murphy@voder.UUCP (Neil Murphy) (03/09/85)
I could use some help setting my cartridge VTA. (For those who don't know what I'm talking about, Verticle Tracking Angle, also called stylus rake angle, I believe, is the angle at which the cantilever/diamond tip mechanism of a cartridge meets the plane of the record surface. The idea is to match the angle used by the cutting lathe when the record was produced). I realize that all I can aim for is a good compromise. The Journal of the Audio Engineering Society ran (several months back) and excellent article on the subject. Because of vinyl deformations the actual angle has been quite difficult to measure with any real accuracy, and it can vary from cutter to cutter, disk to disk by a surprisingly large margin. Idealy, one would be able to adjust VTA for each disk, much like one would tweek azimuth for tapes played on different playback systems. That's obviously a hassel and probably quite unnecessary. My set up is forgiving of mis-tracked VTA, and I don't hear much difference as I change the angle through a surprisingly large arc...I'd guess +/- 3 or 4 degrees. I'm using a modified AR, Premiere MMT arm, and an Audioquest 404. I spoke directly to the cartridge's designer, and he said to lower the rear of the cartridge several degrees from the horizontal. The actual amount to be determined by ear. He said he uses a Joni Mitchel album as a reference, and when she starts to sound "nasal", he's gone to far. That's nice, but I'd like to know a more precise method. I bought the arm at Garland Audio in Santa Clara, and they will set it up for me, but not while I'm around. Seem to want to keep the method a dark secret. I purchased several CBS test records that were advertised to test cartridge tracking. One, a square wave test record, is cut at 15 degrees. They claim this is now the industry standard. On a scope, I don't notice much difference in waveform shape as I change VTA. (There were no hints included about setting any of the pertinent parameters, by the way. Assumption seems to be that I knew it all.) I don't have a distortion analyzer, so I can't look at this, perhapse, most obvious parameter. The records seem to be most useful for setting anti-skating and tracking force. So how have you folks out there handled this problem. Do I need to have a cartridge that's more sensitive to VTA to hear the differences I read about? (If so, I'll stick to what I've got!) By the way, my system sounds just fine. I just like to make it sound "finer". Thanks in advance for your ideas- Neil Murphy National Semiconductor Speech Lab, Santa Clara, Ca.
kimr@tektronix.UUCP (Kim Rochat) (03/18/85)
First, for the entertainment of the audience, there are a large number of cartridges that have vertical tracking angles that are impossibly too large - The Sonus line springs to mind - VTA with the top of the body parallel to the record has been measured at 35 degrees, and the back of the cartridge hits the record before you're anywhere close to the right VTA. However your Audioquest 404 doesn't suffer from this problem. Second, the shape of the stylus affects the sensitivity of the VTA adjustment. Spherical stylii are impervious, elliptical more sensitive, and line contact (Shibata, Micro-Ridge, Van Den Hul) being the most sensitive, proportional to the length of their contact line. You should first make certain that the cartridge is properly aligned in all other parameters, using an alignment gauge. There are 2 methods I use to adjust VTA. 1) Treble brightness/tone. You ought to be able to hear this with a JC Penny's special. When the VTA is low, the lower midrange is pronounced and muddy, and the treble is depressed. When the VTA is high (usually the case), the treble is zippy, zingy, and harsh. Violins sound steely instead of organic. Cymbals sound harsh and painful (at loud levels) instead of having a pleasant "ding". It's best to start with the back of the arm as low as it will go, and raise it in small increments until the treble becomes alive, but not harsh. Try a piano recording, and adjust it up until you can hear life-like hammer strikes (they'll be absent with a low VTA), or use a violin recording and adjust up until you're aware of the "bite" of the bow, which is also absent at low VTA. Female vocals are also particularly good. The sibilants (f, s sounds) should be clearly audible, but not hissy or SSSSSSSSy. VTA too low makes them inaudible, and too high makes them spitty. 2) Soundstage. This effect is more subtle, and requires the use of stereo miked recordings. When the VTA is too low, there will be a hole in the middle of the soundstage. When too high, the sounds will be squashed together in the middle. Wilson Audio recordings actually have written descriptions of what the proper soundstage was like, and what it will sound like if the VTA is off. It's best to try this on a stereo-miked piano recording, and adjust until the piano assumes normal proportions (e.g. not squished up or stretched out with respect to its apparent height. Since the proper VTA for each record is different, you'll have to be aware of the general class of effects adjusting the VTA has, and listen critically to each record to analyze the sound for characteristics that might indicate an incorrect VTA. Some recordings (like organ) lack the obvious indicators and are therefore more difficult to set VTA on. I do adjust VTA for each record I play, and pencil the setting from my calibrated arm onto the liner of each record. My arm has a 7mm total height adjustment, which is not quite adequate to cover the full variation of records. Note that this allows for about 2 degrees of VTA adjustment in my 242mm arm. For my previous cartridge with a Shibata stylus, I adjusted arm height in increments of 0.25mm (changing the VTA about 4 minutes). My current cartridge has a Micro-Ridge stylus, and I have to adjust it in increments of 0.125mm, for a 2 minute VTA change. The difference of this small a change is clearly audible on a good quality recording when you're changing between "right on" and slightly too high or two low. If you're way off to start, it won't make much difference. You can do a "binary search" (if your arm height is calibrated) to converge on the proper VTA. I know this all sounds like a lot of fooling around, and it is. But the rewards are worth it. Good listening, Kim Rochat tektronix!kimr