Mesa/Boogie Mini Rectifier Twenty-Five User Manual

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WithapologiestoFriendsandRelativesfromtheEmeraldIsle-whowillmaketheirappearancesoonenough-thehumorwhich
followsisdedicatedtothememoriesofSpecMcAuliffandFae(Rafael)McNally,twooftheTrueGreats.
Astheirnumericalreferencessuggest,thetermsDiode,TriodeandPentodeindicatethenumberofelementswithinthevacuum
tubei.e.two,threeorfive.Alltubesalsorequireafilamentorheaterwhichisnotincludedinthecount.Itspurposeistoexcite
electronsfromthecathodecoatingbyraisingthetemperaturesuchthattheyareabletoboiloutoftheelectron-richcoating
materialandformacloudoffreeelectronsinthevacuumspacesurroundingthecathode.
Althoughthetermfilamentandheaterareoftenusedinterchangeably,therearespecificdifferences:Afilamentisadirectly
heatedcathodewherecathodecoatingisapplieddirectlytotheheatingelement.Examplesare5U4twindioderectifierand
300Btriodeamplifiertubes.Aheater,ontheotherhand,isaheatingelementwhichisseparatefromthecathodeandisusually
insertedwithinthetubularcathodesleeve.Examplesare12AX7twintriodeamplifierand6V6orEL84beampowerpentode
tubes.Inallcasesthisfundamentalaspectofeachtube’sconstructionisclearlyvisible,especiallywhentheheatingelement
isglowingredhot.
Thecathode,then,wouldbeconsideredthefirstnumberedelementbecauseitisthesourceoftheelectrons.Theworditselfis
fromtheGreekliterallymeaningcompletelydown,whichimpliesasenseofcentralorigin-likethecenteroftheearthwhere
Tonebegins.Itmightbesaidthatanecstaticaudiophileexperiencesapositivecatharsis,hissoulbeingpurifiedwhenhissystem
transportshimtoAudioNirvana.Theonlytroublewithtakingthispositiveimagerytoofaristhatthecathodeis,unfortunately,
negative...atleastelectricallyspeaking.Howeverthisiseasilyrememberedsincevirtuallyallmusiciansandaudiophileshave
alsoexperiencedthemorecommonnegativecatharsiswhentheyemergefromtheemotionalrebirthkickingandscreaming
inrageandfrustration.
Onceheated,theintrinsicallynegativeelectronsareenergeticlittlefellowsofalmostnomass.Thustheymaybeaccelerated
almostinstantaneouslyandwilltravelthroughavacuumanearlythespeedoflight.Beingoflike,negativecharge,theytendto
repeloneanotherandthuswithintheelectroncloudsurroundingthecathode,thereismuchjostlingandelbowingaseachone
triestomaintainhisdistancefromalltheothers...unlessthereisastronganduniversalattractionfromanoutsideinfluence.
Visualize,ifyouwill,agroupofsub-atomicIrishmenmillingaboutandinarepellent,negativestateofmind.Allarescowling
andnonewantstohaveanythingtodowiththeother.Nowintroduceastrongattractionsay,apublicbar,andyoucaneasily
pictureanorderly,ifrapidmovementofthelotinasingledirection.Thisiswhathappenswhenapositivelychargedelement
calledtheanodeorplateisintroducedintothevacuum.
Theplateisthelargemetalelementmostprominentlyvisiblethroughtheglassofanelectrontube.Itistheoutermostelement
ofatube’sstructureanditsurroundsalltheothers.Thecathodeisatthecenterradiatingelectronsoutwards.Ashigherand
higherpositivevoltageisappliedtotheplate,theattractionfortheelectronssurroundingthecathodeisincreasedandwithnoth-
ingstandingintheway,fulluninhibitedflowtotheplateoccurs...sortoflikeremovingthedoorsandofferingfreedrinkstothe
crowdofsurlyIrishmenmillingaroundoutside.Aselectronsflowtotheplate,thespacechargewillcontinuallybereplenished
byfurther‘boiling’ofthehot,electron-richcathodeasyoucaneasilyimagineotherIrishmenimpatientlytakinguptheplaces
ofthosewho’vegoneinside-untiltheentirevillageisdeserted.
Now,wheredotheycomefromandhowdotheyemerge?Well,agrandandelegantladyonceshowedmehowtorevive
flatchampagne:Shedroppedaraisinintotheglass.Therewasadramaticandimmediateincreaseineffervescencewiththe
introductionofacathodingsurface.Thousandsoftinybubblessuddenlyappeared-andcontinuedtoflowfromtheraisin.Of
coursethebubblesweremadeupofgasdissolvedinthebeverage,buttheanalogymakesiteasytovisualizethelooselybound
electronsdissolvedintherichcathodecoatingastheyeffervescefromitsheatedsurface.
ON TRIODES, PENTODES & IRISHMEN:
ALookIntoTheInnerWorkingsoftheVacuumTube:
AFeatureArticlebyRandallSmith

Mesa/Boogie Mini Rectifier Twenty-Five Specifications

General

Brand	Mesa/Boogie
Model	Mini Rectifier Twenty-Five
Category	Musical Instrument Amplifier
Language	English