Analog Tape Machine Alignment (3)

Frequency Response Test

The Music Telegraph | Text 2019/12/24 [12:53]

Analog Tape Machine Alignment (3)

Frequency Response Test

The Music Telegraph| 입력 : 2019/12/24 [12:53]


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Analog Tape Machine Alignment (3)


Frequency Response Test

Normally when aligning a machine, you would not be interested in how out of alignment the machine is. You are interested in getting the machine aligned for the session. For our purposes it will be helpful to understand the adjustments that you will be doing, so it is useful to start by looking at the tape machine's frequency response before doing an alignment. This operation will guide you through a 'frequency response test'. You will use the reproducer alignment tape. This is an essential tool in all analog tape machine alignments.



1) The equipment has been connected as shown and described below.


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*How it's Hooked Up

A) The Signal Generator goes to two devices:

- the line input of the tape machine electronics

- the input to an ACVM for measuring the signal level going to the tape machine in dBv


B) The output of the tape machine electronics goes to three devices:

- the input to an ACVM for measuring the signal level from the tape machine in dBv

- the input to the Oscilloscope to view distortion

- the input to the headphone amp to audibly monitor the signal



2) Turn on the tape machine.

Turn on the power by selecting the 15 ips speed.



3) Put the machine electronics in the safe mode.

This will prevent the operator from accidentally entering the record mode thereby erasing the (expensive) alignment tape.


To do this, locate the control that locks out the record function. On the rotary function control  switch located to the right of the electronics, turn the selector to the "SAFE" position. This will  prevent you from accidentally putting the machine into record mode.



4) Thread the reproduce alignment tape onto the machine.

To do this, take the tape out of the box and notice how it is wound. If the free end of the tape is  held down with 'blue tape', that means the reel is wound 'Tails Out' or, the Tail end of the tape  is on the Outside of the reel. Place the tape on the right (take up reel) side of the machine and thread it back to the supply reel side. Now rewind the tape to the beginning. When the tape is at the beginning of the reel, park it at that location (push the "Stop" button).



5) Make sure the tape machine electronics are in the reproduce mode.

To do this, put the meter selector lever to "Repro". You will find this control on the left side of the VU meter.



6) Play through the beginning of the reproduce alignmnet tape.

Listen to the voice announcement and answer the questions below.


To do this, press the "Play" button and listen to the voice announcement from the tape. You may rewind the tape as often as you like to hear all the information. Answer the following questions based on what you have heard:


- What is the Fluxivity level of the reproducer alignment tape?  _____ nW/m

- What is the equalization standard of the reproducer alignment tape?  _____


* Conducting a Frequency Response Test

You will now conduct a frequency response test using the tones already recorded on the alignment tape. You will play each tone on the tape and record its VU level as read from the machine'smeter. 



7) Play the tape from where it is now parked and stop when you come to the announcement of  the 32 Hz alignment tone. 

This is the beginning of the frequency response section.



8) Play through the frequency response section of the tape and enter the levels that you read on the VU meter for each frequency. 






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