Ok, let everybody know when you get rich from your audio commercial enterprise, and you're desperately looking to hire half a dozen of audio engineers to expand your business.
Meantime, hobby DIYAudio is entitled to live, as much as DIYAstronomy (I polished a 6" parabolic mirror no more or less than 40 years ago, sounds familiar?).
Audio is dead and buried, beneath dignity, yet here we all are prattling on about it . . .
"We take our obsolete technologies and turn them into art" - McLuhan
That you didn´t repeat is the fact, and correctly i´ve marked the speculation about the reason for this fact.
As before, compare it to your labeling of "purely subjective/emotional interpretation" as fact.
As i´m participating as Jakob1863 in other forums, why should I?
And please remember this is the kind of statements that you should back up with hard evidence:
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Flap. Flap. Flap. Flap.
And what does that mean?
@scott wurcer,
This short thread is a good example for the mentioned spread within the members (even moderators) from "cult section" to interested in a more scientific approach:
ABX
Quite what prompted that Syn08 I have no clue. I don’t need the money (sorry if that offends anyone, it’s not intentional).
I do audio purely for the fun of it, like you do, and to keep me busy. Otherwise I’d be growing roses or something else.
Hi Nelson,
I was simply paraphrasing what others had said a few posts earlier. It’s certainly not what I think about audio - DIY or otherwise.
Have you considered adding a link or a catchphrase to your signature line? See below..... I take credit for the increasing popularity of the term WAW...... Planet 10 probably thinks it has something to do with him
More accurately, it seems to be fact to you.
The value of objective comparisons has been explained to you on that forum by those who are at the leading edge in this field and yet you continue to act as if that hasn't happened by keep repeating your worn out smear job on DBT and audio measurements.
Also important for channel matching, which potentially doubles the error.
It is very important for both channels to be as identical as possible.
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I find it surprisingly difficult to get RIAA accuracy specifications for the various cutting systems, but for example Gotham reported +- 2dB (30 - 15 kHz) in 1959 for the amplifier cutting head combination (Grampian cutter head & Gotham amplifier), a number that could have been presumably improved already back then by the half-speed process.
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Yes, I am looking also. But to get +/- 1 DB was rare, it appears. I did find this which shows the depth of the issue.
My point earlier is that to have accurate reproduction, the record and playback curve should be complimentary. But, they are not likely to be if only fixated on playback RIAA accuracy.
-----------------------
"For whatever it might be worth to any of you, I registered only for one point having to do with cutter head amplifiers. This is a story that started about 1961.
The most popular high-end cutterhead at the time was a Westrex 3C cutter head, at least in the United States. They were typically used by the big studios like in the Capitol Tower usually with Scully lathes.
The Westrex 3C cutter head had two coils on each of the two armatures. One coil was the high-power "drive" coil. The second coil on the same armature was a "feedback" coil. The clever concept was to wrap dynamic feedback from the coil around to the front-end (before the RIAA equalizer section) in the cutterhead amplifier, to flatten out distortion, improve linearity. The bobbin/mandrel of the coils was made of magnesium.
That, all by itself, informs that for the most-popular cutterhead of the era, the cutterhead driver was NOT just a PA amplifier.
The problem was that the "feedback" coil in the cutterhead armature, and therefore the dynamic feedback loop modeled as a servo-loop, had a serious phase-inversion. The phase inversion caused by magnetic flux coupling from the drive coil had a high-Q resonance between about 10kHz and 15kHz (by my ancient memory at least). The normal-mode of the feedback loop was supposed to be gain-negative, like any feedback compensation, directed to the amp's front end triode. The resonant phase inversion was a sharp spike of about 10dB (also my aging memory) GAIN.
When the feedback loop flipped phase 180 degrees, it went gain-positive, distorting the drive current spectral profile to the cutter head, and therefore to the "signal on the groove". If a record where being cut high such a +4VU or worse on the peg, and something in the higher spectrum crashed out, like a cymbal, the drive current into the cutter head would take off spontaneously, often blowing up the drive coils!!!! The repair could cost more than a thousand dollars - in 1960's terms. To avoid the damage, the mastering channel engineer would be compelled to attenuate the high end, reducing the "high" of high fidelity stereo, or cut at a reduced drive level, and accordingly groove velocity. The "cut" would be over-equalized, sharp, because the 10kHz to 15kHz band would be gain-high by definition.
A clever mastering engineer by the name of Howard Holtzer had an idea. He worked for Contemporary Records on Melrose place, and he was trying to get rid of the "peak" in the high band in the mastered acetate. The idea was to setup an equalization L-C network to "invert" the phase of the "feedback coil-inverted" phase with a Q and an attenuation notch that would match (invert) the resonant profile of the cutter-head feedback loop.
Then, he took the idea further: he set up a sequential series of equalizers, each about an octave in bandwidth, so that the spectrum "match" of the drive current to the cutterhead would be specifically tuned to each head very precisely. This was a VAST improvement over the simple equalizer-circuit to meet the RIAA curve.
To introduce the idea, Howard built a prototype amplifier at about 200 Watts per channel. He talked Bill Robinson, then recording chief at Capitol, into allowing us to set up a demonstration. Because of the precise tuning required to match a cutter head, hours of setup were required. Mastering channels are expensive to take off line during normal business hours, so Bill said we could work in Capitol all night long if necessary.
Bill allow Howard and myself access to the mastering room at Capitol one night. We set up the prototype, and by the approach of the morning work-shift hours, for the FIRST TIME IN HISTORY, we could cut a master acetate disc, and play it back, with a spectral pattern response that was within 1dB of flat to the RIAA curve.
By the way, the time-constant of the RIAA curve in the time domain was about 40 microseconds, about the same as a Ampex 351 of that era. If the RIAA equalization were removed and the amplified returned to cut the lacquer "flat", the time constant would be about 25 microseconds!
So, Howard got the agreement to produce his amplifiers, initally sold to Capitol, quickly followed by RCA that called the result the "Dynagroove" process, though in my opinion RCA over-equalized the cutter too much. Capitol had a different name, now lost in my memory.
Howard formed a company around the amplifier that we prototyped together. He called it "HAECO" and it changed the state of the art.
Also, by the way, I was looking at "dynagoove" today in Wikipedia, and the article there is not correct. It says that the Dynagroove process was the first to use computers to cut records. NOT TRUE. It was a very clever implementation, all analogue, to compensate for a flawed dynamic feedback loop servo design, then extended to "tunable" EQ over the whole range.
I know.
I was there."
-----------------------------
THx-RNMarsh
The specs for cutter systems were not very accurate. The manufactures had to meet spec and its easier to back off the spec to allow for shop floor differences in the units.
But the cutting facilities of the day all had very good staffs to adjust the units into proper performance. Paul Golds comments in the thread Richard Marsh linked to are indicative of the way vinyl has to be adjusted. By light patterns off the recording, smoke and mirrors. You don't measure a cut LP with an electronic device, its an electro-mechanical process and the way to measure its performance was mechanically. Perhaps Mr Neutron could devise a more accurate method today for use? Laser inferometers, etched micro grids?
End result, a seriously limited mechanical process that gave interesting results for well over 100 years.
Pauls observations (in the linked thread) about crosstalk, noise modulation and lf
cancellation may be more on target as to the sound of LP's than anything else.
It is the imperfections, not the great audio specs that gives vinyl its sound.
Cheers
Alan
But the cutting facilities of the day all had very good staffs to adjust the units into proper performance. Paul Golds comments in the thread Richard Marsh linked to are indicative of the way vinyl has to be adjusted. By light patterns off the recording, smoke and mirrors
. You don't measure a cut LP with an electronic device, its an electro-mechanical process and the way to measure its performance was mechanically. Perhaps Mr Neutron could devise a more accurate method today for use? Laser inferometers, etched micro grids? End result, a seriously limited mechanical process that gave interesting results for well over 100 years.
Pauls observations (in the linked thread) about crosstalk, noise modulation and lf
cancellation may be more on target as to the sound of LP's than anything else.
It is the imperfections, not the great audio specs that gives vinyl its sound.
Cheers
Alan
Richard,
My recollection is that RCA introduced dynagroove as a package of processes that were involved in the cutting process. I recall there being a number of papers in the JAES published outlining the process as they were willing to describe what they were doing.
One of them was probably the process HAECO worked up. I recall they made a big to do about "predistortion" which may have been their market speak for the process.
The Westrex 3D cutter head had replaced the 3C by that time.
and of course the bean counters in RCA pushed the technologies too far to make money and gave the process a bad name. (Dynagroove)
Cheers
Alan
My recollection is that RCA introduced dynagroove as a package of processes that were involved in the cutting process. I recall there being a number of papers in the JAES published outlining the process as they were willing to describe what they were doing.
One of them was probably the process HAECO worked up. I recall they made a big to do about "predistortion" which may have been their market speak for the process.
The Westrex 3D cutter head had replaced the 3C by that time.
and of course the bean counters in RCA pushed the technologies too far to make money and gave the process a bad name. (Dynagroove)
Cheers
Alan
The subtopic of RIAA accuracy at the "cutter side" was just related to the considerations on the replay side. That´s why i mentioned a couple of posts that a "RIAA equalization as correct as possible" might fail if the preemphasis (applied during the cutting process) is off in a unpredictable way.
From the sparse data it seems to be comparable to the situation that Mäkivirta´s study on loudspeaker linearity in various productions facilities described (~2001); the median curve is quite linear but the variability among the different facilities is large. In fact it seemed to be larger than the variation among the RIAA accuracy in the divers cutting systems.
Given the "in house tweaking" that waltzingbear mentioned it is a valid hypothesis to assume a similar distribution around a allegedly linear median curve.
Which means that very good RIAA replay accuracy is a good thing, if one is interested in a broad variety of recordings done in vary different facilities.
Otoh if one is mainly interested in a specific label or music style it might be worth to adjust at the replay side to find a better appromiximation.
From the sparse data it seems to be comparable to the situation that Mäkivirta´s study on loudspeaker linearity in various productions facilities described (~2001); the median curve is quite linear but the variability among the different facilities is large. In fact it seemed to be larger than the variation among the RIAA accuracy in the divers cutting systems.
Given the "in house tweaking" that waltzingbear mentioned it is a valid hypothesis to assume a similar distribution around a allegedly linear median curve.
Which means that very good RIAA replay accuracy is a good thing, if one is interested in a broad variety of recordings done in vary different facilities.
Otoh if one is mainly interested in a specific label or music style it might be worth to adjust at the replay side to find a better appromiximation.
That's how the Swiss turned around the watch industries.
I saw an add for a $900,000 watch last week that advertised it would stand up to being worn while playing polo.
I have never seen a description of Dynagroove that didn't mention the pre-distortion of the groove to fit a .7mil conical stylus
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