hqyy@vax5.cit.cornell.edu (03/06/91)
Hi,
Okay, I guess I'll get the ball rolling on this one... just
how DOES one go about choosing the proper VTA setting??? What records
do I use for listening? What do I listen for???
Thanks in advance,
satish naireacj@theory.TN.CORNELL.EDU (Julian Vrieslander) (03/07/91)
In article <9982@uwm.edu> hqyy@vax5.cit.cornell.edu writes: > Okay, I guess I'll get the ball rolling on this one... just >how DOES one go about choosing the proper VTA setting??? What records >do I use for listening? What do I listen for??? Well, here's what I do: First I make sure that the other tonearm/cartridge adjustments are dialed in (overhang, lateral azimuth, tracking force, antiskate). Some folks recommend starting by setting the tonearm, or top surface of the cartridge, to be parallel with the record. I do that, but then I check the stylus rake angle to see if it's in the right ballpark. This is the angle between the stylus and vertical, when viewed from the side. With a high quality cartridge the stylus chip will be quite small, so you have to get very close to the turntable and have good eyes to see this. Adjusting the light may help, too. Have the stylus on a record, an inch or two in from the lead-in groove. Position your eye at record level, near the edge of the record, and looking perpendicularly at the left side of the cartridge. If you are near-sighted and wear corrective lenses, you may be able to focus better without the lens. Note the line from the stylus' contact point on the record to the point where it meets the cantilever. There may not be a visible line on the stylus, so you may need to just imagine a line through the center of the stylus chip. This line should be close to vertical, or tipped forward a few degrees (5 to 10). By "forward" I mean that the stylus tip should be behind the stylus top, or the tip should be closer to the tonearm pivot than the top. Once you have established this starting position, you can try listening tests at other positions slightly above and below. Raise or lower the tonearm by millimeter increments. Listen for clarity, tonal balance, and a stereo image that seems to snap into focus. If you are way off, you will hear less precise imaging, and transient sounds may seem somewhat disembodied (the highs and lows not in correct proportion). I like to use records featuring complex acoustic sounds that are familiar: violins, female vocals, good recordings of falling water (hard to find), applause, etc. The best overall choice for this kind of tweaking might be a recording of a small ensemble of acoustic instruments, one known to have accurate timbres and good imaging. If you don't hear significant differences as the VTA is changed, that's OK, too. Some cartridges are less sensitive to this adjustment than others. A few warnings. Remember that the optimum VTA for one record may not be the same for another. This means that the best practical approach is to note the optimum setting for a a few records (maybe by using a ruler to record the height of one point on your tonearm) and then set to the average value. And then don't worry about it. -- Julian Vrieslander Neurobiology & Behavior, W250 Mudd Hall, Cornell University, Ithaca NY 14853 INTERNET: eacj@theory.tn.cornell.edu BITNET: eacj@crnlthry UUCP: ..cornell!batcomputer!eacj
eacj@theory.TN.CORNELL.EDU (Julian Vrieslander) (03/08/91)
In article <10019@uwm.edu> eacj@theory.TN.CORNELL.EDU (Julian Vrieslander) writes: >Some folks recommend starting by setting the tonearm, or top surface of >the cartridge, to be parallel with the record. I do that, but then I >check the stylus rake angle to see if it's in the right ballpark. This is >the angle between the stylus and vertical, when viewed from the side. >There may not be a visible line on the stylus, so you may need to just ... >imagine a line through the center of the stylus chip. This line should be >close to vertical, or tipped forward a few degrees (5 to 10). By "forward" >I mean that the stylus tip should be behind the stylus top, or the tip >should be closer to the tonearm pivot than the top. ... After I posted this, I noted a possible source of confusion. The stylus rake angle that I described in the referenced note is *not* the same as vertical tracking angle (VTA). The latter is measured between horizontal and a line drawn between the stylus contact point and the cantilever pivot point. VTA is also related to the orientation of the stylus in the cutting head used in manufacturing the lacquer master disk. You will often hear that optimum reproduction is obtained when the VTA of the playback stylus matches the VTA of the cutting head used to make the record, and that the VTA's of modern LP's range from 15 to 20 degrees. Several years ago, some folks at Shure did some testing in which they varied cartridge orientation and measured distortion. If I rememeber correctly, they found that both VTA and stylus rake angle had an effect on distortion, and that it was not always possible to optimize both simultaneously - because the stylus to cantilever angle is fixed. The Shure folks recommended a visual adjustment of the stylus rake angle, and it was this recommendation that I relayed in my first post. A summary of their results appeared in Audio magazine several years ago. -- Julian Vrieslander Neurobiology & Behavior, W250 Mudd Hall, Cornell University, Ithaca NY 14853 INTERNET: eacj@theory.tn.cornell.edu BITNET: eacj@crnlthry UUCP: ..cornell!batcomputer!eacj
bill@uunet.UU.NET (Bill Vermillion) (03/12/91)
In article <10019@uwm.edu> eacj@theory.TN.CORNELL.EDU (Julian Vrieslander) writes: (In regards to VTA) >Well, here's what I do: > Note the line from the stylus' >contact point on the record to the point where it meets the cantilever. >There may not be a visible line on the stylus, so you may need to just >imagine a line through the center of the stylus chip. This line should be >close to vertical, or tipped forward a few degrees (5 to 10). By "forward" >I mean that the stylus tip should be behind the stylus top, or the tip >should be closer to the tonearm pivot than the top. Julian - admittedly I know a lot more about setting up mag-tape recorders than record playing devices, but this seems backwards to what I have understood. The cutting stylii are normally at about a 15 degree angle with the tip forward of the top. This is to prevent the stylus from digging in to the lacquer during mastering. I should think this geometry should be matched in the playback mechanism. There must be something non-obvious or non-intuitive that I am missing here. Or have I mis-interpreted what you have said. bill -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
eacj@theory.TN.CORNELL.EDU (Julian Vrieslander) (03/14/91)
In article <10137@uwm.edu> bilver!bill@uunet.UU.NET (Bill Vermillion) writes: >In article <10019@uwm.edu> eacj@theory.TN.CORNELL.EDU (Julian Vrieslander) writes: >> Note the line from the stylus' >>contact point on the record to the point where it meets the cantilever. >>There may not be a visible line on the stylus, so you may need to just >>imagine a line through the center of the stylus chip. This line should be >>close to vertical, or tipped forward a few degrees (5 to 10). By "forward" >>I mean that the stylus tip should be behind the stylus top, or the tip >>should be closer to the tonearm pivot than the top. > >Julian - admittedly I know a lot more about setting up mag-tape >recorders than record playing devices, but this seems backwards to >what I have understood. > >The cutting stylii are normally at about a 15 degree angle with the >tip forward of the top. This is to prevent the stylus from digging >in to the lacquer during mastering. I should think this geometry >should be matched in the playback mechanism. The recommendation for setting stylus rake angle excerpted above comes from some Shure engineers, writing in an Audio article of several years ago. I looked for that magazine last night but could not find it. I did find a couple of other articles that seemed to confirm the use of a near zero value for SRA in the playback stylus (J. Gordon Holt, in the 7/90 Stereophile, and A.J. Van den Hul, in the 4/83 Audio Amateur). I'm sure there are more authoritative sources than these. For clarity's sake, I'll recap the geometry and add a few more comments on the VTA/SRA situation, as I currently understand it. A * * * * * B * * |||||||||| \ |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| C This is a crude diagram of the stylus assembly. The asterisks represent the cantilever and point A is its pivot point inside the cartridge (in some designs the cantilever ends here, in others it extends through the pivot, but this is unimportant for the definitions that follow). The diamond stylus chip is fixed to the cantilever at point B, the top of the chip. C is a point near the tip of the stylus. In this side view, line BC parallels the contact line of the stylus on the groove wall. Vertical tracking angle ("VTA") is usually identified with the angle between horizontal and the cantilever (line AB); more precisely it is the angle between horizontal and line AC. The two definitions are essentially the same, since the length of the stylus (BC) is usually much less than the cantilever length (AB). Stylus rake angle ("SRA") is the angle between vertical and line BC. If the stylus/cantilever design is such that BC is not perpendicular to AB , then SRA will not be the same as VTA. In most cartridges, SRA is designed to be smaller than VTA, with the stylus contact line AB nearly vertical. SRA is close to zero when VTA is set close to the nominally correct value (approx. 20 degrees). This makes sense, because a steeply raked SRA (as shown in the diagram) would cause the moving stylus to dig into the groove. A near zero SRA matches the stylus contact patch to optimally trace the ridges and valleys on the side of the groove. These ridges and valleys are represented by the ||||||| characters in the diagram, and in this side view they are nearly vertical. I don't know very much about LP mastering, but I believe that similar geometrical considerations apply to the stylus assembly and cutting head when making a master lacquer disk. The effective rotation center of the stylus motion in the cutter head is positioned to give the desired VTA value. The orientation of the cutting stylus is probably chosen to avoid excessive digging, under-cutting, and slanted modulation ridges. I imagine that it would be harder to accurately mold a vinyl LP if the ridges were high amplitude and very steeply angled: \\\\\\\. (Think about pulling it from the mold.) In the real world, the folks who operate cutting lathes choose different values for VTA, but I don't know why. And I seem to recall that there are practical reasons for setting a small non-zero SRA for the cutting stylus - this may have to do with helping to cleanly remove the excavated lacquer from the groove. -- Julian Vrieslander Neurobiology & Behavior, W250 Mudd Hall, Cornell University, Ithaca NY 14853 INTERNET: eacj@theory.tn.cornell.edu BITNET: eacj@crnlthry UUCP: ..cornell!batcomputer!eacj