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Tape machine alignment is important for getting the best sound out of your machine.
It also keeps your machine healthy and helps it last!
Check out these steps for aligning your tape machine…
So you have a reel-to-reel analog magnetic tape machine! (Or you’re using someone else’s?)
If you’re new to tape, you need to know how to set it up for a session. In this article, we’ll take you through everything you need to know about calibrating a reel-to-reel tape machine.
How To Align A Tape Machine?
The following is a brief overview of some of the tasks you will undertake when it comes to setting up a tape machine. Don’t worry if the terms don’t all make sense, we will go into more detail plus you can read our other article The Basics Of Magnetic Tape Recording.
The following instructions are for the scenario where you’re starting a fresh recording on a blank tape. If you are just setting up to listen to a tape’s prior-recorded audio, you don’t have to do a record alignment.
1. Initial Technical Checkup
Before you do anything, visually look at the machine. The tape machine must be powered off. Pay special attention to moving parts and where the tape comes into contact with the tape path.
See if there is any large debris anywhere and remove it. Look for any wear at the edges of the tape path or at the tape head gaps.
The most likely parts you’d ever end up having to replace would be the motors, the bearings in rotating parts, the pinch roller, and the tape heads.
Unless you are a seasoned professional technician that is well-versed in working with these tape machines or you have a professional technician next to you to make sure you’re doing it right, save yourself time and money by hiring someone else for this task. An attempt to do so by yourself can throw off the alignment by a lot, costing you more time and energy.
You will need a signal generator or oscillator that can generate sine waves for some of the parts of the alignment process. If your tape machine doesn’t have any meters, use an AC voltmeter.
2. Clean The Machine
It’s time to give your machine a cleaning. This will keep the tape path clear of things like dust, old tape residue, or oil.
For cleaning, you will need:
Isopropyl alcohol (90% or above- just one that will evaporate quickly; DO NOT use rubbing alcohol!)
Specially designated rubber cleaner if you can get it, Formula 409 cleaner, Fantastik All-Purpose cleaner, or you can just use water and a small amount of dish soap
Start by getting a cotton swab wet with iso alcohol. You don’t want it to be dripping alcohol, because then it may drip down into the machine while cleaning.
Go through the tape path and clean it with the iso alcohol swab. Take care in cleaning the tape heads- any debris you miss may cause audio dropouts on recording/playback.
MAKE SURE YOU DO NOT GET THE ISO ALCOHOL ON THE RUBBER PARTS!
To clean any rotating parts, hold the swab in one hand, and use your other hand to rotate the top part (the part that won’t be touching the tape) so the swab is dragged across the tape path surface as it rotates.
This is easier and quicker than trying to just use the swab and clean around the whole part while holding it still.
For all surfaces, you drag the swab across the surface and once it shows dirt on it, you throw it out and get a clean swab, or use the other clean end.
Keep doing this until dragging the swab results in no visible dirt. Do not dip a swab, with dirt on it, back into the iso alcohol or rubber cleaner container.
For the rubber cleaner, clean any rubber parts that will touch the tape. Use the same cleaning technique as above. Again the iso alcohol should not be used to clean these parts.
This is not done every time you change the tape. It is done occasionally.
How often the tape machine is used will determine how often it will need to be demagnetized. Different studios and setups will have different demands for their tape machine.
The tape machine should still be off. Get out a demagnetizer (de-mag). Keep the de-mag at least 3 ft. away from the machine. Make sure any recorded media is not nearby, including hard drives.
Power on the de-mag, then approach the tape machine. Once you get close to the tape machine surfaces, continuously and slowly move the de-mag across all the surfaces (don’t drag it touching the surface of the tape path, move it closer, along, or away from the tape path and headstock).
Having the de-mag accidentally touch the tape path won’t irreversibly damage it, but care should be taken in not letting the de-mag physically touch any of the surfaces to avoid scratching them up (especially the tape heads). If the de-mag came with a soft plastic cover on the tip, leave it on.
Once you’ve run the de-mag across all the surfaces you want to demagnetize, slowly move it away from the tape machine. Only when the de-mag is at least 3 ft. away can you switch off the de-mag.
4. Choose Your Alignment
Magnetic tape comes in different brands and materials. How you align the tape machine will largely depend on what tape speed you will record with and the type of tape you’re going to record on.
You now get to start working with the calibration tape. It contains test signals that are used to align the tape machine so it conforms to accepted standards for different tape machine parameters according to the desired tape speed and fluxivity.
This allows much easier alignment across different tape machines and tape types. Each calibration tape has, at the very least, sections for reference fluxivity alignment, azimuth alignment, and amplitude and frequency response alignment.
Select your reference fluxivity, or recording level, usually by reading the packaging of the calibration tapes. It is expressed in nanoWebers per meter (nWb/m) at 1kHz . Use the provided chart to figure out the fluxivity level you will be calibrating to on the meter.
Also note, use tape speed and reference fluxivity to figure out which set of recorded tones you will be using on the calibration tape. There will be different sets for different tape speeds.
5. Playback Azimuth Alignment (If Needed)
Now you can turn on the tape machine. Make sure it is set to play back at the tape speed you want to record with.
Set the calibration tape on the tape machine, rewinding back to the part where the tones (for the designated tape speed) start.
Some engineers view the azimuth as something that needs to be aligned each time the tape machine is aligned. Others believe that it only needs occasional alignment.
For tasks such as archiving and when the next tape is a different tape type/brand, the azimuth should be aligned. If the next tape being used is the same type/brand as the previous aligned one, the azimuth alignment can be skipped.
If needed, start by aligning the azimuth (analogous to turning your head left or right) of the repro and sync head. Set the tape machine to record safe and turn monitoring off on the repro head.
The common method uses a dual-channel oscilloscope. Patch the second outermost tracks’ (ie tracks 2 and 23 in a 24-track tape) tape output to the two inputs of the oscilloscope. Set its view to XY display.
An alternative method has a similar routing, except the tape output is patched to an AC voltmeter.
In both methods, sum the two tracks’ outputs to mono.
Adjust the azimuth so the oscilloscope displays a straight 45-degree line. With the other method, adjust the azimuth so you get the highest AC voltage reading.
Do this at 500 Hz, 1 kHz, 10 kHz, 16 kHz, and then check 500 Hz again. Do the same for the sync head, but monitor off of the sync head instead of the repro head.
6. Repro & Sync Alignment
If you skipped the azimuth alignment, the tape machine should be turned on, the calibration tape should be at the part with the correct set of tones, and monitoring should be done off of the repro head.
It would be wise to set the tape machine so it automatically shuttles back to the start of whatever tone you’re working with upon reaching the end of the said tone.
Find the part on the calibration tape that plays a 1 kHz tone. Adjust the repro gain/level potentiometer (pot) until the meter for the corresponding channel reads 0 dB (it can be on a VU meter or PPM meter). Do this for all channels.
Repeat using the 1 kHz and 10 kHz tones to do the same with the sync gain and sync EQ pots on all channels.
7. Input/Monitor Alignment
Take the calibration tape off the machine and put it on the blank tape you plan to record with. Plug the signal generator into the tape machine inputs.
Usually, the machines have a special input for signal generators. If not, you route the signal generator through a mixing console and send the signal to all of the tracks at 0 dB leaving the console.
Switch all of the channels to record ready and set to monitor off of the repro head (since you’re in record ready, it’ll actually be off the input point). If your machine has an input/monitor pot, adjust it for a 0 dB reading. Do this for all channels.
8. Setting the Added AC Bias
With the same settings (record ready, monitor off repro), change the frequency of the signal generator to 10 kHz. Hit record. Find the pot for the bias setting.
For all channels, you first turn down the setting so the meter reading goes very low. Then you turn the setting back up, so the meter rises back up.
You continue to keep turning the bias pot up as the meter hits a peak level and then begins to go back down. You can keep adding the bias until the reading decreases from the peak.
It varies with different machines and different tape formulations, but commonly is 1.5dB below the peak for 30 ips and 3dB below the peak for 15ips. Do this for all channels.
Most machines will have a master bias setting that affects all of the channels simultaneously.
This is useful if you know the bias on each channel is already aligned and you merely need to change the bias due to changing the tape.
9. Recording Alignment
You use the same settings on the tape machine as you did for the bias setting. Switch to generate a 1 kHz tone, then start recording.
Adjust the record gain pot for a 0 dB reading. Then use a 10 kHz tone to adjust the record high EQ (30 ips) or record low EQ (15 ips). Sound familiar? Once again, do this for all channels.
10. Low Comp or LF Gain Alignment
Same settings as the recording alignment settings. Switch to a 100 Hz tone. Start recording. Adjust the low comp (sometimes called LF gain or repro LF EQ) pot for a 0 dB reading.
Do this for all channels. Due to the phenomenon called fringing (low-frequency info bleeding onto adjacent tracks), this low-frequency alignment has to be done after you set the record levels.
After that, go back and check the alignment of the 1 kHz for record gain and 10 kHz for record high/low EQ. Do so with the same method as the initial record alignment (monitor from repro, tracks in record ready, recording while aligning).
Make any needed adjustments so that all three result in a 0 dB reading.
11. Print Project Tones, Recheck Low Frequency
Print the aligned project tones so that there is 1 minute each of a 1 kHz, 10 kHz, and 100 Hz sine wave at either the start or end of the blank tape. Separate them from the rest of the tape with leader tape.
If overdubbing, the following step isn’t needed. Switch to monitor from the sync head then rewind to the 100 Hz tone that was just recorded, monitoring from the sync head. If needed, adjust the low-frequency EQ for a 0 dB reading. Usually, there isn’t that much adjustment needed. Do this for all channels.
Separate about one minute of blank tape with leader tape. This will be the record pad that is used for record alignment due to further tracking on a different tape machine, working on the same machine with altered alignment settings, or checking when overdubbing on the same machine.
Finally, it is wise to put the record pad at the end of the project, so it doesn’t accidentally record over the project test tones or music!
When beginning to practice the alignment procedure of a tape machine, take the time to absorb each step and understand why it is important. Practice makes perfect, so don’t get frustrated if the first attempts take a very long time.