On Thursday, April 02, 2009 11:10 AM, Michael Biel wrote:
Victor and other companies routinely polished their masters or stampers with jeweler's rouge which probably removed the rough edges of the sound wave -- namely the high frequencies. George Brock-Nannestad discovered a document at EMI that discussed Victor running a knurling tool thru the grooves to likewise smooth them out.
and
There is evidence that Victor "dumbed down" their recordings, so it is important that you have access to those test pressings which might not have been compromised. But maybe some of the things Victor was polishing off were cutter-head transient ringings.
Mike, you've got me thinking more about the manufacturing process - thanks!
I have noticed on these test pressings that the outer edge/rim of the disc was manually ground down - quite roughly I might add. The edge is even chipped, presumably from the grinding process. Not all the discs were roughly ground down in this matter, some have the smooth outer edge that you normally find on commercial discs.
The grinding is quite non-uniform - to the point that the radius of the disc varies by as much as 1/8-inch (3 mm) even though the spindle hole is properly centered.
If it matters, these test pressings are single-sided web-back discs.
I also have the Victor QA/QC label from the back of the disc. Most of these are not filled out, but I am curious what all the abbreviations mean and how these were used. I have an image scan (jpeg) of one of these for those who are curious.
Looking for more hints and enlightenment on how these test pressings might have been manufactured...
Eric Jacobs
The Audio Archive, Inc. tel: 408.221.2128 fax: 408.549.9867 mailto:EricJ@xxxxxxxxxxxxxxxxxxx http://www.TheAudioArchive.com Disc and Tape Audio Transfer Services and Preservation Consulting