Playback and Recording (Vinyl)
- 1 Sources of Distortion
- 1.1 Turntable
- 1.2 Tonearm, Cartridge and Stylus
- 1.3 Preamp
- 2 Objective Requirements Of Vinyl Playback
- 3 Forum Posts and FAQs
- 4 Links
Sources of Distortion
Tonearm, Cartridge and Stylus
Objective Requirements Of Vinyl Playback
These statements are derived from psychoacoustics and electrical constraints that would be necessary to yield objectively optimal playback. These statements also form a concise summary of the audible issues with vinyl.
Pitch, wow and flutter
The playback speed of the turntable must be within 0.3% of 33 1/3 RPM at all times - or 5 cents. Variations of pitch must stay witin the 5-cent requirement and the modulating frequencies must not be audible.
Shockingly, this is extremely hard to achieve in belt-drive turntables for a number of very important reasons. Good direct drives are much better at pitch. (Bad direct drives are much worse at flutter.)
The low frequency noise (rumble) of the turntable must not impinge on program material, must not distort amplifier or speaker stages, and must not be audible.
Rumble is an intrinsic part of both the vinyl medium and the turntable. Often times, 5-10dB of the peak amplitude of a vinyl recording is contained in the rumble, and removing it can help increase the loudness for essentially free.
After RIAA equalization, the system must be able to reproduce frequencies from 20hz to 20khz to within 0.1dB of the source media.
0.1dB is close to the theoretical JND of amplitude for a single sinusoid; tolerances around 1dB in response are usually acceptable.
MM cartridges are well-known for boosting the high end if improperly loaded. Stylus or record wear will eliminate high frequencies. Rumble may make low frequency reproduction difficult.
Forum Posts and FAQs
- What sample rate to record with? (thread thread) In general 44.1khz will work fine. There are not significant reasons to choose either 44.1khz or any higher sample rate. Some postprocessing tools for vinyl recordings only operate at 44.1khz. Additionally the dynamic range and distortion specifications for many sound cards are better at 44.1khz than at higher sample rates.
- What bit depth to record with? (thread) Similar to the sample rate question above. In general 16 bits actually does work well. It's a common misconception that the quantization noise will significantly raise the noise floor of the recording; as long as the signal peak is -10dbFS or higher it is not an issue. If you plan to perform a very large amount of digital processing on the recording, the rounding errors could build up sufficiently that they impinge on the background noise level of the vinyl. In that case the recording should be made at (or converted to) 24 bit resolution prior to the processing stages to reduce the effect of rounding errors. That said, you would need to do a very great deal of processing before a 16 bit recording of vinyl became degraded in this way. A few passes of EQ, noise reduction, amplitude adjustment, etc. isn't going to bring the quantisation noise up above the vinyl noise floor.
- How low of a frequency can LPs produce? (thread) The common wisdom is that they don't have much below 60hz, but there is evidence that the signal extends as low as 20hz and possibly lower on some LPs. Note that low bass on vinyl records will be mono, but this is not a problem because low bass is non-directional. (The reason for this is that low bass signals cause the largest groove excursions, and of course the vertical (out of phase) component of the groove must never be so great that the groove rises above the surface of the record, so the out of phase component of the low bass is removed when mastering for vinyl).
- How much bandwidth is on an LP? (thread) This is a hard question, because the dynamic range has to be considered and it is frequency-dependent. It is almost certainly lower than CD, and certainly far lower if the theoretical bandwidth limits of the CD medium are considered, rather than the digital specifications. Although some sort of signal above 20kHz can be recovered from an LP, it is highly unlikely to be related to the programme material; in other words it is noise. The majority of LPs probably contain nothing of significance above about 16kHz.
- What recording level should LPs be recorded at? (thread) As high as possible without clipping. -3db is usually safe and some sound cards may distort if driven past that. If you are recording on a sound card with a good noise floor (100db or greater) then you can go as low as -18db without ill effects.
- How to remove sibilance? (thread)
- How should mono LPs be recorded? (thread)
- What are some examples of good and bad vinyl rips? (thread thread thread thread)
- Can/should LPs be ripped faster than real time, ie at 45rpm or 78rpm? (thread) No.
- http://www.delback.co.uk/lp-cdr.htm cliveb's excellent guide to recording LPs to computer. Includes discussion on cleaning, sound cards, recording, and postprocessing.
- Wikipedia articles on the:
- The Vinyl Engine: Detailed discussion on all aspects of vinyl playback and maintenance. Check out the Library section for good articles and free protractors.
- The Vinyl Asylum at the Audio Asylum: true to its name, this has more voodoo audiophiledom than perhaps anywhere else on the Internet. But there are many good discussions, as long as you take some hefty grains of salt.
- Stereophile forums: Almost as much voodoo audiophiledom as Audio Asylum.
- Turntables & Tape forum at AudioKarma.org
- Head-Fi: Discussions on turntables under the "Dedicated Source Components" forum and the TTVJ forum.
- Steve Hoffman Forums: Excellent technical discussions.