RIAA accuracy at recording studio

[Walter]

Is the RIAA as applied at original recording always exact?
If not how are we sure that the reverse RIAA is accurate

[Brian]

When dealing with LPs, the "original" RIAA, or "pre-emphasis", is applied as the master disc is being cut on the recording lathe. This occurs after all recording has been completed and usually not at the recording studio. Today, it is being done at special "mastering facilities" by highly trained professionals and it is done quite accurately. (In the past this was not always the case and, of course, over the years there have been many different pre-emphasis curves in addition to RIAA.)

Since each preamp has its own implimentation of the RIAA de-emphasis curve designed into its circuitry, and these circuits vary wildly in quality from the $50 kid's turntable to the $10,000 audiophile preamp, it is the playback system that is most likely to vary from RIAA specs. Your flat pre-amp lets you skip this source of potential variance and instead rely on the Diamond Cut software's computer generated RIAA de-emphasis curve - which follows the RIAA spec to the point probably no variance could be measured and certainly none heard by even the most "golden ears".

Hope this helps
Brian

[DougMac]

Virtual PreAmp

Walter,
RIAA EQ curve is a standard. The best DC7 can do is work from that standard. If the RIAA standard was not applied correctly when the disc was mastered, perhaps because of poor design or variances in the componants used in the circuitry, it would be pretty much impossible to know how the EQ varied.

Personally, I record with a flat amp and use the Virtual Phono Pre-Amp. I enable the tone controls and make modest adjustments if necessary. If I feel more EQ is in order, then I use one of the other equalizers.

There's a similar discussion regarding 78 recording speed. One camp works hard to adjust to the correct speed. Another camp claims that unless we know for certain the original recording speed (eg Pathe @ 80rpm), then unless there's documentation regarding the key in which the record was performed it is practically impossible to adjust playback to the recording speed. Even with notes it's not certain. Perhaps the instrument used as a tuning guide, such as a piano, has an out of tune concert "A". Then all bets are off.

Some early recordings would actually include a tuning note before the song. That's about as close as we can get to finding the right playback speed.

Doug

[Walter]

Riaa

Thanks for your reply.

I also asked on another thread about Flat phono amp verses
mike inputs on sound board.

[Craig Maier]

Quoting Brian:

"Since each preamp has its own implimentation of the RIAA de-emphasis curve designed into its circuitry, and these circuits vary wildly in quality from the $50 kid's turntable to the $10,000 audiophile preamp, it is the playback system that is most likely to vary from RIAA specs."

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Some time back, I reversed engineered an Audio Research and a Paragon tube preamplifier. These sold in the $10,000.00 price range. I noticed that the time constants used in the feedback loops for the RIAA front-end (both were 12AX7 vacuum tube triode based designs) had incorrect time constants for properly reversing the RIAA EQ curve.

I doubt that was a mis-calculation. The errors were beyond circuit component tolerances. I suspect that these so called audiophile preamps obtain part of their unique characteristic sound (that would get the attention of such pubs like the Absolute Sound Magazine) through such trickery. Add that to around 4% harmonic distortion and you have what is known as an "Audiophile Audio Preamplifier".

Isn't it interesting that they do not generally use these kinds of (vacuum tube) things in recording studios where the music is actually created? Seems that recording studios like to use circuitry that have tons of op-amps to create the various mixing buses.

Craig

[Drew]

There are more & more tube mics coming out; and tube mic pre's that are on my wish list for my own studio, most are quite expensive. There are also some OLD tube mics that are still in demand for recording; I've used some in the past from the 40's & 50's for my own recording sessions that were quite beautiful.

Drew

[Dan McDonald]

I guess what it means is that people have preferences for different sounds. Some people want to reproduce sound as exactly as possible, while others want to produce the best sound possible (to their ears). I think both are fine viewpoints, just a matter of taste and purpose.

Dan

[Brian]

I think both are fine viewpoints, just a matter of taste and purpose.Dan

Totally agree - but there is some irony. This was always also the final verdict for equalization and other "effects" - but the initial recording was done "straight" and all the "season to taste" equalization, etc. was done later to permit experimentation, fine tuning, mind-changing, etc. However, with mics that color it seems very important to some that is done in the initial recording. I prefer the technique used in DC and many other "emulators" - record it "dry" and then color it as you choose -- but retain the original "accurate" recording for future use. I guess that was probably a big reason I was an early-adopter of the flat LP transfer technique.

Brian

[Dan McDonald]

I'm on your side of this, too Brian. I always think it best to record as faithfully as possible and then color it as needed. I'm made enough mistakes altering sound to know that any particular way I think sounds good with one set of speakers or headphones may not sound very good on other sets, so I try my best to get an overall sound that is pleasing on a variety of equipment, but to do that, you need to start with what actually transpired.

With cylinder transfers you get a similar argument as to whether it is better to reproduce the sound of the cylinder player or to get as close to the sound that was going on in the room when the cylinder was recorded. I try to get at the original sound; others like to get the sound of the cylinder reproduction.

When someone dies and they make me king sh>>, as the story goes, I'll set the standards for everyone, but until then, whatever people want to do is ok by me.

Dan

[quartet87]

Added to the factors previously mentioned in this thread, is another factor i.e. the tonal characteristics of any given phono cartridge...which, in my way of thinking, can easily make it difficult to produce a truly flat playback of any given phonograph record.

[Brian]

I always think it best to record as faithfully as possible and then color it as needed.Dan

Dan probably said it better than I did: "faithfully AS POSSIBLE" (emphasis added). Just because we can't build a totally flat cartridge isn't a reason to intentionally add in even more "color". This is kind of like the argument (to really open a can of worms) some "journalists" make when they point out "no one is perfectly objective - so it's ok to intentionally distort the facts". (If memory serves me correctly, I believe this is one of the three "fallacies of the false alternative" in formal logic.) I don't have any problem with adding EQ to a recording or network commentators - there are good arguments for both.

[Craig Maier]

Regarding phono cartridge flatness, I placed a preset on the Presets Sharing section of the forum some time back that flattens my Stanton 500 to within a dB from 20 Hz to 20,000 Hz.

There are two caveats:

1. How accurate was the test record that I used? I think that I specified the test record along with the preset (Hi-Fi News, I think).

2. How much manufacturing tolerance exists from one Stanton 500 to the next. That is not known or published data.

Craig

ps - I recall that someone created a correction curve for another phono cartridge model and posted it on the Preset Sharing area. So, there are two corrected curves available.

[Craig Maier]

I just double checked the presets sharing portion of the forum and indeed the record used for the Stanton 500 was the one offered by Hi-Fi News, an English publication.

The other cartridge that has a compensation curve set up is for the M97ex. It was created by glenntsc.

Following this link to find the presets sharing area:

http://www.diamondcut.com/vforum/forumdisplay.php?f=13

[quartet87]

I agree with Brian's stance on coloring. My previous comment about cartridge tonal fidelity was a passing observation. Here, again, I agree with Brian's comment regarding a truly flat cart.

In fact, I can't think of any digital cleaning filter offhand that doesn't color the original RIAA file at all...hence my usual application of the Harmonic Sweet Spot preset in VVA after declicking and before running CNF. For my ears, that almost always produces fine results without using an EQ. But there are those rare occasions when I encounter a LP which was produced from a grossly bad master tape...tone wise. That's when I'm not hesitant to use one of the EQ's in an attempt to make the final file sound decent.

As Brian's point was, it's all a matter of personal taste.

[Craig Maier]

Quoting Danny:

"As Brian's point was, it's all a matter of personal taste."

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Of course, that is true, unless you are re-mastering for a customer or for a high - volume CD release. If you are not careful, you can damage the release with too much "personal taste" resulting in poor sales.

Craig