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Old 23rd June 2011, 01:24 PM   #221
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Quote:
Originally Posted by scott wurcer View Post
Yes actually, there is no closed form solution for these kind of biquad filters to arbitrary accuracy. If you search for Bob Orban's solution you find one mathematically correct way. I did it using thermal annealing to best solution. It is amazing that you can ripple four or five numbers through a .wav and get .00006dB accuracy.
Wow. I've seen discussions of the audibility of everything from thin-film and thick-film resistors, to whether one of the RIAA time constants should be translated to frequency as "500 Hz" or "500.5 Hz", to whether 0.05dB amplitude accuracy is sufficient. And yet I have also seen, in this same discussion, mention of various digital implementations of the RIAA EQ curve that only match its amplitude characteristic.

The RIAA EQ curve specifies both an amplitude characteristic and a phase characteristic. A digital RIAA implementation does not match the phase characteristic unless it is specifically designed to do so. If one can hear the difference between a 500 Hz pole and a 500.5 Hz pole, then certainly one must be able to hear several degrees of phase shift!

See here for a similar discussion of the EIAJ de-emphasis curve -- the arguments are fundamentally the same for RIAA or any of the other phono EQ curves.
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Old 23rd June 2011, 02:24 PM   #222
AndrewT is offline AndrewT  Scotland
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Thank you Moderator Wintermute.
It was about time we got back on track and discussed what the thread title declares.
__________________
regards Andrew T.
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Old 24th June 2011, 05:05 AM   #223
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Hi,

first, the RIAA equalization is not a standard. And it will not become one, no matter how often it is called a standard. The RIAA is not a standards organization.

At most it could be called a "de facto standard" however "convention" would be a more correct term.


Second, does anyone have a record where the mastertape is recorded without processing (mixing) other than applying the RIAA equalization? IIRC even Brad Miller (MFSL) noted that he processed (mixed) his recordings of sounds of nature.


Third, for example I have the well known Telarc 1812 recording, three versions (2 mastered by Stan Ricker - one without markings, one with "SR", one by Bruce Leek "BL), they sound pretty different. So even if we assume that most recordings did follow the RIAA equalization within a +/- 0.25dB tolerance, does that really matter? I would assume that the sound engineer did much more to the sound than a 0,25dB deviation upon deequalization can do.

So do we really need to care?

Regards,

Tom
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Old 24th June 2011, 07:09 AM   #224
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The NAB document "AUDIO RECORDING AND REPRODUCING
STANDARDS FOR DISC RECORDING AND REPRODUCING" states:
"Reproducing characteristic-with constant velocity of the reproducing stylus tip the curve of voltage output of the reproducing system versus frequency shall be that which results from the combination of three curves as follows:
one falling with increasing frequency in conformity with the impedance of a parallel combination of a capacitance and a resistance
having a time constant of t1; (75 usec)
one falling with increasing frequency in conformity with the impedance of a series combination of a capacitance and a resistance having a time constant of t2 ; (318 usec.)
one rising with increasing frequency in conformity with the admittance of a series combination of a capacitance and a resistance having a constant of t3 ; (3180 usec.)
It is recommended that the system response below 30 cps and above 15,000 cps be attenuated at least 6 db per octave with the 3 db points at 20 cps and 16 kc."
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Old 24th June 2011, 09:26 AM   #225
oshifis is offline oshifis  Hungary
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From Wikipedia:

"RCA Victor and Columbia were in a "market war" concerning which recorded format was going to win: the Columbia LP versus the RCA Victor 45 rpm disc (released in February 1949). Besides also being a battle of disc size and record speed, there was a technical difference in the recording characteristics. RCA Victor was using "New Orthophonic" whereas Columbia was using the LP curve.

Ultimately the New Orthophonic curve was disclosed in a publication by R. C. Moyer of RCA Victor in 1953. He traced RCA Victor characteristics back to the Western Electric "rubber line" recorder in 1925 up to the early 1950s laying claim to long-held recording practices and reasons for major changes in the intervening years. The RCA Victor New Orthophonic curve was within the tolerances for the NAB/NARTB, Columbia LP, and AES curves. It eventually became the technical predecessor to the RIAA curve.

It is generally thought that by the time of the stereo LP in 1958, the RIAA curve, identical to the RCA Victor New Orthophonic curve, became standard throughout the national and international record markets"
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Old 24th June 2011, 10:06 AM   #226
oshifis is offline oshifis  Hungary
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I found a very interesting reading with exhaustive info in our subject:

http://www.bl.uk/reshelp/findhelpres...estoration.pdf
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Old 24th June 2011, 10:46 AM   #227
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It's interesting that the NAB were recommending poles at 20Hz and 16KHz, long before the IEC rumble filter amendment and the ultrasonic frequency response needed by CD4. The 16 KHz pole could be one reason why so many MM cartridges have peaking around there
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Old 24th June 2011, 11:16 AM   #228
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Here is how to evaluate nonsense that become standard? Time goes by and you can not live on. All boshemu number of engineers and students to become clear that there is a bug in the logic.
Does it make sense ispralyat paramentrov deviation of 0.3 -0.5 Hz when lost as much as 20 Hz at the origin? 20 / 0.5 = 40 (!) - LOL cheerful relationship of truth and error. Given that the theoretical dynamic range of head-type MM = 72 dB does it make sense to have fun with high-precision low-noise resistors phono-corrector?
Of course, all these investigations with the shares of decibels, and have a great attitude to mathematics, moderate attitude towards physics, and almost remote quality to the real sound.
But I must say a few words about the number pi. In 1927, a second letter koolitsionnogo unit UVR directly stated that this number is relatively constant exposure to fluctuations.Maybe not to be unfounded if I put the video electronic clock ran away yesterday at 1.5 hours for 5-7 minutes real time? Or refer to the "miracles" of the clock from Italy? I do not know ... The apparent before the eyes but no one wants to ignore it.

Maybe not to be unfounded if I put the video electronic clock ran away yesterday at 1.5 hours for 5-7 minutes real time? Or refer to the "miracles" of the clock from Italy? I do not know ... The apparent before the eyes but no one wants to ignore it.
Rely on such an unstable "constant" (pun indeed!) As Pi can not without an idiot with 6 characters after the decimal point, OK?


And about the noise frequency (7.5 - 7.85 Hz) would like to add that this is not just a characteristic of the magnetic field of the planet, but the frequency of alpha rhythm brain. And there are the derivatives 2 and 3 harmonic - beta and gamma. They are in a real live music. Again, we come up against a complicated theory study nizhengo limit audiootscheta 20 Hz ... What is there to smell the antics hit the enemy of man, eh?
People die for metal!
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Old 24th June 2011, 12:29 PM   #229
oshifis is offline oshifis  Hungary
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Hmm, Google Translate made garbage of your original words
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Old 24th June 2011, 01:00 PM   #230
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Default sorry

Sorry.
English is not my native language. At school I learned German - or rather playing football.
I'm trying to express their thoughts as possible. All this concerns the construction really lively music playing devices. And do not those who are well izmereyamye parameters (although up to 6 decimal points) but no sound.

Well I will not torment anybody - I wrote enough about his concept of the technology of live sound in Russian. This deysvitelno General will move into the third millennium. And frankly, too good numbers of measurements = 4 decimal points.
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