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In Reply to: VTA...Does it make much difference? posted by John Elison on October 13, 2007 at 17:58:57:
I just wanted to find out what others thought about the importance of VTA.According to an old Audio Magazine article, adjusting for the correct VTA reduces frequency intermodulation distortion. The following test plot demonstrates how FIM is minimized at the correct VTA using a DIN 45-542 test record. Two groups of bands are involved: One is a high frequency IM tone consisting of 1.85-kHz and 3.15-kHz with a high-side IM product of 5-kHz, where as the other section is a low-frequency IM tone consisting of 370-Hz and 630-Hz giving a high-side IM product of 1-kHz.
It's interesting to note that correct VTA is slightly different for high and low frequencies. This was apparent with elliptical and line-contact styli. With conical styli VTA was the same at both frequencies. SRA was stated to be the reason for this difference.
Thus, our investigations clearly show SRA to be a more important controllable variable than VTA. Our dialog with cutting engines indicates that VTA currently varies between 16 and 22-degrees, depending on the lathe system. SRA, however, is generally 91 to 95 degrees relative to the record surface in order to facilitate lacquer "chip" (cutaway strand) removal.
Here are some more data published in the article when using the CBS STR-112 test record with 400-Hz modulating a 4-kHz test signal.
It's interesting to note that the CBS STR-112 test record is recorded with VTA very close to the old standard of 15-degrees. When I used this record for testing my cartridges, I got lowest distortion with my DL-103R in comparison to my OC9ML/II and my Shure V15VxMR.
Best regards,
John Elison
Edits: 10/15/07
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Follow Ups
- Thanks for all your responses.... - John Elison 17:38:41 10/14/07 (2)
- Questions for you John - Thomas_A 04:23:31 12/08/07 (0)
- Thanks for the info John... - EdAInWestOC 07:16:38 10/15/07 (0)