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Jargon/Glossary :
Jargon and lingo glossary - P & Q.
PA = Public Announcement
A term used for the types of sound reinforcement systems that are specifically designed to carry verbal information rather than music.
Packrat See --> Magpie
PAM = Pulse Amplitude Modulation
An approach to digitising sound, technically slightly more complex than PCM but implementation is cheaper, or was at the least in the valve and early transistor/IC era so it was used quite a bit for early digital transmission of audio signals, mostly experimental voice telephony and radio interlinks, but never used for audio recording as far as I know. Invented by Telefonaktiebolaget L. M. Ericsson or the practical implementation of it as an analogue switching method anyhow, but there were problems with crosstalk which meant that it was never used for large switching installations.
Parallel Interface
A digital interface capable of sending multiplies of bits usually a byte, at each clock cycle, as opposite to serial. The best known example of this is the Centronics Interface that is used on PC compatible computers amongst others or the updated Bitronics bi-directional variant of the same, in daily usage these two are simply referred to as a parallel interface..
PASC = Precision Adaptive Sub-band Coding
A variant of the Musicam perpetual coding & compression system that was developed by Philips for use in the Digital Compact Cassette and early versions of it are very similar to a MPEG layer 1 codec. Basically an audio signal is split into bands in a linear fashion (i.e. same width regardless of the frequency), all data that is duplicated inside each band is then removed, all data that the processor thinks the user will not hear due to the masking effect of the ears and all data that the processor thinks is superficial (i.e. silence) is also removed until the data has reached a reduction of 4:1. Much better worked out than its Sony ATRAC counterpart at the time but no development has been done on the codec since 1997 so it's getting a bit stale.
PCB = Printed Circuit Board
A board usually made out of plastic or plastic like materials that has electrical conducting tracks printed upon it, electronic components are soldered onto the board and the conducting tracks become the electrical connections between the components. In most cases the tracks are only printed on one side of the board for economic reasons but were more complex electrical routing is required such as with advanced digital products there may be layers of tracks, this is archived by making very thin boards, a number of which are then glued together to form one board, this type of board is usually referred to as a sandwich.
PCM = Pulse Code Modulation
The most common approach used to convert analogue audio information into digital information. Initially used in digital audio products since it was an inexpensive format to implement and since the introduction of the CD it has become even more so, other types such as Delta Sigma where considered technically better though.
PCOCC = Pure Copper Ohno Continuous Casting
Sometimes just OCC = Ohno Continuous Casting or single crystal casting. Both a name for a specific type of copper wire casting process and a trademark held by Furukawa Electric Co., hence any cable or interconnect that features a cable cast using this technique ultimately originates from that company. Invented in the mid 80's by professor Ohno then based at the Chiba Institute of Technology in Japan, hence name. In this process the copper wire is cast under strain, not unlike what is used for extrusion of high strength plastic fibres, this has the effect of almost completely getting rid of any crystal structure inside the copper wire and oxygen levels are only half of what you can expect from a high quality OFC wire.
There is also a variant from Furukawa called PCOCC-A that is an annealed variant of the cable that has about 3% better conductivity. This is a somewhat more expensive process that typical OFC casting specifically because testing for crystals in bulk is expensive, but some of Furukawa's Japanese competitors have developed similar processes primarily to meet the needs of the Russian market but in addition to better conductivity OCC cables perfom considerably better in extreme weather conditions than normal cables.
Permalloy
An magnetic alloy of Nickel (80%) and Iron (20%), in this case magnetic means that the metal is easily magnetised and demagnetised and if heat treated will show a high degree of permeability (the ability to maintain magnetisation over time). Permalloy is very cost-effective for applications that require such behaviour and is typically used in transducers such as moving magnet pickups and tape recorder heads but also in the laminations of transformers.
Originally to be called Permalloy the an alloy had to have the composition as above but more recently most magnetic Nickel & Iron alloys are called by that name and to differentiate between them the percentage of Nickel is added to the end of the name , thus Permalloy 60 has a 60% Nickel content and 40% Iron. Variants with high Iron content are almost never used in transducers or transformers since they are more susceptible to rusting.
Molybdenum Permalloy is 81% Nickel, 17% Iron and 2% Molybdenum, this variant occasionally shows up in vintage USA made audio equipment but it's main advantage over normal Permalloy is that it has better capacitive reactance compensation characteristics and this is really not an issue with the simple magnetic circuits of transducers, especially considering the extra cost.
Mu-Metal is Permalloy with 75% Nickel, 15% Iron plus added Copper and Molybdenum that has been annealed in hydrogen gas, the treatment increases the permeability of the alloy significantly (allegedly 40 times) and thus you will find this metal in transducers that are more or less permanently magnetised, noticeably loudspeakers, specialised microphones and musical instrument pickups, Mu-Metal is however considerably more expensive than plain Permalloy. Note that actual amounts of Copper and Molybdenum in addition to specifics of the post process are hard to come by, so I assume they are trade secrets.
PD = Phase change Dual disks
A type of rewriteable optical drives that uses phase-change technology designed by the Matsushita company and originally introduced in 1995 to replace the earlier (and incompatible) PCR system, the media has a maximum capacity of 640 Megabytes and is supposed to withstand 500k re-writes. Out-dated now and the technology was never as reliable as the MO drives from Fujitsu but Matshushita still provides support for the format in newer DVD-RAM drives that utilise similar technology and caddie system which can read older PD disks, so all is not lost if you have music data stored on some of these.
PD = Public Domain
Any sort of intellectual work or IP were the creator of the work has expressively denied any rights to his work or were the rights granted have run out and can thus be used by anyone for any purpose without limitations or restrictions.
Pecan
Also known as Carya illinoinensis, a Pecan is a North American tree closely related to Hickory, like hickory the Pecan wood is both strong and light but it is much finer grained than hickory and is often used in small audio products where the resonance characteristics of wood are preferred to plastics or metals, the housings of Pickups come to mind.
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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