7
DESCRIPTION
TheremotecontrolledCodaControl AmpliferCSiBalancedisdesignedwiththoroughness
reservedonlyforthefinestpreamplifierandamplifiergainstages. Analyticaldesign
techniques,bothobjectiveandsubjective,wereappliedinanopen-mindedfashionwith
musicalperfectionasthegoal. TheCSiBfeaturesawiderangeofdesigntopologiesand
componentsportedfrombothbroadlineageandthemostrecentadvancesintheCoda
productsanddesigntopologies.
Unlikeotherintegratedamplifiers,theCSiBofferstrue “separates”performance. TheCSiBis,
internally,essentiallyaStereo Amplifier Tswithaseparatepreamplifiersectionbasedonthe
circuittopologyoftheCoda07xPreamplifier.
Onthefaceplate,thestraightforwardcontrolsanddisplayprovidecomprehensive
functionalitytotheuser. AllinputselectionshaveLEDstoshowwhentheyareinuse.Buttons
controlbothvolumeandbalance,withanLEDdisplaytoshowwhichchannelsarebeing
adjusted.GainiscontrolledbyahighperformanceBurr-BrownPGA2310analogattenuator.
Thisdigitallycontrolledanaloguedevicefeaturesanimprovedoutputbufferandincreased
voltageswingforhighlevelinputsignals.Digitallycontrolledleveltrackingallows1dBper
stepattenuationwithouterror. Thedigitallycontrolledsteppedresistors&zerocrossing
detectioncircuitallowfor “zipper-free”operation. Totalharmonicdistortionislessthan0.04%
withasignaltonoiseratioapproaching130dB.
Thepreamplifiersectionhasitsownseparatepowersupplywithmultipleindependent
transformertaps. A referencevoltageisdevelopedbydeliveringconstantcurrenttozener
diodes. Theresultingvoltageisheavilyfilteredanddeliveredthroughclass-A followersto
provideabsolutelystablepowertothepreamplifiersection. A separatepowersupplyis
providedforallcontrolsandmicroprocessorcontrolsystem.
IntheamplifiersectionoftheCSiB,differentialvoltagegainthroughoutprovidesexceptional
rejectionofexternalnoiseandcontributestotheinherentstabilityofthecircuit. Thefrontend
isdesignedtoprovideaslewrateof50V/uswithoutenteringclassBoperationasiscommon
inmanyotherdesigns. Thiscombinedwithexcellenthighfrequencydesigninsureslinear
operationathighspeed.
Theamplifer’soverbuiltpowersupplytakeaverydirectapproachtohighperformanceby
utilizingatopquality3.0kVA customtoroidaltransformer,highcurrentrectifersanda
80,000 FcapacitorfilterbankwithverylowESRandinductance.
Thislatestgenerationoutputstagedesigniscapableofproducingpeakcurrentsinexcessof
100peakampereswithadegreeoflinearityandspeedunmatchedbyotherdesigns
producingonlyafractionofthismassiveamountofcurrent. Thisisachievedbythe
implementationofseveraldistinctcircuitfeatures.Eachchanneluses20individualoutput
transistorswithacombinedpowerratingofover4,000wattsand125amperesanda
bandwidthof30MHz. TheCSiBV3operatesinClass A uptoapproximately~8watts. At
higheroutputlevels,thebiassectionisdesignedtoproduceaprecisiontransitionwithno
abruptchangesindistortionoroutputimpedance. This “PrecisionBias”techniqueyields
seamlessperformanceregardlessofthecomplexityoftheload.Withsuchlinearityand
bandwidth,only6dboffeedbackisusedtomaintaindampingfactorwhilepermittingthe
minimalvaluecustomemitterresistorstoprovidecurrentlimitingonlyunderextreme
conditionsthatwouldexceedtheoutputstageshighcurrentcapabilities.Oneadvantageof
thisisahighdegreeofimmunityfrominteractionswithcomplexspeakerloadsorcables.
μ