Sound issue
in [UK Mac]
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From: Adrian Tuddenham on 29 Dec 2009 06:36 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > [...] > > Grooved media have a lot of limitations due to the geometry of the > > system; the cutting was done with a sharp-edged tool, but the playback > > tool is rounded and cannot follow exactly the same path. This becomes > > significant when the dimensions of the modulation become comparable with > > the dimensions of the groove (high frequencies and/or low surface speed > > at the centre of the disc). Truncated elliptical styli can reduce this > > effect - but they show-up other problems and are noisier with worn > > records. > > `Truncated' - erm? Not sure what you mean by that - could you > elucidate? The traditional shape of a jewelled stylus is like a cone with half a sphere on the end where the point would have been. In the 'Truncated Elliptical' stylus, the hemisphere has been replaced by half a rugby ball with its long axis horiziontally across the width of the groove. The strange name is because the manufacturers (Expert Stylus Co,) start with a standard conical shape and then truncate it to an ellipsoid with an extra lapidiary process. > > > At high frequencies, the curvature of the modulation waveform can > > approach the radius of the stylus tip, so waveform distortion occurs on > > playback. > > Surely that distortion can be engineered out with a suitable approach to > cutting, if one assumes a particular stylus tip profile? That was the basis of the RCA 'Dynagroove' process, but the playback process may not always match the one it was designed for - and then there will be distortion again. > > With a truncated elliptical stylus, parallel tracking is particularly > > important. A large angular error can give a comb-filtering effect on > > the mono signal because the stylus tip is picking up the waveform at two > > displaced points on the two groove walls - so cancellation occurs. > > Oh! Yes. I'd never thought of that. Coo. Hmm.... It makes a big difference on some 78s. The recording engineers would sometimed twist the cutting stylus a bit, so as to direct the swarf into the centre of the disc or towards the outer edge (depending on what sort of swarf-removal device they were using). A.D.Blumlein's moving-coil cutterhead was a particular problem in this respect because it used a vertical axis of rotation for the coil (like a mirror galvanometer) with the cutting tip overhung on a cantilever beneath it. The stiffness of the system was low and, if the cutting face were slightly angled so that a line normal to it did not cut the rotational axis, there would be a servo effect due to the pressure of cutting the wax which would drive it even further off-centre and increase the angular error. Unless the playback stylus can be accurately set to the same angle as the cutting face (and to maintain it right across the playing area) there will be noticeable distortion and a spurious vertical component due to the stylus being pinched by the difference in the groove walls at the two points of contact. I analyse the vertical and horizontal vectors of stylus movement with an X-Y scope and the pattern of azimuth misalignment is quite distinctive. Some Blumlein discs were over 30 degrees azimuth skewed, some swarf-inwards and some swarf-outwards. It is usual to find that the studio recordings were swarf-outwards because an external swarf-sucker was used. For location recordings, a swarf-inwards azimuth shows that they were collecting the swarf in the middle (presumably because suction wasn't available). > > A huge amount of information on the correct playback of discs is > > contained in Chapters 3,4 & 5 of Peter Copeland's book: > > http://www.bl.uk/reshelp/findhelprestype/sound/anaudio/analoguesoundrest > > oration.pdf > > I got no such page when I followed that link. So I did a search and got > this link, which did work: > > http://www.bl.uk/reshelp/findhelprestype/sound/anaudio/analoguesoundrest > oration.pdf > > except it's the same url. Can anyone explain that strangeness? > > Firefox latest version, MacOS X 10.6.2. Was there a problem copying the URL due to the line-break? > > > ...this is an absolute 'must read' for anyone who transfers discs to > > digital and wants to understand what they are doing. > > I can't help feeling that almost everyone who's done that has failed to > do it properly. There's a lot of audible evidence on the internet to support that theory. It is very difficult to be sure if a less-than-perfect transfer is caused by lack of operator skill or because the original material was so dreadful that even the best possible result still sound inadquate - but sometimes it is very obvious where the problem lies. Compare: http://www.poppyrecords.co.uk/HXP103/hxp103.htm [Track 5 - click on musical notes RHS to download a sample] http://www.archive.org/details/TheColumbiaVocalGemChorus-MercenaryMary19 25 [Download from the "Listen to Audio Panel on LHS] -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: Rowland McDonnell on 29 Dec 2009 08:15 Rob <patchoulianREMOVE(a)gmail.com> wrote: > On 28/12/2009 11:07, Adrian Tuddenham wrote: > > J. J. Lodder<nospam(a)de-ster.demon.nl> wrote: > > > >> Rob<patchoulianREMOVE(a)gmail.com> wrote: > >> > >>> On 26/12/2009 12:51, Rowland McDonnell wrote: > >>> > >>>> > >>>> It is a technical error, these days, to mix the typical audio recording > >>>> in a fashion optimized for vinyl discs, > >>> > >>> In what way is audio recording optimised for vinyl? Do you mean mixing, > >>> or some form of filter? I only ask as someone interested in recording > >>> *from* vinyl, and asithappens, listening to LPs. > >> > >> A better way to put it would be that the audio signal to be put on disk > >> is constrained by the limitations of vinyl and PU elements. > > > > I would have said "constrained by the limitations of groove geometry and > > the intended playback equipment". > > > > The vinyl itself does impose some limitations, but most of the problems > > would still occur if they had used "Shellac" (slate dust with shellac > > binder), "Acetate" (cellulose nitrate), gelatine, wax, rubber, > > chocolate, thermosetting resins, catalytic resins or any of the hundreds > > of other materials which have been tried over the past century. > > Ah, thanks. I suppose what I'm after is an understanding of how the > sound is changed by processing (optimising) (rather than limitations of > vinyl) from the master tape - would it be 'duller', 'bassier' etc. The point is that if the job's done properly, what you hear when you listen to the recording gives a listener the same impression as would be experienced if listening to the original performance. This is achieved by fiddling on the part of an experienced engineer or few, to transcend the limitations of the recording process as best as possible. Don't ask me about the details, 'cos I don't know 'em. Thing is, it's all very tricky - where in the audience is the best place to sit? How do you get yer multiple-mike-detected signal to produce that ideal wave front when your final two channel recording is played back in someone's home? Through who knows what gear, with speakers in who knows what position? Etc. Well, your only hope is to assume that the speakers at least are sensibly arranged, and then try to deal with all the other highly variable variables. It's very tricky... Except... in the case of studio recordings of popular music, the `original performance' doesn't really exist, at least not in the `wave front from the instruments hitting the ears of the audience' point of view. So what you get is whatever the hell the people making the record want you to hear. Rowland. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking
From: Adrian Tuddenham on 29 Dec 2009 10:51 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > > Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: > > > > > > > J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: > > > > > > > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > [...] [...] > > Even > > then, really heavy modulation or a frequency which coincided with a > > badly-damped arm resonance could well fling the pickup out of the > > grooves sideways; > > <snigger> Good grief. One 'trackability' test was to play a 45 single with a knocked-out centre at 78 rpm, with the record displaced from centre as far as it would go. It didn't show up resonances, but it told you if you had set the tracking weight too low for the effective arm mass. > > so the problem was mainly one of cheap and nasty > > playback equipment, not one of which direction the bass was recorded. > > Righto - but there was plenty of cheap-and-nasty kit around, wasn't > there? Oh yes. >Mind you, now I understand why the old stereo record pickups > included instructions for mono wiring - you'd want a stereo cartridge > for mono electronics if you had stereo recordings to play, bearing in > mind the above, wouldn't you? That would help enormously, although there were a few quite good 'stereo compatible' mono cartridges available at throwaway prices once stereo became the norm. [...] > My other half works near enough to the audio-visual people at her uni to > find out part of the problem behind modern recording staff: management > seem to have the idea that all your problems can be solved by just > pressing a button on the computer and so expensive highly skilled highly > trained staff are no longer needed to produce output. The problem is that most of the listeners can't tell the difference between good and bad sound - or should I call them 'hearers' because so few people really listen nowadays. When VHF/FM radio is switched off, there will be no everyday standard left for comparison. > > All the techie types scream in horror at this attitude, of course. > Doesn't help. Management just carries on - and this is at a university, > which is supposed to be training the next generation. Training. Huh. > Since when were universities supposed to /train/ anyone? > > Bring back the polys, I say. I'm not sure about that. I read a book that was written by the Head of Department of a college/poly which specialised in training local radio presenters and interviewers. It was apparent that he had no idea how a microphone worked or how to use one properly - and was unaware that there were BBC training manuals on the subject. > > Rowland. > (who's got one degree from a uni and one from a poly) Likewise. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: James Jolley on 29 Dec 2009 11:21 On 2009-12-29 15:51:31 +0000, adrian(a)poppyrecords.invalid.invalid (Adrian Tuddenham) said: > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > >> Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: >> >>> Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: >>> >>>> Adrian Tuddenham <adrian(a)poppyrecords.invalid.invalid> wrote: >>>> >>>>> J. J. Lodder <nospam(a)de-ster.demon.nl> wrote: >>>>> >>>>>> Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: >>> >>> [...] > [...] >>> Even >>> then, really heavy modulation or a frequency which coincided with a >>> badly-damped arm resonance could well fling the pickup out of the >>> grooves sideways; >> >> <snigger> Good grief. > > One 'trackability' test was to play a 45 single with a knocked-out > centre at 78 rpm, with the record displaced from centre as far as it > would go. It didn't show up resonances, but it told you if you had set > the tracking weight too low for the effective arm mass. > >>> so the problem was mainly one of cheap and nasty >>> playback equipment, not one of which direction the bass was recorded. >> >> Righto - but there was plenty of cheap-and-nasty kit around, wasn't >> there? > > Oh yes. > >> Mind you, now I understand why the old stereo record pickups >> included instructions for mono wiring - you'd want a stereo cartridge >> for mono electronics if you had stereo recordings to play, bearing in >> mind the above, wouldn't you? > > That would help enormously, although there were a few quite good 'stereo > compatible' mono cartridges available at throwaway prices once stereo > became the norm. > > [...] > >> My other half works near enough to the audio-visual people at her uni to >> find out part of the problem behind modern recording staff: management >> seem to have the idea that all your problems can be solved by just >> pressing a button on the computer and so expensive highly skilled highly >> trained staff are no longer needed to produce output. > > The problem is that most of the listeners can't tell the difference > between good and bad sound - or should I call them 'hearers' because so > few people really listen nowadays. > > When VHF/FM radio is switched off, there will be no everyday standard > left for comparison. > >> >> All the techie types scream in horror at this attitude, of course. >> Doesn't help. Management just carries on - and this is at a university, >> which is supposed to be training the next generation. Training. Huh. >> Since when were universities supposed to /train/ anyone? >> >> Bring back the polys, I say. > > > I'm not sure about that. I read a book that was written by the Head of > Department of a college/poly which specialised in training local radio > presenters and interviewers. It was apparent that he had no idea how a > microphone worked or how to use one properly - and was unaware that > there were BBC training manuals on the subject. > >> >> Rowland. >> (who's got one degree from a uni and one from a poly) > > Likewise. What was that degree in Rowly? Twatonomy from the university of fuckwits?
From: Graham J on 29 Dec 2009 11:29
[snip] > I'm not sure about that. I read a book that was written by the Head of > Department of a college/poly which specialised in training local radio > presenters and interviewers. It was apparent that he had no idea how a > microphone worked or how to use one properly - and was unaware that > there were BBC training manuals on the subject. My brother in law once worked a some sort of further education establishment. It offered computer courses. There was some problem with the computer system used to assist with administratino, so I asked whether the computer teaching staff had been asked to investigate - the answer was that the computer teaching staff were all completely incompetent!! Yet the establishment was supposed to be turning out people trained in the design of computer systems !!! -- Graham J |