This topic as it relates to both grooved media playback and tape azimuth alignment BEGS for a ARSC Journal article, written in as plain English for non-math majors as is possible! -- Tom Fine ----- Original Message ----- From: "Richard L. Hess" <[log in to unmask]> To: <[log in to unmask]> Sent: Thursday, May 07, 2015 11:44 AM Subject: Re: [ARSCLIST] Phase vs. Polarity (was Playing Edison Diamond discs) > Jamie, > > You are not being a pain in the ass. I alluded to the complex adjustments of the cartridge that > Doug Pomeroy has explained so well at other times/places. > > My goal is for everyone to understand that a polarity flip/inversion/reversal is not the same > thing as a phase shift. > > The M/S transform involves polarity inversion and summing. Yes, there may be phase errors at the > higher frequencies introduced (mostly by) designed-in capacitance that was intended to maintain > unconditional circuit stability. > > I have done far more research and experimentation on summing dual-mono tape playback to true mono. > The theoretical goal there is to properly adjust the azimuth to minimize single-channel > high-frequency combing roll-offs. Once that is done, then adjusting the inter-channel delay using > an outboard processor finishes the job. > > In reality, it is not easy (or even possible on program material) to adjust azimuth to a single > channel by ear. The Nakamichi Dragon cassette players will do that with some program material as > the inner (right) track heads are split and the system compares one half of the right channel to > the other half of the right channel. This defines the playback head, in reality, as a six-track > head. > > In most instances, with well-designed and well-manufactured heads like those from Nakamichi in the > Dragons and even the MR-1s, proper single-channel azimuth will occur close to the point of > time-alignment between the two channels (assuming again a mono (single track) recording). So it > seems OK to use that to make the mechanical alignment. > > Still, after doing the mechanical alignment, there are end-to-end variations and also once-around > cyclical variations, which can best be accommodated by a product such as StereoTool or the > "Azimuth" correction in iZotope RX Advanced. > > I do not know how much the alignment of the groove walls change during playback. I think it is in > great part due to the differences between the linear-motion cutter head and the pivot-motion > tone-arm. I wonder if StereoTool or iZototpe could offer that final correction. > > Yes, I could see in theory how the very highest frequencies could be improved by tracking and > correcting this inter-channel timing error. On the other hand, when I attempted a calibration of a > disk playback system over a decade ago, the output above about 12 kHz was not stable enough for a > truly accurate adjustment, and low-frequencies introduced by centre-hole eccentricities (I think) > also made reading the meters more difficult. > > However, I was pleased that I think my system was within 2 dB at 12 kHz and I had gotten it there > by comparing CD and LP releases of some of my favourite albums and throwing out the ones that > obviously had been remastered. > > I don't do professional disk transfers because I lack the production cleaning tools, the > collection of stylii, the ability to deal with off-centre pressings, or the ability to play > 16-inch ETs. I am, however, building up an SP-10 with a short SME arm in a made-up wood base on > sorbothane pads to see if I can hear a difference between that and my SL-1200 MK II. Most of this > stuff came my way, but the two SP-10s' bearings seem to be in great shape. > > The caveat with StereoTool is that I believe (at least at one time) its internal processing was > limited to 48 kHz sampling frequency and it downsampled internally when inserted in a 96 kHz > stream with no warning. I have not tested the latest versions. > > While in all practical purposes, I think Goran might be correct that the inter-channel delay in > disk reproduction may be insignificant, going after that last bit of correction (as long as > nothing else gets harmed) might fulfill at least a desire for perfection that may or may not be > practical to implement on a large-scale basis. > > Cheers, > > Richard > > On 2015-05-06 9:54 PM, JAMES HOWARTH wrote: >> Not to be more of a pain in the ass than I already am, but I was referring to phase, and not just >> polarity. Perhaps interchannel timing is more precise, but that manifest as rotated phase between >> the two groove walls. >> >> You guys are talking about polarity as if that were the only variable, and in my humble >> estimation, despite Goran’s opinion that it’s insignificant I respectfully submit that there’s >> times recently that taking a more granular approach than a simple polarity flip. >> >> Also this is for me at least pursuant to the statement that hill and dale can’t be derived from >> MS encoding of the Left and Right channels: it clearly can. The S is the vertical, is the hill >> and dale, QED. > -- > Richard L. Hess email: [log in to unmask] > Aurora, Ontario, Canada 647 479 2800 > http://www.richardhess.com/tape/contact.htm > Quality tape transfers -- even from hard-to-play tapes. > >