The original recording was made on Scotch 207 magnetic tape using a Sony 350 analog tape recorder. Format of the analog recording was quarter track monaural. The microphone used was a Turner model 500 dynamic microphone with a diaphram of approximately 1 inch, positioned near the countdown clock adjacent to the turn basin across from the VAB (in front of the press-site). The microphone stand, an Atlas MS-25 was elevated approximately 10 feet to place the diaphram of the microphone 6 to 8 inches in front of an Atlas PA loudspeaker placed by NASA for Launch and Mission Control Announcements.



The placement of the microphone, in close proximity to the PA speaker, necessitated padding (attenuation) so as to not overload the preamp of the Sony 350. The attenuation, combined with the natural low frequency roll off of the Turner Microphone allowed the full available dynamic range of the analog tape (approximately 65 dB) to be utilized. In effect, the smooth monotonic low frequency rolloff of the microphone de-emphasized the low frequencies, thus saving the recording from distortion while preserving the low frequency spectrum. Surreptitiously, the combination of microphone placement and response provided an exquisitely balanced combination of the low frequency energy of the AS-506 first stage with the announcements coming from the LCC, MCC and downlink audio through the press site loudspeaker.

In 2004, digital audio tools have allowed an accurate inversion of the low frequency rolloff characteristics of the microphone to be applied to the recording. Because little effective systemic noise from the actual magnetic tape exists below 200 hertz, this inversion is applied without negative effect to the analog recording.



The analog recording was played on a Technics RS-1500 with an isolated loop capstan. The quarter track playback head was relapped specifically for this project. 24-bit, 96KHz sample rate analog to digital conversion (88.2 KHz for the CD version) was used to capture the tape playback audio. Inversion of the microphone's low frequency rolloff response was accomplished with Adobe Audition using 32 bit floating point arithmetic. This procedure effective increased the dynamic range of the resultant digital archive at the low frequencies by the same amount of low frequency inversion used (approximately 20 dB).



The result of this technique allows a CD quality representation of the original event, even though the limitations of analog were used to capture the original source.