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.
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.