Frequency Response of Vinyl
Reply #33 – 2012-12-07 02:02:56
... The information you have been given so far is mostly wrong. ... Regrettably, so is the information you have given, for the cutting part of the process at least. (The reproduction side info is OK.) Your explanation appears to assume that the cutting stylus has the same shape as a reproduction stylus, which is far from the case. Cutting is done with a "chisel" profile stylus. It is basically a shallow triangle in profile as viewed from above. The major flat face faces the direction of cutting. There are minor facets cut on the "corners" to burnish (smooth) the walls after cutting, and often other slight modifications to the profile. The maximum frequency that can be cut by the stylus is determined by the size of the burnishing facets, and by the frequency / excursion / tracing speed product - if you move the stylus side to side too fast and too far, the back sides of the triangular stylus will slam into the previously cut walls. In practice, the cutting HF limit is usually determined by the design of the stylus driving system. Remember that the signal being fed to the head has a reverse RIAA response curve - the HF energy is incredibly boosted. The drive coils in the head are very small and have a low thermal inertia. A second or two of excess HF energy will burn them out. CD-4 records, with frequencies up to 45 KHz, were actually cut at half speed (16 2/3 RPM). This only required 1/4 of the HF energy that full speed cutting required. They still had to be cut about 6 DB lower in level than a standard stereo disc. For the original question, I would suggest applying whatever processing is required to make the result sound acceptable to the user. In my limited experience, it's not worth saving it "warts and all" unless there will be no opportunity to re-rip it later. The user may well find that a turntable or cartridge upgrade will result in reproduction better enough that he will want to re-rip anyway. I've found that most high-end turntable/arm/cartridge combos do a competent job of reproducing the music. They tend to differ more in how well they de-emphasise vinyl shortcomings such as surface noise.