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)
> 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
> 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.
> 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
> Quality tape transfers -- even from hard-to-play tapes.