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zmix

Aqua Marine

Posts: 3,887 Member Since:20/01/2011

#21 [url]

Mar 8 17 12:37 PM

He specifically stated that it is the RIAA curve.


MT: Tell us about half-speed mastering – how does it differ?

MS: Half-speed mastering is a vinyl-cutting process where both the source is played out and the cutting lathe is running at half the real-time rate (effectively the source and the disc cutting lathe are locked together, but both are running at precisely half the correct speed). The advantage of this is the system is not stressed.

The cutter-head draws somewhere between a quarter to a third of the current from the drive amplifiers than would be required for real-time cutting, and the recording stylus has twice as long to carve the intricate groove into the lacquer master disc. All the difficult-to-cut high-end frequencies become relatively easy-to-cut mid-range frequencies. This results in cuts that have excellent high-frequency response (treble) and very solid and stable stereo images.

Remember, the only way a pressing plant can press a really high-quality record is if the process starts with a really high-quality cut. Unfortunately, however, it’s not as simple as running everything at half rate. There is an EQ curve (RIAA) applied to all vinyl records and by running the lathe at half speed, all the frequencies are wrong.

Abbey Road have installed custom designed and built RIAA filters into the cutting amplifiers that feed the modified VMS 80 lathe. These custom filters apply the correct EQ curve when cutting at half-speed.

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gold

Platinum Blonde

Posts: 1,468 Member Since:27/01/2011

#22 [url]

Mar 8 17 1:01 PM

Well, he's obviously not technical. He says 'all the frequencies are wrong with the RIAA'. There are two time constants in RIAA pre/deemphisis. Neither of which can be duplicated with a Sontec."All" is a strange word to use if he knows what he's talking about.

Like I said the RIAA is applied inside the SAL74 Drive Amplifier Rack. In the SAB74 module. The SAB74 module has to be modified which is what they did. I spoke to a tech about exactly how they did it.

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