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2 Track Azimuth Alignment
(For all those who may or may not own an oscilloscope.)

Azimuth scares the pants off everybody. Why? Because it's done with a mechanical screw on the heads that the manufacturers often put that transparent "don't-mess-with-this" glue on - so we all assume that it's so delicate, we'd better not mess with it. Not a bad idea, but it's also not that difficult. Many studio owners don't own an oscilloscope (best method), but it can be done with a simple meter on your console (VU is best). This adjustment is best done before the record eq settings -- but you may need to do the other alignment stuff (see previous page) first to get things in the ballpark - particularly if the machine hasn't been used in a while or maintained well. 

Put on the 1k tone from your alignment tape at the speed you're going to record. Set the output to REPRO (playback) so that you're reading the signal coming off the alignment tape - it's helpful to set the output to the elevated level you plan to use.  If there's a switch that allows you to pick a manual knob to change the output level -- and a smaller internal preset level -- select the preset level.  Don't use the knob for now - it's more designed for on-the-fly adjustments. 

Bring both channel outputs of the machine up on two console faders panned to the center of the stereo buss (or simply assign both channels to a regular buss that's easy to meter). Set the your faders so that the signal you see on the console reads 0 VU.

Uncover the head stack so you can see the mounting plate that holds the heads. On the playback head (to the right) you'll see several screws, or possibly some holes where either a long small screwdriver or hexwrench will fit. CHECK YOUR MACHINE'S MANUAL TO BE SURE which adjustment is the one to make azimuth adjustments (or contact the technical/repair department of the company).

(1) Playback head rough azimuth adjustment: Now play the mono-summed 1k tone off the L-R outputs of the playback head, looking at the buss output meters (turn those monitors LOW).  Carefully, get a non-magnitized screw driver (probably phillips or hex wrench) and slowly turn the azimuth screw. Here's where I put the disclaimer that I'm not responsible for any screw-ups. You should see the output of your buss meter change. No need to make huge movements - you're not installing a door!  Turn the screw until you see the console meter reading go down a bit and then back up to 0 VU. Look carefully - you'll find that turning the screwdriver either direction should make it go down and up, depending on the closeness of the phase of the L-R channels. Don't do this by candle light. Rechecking is a good idea.  In most cases, heads will be decently close to a peak (high output) if the machine hasn't been thrown off a pier. 

(2) Record head rough azimuth adjustment (optional): You can now put the machine into sel-sync (playing off the record head) and repeat the above process for the record head, but ideally, you want to wait and use some blank tape and actually be in record to do this.

(3) Playback fine azimuth adjustment: Now play the 10k tone in the repro mode and do the same thing, only slower. Often the 10k region isn't as stable as the 1k. It's smaller frequencies up there.... Do the same thing as step (1) - slowly turn the screwdriver left, then right.  You'll see where the VU reading will go down and back up.  You want to leave it set when the console VU reading is at it's max, whether or not it's at ) VU or not.  You want the max (peak) reading.

Go back to 1k (we're always in playback mode doing this) and check to see that the 1k tone is still up around ) VU.  If it's changed, reset the console faders so that the meter reading is 0 VU. 

Go back to the 10k tone and double check to be sure you're seeing a peak.  Slowly turn the screwdriver left then right then back till you see the maximum readout on the console meter.  It doesn't have to be 0 VU like the 1k tone, it just has to be the greatest ouput.  Things will continue to change as the alignment goes along. 

(4) Record rough azimuth adjustment (the real one): Now TAKE OFF THE ALIGNMENT TAPE and put on some blank tape, preferably preferably  1 1/2 to 3 mintues of the kind that you'll be using for the session. Put some white leader tape at the beginning and the end of this section of tape.  Do not plan to record any music on this section of tape.  This is called a "record pad."

On your record pad (see here), send a 1k tone from your console oscillator or tone generator to your machine. Record 1k onto the blank tape. The console and machine should be set up the same way. You should still be in playback - you're seeing your setting via the playback head's output. Turn the comparable azimuth screw on the record head (NOT THE PLAYBACK HEAD) (check your manual) and adjust the record azimuth to give you the greatest peak meter reading.

(5) Record fine azimuth adjustment: Turn your oscillator to 10k, roll back the tape (you can go over the same section of tape to make these adjustments) and adjust the fine azimuth setting. Same stuff as above - record 10k to tape, and still reading playback, turn the screwdriver left then right (on the record head) till you see the maximum meter reading on the console. Recheck. Leave the playback screw alone or you get to get out the alignment tape (and turn off record ready) and start over!

Recheck your 1k setting. Recheck your 10k setting. Recheck your playback settings. You're done setting the azimuth!

Whew! Later, I'll get into setting erase peak adjustments... for now I think I'm ready to go watch a movie or something...
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Ok, I'm back from my movie. Erase peak is a cinch. Er, well, you have to be very careful with this one or you could turn you speakers into shrapnel...

Get some blank tape, preferably the kind you're using for most of your sessions (BASF rules, in my opinion). Record a test tone (from your oscillator or tone cd) for a good two or three minutes, usually anything from 400 to 1K, at 0 vu on tape. Now roll back the tape, and TURN DOWN YOUR MONITORS. Click here to see the best monitor controller available on the market today!

Turn your oscillator OFF and just start recording dead air on tape... and bring your monitors up (listening to one channel only of the tape playback) slowly till you are just hearing tape hiss, or some remnant of tone that's being erased on your tape. Find the erase peak adjust control (of that channel) inside your machine (manuals can help) and turn it down slowly till you start hearing the tone come up. Start turning the erase control pot back up and you should hear the tone go away. (If you hear no change, be sure you're monitoring the same track that your adjusting.)

Keep raising it till you hear the tone appear again. Turn the pot down and up till you sense the peak, or middle spot where the tone is erased down the farthest. That's the peak point where the erase bias is working the best. Erase bias is just a LOT more bias than the amount that goes to the record head.

Then just repeat the same process for the other channel. BE SURE BE SURE BE SURE that whenever you stop the tape YOUR PLAYBACK MONITORS ARE TURNED DOWN. You have to crank them up in order to hear this process, and if you take the machine out of record when there is still tone going, it will come on LOUDLY and abruptly if your speakers aren't turned back down!

This process can be done even using plain old music on tape - it's simply finding the place where the erase bias works best. Not rocket science, but if holding your alignment tape makes you queasy, this wouldn't be the first thing I'd recommend that you do. If you want even more precise alignment, contact a super-duper tech person who knows machines and have them do bias choke optimizing, erase wrap and full head alignments. These pages are designed for general analog machine use, and are part of full maintenance upkeep that makes analog recording ...still... the best sounding to date.


© Copyright 2001 - 2010 Vestman Mastering
Created 2/2/01 • Modified 03/13-06
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