Phenol See --> Bakelite

Photocell
A transducer that converts light into electrical energy.

Polynorbornene Rubber
A polymer based on Norbornene which in turn is simply a condensation of ethylene and cyclopentadiene, best known under the trademarks Norsorex owned by Astrotech Advanced Elastomerproducts GmbH and Sorbothane that is owned by a company of the same name but there are a number of other trademarks and names used for this product.

Polynorbornene has a number of unusual properties that make it interesting for use in audio products, it has a low resilience and absorbs kinetic energy, e.g. it is acoustically and mechanically mostly dead while still being elastic and can as such be used for applications such as loudspeaker driver surrounds or any type of vibration absorbers, in fact it can be used as a highly efficient sound absorber as well although a tad expensive for that job and has even been used in bullet proof west's.

Pure PR has a glass transition temperature of only 35°C which means it becomes less efficient as an absorber above 35C but since the material is synthetic the amount of elasticity and hardness can be controlled by adding various oils to the manufacturing process, it can also be used as a direct substitute for natural rubber, can in fact be treated by many of the same processes as rubber such as vulcanisation etc. and has in many cases replaced rubber and styrene butadiene copolymers in the marketplace.

Most manufacturers of the chemical should be able to supply you with needed variants of PR but they are not all 100% the same, Norsorex is usually the strongest and most often the product you will see in loudspeakers while Sorbothane is most often seen as a mechanical vibrational isolator for things such as turntables, CD players and cassette recorders, although there may be historical reasons for this.

Postscript Media See --> WORM

Power Conditioner
A "power conditioner" is a device intended for use with hi-fi products that "conditions" the electric power signal in order to make your existing system sound better or in the case of transistor amps to be more efficient. This is archived typically through the use of active or passive filtering but more exotic variants exist. This type of device is increasingly popular in countries such as the USA were we see more variations in the quality and age of electrical installations and infrastructure than we typically see in other western countries and in the UK were standards and work practices in electrical wiring date back to the stone age, but theoretically a conditioner (depending on design) should offer at the least a minimal benefit to any system regardless.

We first see these units in used in the medical sector were they were used to shield very sensitive equipment from minor variations in input voltages and shapes but those devised leaked into the hi-fi world in the 80's. You should not confuse them with battery based power back-up devices, these have an electrical output that is not sinusoidal which may cause trouble with audio equipment with linear power supplies, in particular with amplifiers since the further away from a pure sinus wave the power signal is the less efficient the amplifier becomes. There do exist however battery based power conditioners that mix rechargeable battery technology with more normal filtering techniques to create ultra pure sinus waves, these are rare and expensive however.

Alternatively : A power conditioner is a device expressively designed to con nonplussed audiophiles out of their hard earned money..

Prussia (Pruss, Prússland)
A Baltic country in northern Europe that stretched from Lithuania in the east to northern Germany in the west, was one of the states that unified into Germany in the latter half of the 19th century.

PSU = Power Supply Unit
A Power Supply is a device that converts the available electric power, typically 110 or 230 volts AC, into something more appropriate to run electronic equipment off, typically 5 to 12 volts DC. A power supply is in most cases built into the device it is intended to power but it is more and more common to see them being external, this is due to three factors:

• More and more devices are supposed to be portable or transportable in which case having an optional power supply is a bonus.
• Smaller companies in particular can save costs by buying a power supply from a third party that has already gone through type approval in various jurisdictions in the world.
• In high end audio products, particularly those with sensitive high bandwidth circuits or small DC motors, having an external power supply can help isolate the effects that the transformer in the supply can have on the circuit.

All products that have analogue circuits will benefit from having a good quality power supply but for devices such as turntables and amplifiers the quality of the power supply can have a huge impact on the overall quality of the unit and in the case of an amplifier the power output rating as well.

Psychoacoustic Masking
Actually a set of techniques used to "fool" the ear or rather to get around various shortcomings in devices or techniques by exploiting certain defects, non-linearietes and other abnormalities in how your ears work and how the brain makes use of audio information. The simplest and the most commonly seen technique is to make use of the integration tendencies of your ears, for instance you cannot detect distortions that are less than 1ms since the ear will simply ignore them and integrate what became before and after into one distortion free sound, so if a distortion can be shaped into extremely sharp transients by concentrating the energy, you will not hear it.

PVC = PolyVinyl Chloride
Oil based plastic, cheap, flexible, resonably strong and very stable chemically and thus heavily used in industry. Initially taken on in the 30's by the food packaging industry but after 1945 it started to get used for the pressing of records as well since it was not only cheaper than the Shellac and filler mixes it replaced but also stronger and made the pressing process simpler and thus cheaper. The use of one material rather than the often coarse mixes used in the shellac process also meant that the audio quality of pressed records got better over time. The problem with PVC is that it breaks down easily if exposed to direct sunlight for extended perioids of time.

PWM = Pulse Width Modulation
In amplifiers : A technique were an audio signal is converted into pulses with the width of the pulse representing it's slope, the pulse signals are sent to a dual output stage that switches between + and - and the speaker then averages out the signal thus reconstructing the slope. Very efficient, typically over 95% in modern examples and theoretically should sound excellent but the switching action of the output sage creates noise and the higher the frequency is, the more noticeable the noise and related distortions are.

This technology is widely use in subwoofer applications were this phenomenon is less of a problem. PWM amps are sometimes described as a "digital amplification", that's not quite correct although they can be viewed as hybrids, but it is possible to make a converter less amplifier using this technology and driving it directly with PCM or DSD streams. Better sounding propriety variants of this technology have been developed over the last few years by a handful of companies, they all involve amplifiers operating at very high switching frequencies that use computer circuits to modify the behaviour of the output stage in real time, the use of a high switching frequency is an attempt to keep some of the inenvitable distortions outside of the audible range.

In electronic music : This term is used when an oscillator playing a pulse waveform has the width of the pulse changed by a signal from another waveform generator, an event generator or a tactile interface.

Quad = Quadraphony
The term Quad is often used denote 4 channel stereo systems although some 3D/height info systems that utilised 4 channels also used this term (Tomita Quad for instance). A traditional Quad system differs from a modern type of a surround system in a number of ways. The back speakers are meant to be similar and preferably identical to the speakers used at the front, all four speakers are meant to be placed an equal distance from the ideal listening position and all channels are supposed to get a discrete and equally information rich signal but in a modern home theatre type stereo system the 2 front speaker get a much richer signal than the rest of the system..

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