Analog Tape Machine Alignment (9)

The Music Telegraph | Text 2020/10/09 [10:50]

Analog Tape Machine Alignment (9)

The Music Telegraph| 입력 : 2020/10/09 [10:50]

 

▲ Studer A80 Master 2 Track Recorder

© Wikimedia Commons



Analog Tape Machine Alignment (9)

 

(Continued from the previous article)

 

*In this article, I am dealing with 'Studer A80', an industry standard analog tape machine during 1970-80s.

The tape machine is now completely aligned. You have aligned the reproduce side to a reference tape, and then aligned the record side to the reproduce side. What you will do now is to determine the complete input electronics → record head → reproduce head → reproduce electronics frequency response. You will compare the frequency response of the record head with that of thereproduce head reproducing the machine's own recording.

 

 

1) Rewind the tape to near the beginning of the reel.

 

2) Set up the signal generator to output a 32 Hz sine wave at a level of +4 dBv.

 

3) Put the machine into the record mode.

To do this, press both "PLAY" and "RECORD" buttons at the same time.

 

4) As the tape machine is recording, monitor the output level of the reproduce head as shown by the VU meter.

Enter this level reading in Table #1 under the column labeled "Record/Repro" on the line for 32 Hz.

 

5) While the tape machine is still recording, readjust the frequency of the signal generator to the next frequency listed in Table #1.

Using the ACVM that is connected to the output of the generator, make certain that the signal level you are feeding to the tape machine is always +4 dBv at each frequency. Enter this level reading in Table #1 under the column labeled "Record/Repro" for this frequency.

 

6) Repeat the last step.

Changing the frequency, measuring the level, and entering the data in Table #1 on the line for each frequency until you have an output level reading entered for all the frequencies listed in the table. When you have finished, stop the tape and rewind it to the beginning.

 

 

Table #1

  Reproduce Response Record
Frequency Uncorrected Corrected Record/Repro
  Track 1 Track 1 Track 1
32 Hz (example) +0.25   (example) +1.1
63 Hz -0.60   -0.65
125 Hz +0.40   +0.5
250 Hz +1.0   +0.65
500 Hz +0.7   +0.25
1 kHz 0   0
2 kHz +0.1   +0.1
4 kHz +0.4   +0.4
8 kHz +0.1   +0.5
10 kHz 0   +0.5
12.5 kHz -0.6   -0.1
16 kHz -1.8   -1.0
20 kHz -3.5   -2.2

 

 

7) Scan your data from this operation and answer the questions that follow.

 

• Does your input/output data vary by less than 2 dB from the level at 1 kHz? (Yes / No)

If the answer to the question is "Yes", you have successfully completed an alignment of this tape machine. If "No", go back and check your alignment.

 

• What would be the quality of the audio signal if there were "no bias" added to it?

 

• What is recorded on a Reproducer Alignment Tape?

 

 When do you use an MRL® (Magnetic Reference Laboratories) Alignment tape?

 

 Will the fringing effect result in a different low frequency output for a 16 track head stack than a 24-track head stack, even though both of them are using the same alignment tape?

 

 

 

 

 

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