How To Align An Analog Tape Recorder

Why do it?

The fact that analog machines are living in an environment, which changes with humidity, temperature, and age, one would think that logic dictates that these machines need maintenance regularly. But nooooo , Mr. bad breath, this document has to explain why analog machines need regular care.

Here is an analogy:

When you buy a car you...

1. Drive it from the showroom floor and put gas in it only when it needs it for the rest of the life of the car, and until you decide to sell it. and...
2. Magically, oil is injected into the oil pan in precisily the correct incremenets when car needs it and (of course) the oil is somehow transformed from dirty fluid into a clear smooth lubricating substance... and...
3. Over the course of 3-4 years, your tires somehow manage to re-tread themselves with new tough fibers, resisting all forms of road conditions, including nails, glass, and construction. and...
4. Every week, the weather is PERFECT and it RAINS in exactly the correct amount at EXACTLY the right time with the wind following at exactly 15 MPH with the only elements in the breeze being pure oxygen... dust free so that you never have to worry about washing your car...

The only way your analog machine will stay aligned is if You do it... and you do have to do it!

The Steps:

1. Degauss the tape recorder heads.
2. Clean the Heads , Pinch Roller , and the Capstans.
3. Physically Align the Reproduce Heads.
4. Electronically Align the Reproduce Electronics.
5. Physically Align the Record Heads to match the alignment of the Reproduce Heads.
6. Bias the tape machine's record electronics to match the particualar type of tape you are using.
7. Adjust the Record Electronics. to match the Reproduce Electronics
8. Record a Known Audio Source and monitor the output using first your ears, then your test gear.

Explanation of Terms:

To properly physically align the heads of an analog tape recorder, you must first know what correct alignment is.

Theoretically, perfect tape head alignment is the optimum orientation of the tape head to the tape that provides the most information to the tape head available from the tape.

This usually means that the Tape Head Gap is 90 degrees perpendicular to the tape path.

Many people use Calibrated Test Tapes as a reference to align the tape heads. Although these tapes are expensive, they are the most convenient and accurate way of calibrating the Azimuth , Zenith and Wrap of tape recorder heads.

You don't have to buy an expensive tape head de-magnatizer to degauss your tape recorder's heads.

What I use is an easily available Radio Shack bulk tape eraser. You can buy these for less than $50 (US) from your local store. And it works just fine!

In the following, when I say "de-mag unit", I mean the bulk tape eraser that you can buy from Rat Shack.

Here is what to do...

1. Make sure your analog tape recorder is off and unplugged from it's power source.
   If your analog tape recorder's outputs are plugged into your console, turn your console off for (your speaker's) and your safety's sake.

2. Make sure the switch on the de-mag unit is set to the off position.
3. With the de-mag unit off, bring the de-mag unit as far away from the tape recorder heads as possible and then and only then turn the de-mag unit on.

   NOTE:

   Do NOT turn the de-mag unit OFF unit you are back at this starting position. Failure to do so WILL cause you to Magnatize your analog tape recorder's heads! (and this is bad)

4. Slowly, and I mean SLOWLY, bring the de-mag unit in closer to the analog tape recorder heads.
   Your movements should be very smooth with no jerking. As close to a slo-mo film shot as possible.

   The speed at which you bring the unit to the heads should be approx 12 inches every 5 seconds (or slower).

   If you don't know how slow that is, just go as slow as you can, and that will probably be slow enough. If, you're on any drugs (especially SPEED) you'll NEVER get slow enough.

5. As you approach the tape recorder's heads, slow down even more. Make this motion very smooth and very slow!.
6. Slowly, as you get closer to the heads, bring the de-mag unit up to each one of the three tape recorder heads. (erase, record, and playback). Make SURE you do NOT make any jerky motions as this will cause these actions to Magnatize the heads.
7. After slowly moving the de-mag unit across the heads for a few seconds, (usually 5 seconds for each head is sufficient) start bringing the de-mag unit away from the tape recorder heads VERY SLOWLY!.
8. Once you have brought the de-mag unit as far away from the tape recorder's heads as possible (preferrably back to your original starting point, turn the de-mag unit off.
9. Stop and get yourself something to drink, or take a smoke break. That is enough stress for the next few minutes. Your tape recorder heads are now de-magnatized! Yeah!

There is always a trade off between distortion and high frequency response and noise. And once you understand this, you can do some neat tricks with bias and high frequency eq.

For instance, if you would like to have lower distortion and don't mind a bit more noise and reduced high frequency response, you can increase the bias level. If you would like to have a lower noise floor and with an increase of high frequency response (at the expense of higher distortion) you can decrease the bias level.

The Detailed Procedure:

1. Degauss the TASCAM analog tape recorder heads. (ask Frank how to do this if you don't know how).

2. Clean the TASCAM analog tape recorder heads and capstans and pinch roller.

3. Put on the analog tape recorder alignment tape.

4. Locate the 1K tone that exists on the analog alignment tape. There are 2 (two) sets of tones for the TASCAM analog machine on that alignment tape. Both 15 AND 30 ips exist on the alignment tape. Be sure to find the correct tones for the speed you are wanting to calibrate for!!!

5. Set the TASCAM analog tape machine controls to the correct speed and then select 'REPRODUCE' mode on the tape machine remote control. Locate the 1K tone on the alignment tape and push PLAY on the TASCAM analog tape machine. While playing the 1k tone from the alignment tape, adjust the reproduce playback level trim controls of each track of the analog machine to show the proper playback levels on the analog tape machine playback meters. Valid playback levels are as follows:

+3 for 0 standard operating level (185 nw) +2 for +1 over standard operating level +1 for +2 over standard operating level * 0 for +3 over standard operating level (250 nw) * (NORMAL +3 level) -1 for +4 over standard operating level -2 for +5 over standard operating level -3 for +6 over standard operating level

6. Rewind the alignment tape to the beginning of the 1K tone. Set the TASCAM analog tape machine controls on the remote to 'SYNC' and play the 1k tone that exists on the analog alignment tape. Adjust the 'SYNC' playback level trim controls of each track on the analog machine to match (on the analog tape machine meters) the setting selected in step (5).

7. Locate the 10k signal that exists on the analog alignment tape. Be SURE that it is the 10K tone for the speed that you are calibrating for!!! Set the analog tape machine remote control to 'REPRODUCE'. Push play on the analog tape machine to play the 10k tone found on the analog alignment tape. Adjust the reproduce playback level trim controls on the TASCAM analog tape machine to make the meters on the analog tape machine match the same levels used in step (5).

8. Locate the 10k tone that exists on the analog alignment tape. Be SURE that it is the 10K tone for the speed that you are calibrating for!!! Set the analog tape machine remote control to 'SYNC' and play the 10k tone found on the analog alignment tape. Adjust the sync playback level trim controls to the same level used in step (5) (as displayed on the analog tape machine meters)

9. Repeat steps 5 through 8 until BOTH REPRODUCE and SYNC levels are within +- .5db of tolerance of the alignment tape shown on the TASCAM analog tape machine!

10. Remove the alignment tape and place it in a safe place away from stray magnetic fields. Locate the tape you want to record onto and load it onto the TASCAM analog tape machine.

=== NOTICE!!! ==

11. If you are using Dolby SR, push the hardware bypass buttons IN. These buttons are located at the bottom of each channel of the SR unit. These are the buttons NOT the lever switch! THESE BUTTONS MUST BE IN THE BYPASS (IN) POSITION TO PROPERLY ALIGN THE ANALOG TAPE MACHINE!

== END OF NOTICE ===

12. Go to the patch bay and patch ALL of the outputs of the ADATs (in this case, channels 1 through 24) to ALL of the inputs of the TASCAM analog tape machine (channels 1 through 24).

13. Patch ALL of the outputs of the TASCAM analog tape machine to ALL of the inputs of the console (1 through 24).

14. Find the ADAT test tapes that I made and put them into the ADATs. LOAD the SETUP that exists on those ADAT tapes into the BRC. After the BRC has loaded the setup of the ADAT test tapes that I made, goto the 10K tone section of the ADAT tapes and LOOP the section that contains the 10K tones.

15. Put the TASCAM analog tape machine into 'RECORD' on all tracks and set the TASCAM analog tape machine to read 'REPRODUCE'.

16. Push PLAY and RECORD on the TASCAM analog tape machine. While the TASCAM analog tape machine is recording AND while you are looking at the meters on the TASCAM analog tape machine that are reading the reproduce levels, adjust the BIAS control on the TASCAM analog tape machine’s trim controls display their HIGHEST level (peak the 10K level). You will probably have to turn the trim controls counter-clockwise for a while. While you are turning those controls counter-clockwise, look for the 'PEAK' level displayed on the analog tape machine’s meters. When you have found that peak, remember what level that is showing up on the TASCAM's meters. Now, turn that same bias control of the analog tape machine CLOCKWISE (over) until the meters on the analog tape machine read 3db BELOW (lower than) it's peak level (the level that you remembered!). Do this for each channel of the TASCAM analog tape machine. You use 3db over if you are overbiasing 3db. If you are overbiasing something OTHER than 3db, do that! The AMOUNT of overbias is determined by several factors. They are:

a. Speed of the analog tape machine. b. Width of the analog tape machine's record heads. c. Bias frequency.

Usually, tape machine manufactures will specify the amount of overbiasing required for their machine. Sometimes, they do not. A good rule of thumb is this:

a. overbias 1 to 3.5 db for 30 ips. b. overbias 3 to 6 db for 15 ips.

Do not confuse overbiasing (usually 1.5 to 3.5 db over at 30 ips) with operating level (usually 0 to 6 db over). These are two different specifications!

17. Once the biasing for each channel of the analog tape machine has been done, (described in step (16)), locate the place on the ADAT tapes that contain the tones that I created for the calibrated 1k tones. Place the TASCAM analog tape machine in record for all tracks and while continuing to have the analog tape machine read 'REPRODUCE', record the 1k tone from the ADAT tapes while viewing the meters on the TASCAM analog tape machine. Adjust the RECORD level on the analog machine to read 0 VU on the TASCAM analog tape machine. Do this for all the channels of the TASCAM analog tape machine.

18. Once the 1k tone record level from the ADAT tapes has been set for ALL channels of the TASCAM analog tape machine, locate the place on the ADAT tapes that contain the 10K tone. Make the ADATs play the 10K tone that exists on the ADAT tapes and put the TASCAM analog tape machine into 'RECORD' and record on all tracks the 10K tone from the ADATs while monitoring the output level of the TASCAM analog tape machine (as in step 17). Adjust the hi-freq RECORD EQ level trim pots on the TASCAM analog tape machine to show up on the TASCAM meters as 0 VU on the TASCAM analog tape machine's meters. They should match the levels found in step (17).

19. Once the 10K tone record level has been set on the TASCAM analog tape machine, locate the 100Hz tone on the ADAT tapes. Make the ADATs play the 100 Hz tone and put the TASCAM analog tape machine into record on all tracks while watching the output level on the TASCAM analog tape machine 'REPRODUCE' meters. Adjust the LO-FREQ COMPENSATION PLAYBACK EQ on the TASCAM analog tape machine to show up as 0 VU on the TASCAM analog tape machine meters. As you probably have noticed, this is a slightly different step from the other steps we have done so far. The other steps involve setting the RECORD or RECORD EQ levels of the TASCAM analog tape machine. But this step involves setting the PLAYBACK LO-FREQ controls of the TASCAM analog tape machine while using the calibrated circuits of the RECORD section of the TASCAM analog tape machine!!! On 100Hz signals, the TASCAM analog tape machine’s LO-FREQ COMPENSATION PLAYBACK EQ MUST BE SET using the record circuit of the TASCAM tape machine!!! Adjust the LO-FREQ COMPENSATION levels of the TASCAM analog tape machine to match the levels used in steps 17 & 18!

20. The TASCAM analog tape machine is now calibrated. You can now lay down the required 1 minute of 1K audio tones from the ADAT tapes that I made and the 1 minute of 10K tone from the ADAT tapes that I made, and the 1 minute of 100 Hz tones from the ADAT tapes that I made onto the TASCAM analog tape machine. These tones should be placed at the HEAD of each reel that an artist wants to use. Each roll of tape from ALL suppliers is DIFFERENT! One would think that if SCOTCH sends us 2 Rolls of 996 that each roll would be the same, and if AMPEX sends us 2 rolls of 499 that each roll of their tape would be the same, but NOOOOOO!!! Many times, they are NOT! So if you want to be the ULTIMATE techie (and receive many brownie points from Frank) check EACH ROLL for proper BIAS, EQUALIZATION, AND SR SETTINGS!!!!!!

=========================================================== *E*N*D* O F A L I G N T H E A N A L O G T A P E M A C H I N E ===========================================================

21. If you are using Dolby SR, it is now time to align the Dolby SR. Push the hardware bypass buttons OUT. This places the SR unit in the circuit. These buttons are located at the bottom of each channel of the SR unit. These are the BUTTONS, NOT the lever switches! These buttons MUST be in the 'OUT' position to use and calibrate the Dolby SR!

22. Make sure the patches from the ADAT 'OUT' to the TASCAM 'IN' are correct. Also, make sure the patches from the TASCAM 'OUT' to the CONSOLE 'IN' are correct. Look at the SR unit and you will notice that there is an LED meter on each card. Also notice that there are 4 (four) adjustment screws on the bottom of each of the Dolby SR cards. They are marked as follows:

1. Input to SR from ADATS (or from Console out) 2. Output to analog tape machine (or to analog tape machine) 3. Input to SR from analog tape machine (or to SR DECODE input) 4. Output from SR to console in. (or to CONSOLE in from SR out)

Locate the 1K tone that exists on the ADAT tapes that I made. Locate the top adjustment screw (1) [the input to the SR] on the SR unit and push PLAY on the ADAT units to play the 1K tone from the ADAT units. While the ADATs are playing the 1k tone, adjust the adjustment screw (1) on the SR unit so that the LED meter on each channel of the SR unit shows both green lights to be equal in intensity for each channel.

23. On the TASCAM analog tape machine remote control, set the analog tape machine to read INPUT on the meters. Adjust the SR adjustment screw marked (2) (in step 22), [Output to tape machine] to read 0 VU on each channel of the TASCAM analog tape machine meters. Be sure to set the analog tape machine remote to read INPUT. Look at the VU meters on the analog tape machine and adjust screw (2) on the SR unit to read 0 VU on the analog tape machine INPUT meters.

24. Once ALL 'SR to tape machine controls' (2) have been adjusted properly, go to the TASCAM tape machine remote control and put the TASCAM analog tape machine into 'RECORD' mode on ALL channels. Locate the 1K tone that exists on the ADAT tapes and record about 2 minutes of 1K tone from the ADAT units onto the TASCAM analog tape machine. Once you have finished recording the 1K tone onto the TASCAM analog tape machine (through the SR unit), rewind the TASCAM analog tape machine to the point where you started recording those 1K tones and play the recorded tones from the TASCAM analog tape machine. Locate the adjustment screw on the SR unit that adjusts the input to the SR from the tape machine (3) [Input to SR from tape machine] and adjust that screw so that the 2 green LEDs on the SR meters are equal in intensity.

25. Once all SR from tape machine channels have been adjusted properly, (described in step 24), rewind the TASCAM analog tape machine and play the 1K tones you recorded in step (22) from the TASCAM analog tape machine and adjust the screw marked (4) [Output from SR to console] to read 0VU on the console input meters. Have someone look at the console input meters and tell you when the adjustment screws on the SR unit are correct to show (CAL) on the console meters.

26. You have now calibrated the SR unit!

27. Rewind the tape and put Dolby SR tone at the tail of the 1K, 10K and 100Hz tones at the head of the reel. You do this by:

a. Look at the SR unit the locate the 'SETUP' button on the top right of the SR unit. b. While the SR unit is in 'SETUP', record about 1 minute of the tone generated from the SR unit onto the TASCAM analog tape machine.

28 You have now completed the calibration steps necessary for both the TASCAM analog tape machine AND the Dolby SR unit!

a. WOW! Does this mean I get a medal? b. Uh, where's the drugs, man? c. I don't understand a damn thing I did. d. Whew! I'm sure glad this shit's over with!

Contact:

This web page was modified May 1, 2008 You are visitor number since

Larry Seyer Acoustic Drums
Larry Seyer Main Page
Electric LarryLand
SPACEMUSIC.COM