Kenwood KA-907 Instruction Manual

Also see for KA-907: Instruction manual

BLOCK DIAGRAMPHONO SELECTOA‘Ss ,” EQUALIZERPHONO |MUTINGTAPEPHONO 2 MON MODETUNEROC COUPLED POWER AMPO—o A SPEAKERS——TAPE PLAY A@TAPE PLAY B@AUXTAPE DUBBING °TAPE REC A @ LOUCNESSTAPE REC B @TO PRE AMPreeFo FLAT ane franarnf$e T)pe —REGULATORFae = 0SUBSONICiSPOWER IN ‘' O—o B SPEAKERSPHONESPROTECTIONMeco gee See- eraloesie POWER-B5 ACGND+BTECHNICAL DESCRIPTIONDC Power AmplifierIn many ways the direct current (DC) amplifier isthe ideal amplifier for audio use.Kenwood audio engineers have taken up thechallenge of producing this ideal amplifier. The resulthas been success in producing a power amplifierwhich makes this concept a reality.Characteristics of DC Amplifier1. They make reproduction of low frequenciesdown to subsonic and DC levels possible.The result is to give a greater sense of power inthe audio reproduction which greatly increasesenjoyment of music and reproduces the low-frequency high-energy sounds of a live perform-ance as only a DC amplifier can.. There is zero phase difference between input andoutput.Because there are no capacitors in the signalpath to cause phase rotation, phase distortion isabsent.. Output waveform is a faithful duplication of theinput waveform. Although this would seem to bea natural prerequisite for a hi-fi amplifier, it is afact that only a DC amplifier makes this duplica-tion possible.The performance of a DC amplifier depends uponthe stability of each individual circuit within it. In theinput stage, special dual FETs are used, intended forthe most demanding electronic computer applica-tions {in packs of perfectly balanced pairs). This isfollowed by a three-stage differential amplifieroperating in Class A, in which the open loop gain ishigh, and in which a predetermined degree ofnegative feedback is applied. The pre-driver load cir-cuit includes a power transistor for which bias isstabilized by a constant current supply. This circuitconfiguration gives excellent stability and extremelywide frequency response.KA-SO7(K}

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