Analog Tape Machine Alignment (10)

The Music Telegraph | Text 2020/12/22 [12:03]

Analog Tape Machine Alignment (10)

The Music Telegraph| 입력 : 2020/12/22 [12:03]

 

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Analog Tape Machine Alignment (10)

 

(Continued from the previous article)

 

So, we have aligned the analog tape machine and determined that it has a pretty flat frequency response. Now, the machine will record and playback audio in a reasonably accurate fashion. Why only in a "reasonably accurate fashion"? Well, to be highly accurate, the machine must be capable of reproducing the full sonic spectrum of 20-20 kHz, and with the same dynamic range as the sound it is recording. But it can't.

 

The analog tape recorder cannot respond to the full 120 dB of dynamic range that our ears can. Therefore it can never really "fool" the ear into thinking the recording is real. So how bad is the analog tape recorder? A well aligned, properly cared for machine with perfect tape tension, no ground loops, etc., is capable of about 60-65 dB dynamic range. The extremes of the levels are bounded by the Maximum Output Level (MOL) before distortion and the noise floor due to tape hiss. The difference between these two levels as measured in dB is the recorder's dynamic range.

 

Many factors affect the dynamic range of a tape machine. Two of the most important are the speed of the tape machine and the tape formulation. For a given tape formulation, the faster the tape speed (a choice of 15 ips or 30 ips) the better the dynamic range. This is because at higher tape speeds, more tape crosses the record head in a given time and that means more magnets are available for recording. This means more energy, louder signal, farther away from the tape hiss, hence greater dynamic range. There are other variables involved in increasing dynamic range than just tape speed, but this is the one that the studio operating engineer can exercise control over.

 

Next, we will determine the recorder's MOL and noise floor and then calculate its dynamic range.

 

 

 

 

  

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