Myths (Vinyl)
Vinyl always sounds better than CD
Many people do prefer listening to music to vinyl rather than on CD or digital formats. Many of those reasons have nothing to do with actual sound quality, and have more to do with the tactile differences - of larger artwork, and the required playback ritual for a record. Others prefer listening to CDs for a different set of reasons. (If they didn't, CDs would not have completely displaced vinyl in the marketplace in the 1980s.)
As other myths here show, there is no technically correct argument for vinyl having a superior sound quality to CD. Vinyl records may sound better than equivalent CDs for extremely specific reasons that do not apply to the media as a whole.
Vinyl requires a better-sounding master because it is physically incapable of reproducing the hypercompressed sound mastered to CD
Different masters can substantially improve or reduce sound quality. Some have less background noise. Some alter the dynamic range. There are other mastering techniques that can also affect the sound.
There are documented instances of different masters being used on vinyl releases compared to CD releases. One notable example is The White Stripes' Icky Thump'. There are also documented instances of the same masters being used on vinyl releases compared to CD releases. There is much anecdotal evidence, judging from digital analysis of vinyl recordings, that many more modern LP releases use largely the same masters as are used on CD. Alternative masters cost money, and mastering is a significant cost of producing a record. It is very likely that some producers - believing in the myth that vinyl is an inherently superior medium, as mentioned in other myths described here - will simply use the CD master for the vinyl release, believing that it will yield in a superior sound. The technical details behind this myth are as follows.
The cutting heads used for creating the vinyl lacquer (or metal mother) are speaker-like electromechanical devices driven by an extremely powerful amplifier (several hundred watts). At extremely large/fast cutting head excursions, the cutting head coils may physically burn up, much like how a speaker's voice coils may be destroyed by an excessive current. Also, the diamond cutting head stylus may prematurely wear or break. This places important constraints on the maximum levels that can be recorded to a record.
A very high power output is required to cut grooves with a high acceleration. Acceleration at the same signal amplitude is higher for higher-frequency signals. Heavily clipped and limited CDs in the modern mastering style have more high-frequency content than earlier masters. In general, increasing the perceived volume of a record - whether by increasing the recording level or by limiting/clipping/compression - raises the cutting head average power.
Additionally, during playback, the turntable's stylus has limits on what grooves it can successfully track. Cartridges can only track grooves of a finite modulation width (measured in microns) that decreases in frequency. For instance, a cartridge may only be able to track a 300um-wide groove at 300um, and yet only 50um at 20khz. This also places limits on the acceleration and velocity limits the record master can take.
The most obvious way to work around these issues is simply to reduce the recording level of the vinyl master. Multiband acceleration limiters exist for recording purposes that dynamically reduce the treble content of the master, to limit the cutting head power usage.
The vinyl surface is heated to several hundred degrees on playback, and repeat play of the same track should wait at least several hours until the vinyl has cooled
Professional estimates for the stylus surface temperature during playback are 300-500 F. Obviously, the temperature of the record is at or close to room temperature except at the stylus contact point - otherwise the record would completely melt. Back-to-back playback will introduce slightly more distortion than a fresh play. This is believed to be a temporary effect and goes away after approx. 10 minutes.
Repeated playback (no matter what the timeframe) carries the risk of permanent damage. Obviously, records are observed to wear out with repeated play. No published evidence exists of back-to-back playback causing any more permanent damage than if repeated plays are separated by any longer period of time.
Proper vinyl playback is click-free
Pops and clicks are often not audible during a song on a well-maintained record and should not distract from the listening experience. No evidence exists of a record that is shown to be played back with absolutely no pops or clicks whatsoever. They are introduced at virtually every stage of production, from cutting the laquer to the pressing to the playback itself. Some pops and ticks are pressed into the record itself.
Some pops and ticks result from static discharges during playback. However, this may be mitigated by the use of topical treatments on the record.
Because of the lack of evidence for a tick-free record and the engineering factors making such a record extremely rare, it is quite likely that no record exists that is truly free from all pops and ticks.
Vinyl is better than CD because it reproduces higher frequencies than CD and avoids antialiasing filter issues at the frequencies CDs can reproduce
The recording/tracking ability of vinyl is easily at least 50khz and perhaps as high as 100khz. The most notably proof of this is the CD4 quadraphonic system which relied on a 45khz bandwidth to be accurately reproduced. That said, the high-frequency response accuracy of vinyl varies tremendously. Frequency deviations of 5-10db or greater are not uncommon in the 20khz range for many records.
Playback of ultrasound frequencies is still not guaranteed. Many MM cartridges have resonant peaks defined by the preamp loading, or stylus tip resonances defined by the cantilever, that attenuate high-frequency content.
When groove wear does occur, it occurs much faster at high frequencies than at low frequencies. For modern stylii this is not as much of a concern, though.
Finally, on top of all of these issues, there is simply no scientific evidence that frequencies beyond the 22khz limit of CD audio are audible to any known group of people. There is no evidence that reconstruction and antialiasing issues are audible.
Vinyl is better than digital because the analog signal on the vinyl tracks the analog signal exactly, while digital is quantized into steps
PCM encoding (used on CDs and DVD-A) records audio data in a quantized format. Analog formats do not have a measurable time or signal resolution.
Analog encoding still has many measurable and audible faults, potentially including total harmonic distortion, noise and intermodulation distortion. These distortions have invariably measured higher than for digital formats, including CD.
PCM can encode time delays to any arbitrarily small length. Time delays of 1us or less - a tiny fraction of the sample rate - are easily achievable. The theoretical minimum delay is 1ns or less. (Proof here.)
Signal quantization (ie 16-bit or 24-bit) only results in increased noise in a correct implementation. No distortion is introduced and the noise is of questionable audibility under most listening conditions.
The term "analog", by definition, means that the signal is not and cannot be a perfect reproduction of the original - it is merely an "analogue" of the existing signal, corrupted in the process of encoding.
In short, by any numerical basis, vinyl is not as accurate as competing digital formats.
Vinyl has greater resolution than CD because its dynamic range is higher than for CD at the most audible frequencies
The dynamic range of vinyl, when evaluated as a the ratio of a peak sinusoudal amplitude to the peak noise density at that sine wave frequency, is somewhere around 80db. Under theoretically ideal conditions, this could perhaps improve to 120db. The dynamic range of CDs, when evaluated on a frequency-dependent basis and performed with proper dithering and oversampling, is somewhere around 150db. Under no legitimate circumstances will the dynamic range vinyl ever exceed the dynamic range of CD, under any frequency, given the wide performance gap and the physical limitations of vinyl playback. More discussion at Hydrogenaudio.
Adding a penny to the headshell improves tracking/sound
The trackability of a cartridge is related to the mechanical parameters of the tonearm and stylus assembly. Adding weight to the headshell (and adjusting the counterweight to compensate) increases the effective mass of the tonearm and reduces its resonant frequency. If the resonant frequency is excessively high - 15-20hz as measured by a test record - the weight may improve trackability by moving the resonance out of the audible range. Otherwise, it will generally only reduce trackability.
A cartridge is permanently damaged and should be replaced if the stylus appears even slightly bent
Bent stylii cause azimuth and alignment errors which may be audible. In extreme cases they can cause record damage. Cartridges are hand-built and always have some finite tolerance in their construction. No stylus is perfectly straight. That said, if a brand-new cartridge arrives visibly bent, it is probably a good idea to return it.
Belt-driven turntables are better than direct-drive turntables
Belt drives are far easier to implement than direct drives, easier to improve, and arguably easier to repair. Well built direct drives have speed and rumble tolerances as good or better than well built belt drives.
Subjective claims to the improved musicality and audio quality of belt drives are disputed and not well agreed upon by all listeners.
Belt drives hold their value just as poorly in the used market as direct drives.
Direct drive motors tend to last a very long time (some original-model SL1200s may still run without any maintenance). Belt drives need new belts on a semi-regular basis and tend to have noisier motors at the same price ranges as direct drives.
There is a common myth that a direct drive will "hunt" for the correct speed and cause audible speed variations. This has no basis in reality.
It is believed that direct drives are better at handling dynamic stylus friction than belt drives, except in cases of very poor direct drives or very good belt drives.
Some examples do exist of direct drives of inferior quality.
Stock tonearms on direct drives tend to be much less expensive than the tonearms that come with belt drives at similar price points.