Electrocompaniet-MC2-riaa-sch维修电路原理图.pdf

RadioFans.CN 收音机爱 好者资料库E L E C T R O C O M P A N I E T ASElectrocompanietMC-2Moving Coil InterfaceThe Electrocompaniet MC-2 is a unique step-up device. It willmake extremely low output moving coil cartridges compatiole withany preamp. There are basically two parts of the MC-2 design,each contributing to what is theoretically an ideal movingcoil-amplification interface. It not only responds to thedynamic impedance demands of moving coil cartridges when amusical signal is introduced, but the design also gives specialconsideration to the dramatic influences of noise and distortionon the amplification of the extremely minute signal that comesfrom a moving coil cartridge. The Electrocompaniet MC-2 providesa more exact and complete moving coil-amplification interfacethan high-gain preamps and voltage-gain step-up devices.The first part of the moving-coil interface circuit design isa current-sensing device. The interface senses the currentcoming from the moving coil and automatically adjusts to itsimpedance characteristics. It is a dynamic interface, and isconstantly adjusting to the demands of any moving-coil cartridgeas it responds to musical signals. Voltage-gain step-ups aredesigned to operate with a nominal static impedance measuredunder laboratory conditions that will provide the flattestfrequency response for a given moving-coil cartridge; however,when an actual musical signal is introduced these devices tendto damp full dynamic and frequency response. The dynamiccurrent-sensing capabilities of the Electrocompaniet MC-2 donot damp cartridge performance as is the case with step-upsthat require cartridge loading with resistors.The second part of the circuitry is a user-adjustable feedbackloop. The appropriate setting provides the degree of feedbackthat will result in the lowest noise and distortion for aparticular moving-coil cartridge. The importance of eliminatingas much noise and distortion as possible at the crucial inputstage where the signal is very small was only recentlydiscovered. As a result of years of trial-and-errorexperimenting with the effect of closed-loop feedback on sonicperformance, the designer of Electrocompaniet electronics foundthat a relatively small amount of feedback in the first stageof amplification results in far more dramatic sonic improvementthan larger amounts of feedback elsewhere in the signal path.RadioFans.CN 收音机爱 好者资料库Although there is only 6 db of feedback throughout the entirerange of the 16-setting potentiometer in each channel of theMC-2, adjustments of only one or two positions result in obvioussonic differences. Most moving coil cartridges perform bestwith settings between 0 and 7, with 0 representing the leastamount of feedback. The user may prefer that the dealershippreset the MC-2 according to Electrocompaniets recommendations,or the user may want to experiment with the settings. Thepotentiometers- that control the feedback loop in each channelare readily accessible through openings on the bottom plate ofthe device.Electrocompaniet has experimented with a number of moving coilcartridges with the MC-2 and has determined that the followingranges are most suitable:Koetsu 1-3Dynavector 2-4Asak 3-5EMT 3-5AC-2 4-6Alpha-1 3-5The exact setting within the recommended range is dependent upona number of variables such as the sonic character of othercomponents in the system and the acoustic interaction of thelistening environment.In general, a setting that is too low results in audibledistortion. The listener can readily recognize that bass andhigh frequencies are soft and lacking in dynamic impact. Asetting that is too high results in increased low-leveltransistor noise. Bass will be very tight, but high frequenciesoegin to sound unnaturally hard and sharp. Finding the rightsetting is a matter of starting with a low setting and increasingfeedback until the listener recognizes unnaturally hard and sharphigh frequencies. Turning each potentiometer back one or twonotches should result in an optimum amount of feedback wherenoise and distortion are at a minimum.Musical intruments and performers will become more focused onan amazingly dimensional soundstage. Tonal quality is accurateand natural. Many listeners have commented that the sense ofelectronics in their audio systems actually seems to disappear,and they are closer to the vitality of the performance ascaptured on the source.Mailing address: P.O.BOX 92, l473Skdrer, Norway. Office address: Stremsveien 72, l473Skdrer, NorwayTel:(02) 706410. Telex: 18225otegr. Bank: Den norske Creditbank 7104.05.06092