Hi, Don, The time/phase error at the stylus tip could cause significant problems if an attempt was made to create a mono sum of the signal. It's the same thing we see with tape azimuth. The 1/400,000 of a second at 78 rpm would translate to approximately 32 degrees of electrical phase angle difference at 15 kHz at 33.3 rpm, which is not huge, but significant. This is the order-of-magnitude of azimuth wander seen on less-than-ideal, but not horrid 3.75 and 7.5 in/s tapes. But you are certainly correct that a one foot path length difference would produce an error of a full cycle at about 1120 Hz, but somehow we don't hear that path length difference in the same way we hear a mono sum before the signal is fed to the speakers. Cheers, Richard On 2011-12-20 8:59 AM, Don Cox wrote: > On 18/12/2011, George Brock-Nannestad wrote: > >> > From: Patent Tactics, George Brock-Nannestad >> > >> > >> > Hello, >> > >> > Eric Jacobs has given a very full answer to the S- and straight arm >> > question. >> > >> > However, there is one further aspect of the tangential tracking arm >> > question and pivoted arm question that has to be kept in mind. The >> > original derivations of the advantages and disadvantages of the >> > various pivoted arm geometries was based on mono only, and >> > coarse-groove dimensions. Percy Wilson pointed out a special form of >> > time distortion: the overhang in his elaborated example meant a >> > gradually slower reproduction because in effect the needle tip moved >> > along the groove during play. However, he calculated that on one >> > revolution at 78rpm the delay only amounted to 1/400,000 second. That >> > is not discernible to a listener. However, in the stereo case, and in >> > particular with line contact or elliptical stylii, the situation is >> > different, and the time scale between the two channels shifts. With a >> > slower speed and higher recorded frequencies there are definite time >> > delay shifts between channels at the high frequencies. >> > > I think this would be negligible compared to the effect of not being > precisely equidistant from the speakers. > -- Richard L. Hess email: [log in to unmask] Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX http://www.richardhess.com/tape/contact.htm Quality tape transfers -- even from hard-to-play tapes.