Basic Alignment Procedures
for Ampex and other Professional Machines
see note at end of alignment procedures for Studers !!
the material below is copyright 1993, By M. Gore. used by permission.
Use of this material ONLY FOR PERSONAL NON-COMMERICAL USE is granted.
Any other use is prohibited.
THIS IS A VERY DETAILED ALIGNMENT PROCEDURE...
Basic Alignment Procedures
for Ampex and other Professional Machines
Please do a few test alignments to get familiar with the procedure!
Notes for STUDER Machines: the basic alignment procedures are ALMOST the
same as for Ampex and MCIs except that you must set the INPUT level BEFORE
you adjust the Record level. In these machines the Input level also affects
the record level, so if you adjust the Input last, as you would on an Ampex
you would mess up the whole record alignment....
1) Turn off the machine. Carefully de-mag the heads and all other
If you don't have a head demagnetizer buy them
directly from R.B. Annis at:
2) Turn the machine on. Carefully clean the machine, using cotton
swabs and Isopropyl Alcohol or Head Cleaner. Do not drip any liquid
down the capstan (you will destroy the motor bearings!)
Look at the heads and check for dirt and wear.
NOTE: Some brands of head cleaner will melt plastic, so be sure not
to drip any cleaner on plastic parts!
3) Make sure the machine is in the NON-RECORD mode (SAFE)
4) Select REPRODUCE mode. Select correct speed
5) Decide on your REFERENCE LEVEL (0 VU should equal your
reference level). Most studios use a '0VU' magnetic level
between what is known as a "'+3 level " up to a "+9 level".
NOTE: This is amount of magnetism that is recorded onto magnetic
tape when you record a "0vu" tone.
A '+9 level' recording has more magnetism at "0vu" than
a "+3 level" recording at "0vu".
Say you want an Operating Level of '+5' on tape,
and only have a +3 level test tape.
Since 0 VU (your reference level on the RECORDER'S VU METERS)
should equal +5 level, you would see -2 on the VU meter
when a tape 2 db lower is played back.
Since +3 is 2 db lower than +5, you would set the Level Set
Section of the test tape so the meter reads -2db VU. Thus '0VU' now
equals +5, your chosen Operating Level. Then all the tones on the
Test tape should equal that same '-2 VU' since all the tones on the
tape are equal level...
(remember in this case our Test Tone Tape is a "+3 level tape)
NOTE: We are only using the tape recorder's VU meters.
What this means is that when we playback a signal we recorded
at our 'operating level' the VU meters on out recorder will
read '0vu'.... the output of the tape recorder will be the standard
'+4dbm' of course, since that's the way machines are set up.....
Thus ANY REFERENCE LEVEL at '0vu' will be '+4dbm' at the machine's
output jacks. We set the playback and record levels to record
a MAGNETIC LEVEL onto tape that corresponds to our desired 'reference
level', but that reference level should always be adjusted so it reads
'0vu' on the machine's vu meters... no matter if we choose a "+3" level,
a "+6" level or a "+9" level... they all should read '0vu' on the
TAPE RECORDER's VU meters.
Zero VU on the tape recorder (in playback
and recording) is always equal to our desired 'reference level
if the machine is aligned correctly.
I know this is confusing, but you need to grasp this in order to do correct
alignments for your clients - so spend some time on 'Operating Levels'
6) Play your test tape. Play the LEVEL SET SECTION (700 hertz or
1000 hertz). Set this to 0 VU (if your test tape is at your desired
reference level!!! if not you must compensate!! see above) Adjust only the
REPRO LEVEL. Set the Level Set Section of the test tape for the
correct VU meter reading if your operating level is different
than the level on the Test Tape!!!
We no longer sell MRL Test Tapes...
if you don't have your own Test Tone Tape, you can buy them from
MRL directly at:
7) Set up the oscilloscope to show phase. Make sure you know what
head screw is used to adjust azimuth!! IF YOU DON'T KNOW - DON'T
DO IT !! Only a technician should adjust Multi-track Azimuth!!!!
8) Play the azimuth section of the test tape. Adjust REPRO HEAD
AZIMUTH for proper reading (straight line from lower left to upper
right, facing the oscilloscope)
9) Play another frequency. Check that this frequency is again in
proper phase alignment. (if not readjust azimuth, and look at another
different frequency to check it)
Don't have an O'scope? You can still set correct Azimuth ! Go
to the following page for details on how to check azimuth without a O'Scope!
10) Replay the LEVEL SET SECTION of the test tape. Set level.
11) Go to the 10 khz section. Adjust REPRO HIGH FREQ EQ for the
same setting as the Level Set Section. You may want to check the
machine by playing various frequencies back and checking the output
levels. Note that for low frequencies, fringing will take place and you
will get incorrect low frequency readings (below 200 hertz). But you
can see if the machine is "in the ballpark" using a test tape's low
repeat the above steps in Sync mode making the same adjustments
but adjusting the sync controls rather than the Repro controls...
Sync level, Sync eq and so on....
12) Remove the test tape from the recorder.
----------------- RECORD ADJUSTMENTS -------------------------------
Need alignment tones??? I've made a basic set of tones you can use!
1 khz, 10khz, 15khz, 100 hz and 50 hertz.
You'll need to download the tones, then burn them on a CD. Feed the CD output
into your console, bring up the levels to your 0vu reference on your console
that would be 0VU on a classic Analog Console or -16 on a peak meter.
here's the link...
13) Place a roll of the same type of tape (456, 499 or GP9)
you will be recording onto the machine and of course one
you can erase. Place the machine in RECORD READY.
14) Feed a 1000 (or 700) hertz sine wave at +4 dbm to both channels
of the recorder. Begin recording. Set the machine so it monitors
REPRO, and the VU meter shows the REPRO output.
15) Adjust RECORD LEVEL till the meter reads 0 VU. This is now
recording at your chosen operating level.
16) Feed 10khz to the recorder at +4 dbm. Set the oscilloscope to read
phase. Adjust the RECORD HEAD AZIMUTH (only if you know how
to do it), for proper AZIMUTH and phase on the 'scope, Monitoring
17) Feed another frequency to the recorder again at +4 dbm. Check the
Phase on the 'scope. If not in phase, readjust the RECORD
AZIMUTH, and check with another frequency.
18) If you need to BIAS the recorder, see the BIAS section described
below and perform the BIAS procedure now....!!!!
19) Feed 1000 hz to the recorder at +4 dbm. Adjust RECORD LEVEL
until the VU meter reads 0 VU. (Monitoring REPRO)
20) Feed 10khz to the recorder at +4 dbm. Adjust RECORD HIGH
FREQ EQ (proper speed) until the VU meter reads 0 VU. (Monitoring
REPRO). See notes below if you are at speeds less than 15 ips !!
21) Feed 50 hz to the recorder (at 15 ips) or 80 hz to 100 hz (for 30 ips),
to the recorder at +4 dbm. Carefully adjust the
REPRODUCE LOW FREQUENCY EQ (proper speed) until the VU
meter reads 0 VU. (monitoring REPRO).
22) Stop the machine. Select INPUT. Adjust the INPUT LEVEL for a
0 VU reading (monitoring INPUT) Note that on some machines this
step must be done before adjusting RECORD LEVEL, since INPUT
LEVEL feeds RECORD LEVEL. Check your machine to see if this is the case!
23) Begin recording again. If you have changed BIAS, select BIAS,
and adjust BIAS CAL until the vu meter reads 0 VU (monitoring
BIAS). Careful , don't adjust BIAS LEVEL, just BIAS
CAL (on Ampex machines).
24) Begin recording your tones at the head of the tape. Label your
tape as to operating level, frequency of the tones you've put on the tape
(1khz, 10khz, low freq.), state Dolby 'A' or 'SR' or state NO DOLBY,
and note track format and speed, as well as type of tape. If DOLBY A,
put Dolby Tone after low freq. tone, if Dolby SR put the SR set-up
signal onto tape.
Example of label on tape box and a +3 reference level:
2 Track, 15 ips, 456 tape : Tones at head
1khz, 10khz, 50 hz at 0 VU (+3 level: 250 nW/m)
25) Use 30 seconds for 1 khz and for other tones. You
may also want to put 1 khz on your left track only to establish which
track should be left.
---- you should do a few practice alignments before you do any serious
recording. Make sure all the levels match, and that the machine
1) Bias should be done at the proper audio frequency for the speed
you're using. Note that there IS a relationship between gap distance
and the frequency you should use to set the bias, but as a general rule
you everyone uses 10 khz for all speeds, except 7 1/2 ips and slower speeds.
The "Proper" frequencies are 10 khz for 15 ips; 20 khz for 30 ips
and 5 khz for 7 1/2 ips. Almost everyone uses 10 khz, and changes
their "Overbias" level to compensate for the different speeds.
2) After setting rough RECORD LEVELs, Feed 10 khz to the recorder
at +4 dbm ( "0" VU) from your console. Begin recording, MONITORING REPRO.
(Azimuth MUST be already set on both the RECORD head and the REPRO head!!)
3) Turn the BIAS LEVEL pot Counter-Clockwise (less bias) until the
VU meter (which is monitoring REPRO) drops by about 2db or more.
Then turn the BIAS LEVEL control Clockwise until the VU meter shows
the maximum output of your 10 khz you are recording. Turn the
bias pot a little back and forth to make sure you are on the "peak".
THEN CONTINUE TURNING THE BIAS LEVEL CONTROL
CLOCKWISE (more bias) UNTIL THE VU METER DROPS 3.5db PAST
THIS PEAK READING... for Ampex 456. If you're using 499
or GP 9 tapes overbias by 4 db, at 15 ips...
THESE SPECS ARE FOR 15 ips !!!!
go to step 4 below..
NOTE: As a general 'rule of thumb' guide ....
456 bias using 10 khz - 15ips = 3.5 db overbias / 30ips = 2 db overbias
499 bias using 10 khz - 15ips = 4db overbias / 30ips = 2db overbias
GP9 bias using 10khz - 15 ips = 4db overbias / 30 ips = 2 db overbias
different engineers and techs may like different bias levels
and often different machines require more or less bias than above
NOTE: In reality, you should use 20khz as the bias record signal
at 30ips rather than 10khz as we do with 15 ips....
speed doubled from 15ips to 30ips, and bias audio frequency should be doubled as well.
This means the frequency vs. headgap relationship remains the same
for 15 ips and 30ips. But using 20 khz often is tough to do
since many worn machines may 'waver' or fluctuate too much
for a good VU meter reading.... thus we compromise and use
10khz audio for biasing at 30 ips but in order to do this we
must set the bias for about half the normal bias for 15 ips.
All this basically equals out the changes between 15 and 30 ips,
and makes biasing somewhat simple.... using a 10 khz tone for
SEE STEP 7 FOR 7 1/2 ips BIAS INSTRUCTIONS!
4) This is the OVERBIAS point for 456 tape (3.5 db overbias at 15 ips)
This places you in the best operating range for 456, while 499
wants about 4db overbias at 15 ips (2db overbias at 30ips!!). Each studio
will have it's own chosen overbias level for the type of tape they're
using and the type of machine they're recording on, so always ask!!
You can overbias anywhere from 3 db to 5 db and still get good results.
5) Bias controls the amount of distortion, noise recorded onto tape and
other parameters, so be careful with bias. Note that some machines
must be overbiased slightly more or less than the norm, depending
on head wear and the type of heads. Always ask the studio what
their standard is.
6) The final adjustment is to set the BIAS CAL control. Select BIAS,
and adjust the BIAS CAL (on Ampex recorders) pot until the VU meter reads 0 VU.
Bias Cal is just a reference, and it does not change actual bias level
being fed to the record head. Setting this reference allows you to
return to this preset bias level without having to completely rebias the
machine, and it will show you if something has changed in the bias
6a) Many machines also have a "Master Bias" adjustment which will change
the overall Bias level to all channels. If your machine has this control,
you'd make a choice as to biasing each individual track to it's
"correct" bias, or to set each track to the "peak" level, and then
use the "Master Bias" control to set the overall bias correctly.
Usually you'd want to "peak" bias each track individually, and then
set the bias using the Master Pots.
7) If you are using 7 1/2 use 1 khz instead of 10 k, and only go 1/2 db
past the peak reading. You may use this as a rule of thumb: 1/2 past
the peak (clockwise= more bias) for any speed and for any tape, at 1 Khz
Using 1 khz is not as accurate as using 10 khz, but always puts
you in the general range you need to be in.
Now Go BACK to the RECORD ALIGNMENT above and start again from Step 1
Tape Recorder Tests and Checks.....
There are other tests you may want to make if your recorder is either
new or hasn't been in use often.
The first is to test erase by recording a 1 khz signal at operating
level then rewinding the tape to the pre-recorded 1 khz section.
Then remove the input signal and begin recording again.
Monitor REPRO. Increase your monitor level (board or power amp level)
until you hear hiss. Only a extremely small amount of the tone should
come through, if any at all. If a lot of tone comes through, the machine
is not erasing properly, and it should be brought to the attention
of a technician.
The second test is to go to a blank section of the tape, and record,
without an input signal, monitoring REPRO. All you should hear is a
nice constant hiss, not pops or "tape gravel", and there should be no hum.
This indicates that the machine is in good operating condition and does not
have any noise problems.
A third test is to record a 1 khz section at the head of a tape, then turn
the tape over (the recorded tone is now at the tail) and replay the
recorded tone, and compare it to the oscillator that fed the recorder.
Listen for a change in frequency between the oscillator and the tape.
If drastic, the speed is changing between the
head and tail of the tape. Note that you WILL hear some beating, since the
2 frequencies cannot be in the same phase!
If you don't have an oscilloscope, you can still adjust azimuth, and be
as accurate as with the o'scope. Remember that all consoles are
Voltage amplifiers, and that all of the VU meters on a professional
recording console (as well as most Semi-pro boards) read the output
voltage (and NOT THE POWER). Two equal and in-phase voltages
will add by 6db when selected to the same output buss. Thus you first
patch the tape recorder to 2 different input channels of your board,
making sure that the board's eq is out, and that there is no Echo Send
or Aux Sends on. Then select just one channel (Track #1) and send it to
any one buss. Set that one channel's fader level so that your buss output
VU meter reads -6 VU. Then turn off that channel.
Next turn on your other channel, (it would be Track 16 for a 16 track,
track 24 for a 24 track and so on...) send it to the same buss as the
other channel, and again set that track's channel fader level so the buss
output meter again reads -6 VU.
Then turn both channels on. Since two in-phase signals should add
together by 6 db, you now should be reading 0VU on the meter. If the meter
is near 0 VU and is stable (not moving around much), you're ok. If the
meter reads less than 0 VU, adjust azimuth until the meter reads as close
to 0VU as possible, with as little meter movement as possible. Make sure
re-set your -6 vu levels on each channel after making any azimuth
This then will allow you to set azimuth quickly and accurately without
having to use an oscilloscope. In case you forget how much two in
phase signals add, you can always first try it with an oscillator (which
every good board has), connected to two input channels of the board.
Try it.... it really works!!
The following steps are for 7 1/2 ips alignments ONLY !!!!
The only difference in 7 1/2 ips or slower speed alignment is that you
CANNOT RECORD HIGH FREQUENCY TONES AT OPERATING LEVEL !
Because of the amount of EQ required, if you try to record
tones at operating level the high frequency tones will go into
SATURATION, that is the tones will be a maximum level and no
further increase in EQ will get more out of the machine. Setting EQ
or biasing at operating level at 7.5 ips or slower will result in a
SEVERLY misaligned machine.
SO most test tapes for low speeds give you a LEVEL SET section at
operating level, then all the rest of the tones are at -10 db below the
operating level. This is to remind you that you cannot do a record
alignment at operating level.
You must align the machine at -10 db, except for the first and last
tones, (LEVEL SET) which are at the tape's reference level. Set the
LEVEL SET for 0 VU, then the next tone for -10 VU. Set REPRO EQ
so the -10 db 10khz tone plays at -10 VU. Then Reset the REPRO
LEVEL on the LEVEL SET section (which is at the test tape's
reference level) so it corresponds to your chosen operating level.
Next perform a normal record alignment, but ALL TONES SHOULD
BE RECORDED 10 db BELOW OPERATING LEVEL. (-10 VU)
Note that you cannot BIAS the recorder at operating level either, if you
use 10 khz. It is much easier to use 1 khz for bias (1/2 db overbias at
any speed), since there is a almost no EQ Record boost at 1 khz,
you CAN record 1 khz (and frequencies below that) at Operating Level.
But you can NEVER RECORD HIGH FREQUENCIES AT 7 1/2 AT OPERATING LEVELS
for alignments.... normal music and such is fine, but NOT alignment tones!!
The only tone that you should put on a client's 7 1/2 ips tape is 1 khz
at Operating Level.
================= Low Frequency Head Bumps =======================
Each tape recorder will have a specific low end 'head bump' which is a
function of many physical things.. the overall internal length of the head
poles and coils, the length of each of the two internal poles, the way in
which the poles and head are constructed, and even in the width of the head
gap. The length of the poles and coils is the primary cause of the head
bump, and this translates to a head pole length vs. frequency length on tape...
So as an example say a head has an overall pole length of 1 inch , and we
record a tone whose length on tape is also 1 inch (at 15 ips this tone
would be 15 hertz). The output of the head will be reduced or increased
above or below normal because the lengths match.
Think of this as head resonance.
If we now record that SAME tone at 30 ips - (15 hertz), the tone length on
tape is now 2 inches. The head pole length stays the same. The
interaction of pole length and tone length will change, and this same tone
- recorded at 30 ips now - will have much less of a reaction to the full
Now the brightest of you says "Aha ! There are two poles in each head,
thus there is an overall pole length AND the single pole length!".
And you're right... thus there is a full length, half length and quarter
length and so on interaction between frequency length and the head. Which
is why the output of the head - only at very low frequencies - goes up and
down a couple times as frequency rises, each 'bump' about half of the
previous 'bump' until things completely result in a flat signal. The
largest bump is about ±2 db, the next about 1 db and so on.
Also as we record a low frequency tone, the head gap width becomes
important, as the difference in magnetic signal on each side of the gap
becomes less and less the faster the tape goes and the lower the tone...
since the tone length on tape increases with speed.
There will come a point when the low frequency tone is almost a physical
straight line in magnetic level across the gap... no difference in magnetic
level across the gap equals no output from the head. The faster you run
the tape, the less very low frequency output you get.... usually easily
seen when recording say 20 hertz at 15 vs. 30 ips. One of the reasons why
15 ips is the best speed to use for good low end sound.
SO... all this is why you use a lower frequency tone at 15 ips than you do
at 30 ips when doing alignments....
Usually for AMPEX machines we use 50 hertz at 15 ips and 100 hertz at 30 ips.
For OTARI and STUDER machines we usually use 60 hertz at 15 ips
and 100 or 120 hertz at 30 ips.
If I'm lucky you will be able to view the below 'graph' correctly...
A - B - C - D - E - F are different frequencies going up in frequency.
Setting the low frequency correctly gives you the above overall response.
Above we set Frequency 'B" to Zero VU. So WE GET AN EVEN FLUCTUATION
AROUND THE ZERO VU POINT.
But if you use an incorrect frequency you mis-set the head bump above or
below the optimum. In the above case, say you set the low frequency
frequency 'A' to zero.... the overall is now set way below zero VU.... or
say you set the frequency 'C" at zero VU... now you have the overall low
frequencies set too high. The overall curve will remain the same, the
SLOPE of the overall low end needs to be set so the above zero and below
zero tones swing around Zero VU EVENLY.
In a perfect world we would chart each model machine and find the precise
tone to use to give the best overall response.... but this could be
something like 63 hertz or 56 hertz or 70 hertz...and most oscillators
won't give us this choice. So we're stuck using selectable oscillators on
consoles or tape recorders.
Finally, each Mastering house will have a different playback machine they
use, with a different low frequency head bump... in a perfect world they
will be using a tape recorder which matches the original machine you use on
your mixes. Even then they may have different heads on their
machine than those you have, and thus a slightly different 'head bump' on
If they use a different machine then there will be a slight difference in
the low end between the original recording and the mastering machine... but
so slight this should not make an audible difference... assuming the
Mastering House's machine is really properly aligned to each client's tapes
via the tones on those tapes, and they actually know what they are
doing.... and know all the above information.