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Showing content with the highest reputation on 11/17/2014 in all areas

  1. Some MFSL Facts... Supervinyl Early MFSL titles were pressed by JVC in Japan on virgin "SuperVinyl". JVC originally developed this proprietary plastic compound in the early 1970s to reduce record wear on discreet CD-4 Quadrophonic LP records which were introduced in 1972. Supervinyl is a harder and more durable vinyl than traditional formulas. These pressings exhibit a very low surface noise, as well as fewer pops and clicks. Supervinyl remains a proprietary JVC technology and production of this material was discontinued in the late 1980s. Mastering engineers Stan Ricker mastered all of the early MFSL LP releases. Ricker's work can be recognized by the signature "SR/2" carved in the dead wax Jack Hunt ("JH/2") mastered many of MFSL's LP releases in the 1970s and 1980s. Some later titles were mastered by John LeMay and Paul Stubblebine, with a few uncredited releases. Currently, Shawn R. Britton and Rob LoVerde are mastering most LPs for MFSL. CDs, SACDs, and audio cassette mastering have been done by a variety of engineers, most recently Britton. The company has only had a handful of engineers in its history. Specialized audio systems MFSL has used highly customized audio playback systems throughout its history. Since 1998, Mobile Fidelity has been using Studer A-80 1⁄4 inch tape machine, which was custom modified by audio designer Tim de Paravicini. The deck features custom high bandwidth playback heads and custom playback electronics. This machine exhibits frequency response, which is essentially flat from 10 Hz-44 kHz. Using this tape machine and a record cutting system (also designed by Paravicini), Mobile Fidelity engineers accidentally cut a 122 kHz tape bias tone onto a record lacquer. Mobile Fidelity has revisited several albums with their new mastering chain that were previously released on the old UltraDisc 2 system. Some listeners have noted that the new mastering chain exhibits a 'tighter' sound, particularly in the bass frequencies.
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  2. Very interesting read on Mastering for Vinyl. Liked this one. How they get stereo on these things Back in the days of mono, the groove cut on the disc was a simple spiral, and it was shifted back and forth in the plane of the record with the signal (this is called lateral cutting). The engineer could adjust the groove pitch (that is, the spacing between each successive rotation) so that for loud passages the grooves were widely spaced and for soft passages they were tightly packed. This maximized the amount of time on a side, while still allowing a lot of dynamic range on peaks. When stereo came along, there were a number of odd schemes used first off, but the industry quickly settled on what was called the 45-45 system (see Figure 1). With this method, the lateral movement of the groove carries the mono signal (that is, the L+R sum of the right and left channels), while the depth of the groove is varied to reflect the differences between the channels (that is, the L-R signal). This meant that the new stereo records could be played on older mono equipment accurately. The reason it is called 45-45 is that the popular way of cutting this involved right and left channel coils in the cutting head, each of which were arranged 45 degrees from the plane on which the stylus was mounted, so that the sum and difference signals were generated mechanically. Another way of looking at this is to think about the V-shaped groove of the record: the inner groove wall carries the left channel, modulated on a 45-degree tilt to the right, while the right channel is cut on the outer groove wall. As a result, if there is a lot of information common to both channels, the groove is made deeper and shallower, while if there is a lot of information not common to both channels, it slides back and forth laterally. The net effect is that if you sum the left and right channels you get mono, but with the appropriate pickup you can get stereo. However, there are some cutting heads with individual L-R and L+R coils, one mounted parallel to the record surface and the other mounted perpendicular to it. And there are a lot of mastering houses that still generate L+R and L-R signals for separate processing and then recombine them to L and R before sending them to the cutter, despite using the more common cutting heads that take L and R signals as input. The disadvantage of the whole stereo LP scheme is that although the mastering engineer can adjust the groove pitch for loud or soft passages, the maximum and minimum depth of the groove are constant. Cut too much low frequency information with a wide stereo spread, and you get a lot of deep peaks and valleys in the groove and styli tend to pop out of the groove. Turn that down, and your stereo image collapses. So the amount of stereo information has a lot to do with the level that can be cut to disc. No matter what you do beforehand, out-of-phase low frequency content will lift the stylus from the groove or drive it into the substrate. On the other hand, in-phase low frequency information causes lateral excursions wide enough to cut into the previously cut groove and into the area where a groove would be cut in the next revolution. And this one. The mastering process Mastering today has become a catch-all term for any kind of post-mixing audio processing, but LP mastering is the process of making an acetate out of the original tape. The processing is secondary. However, the processing is almost essential to get the most out of the limited channel. There is a lot of poking and prodding that is often done to get the stereo signal to fit into place, because the LP has less information on it than the original master tape does. Often, you’ll see mastering engineers roll off a lot of the very low bass and add a false bass peak around 200 Hz or so, just to compensate for the mechanical limitations of the equipment. The other alternative is to reduce the running time per side radically. The one thing that saves us from bass being a big problem is the RIAA pre-emphasis curve. Most of the noise in the recording process is at higher frequencies. So on record, we pre-emphasize the signal by pumping up the highs, and then on playback the phono amplifier has a roll-off curve that is the exact inverse of the curve in the record chain, which rolls them off. This means that the music has the same frequency response, but the noise is reduced, primarily on the high end. Even with this, though, the mastering engineer is constantly juggling signal processing versus recording time versus groove pitch. Most systems today automatically control the groove pitch, although an expert engineer can override them to some extent and make constant tweaks to get that last bit of performance out. Traditionally, the way this is done is with a “margin control” system. The tape is played back on a machine with a special “pre-hear” or “pre-listen” head that picks up the signal about half a second before the playback head (i.e., for 30 ips tape, the head is about 15 inches away from the playback head), and feeds that signal into some control electronics. This means that that control system has information about what the signal level is going to be like on the next rotation of the disk. It can constantly ride the groove pitch up and back so that the grooves don’t get too close that the walls between them get deformed. But they are still as close as possible so that the maximum running time on the disk occurs. This, incidentally, is why 12" singles are invariably cut much, much hotter than conventional LPs. There is plenty of space for very wide groove spacing, so they are cut as hot as possible and therefore play back much louder. Some of the 12" singles are even cut constant pitch, without any margin control, because there is just too much safety margin available for the mastering engineer. When working with a digital signal source, a digital delay line today usually replaces the deck with the pre-hear head, but still the overall principle is the same. Another issue here is that the frequency response of the disc is different in the outer grooves and in the inner grooves, because the stylus is moving much faster across the outer grooves (it goes through a greater distance per revolution). This means that the mastering engineer may have to tweak the high end response up progressively during the cutting process. It is a good idea to leave a large blank area around the label, because the very inner grooves have serious sonic problems. Not only do they have high frequency loss, but the tracking distortion is a lot higher, especially as the records wear. The less time you try and get on a side, the more space the engineer is able to leave there to keep things clean. Hmmmmmm, must be why they made Endless River a double LP instead of squeezing it all onto one LP.
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