro and sync levels and hi freq eq so that the machine meters read "-3". Complete the remainder of the alignment instructions exactly as written. What you're doing is setting the playback side of the machine to "-3", then setting record to"0". Because "0" is 3 dB hotter than "-3", we have elevated our recording level 3 dB above the level of the alignment tape. If we wanted to elevate our recording level only 1 dB, we'd set up the repro and sync pots to read "-1". An easy way to remember it is that as long as the alignment tape is on the machine, you set the pots to "-x", x being whatever amount you want to elevate the level. Once the alignment tape comes off, all the adjustments will be made so that meters read "0".

Another important thing to mention here is that your recording level should be documented on the tape box. When you record your minute of 1KHz, minute of 10 Khz, and minute of 100Hz, you should write on the tape box: "Tones at head:1K, 10K, 100Hz +3dB/250" This tells anyone who uses the tape that the record level on the tape has been elevated 3 dB over a 250 nW/m reference level.***

AMOUNT OF OVERBIAS REQUIRED BY DIFFERENT TAPE BRANDS

Tape             Tape speed(i.p.s.)        Overbias

Ampex 456        30                          1-1/2

                           15                           3

Scotch 250         30                           1

                           15                           2


Scotch 226         30                            1-1/2

                          15                            3


Agfa 468           30                            1-3/4

                          15                             3-1/2


Agfa 469           30                             1-1/2

                          15                              3


*Fringing is a phenomenon in which low frequency information bleeds over onto an adjacent track. It's just something that happens. Alignment tapes are full-track recordings, not multi-track recordings. That is, there are not 24 stripes of tones lined up on a 2-inch wide piece of tape. It's one big fat 2-inch stripe of information. Therefore you can use the same alignment tape on a 2-inch 24-track AND a 2-inch 16-track machine. Fringing "fools" the low frequency repro and sync meters into reading a little bit high, because they're responding to level from their own track plus those on either side. So, we adjust our low frequency playback eq while recording the low frequency tone.

**Printing tones is important because it establishes the condition of the tape recorder that recorded the project at the time the project was recorded. Even though most professional studios adhere to established industry standards with regard to alignment, individual machines have their own character which is a result of machine age, head wear, etc. In other words, machines in different studios might exhibit slightly different record and playback characteristics. Having tones and setting up to them allows engineers to put their machine in alignment with the machine on which the project was recorded and assures that everything will sound the same as it did in the other studio (at least from a tape playback perspective).

***"Tones at head" means that the set up tones are located at the beginning of the reel.