Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site angband.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!genrad!panda!talcott!harvard!seismo!ut-sally!mordor!angband!sjc From: sjc@angband.UUCP (Steve Correll) Newsgroups: net.audio Subject: Re: 2 questions, 2 replies Message-ID: <48@angband.UUCP> Date: Sun, 3-Mar-85 00:55:46 EST Article-I.D.: angband.48 Posted: Sun Mar 3 00:55:46 1985 Date-Received: Tue, 5-Mar-85 02:29:53 EST Distribution: net Organization: S-1 Project, LLNL Lines: 57 > Are there advantages to a linear tracking tonearm other than the > obvious removal (you hope) of tracking error? An article that I copied > from Stereo Review states that there is no need for anti-skating > compensation. Is this true? Can you explain why?...Also, what is the > audible manifestation of tracking error? Look down on your turntable from above, and imagine a line down the center of your cartridge from front to back. If you have a pivoted tonearm, you'll notice an angle between that line (I'll call it the "centerline") and the tonearm: this angle is responsible for skating force. Friction on the disk surface exerts a force on the stylus, and because of that angle, the force pulls sideways on the tonearm (or, in Newtonian terms, the force has two vector components, one of them parallel to the tonearm and the other perpendicular to it and directed inward). Why the angle? Well, the machine which initially cut the groove kept its centerline tangent to the groove, so one goal of any tonearm is to keep the cartridge's centerline tangent, too. The obvious approach (which nobody uses) is to mount the cartridge with its centerline parallel to the arm and make the arm just long enough to be tangent to the outermost groove. A little Euclidian reasoning will show that as such a tonearm approaches the innermost groove, it must somehow grow longer to remain tangent. The popular solution is to make the tonearm longer in the first place, but mount the cartrige so its centerline is angled inward from the tonearm, retaining tangency at the outer groove. Given the right length and angle, such a tonearm will be tangent at the innermost groove, too, though it will be a little bit wrong in between. (Manufacturers' hype to the contrary, it doesn't matter whether the angle is achieved by bending the arm or mounting the cartridge at an angle at the end of a straight arm.) Tangential (linear-tracking) arms, whether electrical or mechanical, exhibit no skating because all the force exerted on them by the record surface is parallel to the arm. I have never heard any audible manifestation of tracking error. It rarely exceeds a degree or so, whereas the vertical angle of the stylus can vary by 5 or 10 degrees between different brands of cartridge. The minimization of tracking error is popular, however, whereas the standardization of vertical angle is not. People don't seem to worry about the 5 to 8dB resonances which some highly praised moving-coil cartridges exhibit around 15kHz, either. I'm (overly) fond of citing an article in "Audio" magazine about a year ago which concluded that tangential arms actually have about as much error as pivoted arms, because their servos dither a bit. However, tangential arms can be much shorter, and therefore less massive, and therefore (with highly compliant cartridges) more immunity to record warp. (Even if warps don't bounce the stylus out of the groove, they make life harder for the stylus by making the downward tracking force fluctuate.) -- --Steve Correll sjc@s1-b.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc