Shure_SM81_User_Guide 电路图.pdf

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1、Model SM81 User Guide 2005, Shure Incorporated 27C2916 (Rev. 6) Printed in U.S.A. MODEL SM81 UNIDIRECTIONAL CONDENSER MICROPHONE The Shure Model SM81 is a high-quality, unidirectional con- denser microphone designed for studio recording, broadcasting, and sound reinforcement. Its wide frequency resp

2、onse, low noise characteristics, and low RF susceptibility have made it a standard for applications involving acoustic instruments, especially guitar, piano, and cymbals. The SM81 is ruggedly constructed. It operates on phantom pow- er and performs over a wide range of temperatures and humidity cond

3、itions. It is furnished with a swivel adapter, attenuator-switch lock, foam windscreen, and case for carrying and storage. Other accessories are available. Model SM81 Features 20 Hz to 20 kHz frequency response Flat response curve for accurate reproduction of sound sources Low noise and high output

4、clipping level Low distortion over a wide range of load impedances Cardioid polar pattern, uniform with frequency and sym- metric about axis, providing maximum rejection and min- imum coloration of off-axis sounds Low RF susceptibility Selectable low-frequency response: flat, 6 or 18 dB/oc- tave rol

5、loff 0 dB/10 dB lockable attenuator switch Phantom powering (DIN 45 596 voltages of 12 to 48 Vdc) Rugged steel construction for durability Field-usable over wide range of temperature and humidi- ty conditions SPECIFICATIONS Type Condenser (electret bias) Frequency Response 20 to 20,000 Hz TYPICAL FR

6、EQUENCY RESPONSE FIGURE 1 Polar Pattern Cardioid (unidirectional) response-uniform with frequency, sym- metrical about axis TYPICAL POLAR PATTERNS FIGURE 2 Output Impedance Rated at 150 (85 actual) Recommended minimum load impedance: 800 (May be used with loads as low as 150 with reduced clipping le

7、vel) Output Configuration and Connector Balanced, transformer-coupled output; male XLR connector Sensitivity (at 1,000 Hz) Open Circuit Voltage: . . . . . . . . . . . .45 dBV/Pascal (5.6 mV) (1 Pascal = 94 dB SPL) Clipping Level (at 1,000 Hz) 800 Load: . . . . . . . . . . . . . . . . . . . . . . . .

8、 . . 4 dBV (0.63 V) 150 Load: . . . . . . . . . . . . . . . . . . . . . . . . . 15 dBV (0.18 V) Total Harmonic Distortion Less than 0.5% (131 dB SPL at 250 Hz into 800 load) 202000010001000050100 9876543298765432 +10 0 10 Hz dB -20 +20 1 METER 150 120 150 120 180 30 60 90 30 60 0 90 10 dB 20 dB 15 d

9、B 5 dB 150 120 150 120 180 30 60 90 30 60 0 90 10 dB 20 dB 15 dB 5 dB 500 Hz 100 Hz 1000 Hz 5000 Hz 10000 Hz 2000 Hz 5 dB 10 dB 15 dB 20 dB 5 dB 10 dB 15 dB 20 dB RadioFans.CN 收音机爱 好者资料库 2 Maximum SPL (at 1,000 Hz) 800 load:. . . . . . . . . . . . . . . . . . . . . 136 dB (attenuator at 0) 146 dB (a

10、ttenuator at -10) 150 load:. . . . . . . . . . . . . . . . . . . . . 128 dB (attenuator at 0) 138 dB (attenuator at -10) Hum Pickup -3 dB equivalent SPL in a 1 mOe field (60 Hz) Self-Noise (equivalent sound pressure levels; measured with true rms voltmeter) 16 dB typical, A-weighted 19 dB typical, w

11、eighted per DIN 45 405 Signal-to-Noise Ratio 78 dB (IEC 651)* at 94 dB SPL *S/N ratio is difference between microphone output at 94 dB SPL and microphone self-noise A-weighted. Overvoltage and Reverse Polarity Protection Max. external voltage applied to pins 2 and 3 with respect to pin 1: . . . . .

12、. . . . . . . . . . . . . . . . . . . . +52 Vdc Reverse polarity protection: . . . . . . . . . . . . . . . . 200 mA max. (diode-clamped) Polarity Positive pressure on diaphragm produces positive voltage on pin 2 relative to pin 3 Cartridge Capacitance 54 pF Low Frequency Response Switch Positions Fl

13、at; -6 dB/octave below 100 Hz; -18 dB/octave below 80 Hz Attenuator Switch Positions (Lockable) 0 or -10 dB Power Supply Voltage:. . . . . . . . . 11 to 52 Vdc, positive, pins 2 and 3 Current Drain:. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 mA max. Environmental Conditions Temperatu

14、re Storage: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 to 74 C (20 to 165 F) Operating:. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 to 49 C (20 to 120 F) Humidity Storage: . . . . . . . . . . . . . . 095% relative humidity at room temperature (72 to 80 F, 22 to 27 C)

15、 Case Steel construction with vinyl metallic paint finish and stainless steel screens Dimensions See Figure 3 Weight Net: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 grams (8 oz) Packaged:. . . . . . . . . . . . . . . . . . . . . . . 740 grams (1 lb 10 oz) Certification Eligi

16、ble to bear CE marking. Conforms to European EMC Direc- tive 89/336/EEC. Meets applicable tests and performance cri- teria in European EMC Standard EN 55103 (1996) parts 1 and 2 for residential (E1) and light industrial (E2) environments. OPERATION Power The SM81 requires phantom power. This may be

17、supplied to the microphone by a mixer, preamplifier or console with built-in phan- tom power or from an external power supply (such as the Shure model PS1A). Phantom power sources providing between 11 and 52 Vdc are suitable. Use only high-quality cables because intermittent shorts be- tween broken

18、shield wires and balanced conductors will cause ex- tremely large noise transients in the system. Avoid ground loops due to grounded connector shells or the microphone case touching other grounded metal objects. Follow generally accepted audio grounding practices. Impedance A minimum load impedance

19、of 800 or greater should be used for maximum signal handling and minimum distortion. The load may be as low as 150 , but a reduction in output clipping level will result. It should be noted that the power supply itself may add load- ing (3300 in the Shure PS1A power supply) to the microphones. PS1A

20、Power Supply When using the Shure PS1A to phantom power the SM81, con- nect the microphone cable to the SM81 and to the MICROPHONE connector of the power supply. The power supply uses the bal- anced audio cable pair to carry the supply current to the micro- phone and the cable shield as a ground ret

21、urn. Connect the OUTPUT connector of the power supply to a low-impedance microphone input of a mixer, audio console or tape recorder. A second SM81 may be connected to the remaining pow- er supply channel in a similar manner. OVERALL DIMENSIONS FIGURE 3 212 mm 20 mm 23.5 mm RadioFans.CN 收音机爱 好者资料库 3

22、 Low-Frequency Response Filter The SM81 has a three-position low-frequency response filter controlled by a switch located on its handle. The switch is recessed to avoid accidental movement, but may be easily moved with fin- gertips. The user may select either flat response, low-frequency rolloff of

23、6 dB per octave below 100 Hz, or low-frequency cutoff of 18 dB per octave below 80 Hz (see Figure 4). When close-miking instruments or vocalists, an increase in low-frequency response (proximity effect) takes place. Figure 4 illustrates this effect with the switch in each of the three positions. Not

24、e that the low-frequency response filter may be used to compensate for proximity effect or reduce low-frequency noise from stage traffic and other sources. PROXIMITY EFFECT AND COMPENSATION FIGURE 4 Attenuator Switch The SM81 has a switchable 10 dB capacitive attenuator to pre- vent high sound press

25、ure levels from overloading its internal elec- tronics. The attenuator is engaged by rotating the actuator ring, located directly below the grille assembly, until it reaches the “-10 position. This reduces the output of the microphone by 10 dB and increases the maximum sound pressure level at clippi

26、ng by 10 dB. There are no intermediate levels of attenuation available. The attenuator ring may be locked in either the “0 or “-10 po- sition as follows. Unscrew the grille and cartridge assembly by un- screwing counter-clockwise from the top. Turn the actuator ring to the “0 or “-10 position as des

27、ired. Insert the actuator ring lock (small clear piece of plastic) in the area behind the actuator ring be- tween the pin and the edge of the slot. This will prevent the ring from turning. Replace the grill and cartridge assembly. Mixer Overload The SM81s output is about 15 dB higher than most dynam

28、ic mi- crophones. At moderate to high SPLs, this additional output may require attenuation (or padding). If no attenuation is available on the preamplifier, mixer or console being used, a resistive attenua- tor can be inserted between the microphone and the input. The Shure Model A15AS Attenuator (1

29、5, 20, or 25 dB switch-select- able) is specially designed for use with condenser microphones such as the SM81. Alternately, the attenuator design shown in Fig- ure 5 may be used. The resistors shown are 1/2-watt, 1% toler- ance, and the circuit may be packaged in a Switchcraft S3FM adapter housing.

30、 The circuit will provide15 dB of attenuation and can be used between the SM81 and the PS1A (or other power sup- ply), or between the PS1A and the mixer. Two of these circuits may be used in series to provide 30 dB of attenuation. (Note that, due to excessive loading, commercially available 150 atte

31、nuators, such as the Shure Model A15AS, are not recommended when two are used in series.) 15 DB ATTENUATOR CIRCUIT FIGURE 5 Wind Noise The wide frequency response of the SM81 makes it sensitive to wind, breath, and air currents from heating, ventilation and cooling (HVAC) systems. The foam windscree

32、n included with the SM81 can be used to reduce wind and breath noise, while the low-fre- quency response filter can be used to reduce low-frequency room noise caused by HVAC systems. The Model A81G Pop Filter Grille attenuates breath popping sounds when the microphone is close-talked, and permits it

33、s use outdoors with minimal pickup of rushing and rumbling sounds. To install the A81G, slip it over the SM81 until the inside of the A81G touches the top of the microphone. Tighten the A81G by rotating the knurled collar clockwise from the bottom. (Note: When remov- ing the A81G, first loosen the k

34、nurled collar. Otherwise the car- tridge will unscrew with the A81G.) For outdoor use under very windy conditions, use the Model A81WS large foam windscreen. 20100050100 +10 0 10 Hz dB 152.4 MM ( ) 152.4 MM ( ) 152.4 MM ( )12 3 12 3 412 412 215 OUTPUT TO MIXER INPUT FROM MICROPHONE RadioFans.CN 收音机爱

35、 好者资料库 4 BLOCK DIAGRAM FIGURE 6 CIRCUIT DESCRIPTION A block diagram of the SM81 is shown in Figure 6. The capacitor cartridge is followed by a switch-controlled capacitive attenuator stage which provides for 10 dB attenuation at the cartridge output. The signal is fed to a field-effect transistor (F

36、ET) impedance con- version stage. The FET output drives an active low-frequency re- sponse (high-pass) filter controlled by a three-position switch. The filter output from a compound transistor, Class A, emitter-follower amplifier is transformer-coupled, providing a balanced output to the RFI protec

37、tion filter at the microphone connector. An active, constant-current power supply circuit regulates the phantom volt- age, allowing the SM81 to operate over a very wide range of volt- ages. A reverse voltage protection diode guards against miswired cables and equipment. TROUBLESHOOTING If the SM81 f

38、ails to operate properly, verify that the microphone is powered properly. 1. Check the power supply output voltage to the microphone. For the Shure PS1A, this should be 21.5 + 1.5 Vdc open circuit. 2. Check the voltage on microphone connector pins 2 and 3 (at back of connector; cable connector disas

39、sembled from shell but connected to microphone). The voltage at pins 2 and 3 with reference to pin 1 should be between 11 and 52 Vdc. Due to its high packing density and circuit complexity, disassem- bly of the SM81 is not recommended. Contact Shures Service De- partment if problems persist. ARCHITE

40、CTS SPECIFICATION The microphone shall be a condenser microphone with a fre- quency response of 20 to 20,000 Hz. It shall have a unidirectional pickup characteristic, with cancellation at the sides of 6 dB and a minimum cancellation at the rear of 15 dB at 1 kHz. The micro- phone shall have a rated

41、output impedance of 150 for connec- tion to microphone inputs of 150 ohms or higher. The open circuit voltage shall be -65 dB (0.56 mV) (0 dB equals 1 volt per microbar). The microphone shall contain a three-position low-freq-uency response switch and a lockable 10 dB attenuator pad. The overall dim

42、ensions shall be 212 mm (8-11/32 in.) in length by 23.5 mm (15/16 in.) in diameter. The handle diameter shall be 20.1 mm (25/32 in.). The weight shall be 230 grams (8oz). The microphone shall be capable of being powered by a phan- tom power supply with an output of 11 to 52 Vdc, or by a mixer, au- d

43、io console or tape recorder capable of supplying 11 to 52 Vdc. The microphone shall be a Shure Model SM81. FURNISHED ACCESSORIES Swivel Adapter.A57F 10 dB Attenuator Lock .34A830 Carrying/Storage Case .65A1797 Windscreen.49A111 OPTIONAL ACCESSORIES Pop-Filter Grille. A81G Heavy-Duty Windscreen. A81W

44、S Tripod Microphone Stand (4.3 m 14 ft).S15A Stereo Microphone Adapter.A27M Cable (7.6m 25ft).C25F Phantom Power Supply . PS1A REPLACEMENT PARTS Cartridge and Grille Assembly. R104 CAPACITOR CARTRIDGE FET IMPEDANCE CONVERTER LF RESPONSE FILTER CLASS A COMPOUND AMPLIFIER RFI FILTER BALANCED TRANSFORM

45、ER REGULATOR/ REVERSE VOLTAGE PROTECT CAPACITIVE ATTENUATOR 5 MODLE SM81 MICROPHONE LECTROSTATIQUE UNIDIRECTIONNEL Le modle SM81 de Shure est un microphone lectrostatique unidirectionnel de haute qualit, conu pour lenregistrement en studio, la diffusion et la sonorisation. Sa large rponse en frquen-

46、 ce, ses caractristiques de faible bruit et sa faible sensibilit aux parasites haute frquence en ont fait la norme pour les applica- tions intgrant des instruments de musique, surtout la guitare, le piano et les cymbales. La construction du SM81 est robuste. Il fonctionne sur alimen- tation fantme e

47、n duplex et donne dexcellentes performances sur une vaste plage de tempratures et de pourcentages dhumidit. Il est fourni avec un adaptateur articul, un verrou de slecteur dat- tnuation, un bonnette antivent en mousse, une mallette pour le transport et le rangement. Dautres accessoires sont disponib

48、les. Caractristiques du modle SM81 Rponse en frquence 20 20 kHz Courbe de rponse plane pour une reproduction prcise des sources sonores Faible bruit et niveau dcrtage de sortie lev Faible distorsion sur une large plage dimpdances de charge Courbe de directivit cardiode uniforme selon la frquence et symtrique par rapport laxe pour fournir un rejet maximum et une coloration minimum des sons dsaxs Faible sensibilit aux parasite