Absolute phase and integrated cartridge/arms
Once again I seem to have approached another millennial posting. And again, on these occasions, this post will report my musings on aspects of music reproduction. Unfortunately this millennial post has come up on me somewhat unawares, so I don’t really have a single subject on which to write: in place I’ll discuss two topics that have recently engaged my thoughts and listening. I have yet to come to any definite conclusions with either of them, but maybe other members can contribute with their thoughts.
The first topic is:
How important is the preservation of absolute phase? Can we hear it?
Before I discuss my attempts to see if I can detect a change of absolute phase, I ought to explain what is meant by ‘absolute phase’. The start of most notes occurs with an initial overpressure, caused by air being expelled from say the mouth, in the case of vocals and from the horns in the case of brass, woodwinds and reed instruments. This momentary overpressure is then picked up by a microphone and the positive going transient signal passed through the recording chain, so that on replay the speaker cones or diaphragms move towards the listener, themselves re-creating the momentary overpressure. The scenario is perhaps more obvious when one considers a drummer’s pedal operated kick drum: the drum skin nearest the pedal is initially pushed away and so too is the skin facing the audience and microphone. On replay the speaker cones should move out towards the listener as they mimic the behaviour of the drum skins.
The situation is a lot less clear when it comes to plucked or bowed strings or with pitchless percussive instruments such as cymbals or snare drums. Or the initial transients of piano notes, another percussive instrument.
So would it matter if instead of the speaker cone initially moving out, it moved in? Would it be the same as whistling a note by sucking rather than blowing? (Here I’m reminded of the line said by the sultry Lauren Bacall to Harry “Steve” Morgan (played by Humphrey Bogart) in the 1944 film of Hemingway’s To have and Have Not: “ You know to whistle don’t you Steve? You just put your lips together - and blow!”)
http://uk.video.search.yahoo.com/vid...sigs=11auuq8ne
(Apologies for the You Tube clip: it is a necessary piece of titillation to maintain your attention on what might seem to be a rather dull thread!)
Many recordings are multi-miked and it is not at all obvious that the correct phase is preserved with them all, and even if a simple miking technique is used absolute phase may not be preserved track-to-track.
Few preamplifiers have a phase inverting switch and those that do, tend to be of US design and manufacture. In fact it would seem that American audiophiles are far more concerned and aware of absolute phase; even going so far as to mark up their recordings if correction has to be made.
One of my preamplifiers (a Mark Levinson ML26) has a phase inverting switch, so I thought I would listen to a few recordings featuring the vocals, horns and bass drumming with the phase switch in both positions (0º and 180º). I should also point out that the power amplifiers I use (Quad 405-1, heavily modified; Quad 405-2, lightly modified and the Quad 520f, unmodified) are phase inverting, but I have never deliberately corrected for this: so I have been listening to incorrect absolute phase for at least thirty years!
(Image: Wikipedia. The phase inversion switch is top left.)
The recordings I used were as follows:
Joan Baez ‘5’
Sandy Denny ‘Sandy’
Nina Simone ‘Nina Simone at Newport’
Miles Davis ‘Kind of Blue’
John Coltrane ‘Giant Steps’
The Who ‘Tommy’, for Keith Moon’s drumming on ‘Underture’.
Cream ‘Fresh Cream’, for the track ‘Cat’s Squirrel’
Clearly the tests were not blind, but I listened to all the recordings four times, twice with the phase switch in one position and twice with the phase switch in the invert position. I also listened to each recording and changed the switch during the track. Such a move is fraught with error as there is momentary delay of a few milliseconds and ‘instantaneous’ changes are often misinterpreted.
The listening tests took place over several days, so as to minimise listening fatigue with notes being taken. Sadly I have to confess that I could not reliably hear any difference at all. In some ways I’m glad, as that is one less thing to worry about, but maybe I’m missing something. Are other members sensitive to the correct reproduction of absolute phase?
The second topic is:
Is there an inherent advantage in using arms with cartridges, which have been designed for one another?
The subject for this second topic came about recently through listening (and greatly enjoying) a vintage Decca cartridge and arm that had been designed for one another. Before I expand my thoughts on this, a little history is required.
In the early days of the microgroove record, (the early1950’s) there were few top quality cartridges available with which to play them. Those available were either developed by record companies themselves (Decca and EMI) or were developed by specialist audio companies (Ortofon, Shure, Tannoy, Leak and Ferranti, amongst others). All of these manufacturers supplied pick-up arms appropriate to their cartridges. The important thing to note was that these arms were designed to be used only with their respective cartridges (at that time usually referred to as a ‘head’) and with no other; indeed it was physically impossible to use a Ferranti ribbon cartridge in say a Decca arm and vice versa. This was all quite deliberate; the justification being that the arm was designed to offer the perfect environment for the cartridge to operate. Matters of tracking force, vertical tracking angle and stylus overhang were automatically set up, making installation that much easier. There was little standardisation in those days, apart from the adoption of either a 10” or 12” vinyl disc cut with a ‘microgroove’ whose dimensions had been standardised.
Ferranti ribbon (top) and Leak moving coil (bottom) pickups
(Image: ‘Hi-Fi for Pleasure’, Burnett James, Phoenix House Ltd, London, 2nd imp. 1956, p.48)
(1948)
(1954)
Leak moving coil pickup integral with its own arm.
EMI EPU 100 cartridge fitted to its uni-pivot pickup arm.
(Image: ‘Tape Recording and Hi-Fi’, R. Douglas Brown, Arco, 1961)
Standardisation of the cartridge/arm interface was slow to come. It was only through the adoption of the Ortofon bayonet coupling by SME that a more or less universal (now referred to as the EIA bayonet coupling) cartridge-arm interface was established. And the adoption would not have been as ubiquitous as it is, had it not been for the readily accepted SME arm design. Even so, within the broadcasting industry there were several manufacturers who ‘ploughed their own furrow’: EMT in Germany and Pierre Clement/Bordereau in France.
It’s unclear when the ½” spaced fixings became standard for most cartridges, however being an Imperial measurement is likely to have been due to the Americans (Shure/SME ?) but however it arose, Ortofon and others were quick to adopt it.
Even so, a couple of cartridge/arm manufacturers offered their products in two versions: a cartridge which could only be mated with its own arm and a cartridge having the same electrical and mechanical performance but with the now universal ½” spaced fixings: Decca with their Mk IV design and B&O with their SP6/7, 8/9 and later designs.
I have a couple of pickup systems, which are either used with their own arms, or can be used in more universal arms having the EIA bayonet arm/headshell coupling. One of these is the EMT TSD15 cartridge used in the EMT 929 arm, or by using an adaptor (or through using the specially adapted EMT XSD-15) used in an SME arm. The second system is the Decca Mk. V or Mk. VI, used either in a headshell with ½” fixings or via an adaptor in a Decca ffss ‘Super’ arm (the adaptor is necessary to correct overhang and to convert from the three contact arrangement to the four-wire arm wiring).
Decca Mk. III head fitted to a Decca ffss ‘Super’ arm.
(Image: 1971 Hi Fi Year Book, IPC Electrical-Electronic Year Books Ltd)
Decca Mk IV head fitted to Decca ffss ‘Super’ arm.
(Image: BDH)
Until now I had assumed that there was very little difference in performance, regardless of arm used, but recent experience with a Decca Mk. IV used in a Decca ffss ‘Super’ arm has caused me to reconsider my assumptions. (The ‘Super’ designation simply means the bearings have been up-graded to meet the higher compliance of the Mk IV over the Mk III.)
So my findings are based on running an EMT cartridge either in an EMT 929 arm or in a damped SME 3009 (effective arm length and geometry is very similar to that of the EMT), and either a Decca Mk. V (aka “The Blue”, having a spherical tipped stylus) or a Mk. VI (aka “The Gold”, having an elliptical stylus) in the Decca ffss ‘Super’ (an arm having damped pivots) or in a damped SME 3009 (damping being effected through the use of the FD200 damping dashpot and (smallest) black paddle).
In the case of the EMT cartridge (either fitted with a spherical or an elliptical stylus) I can hear no difference in its use with the two arms. The only difference between the two arms is the EMT uses needlepoint bearings in the vertical plane, the SME knife-edge bearings in the vertical plane.
With the Deccas, things are subtler. With either a Decca V or VI mounted in the SME, handling noises are quite manifest, whereas they are completely absent when used in the Decca arm. Furthermore I feel the performance of either Decca cartridge has more poise and assuredness in its own arm than when used in the damped SME. It might be that knife-edged bearing arms are not best suited to Deccas, whereas those using either a damped unipivot or damped needlepoint bearings are. Despite this, I love my Deccas when used in an SME (and others have heard Deccas used in an undamped arm with needlepoint bearings) for all the things that Decca cartridges do so well. It is only for the sake of expediency that I use SME arms so much: I am very tempted to permanently set up the Decca ffss arm or possibly to dig out my old Audio & Design M9BA mercury contact(!), damped unipivot arm. It’s only finding that Decca cartridges are just so well behaved in their own arms (which after all, is precisely what the engineers at Decca wanted to achieve) that have caused me to have these thoughts.
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Originally Posted by Marco
