Sampling rates should be the same, at least per side.
Limit the duration of a side to 9 minutes at 45 rpm and 14 minutes at 33 rpm. (Do not exceed 7 and 12 minutes if you want loud "dance"-levels .) Please remember that a vinyl record is an analogue medium. On CD you can get away with almost anything, a vinyl record has limitations.
Remember vinyl-rule number one: longer sides means lower levels.
If possible, please balance the duration of the sides, i.e. not side A: 7 minutes, side B: 20 minutes.
Beware of extremes.
Low frequencies take more space on the disc than mid- and high frequencies (fig 1), so they will fill the disc sooner, i.e reducing the available playing time at the choosen level or forcing the cutting engineer to reduce the level to fit the track(s) on the side of the disc.
Excessive high frequencies may overheat the cutting head or even clip a 1000 Watt cutting amp or give rise to distortions on playback (fig 2) forcing the cutting engineer to limit or lower the amount of top or lower the overall level. (remember the RIAA curve gives about 18 dB boost at 18 kH)
Do not try to compensate for possible losses; it will usually make matters worse.
Buy a Phase Corellation Meter.
Keep your bass (all instruments with lots of low frequencies) in the middle of your mix, avoid excessive stereo separation and watch out for bad phase-relationships. Excessive stereo separation and out of phase signals, particulary at low frequencies, can result in grooves on the disk that have large vertical excursions. A groove wil be created that varies from the very deep to the very shallow with the cutting head sometimes even leaving the surface of the laquer completely (fig 3). If the width across the top of the narrowest portion of the groove is less than 25 µ, there is a high probability that the playback stylus will jump completely out of the groove. On some turntables with an ideal tone-arm/cartridge resonance frequency, this shallow groove may play through, provided that it is not too long, albeit with some sort of click or noise representing the missing portion of the groove. Some cartridges may have difficulty in playing a groove that has large variations in depth - the result is distortion on playback.
Listen in Mono.
Extreme left or right panning results in large out-of-phase signals and complex record grooves wich may create moulding problems (fig 4).
Most of these problems can be avoided by checking your mix in mono and making small alterations to make your mix better mono-compatible, a better mono-compatible mix usually also sounds better in stereo.
Avoid Distortion.
Beware of distorted sounds, they will maybe still sound OK to you om your digital master but by the analogue nature of the vynil record any distortions might increase during the process and end up totaly unacceptable on the final pressing. We receive a lot of CDR's with heavy overloads, please, please don't use your AD as a limiter: overload still means DISTORTION. This distortion increases with every digital or analogue processing or copying/disc-cutting.
Peak level on your master vs peak level on the vinyl.
You don't have to squeeze the last digital word out of your AD, the digital level on your CDR-Master has nothing to do with the Loudness of your future vinyl record. Remember they are two completely different media. The level of your vinyl disc depends on the total playingtime, the frequency-content and the dynamics of your music.
Weight of pressed vinyl vs sound quality.
The thickness or weight of the pressed disk is purely cosmetic. That it would have any influence on the audioquality of your vinyl record is a myth and a fairytale.
It is complete nonsense.
Fig 1. Low frequencies occupy more space on the disk than do mid and high frequencies. From left to right 100 Hz, 500 Hz, 3000 Hz. Note that in the 100 Hz section the grooves are overcut, one groove is cut into the next. The variable pitch and depth system (Groove Control) of the cutting lathe would automatically space the low frequency grooves farther apart to eliminate the overcut.
Fig 2. Excessive high frequency energy causes tracing distortion in playback. High frequency electronic music resulted in the extremely sharp, short wavelenght grooves, wich cause tracing distortion, particulary at inner diameters.
Fig 3. From left to right 100 Hz, 500 Hz,
3000 Hz, recorded out of phase. The 500 Hz and 3000 Hz portions are not too thin and are trackable. The 100 Hz modulation - first eight grooves on the left - will cause the playback stylus to jump out of the grooves.
Fig 4. Grooves of an LP record that almost went into production ! Note the "unsafe", very thin grooves that could cause skipping in playback, and difficulties in moulding, resulting in a noisy pressing.
Fig 5. Result of excessive stereo separation at low frequencies. From left to right, 90 Hz and 900 Hz. To over come the vertical lifts, low frequency grooves have to be cut deeper. This results in more rapid utilisation of the record space: when the grooves are cut deeper, the recording pitch has to be decreased, causing the cutterhead to move faster across the surface of the disk.
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