V-50 Audio Comparisons – Session 14
 


Click on the following links to hear samples of V-50 audio. Each sample link on the left is accompanied on the right by a description of the corresponding audio file.


• V-50 14A, Moore This is a sample of V-50, Session 14A from the Snakelin Moore version. Notice the high level of tape hiss. Evidently, Moore didn't believe it was necessary to perform any noise reduction.

Even more obvious is the severe crackling from the intermittent microphone connection, which covers up part of AJG's speech, and drives the program level downward due to the actilon of the ALC (automatic level control) circuit on the tape recorder. Moore didn't do anything to adjust the volume or equalization for any of those reduced-volume passages...and there are plenty of them in Session 14, Parts A and B.

In the worst cases, the crackling noise is accompanied by a severe 60 Hz hum, which imposes a far more serious audio restoration problem (see NOTE below).
 Leavethisgoddamtext
• V-50 14A, Denoise tape hiss
Leavethisgoddamtextinherdammit
 This is the same audio segment as the one above, after running noise reduction to remove the tape hiss and other background noise.
• V-50 14A, Declick & Dehum Here's the same sample with declicking to remove the crackles, another noise reduction process to remove the 60 Hz hum and its associated harmonics (up to 8th order), and with special repair to rebuild the information that otherwise would have been lost.
• V-50 14A, Final Bounce
 Here's the same sample excerpted from the final bounce after all DSP functions are complete.
In case you're wondering, Michael Strathman's version of V-50 was vastly superior to the Moore version. Michael did do some noise reduction, and he did some dynamics processing and equalization to greatly improve the quality of the audio program material. However, he did not perform any of the additional noise reduction necessary to remove the crackles or the 60 Hz hum. It was not possible with the software he was using. As a result, his version suffers from the same crackle and hum problems evident in the first two samples above.
Of course, as I previously reported (and informed Michael), there were dropouts in the audio files that he produced, apparently due to the tape sticking to the tape heads — another reason why it was important to use a high-quality tape machine running at 3.75 ips to do the analog to digital transfers.

Fortunately, I had already purchased an iZotope RX license on October 14, without which I could not have done a decent job on Workshop Session 1. I knew that iZotope RX would come in handy again for the remainder of the V-50 audio restoration work. In fact, it provided the only way of mitigating the problems in Session 14 without buying other software costing three times as much.
NOTE: The aforementioned 60 Hz hum is audible in the first two samples above. It's in the two bursts of noise, right after the beginning of the sample, and again just before the last thing AJG says. That big burst of noise consists of two components:
  • Clicks, crackles, and pops – These result from the fact that AJG is using a condenser microphone, which places a DC voltage on the input to charge the capacitor in the mic. The DC voltage doesn't hurt anything as long as the mic is already plugged in when you press "RECORD". But if you unplug it, the capacitor discharges a high voltage spike across the input circuit, which shows shows up — BAM — as a loud pop or click, or a crackle when it happens repeatedly.
  • 60 Hz hum – This is the most destructive noise...BUZZZZ—one that consists of a 60 Hz fundamental and numerous harmonics (the first order harmonic octave at 120 Hz, the second order harmonic 12th at 180 Hz, etc....extending upward into the inaudible range).
The crackle is bad enough, but at least there's some of the original signal underneath the crackle. If the noise consists of crackle only, with great care I can sometimes at least partially reconstruct the audio waveform if the noise isn't too severe.

But where the 60 Hz hum occurs, there's no hope of reconstructing the audio program material. Why? Because it never made it onto the tape in the first place! The 60 Hz hum is the tell-tale sign of the input signal completely shorting to ground. When the signal goes to ground, it doesn't go to tape, and the hum shows up instead. It's not a matter of removing the hum to uncover the signal, as I can do with the crackle to some degree. Rather, when you remove the hum, there's nothing else there. Bummer.

Alas, there are numerous instances of that problem throughout Session 14. It's the way it was recorded on the master tape, which means there's nothing anyone can do to recover the lost information.

The sample above was one such case. Nevertheless, I managed to restore the missing information. "Holy Jeeziss Mother of Dog!", thou exclaimest, "How in hell did you do it, Vito?"

Trade secret. (Hint: I didn't use magic.)








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