The optimization of a modern day record press

Abstract

The WarmTone is a fully automatic, modern-day vinyl record press manufactured by Viryl Technologies. The WarmTone has a wide array of sensors, parameters and settings that can be accessed via it's ADAPT Interface and the front panel. This thesis is a collaboration with Viryl Technologies through the Mitacs Accelerate Fellowship. These advancements in pressing technology enabled a large scale study of the press settings and parameters and how they related to the audio and visual quality of the finished vinyl record. For the purpose of this study a test record was developed and over 400 records were pressed and over 200 recorded. These records were pressed under varying conditions and settings in the press. The surface noise, number of pops and clicks, wow and flutter, stereo bleed and total harmonic distortion are measured from recordings of these records and the audio quality of the record is related back to parameters and settings in the press. Two different PVC compounds and WarmTone presses were used in the testing and overall the difference between the two plastics made the largest difference in the surface noise measured. New clicks were also added to the records as the side b stamper was damaged possibly during the loading of pressing two. When the surface noise is A-Weighted or CCIR/ARM weighted then the difference between press parameters and settings is negligible, press parameters do very little to affect the final audio quality. Unweighted surface noise measurements suggest that cooling in the moulds is the best way to reduce unweighted surface noise and pops and clicks on the records. Coherence in the surface noise is observed when the record audio is separated into ``groove segments", segments of audio equal to the period of rotation of the record. This coherence, and other key press parameters affecting surface noise, such as the rotation speed of the extrusion screw, lead to the hypothesis that it is the size of the vinyl pellets and their residual elasticity that is the primary cause of surface noise and pops and clicks on the records.