Audio disc Transfer
During the early years many private recordings were made on 78 rpm records. Talented family members would often record their favorite ‘musical’ and ‘spoken word’ to keep as valued memories for the future. During the 1940’s Voice Letters were recorded by servicemen at the local USO clubs to send home to family members. More recently 10 & 12 inch classical and jazz recordings of the 1950s – 1960s and vinyl records from the 1950’s to the present became popular.
As standard procedure, all records are cleaned before transfer. Contamination can build up in the grooves over many years affecting the restoration process. After cleaning Creative Audio Works has a variety of cartridges and styli to retrieve the optimum performance of each disc.
Worn records can be digitally enhanced to reduce or remove surface noise such as crackles, clicks and pops. In some cases, the condition of the disc surfaces are so badly worn with severe scratch marks that they would require individual removal by manual editing. This type of work is possible but can be very time consuming.
The Audograph Disc
Audograph discs are a unique and challenging “dead” media to work with. Introduced in the mid-1940s, the Audograph was designed as a portable dictation system using thin plastic recording discs. These discs were very flexible and prone to damage. The spiral groove is also very shallow making it hard for the needle to track correctly on playback. In addition, on playback using modern technology, the sound increases dramatically in speed as the disc is played. Because of this, finding the exact pitch and rendering an accurate restoration becomes a challenge.
Exactly how fast the playback should be at any given point in the recording is always questionable. In the past there has been no benchmark. Now with modern technology we can look at hidden frequencies in the recorded audio that are constant, and use them as a benchmark for speed control.
The Audograph is a Constant Linear Velocity (CLV) disc. To put it simply, 1 second of audio will take up X amount of groove travel distance at the beginning of the recording and the same X amount of travel at the end of the recording. This was done to squeeze more information onto a small disc.
Rather than a constant-speed spindle drive as in a conventional turntable, mechanical rollers mounted close to the cutting head drive the surface of the disc directly as the cutting head travels across the disc. A conventional turntable would record X amount of groove travel distance at the beginning, and maybe ½ that amount at the end of the recording. In the case of the Audograph the turntable platter speed constantly changes from the beginning to the end of the recording as the circumference increases, and as a result the groove travel distance per second is constant.
The main problem with transferring different formats of that era is that the technology is 50+ years old. Mechanical recording devices of that era have many problems built into them that have to be addressed. The unique mechanical aspects of this obscure format add artifacts like wow and flutter. Inferior cutting head design and inferior speed control all add to the issues and challenges in accurately restoring an Audograph recording.
Since there seems to be no documented/published specifications regarding the Gray Audograph recorder, we have to make decisions based on the transferred files themselves. One problem is determining the pitch of an individual’s voice. We could play back a disc on an Autograph player or turntable, but we would not necessarily get an accurate representation of the recorded voice.
We transfer each disc on a modern turntable using a moving coil cartridge with custom stylus and a phono preamp. All files would be recorded at 96Khz/24bit resolution. Then we view the audio spectrum of each recording and look for information generated by both the particular recording and its recording device, to make a determination of how to process each individual audio file.
Using specially developed software, we are then able to correct the playback speed of the transferred digital file of an Audograph disc recording. Your original Audograph recordings are then returned to you as Compact Disc or audio files stored on DVD, or hard drives. Additional noise and distortion removal can be preformed to further remove or reduce ticks, pops, rumble, hum and other background noise that may be distracting to the listener.