Shure SR107 Datasheet

MODEL SR107 AREA CODE 312/866.2200 CABLE: SHUREMICRO AUDIO EQUALIZER TWX: 910-231-0048 TELEX: 72.4381 OPERATION AND SERVICE MANUAL The Shure SR107 Audio Equalizer is a compact, versa- tile unit designed to provide adjustment of tonal balance on an octave-by-octave basis across the audio frequency range. The SR107 is used in sound system applications for the purposes of feedback control in live performances, playback equalization (correcting for equipment response and/or room acoustics in prerecorded performances), and improvement in the sound quality of live performances. Equipment response correction includes the elimination of such problems as transducer incompatibility, overload at low frequencies (rumble), tape hiss and disc surface noise. The SR107 is a balanced input and output line level device, designed primarily for installation between the audio console or mixer and the power amplifier of the sound system. DESCRIPTION The SR107 has ten octave band, minimum phase, com- bining type filters centered on ISO? preferred frequencies from 31 Hz to 16 kHz. Each filter is adjustable for ap- proximately 15 dB of boost or attenuation. The equalized output is adjustable over a 2 1 5 dB range, and overall gain of up to 20 dB may be introduced to compensate for low input signals. A peak-responding overload light- emitting diode (LED) is provided on the front panel. The SR107 contains both professional three-pin and phone jack input and output connectors, and a phone jack auxiliary output. The SR107 is designed for maximum simplicity of op- eration and maintenance. All components are of the high- est quality and are operated well within their respective ratings to assure maximum reliability under normal use conditions. The SR107 and SR107-2E are identical except that the SR107 operates from 108-132 Vac, 50/60 Hz and the SR107-2E operates from either 105-125 or 210-250 Vac, 50/60 Hz (switch-selectable). The SR107-2E is supplied with a detachable ac line cord (without power plug). The SR107 (only) is listed by Underwriters' Laboratories, Inc., and is listed by Canadian Standards Association as certified. All SR107 units are supplied with four rack-mounting screws for mounting in standard 19-inch (483 mm) audio equipment racks or in optional Shure A30A or A105A Carrying Cases. An optional protective cover, Shure Model A107A, is also available. SPECIFICATIONS * Equipment Type ..... .All transistor inductorless active equalizer Voltage Gain: GAlN Control at UNITY ....... .O dB LINE INPUT to LINE OUT- PUT -27 dB LlNE INPUT to AUX OUTPUT -50 dB LlNE INPUT to MIC OUTPUT GAlN Control at +20 dB . . . . . . . +20 dB LINE INPUT to LINE OUTPUT -7 dB LlNE INPUT to AUX OUT- PUT -30 dB LlNE INPUT to MIC OUTPUT LEVEL Control . . . .Provides additional gain adjust- ment of k 1 5 dB over values given above, EQUALIZER IN mode only. Frequency Response . .%2 dB from 30 Hz to 20 kHz, EQUALIZER IN or BYPASS Signal to Noise Ratio . . . . . (20 Hz-20 kHz) .Typically 99 dB at maximum out- put with Filter Controls and LEVEL Control at zero and GAlN Control at UNITY in EQUALIZER IN mode. Output Noise, Maximum (300 HZ-20 kHz . . . at LINE OUTPUT) -84 dBV (63 pV) - 69 dBV (0.50 mV), LEVEL Con- trol at +15, Filter Controls at - 15 -91 dBV (28 pV), EQUALIZER Switch in BYPASS Output Hum and Noise, Maximum (20 HZ-20 kHz at LINE OUTPUT) . . . - 83 dBV (71 pV) - 67 dBV (0.56 mV), LEVEL Con- trol at +15, Filter Controls at -15 -88 dBV (40 pV), EQUALIZER Switch in BYPASS lnput Common Mode Rejection . . . . . . . . . .90 dB minimum at 100 Hz Clipping Level (30 HZ-20 kHz): Input . . . . . . . . . . . . +18 dBm minimum (+15.8 dBV, 6.2V) GAlN Control at UNITY -2 dBm minimum (-4.2 dBV, 0.62V) GAlN Control at + 20dB t International Organization for Standardization Copyright 1979, Shure Brothers Inc. 27Al089 (SF) 'See Page 2 Printed in U.S.A.

Output ........... +18 dBm minimum (+15.8 dBV, Typical filter frequency re- 6.2V) at LINE OUTPUT sponse characteristics are -10.2 dBV minimum (0.31V) at shown in Figures 5A and 58. AUX OUTPUT Filters are minimum phase, -34.2 dBV minimum (19.5 mV) combining type and electrical- at MIC OUTPUT ly isolated. Overload Indicator .... Illuminates 3 dB 21.5 dB before Operating Voltage ......... output clipping occurs and Power SR107: 120 Vac t lo%, 50/60 Input Impedance ..... .70 kilohms actual, balanced Hz; 6 watts maximum bridging (for use with line lev- SR107-2E: 105-125 or 210-250 el source, 10 kilohms or less.) Vac, 50/60 Hz; 6 watts maxi- Output Impedance: mum MIC OUTPUT .... .I ohm actual, balanced (for use Accessory Power . . . a -31 Vdc open circuit, 27 Vdc at with 25- to 600-ohm inputs) 10 mA, maximum LINE OUTPUT ... .I15 ohms actual, balanced (for Temperature use with 600-ohm lines) Operating ........ -7°C to 57°C (20°F to 135°F) .......... AUX OUTPUT ... .630 ohms actual, unbalanced Storage -29°C to 71°C (-2O0Fto 160°F) (for use with auxiliary circuits Dimensions ......... .44.4 mm height x 483 mm width of 600 ohms or more imped- x 218 mm depth (1-314 in. x ance) 19 in. x 8-9/16 in.) (Figure 3) .............. Distortion: Weight .3.5 kg (7 Ib, 12 oz) lntermodulation .. .0.25% max. at 12.2 dBm (3.2V) Finish ............... Matte black (LINE OUTPUT) with a 60 Hz Installation .......... .Equipped for standard 19 in. and 7.0 kHz input at a 4:l ratio (483 mm) audio rack mount- Harmonic ....... . I % max. total harmonic distor- ing; may be operated in op- tion at 12.2 dBm (3.2V) (LINE tional A30A or A105A Carrying OUTPUT), 30 Hz-20 kHz with Case (with other equipment) ........ Filter Controls at +15, GAIN Certifications .Listed by Underwriters' Labora- Control +20 dB and LEVEL tories, Inc.; listed by Canadian Control at +15 Standards Association as cer- Phase Pin 3 and tip contacts of LINE tified (SR107 only) ............... INPUT Connectors are in * Measurement conditions unless otherwise specified: Operating voltage I ~ O V , 60 Hz (SR107). 230V 60 Hz with VOLTAGE SELECTOR Switch in 220V posi- phase with pin of MIC/L'NE tion ( ~ ~ 1 0 7 - 2 i ) . L I ~ E INPUT 7 volt at 1 kHz through 600 ohms. LlNE OUTPUT and tip contacts of OUTPUT and A'UX OUTPUT terminated in 600 ohms, MIC OUTPUT' termi- nated in 150 ohms; GAlN Control at UNITY: Filter Controls and LEVEL LlNE and AUX OUTPUT Con- control at zero; EQUALIZER Switch set to IN. nectors Equalization Filters: Center Frequencies ..... .Octave spaced from 31 Hz to 16 kHz. Accurate to within t 1 0 % of labeled value Characteristics .. .15.5 f 2 dB boost or attenuation at center frequency 6.5 t 2 dB at maximum boost or attenuation at one-half octave above or below center fre- quency OPERATING INSTRUCTIONS I I I WARNING I I TO reduce the risk of fire or electric shock, do not I I expose this appliance to rain or extreme moisture. I I I Functional Description (Refer to Figures 1 and 2) 1. 31 Hz to 16 kHz Filter Controls- Provide _+I5 dB level adjustment at center frequency of each of ten octave band filters. SO/M w. 6 WLlTS 17 16 SR107-2E ONLY 15 7 8 9 10 11 12 13 14 FIGURE 2. SR107 REAR PANEL 2

Disables filters and LEVEL Control in BYPASS position and returns gain of Equalizer (LINE INPUT to LlNE OUT- PUT) to value determined by rear-panel GAlN Con- trol. LEVEL Control -Operative only in EQUALIZER IN mode. Provides adjustment of Equalizer output level of +I5 dB to compensate for changes in gain re- sulting from Filter adjustments. OVERLOAD LED - Provides peak signal visual in- dication when peaks in output signal approach actual clipping level of output amplifier. POWER ON/OFF Switch - Controls ac power to unit. Power-On lndicator Lamp - Indicates ac power is being applied to unit. 30 VDC Accessory Power Jacks - Provide 31 Vdc open circuit (27 Vdc at 10 mA max.) for accessory equipment. AUX OUTPUT Phone Jack- Provides unbalanced low-impedance output for connection to audio con- sole or amplifier-mixer link input. LlNE OUTPUT Phone Jack - Provides balanced or unbalanced line level output to power amplifier. MIC/LINE Slide Switch - Connects line level or low-impedance microphone level signal to 3-pin OUTPUT Connector. OUTPUT 3-Pin Male Connector - Provides bal- anced output at either line level or low-impedance microphone level as selected by MIC/LINE switch. May be unbalanced externally. GAlN Control - Provides gain adjustment range from UNITY to +20 dB to accommodate various input and output requirements. Operates in both EQUALIZER IN and BYPASS modes. LlNE INPUT 3-Pin Female Connector - Provides balanced bridging, high-impedance input connec- tion from audio console or mixer-preamplifier. May be unbalanced externally. LlNE INPUT Phone Jack - Provides balanced or unbalanced bridging, high-impedance input con- nection from audio console or mixer-preamplifier. Ac Grounded Line Cord -Connects unit to ac power source (SR107 only). VOLTAGE SELECTOR Slide Switch - Permits se- lection of 105-125 or 210-250 Vac 50/60 Hz opera- tion (SR107-2E only). AC (MAINS) POWER 3-Pin Connector - Connects unit to ac (mains) power source via supplied line cord (SR107-2E only). General Operating Instructions The SR107 Audio Equalizer is primarily intended for connection in a sound system between the output of an audio console or mixer-preamplifier and the input to the power amplifier(s). A typical installation provides a line level input to the Equalizer and utilizes its line level out- put to drive the power amplifier. In a system using a limiter or compressor between the mixer and power am- plifier, the SR107 should be connected between the limiter or compressor and power amplifier to achieve best signal-to-noise performance. An alternate location for the SR107 is between the Link Out and Link In jacks of a console or mixer equipped with these jacks. The SR107 can provide satisfactory operation at the lower signal levels characteristic of this location and is equipped with an auxiliary output of ap- propriate level for the Link In connection. In the follow- ing general operating procedure, variations in connec- tion for Link operation are indicated where applicable. 1. Using hardware provided, install SR107 Audio Equalizer securely in standard 19 in. (483 mm) rack or optional A30A or A105A Carrying Case prior to making electrical connections. 2. Connect audio console or mixer-preamplifier line level output to SR107 LlNE INPUT 3-pin connector or phone jack (13. 14). (For Link use, connect link output of console or mixer to either SR107 LlNE INPUT Connector.) 3. Connect SR107 LlNE OUTPUT phone jack or 3-pin OUTPUT Connector (9, 11) to power amplifier input. If 3-pin connector is used, place MIC/LINE Switch in LlNE position. (For Link use, connect SR107 AUX OUTPUT (8) to link input of console or mixer.) 4. Place all Filter Controls (1) and LEVEL Control (3) in zero position. Move EQUALIZER IN/BYPASS Switch (2) to BYPASS. Set GAlN Control (12) to UNITY. (For Link use, set GAlN Control to $20 dB.) 5. SR107: Connect ac line cord (15) to grounded 108- 132V, 50/60 Hz ac source. SR107-2E: Move VOLTAGE SELECTOR Switch (16) to 115V or 220V position as appropriate. Attach suitable &pin male power plug to ac line cord and insert chassis connector into AC (MAINS) POWER Connector (17). Connect ac line cord to grounded 105-125V or 210-250V, 50/60 Hz ac source. 6. Position speakers in desired operating locations and aim for uniform coverage of audience area. Position microphones (if used) as required by per- formance or application involved. Basic precautions relative to microphone and speaker locations should be observed to reduce feedback potential. Set all tone controls in audio console or mixer to their zero or flat position. Set output phase switch (if any) to 0" or in-phase condition. 7. Apply power to sound system. Place POWER ON/ OFF Switch (5) in ON position. Power-On lndicator Lamp (6) will go on, indicating operation of unit. 8. Using voice, program material or tone generator (such as Shure Model A15TG) for input to sound system, increase console or mixer output level until SR107 OVERLOAD lndicator (4) flickers. Increase volume control on power amplifier until amplifier clipping distortion is evident. OVERLOAD lndicator now indicates onset of clipping in both SR107 and power amplifier. NOTE: This step does not apply to Link operation. 9. Using voice or program material as source, adjust console or mixer output to provide desired sound level in room. (For Link use, adjust individual chan- nel volume controls for desired mix and set to level that will cause only occasional flickering of SR107 OVERLOAD lndicator on peaks of high level pro- gram material.) If microphones are used as sound source, satisfactory sound level may not be possible due to feedback. In this case, set volume to stable point just below feedback level. 10. Operation of SR107 such that OVERLOAD lndicator flickers slightly, on only the loudest program peaks, is recommended. This will maximize signal-to-noise ratio, but will generally not result in audible distor- tion since lndicator threshold is 3 dB below actual clipping level. Operating with OVERLOAD lndicator always off may result in less than optimum signal-to-noise per- formance.

constantly, operating level is too high and will cause distortion, and may result in less than full power output from the sound system. 11. Set EQUALIZER Switch to IN position. Adjust Filter Controls for particular equalization objective. See procedures for feedback control, and playback and live performance equalization in following sections. While adjusting Equalizer Filter Controls, use LEVEL Control to maintain desired volume in room. Do not attempt equalization beyond bandwidth limits of sound system. For best results, keep number of Filter Controls used to a minimum, and adjust each control no more than required. 12. After equalization, perform listening check of audi- ence area to be sure that sound quality is satis- factory throughout room. Mounting and Ventilation The SR107 Audio Equalizer is designed for rack-mount- ing in a 483 mm (standard 19 in.) audio equipment rack and is supplied with the necessary mounting hardware (see Figure 3). The SR107 may also be operated while mounted in a Shure A30A or A105A Carrying Case. The A30A has a panel height capacity of 88.9 mm (3% in.) for two SR107s or one SR107 and one other unit of 44.4 mm (1% in.) height. The A105A has a panel height of 178 mm (7 in.) and will accommodate up to four units with panel heights equal to that of the SR107. No special precautions are required for ventilation. The SR107 may be operated over a temperature range of - 7" to 57°C (20" to 135°F) in continuous duty without derating. Power Supply The SR107 is furnished with a three-conductor power cable and three-prong grounded plug (15). Connect the SR107 to an outlet which supplies 108 to 132 volts ac, 50/60 Hz power. The maximum power consumption at 120 volts under normal operating conditions is 6 watts (0.05 amperes at 120 volts). If extension cords are re- quired, a high-quality, 18 gauge or larger cord should be used. r 1 8 - 9 / 1 6 IN] 197 mm' 17-314 IN) 4 8 3 mrn I I9 IN]- 4 4 3 rnm 117 7/16 IN I 1 -- I 4 4 4 mm 11-314 IN) "NOT INCLUDING CABLE/CONNECTOR CLEARIWCE DEPTH FIGURE 3. OVERALL DIMENSIONS The SR107-2E is furnished with a three-conductor de- tachable line cord without a power plug. Obtain a suitable 3-pin male power plug and attach it to the line cord. The plug should be installed by qualified service personnel. (Brown lead goes to "hot" or "live" terminal, blue lead to neutral terminal, and green/yellow lead to ground or earth terminal.) Connect the equipment end of the line cord to the AC (MAINS) POWER Connector (17) on the rear panel of the SR107-2E. Select the proper operating voltage (1 15V for 105-125V supply or 220V for 210-250V supply). Maximum power consumption at either operating voltage is 6 watts. A POWER ON-OFF toggle switch (5) on the front panel controls the application of ac power to the SR107 and a red indicator lamp (6) indicates the power-on condition. Functional Circuit Description Input connections to the SR107 Audio Equalizer are made through either a three-conductor (stereo type) phone jack (14) or a three-pin female audio connector (13) (see Figure 4). The connectors are wired in parallel to provide a balanced line level input with either con- nector. Inserting a two-conductor phone plug into the phone jack will automatically unbalance the input. The input signal is passed through a 6 dB stepdown input transformer to an attenuator. The attenuator provides an additional 11 to 26 dB of loss depending upon the setting of the LEVEL Control (3) described later. FIGURE 4. SR107 BLOCK DIAGRAM

of 14 to 34 dB depending on the setting of the rear panel GAlN Control (12). The output of the amplifier is fed to two cascaded differential amplifier stages which com- prise the equalizer boost and cut circuitry. The individual active gyrator resonators for 31 Hz, 125 Hz, 500 Hz, 2 kHz and 8 kHz are connected to the first of the differential amplifiers and provide control of these frequency bands. The second amplifier is connected to the 63 Hz, 250 Hz, 1 kHz, 4 kHz, and 16 kHz active resonators for control of the remaining five frequency bands. Each of the ten octave-spaced filters is equipped with a front panel Filter Control (1) which may be adjusted for up to 15 dB boost or cut relative to its zero or flat position (see Figure 5). This configuration of minimum-phase networks assures correct filter characteristic combinations, minimum am- plitude ripple, and minimum phase shift. The output of the second Equalizer differential ampli- fier is fed to the EQUALIZER IN/BYPASS Switch (2) which selects the input to the line output stage from either the equalizer amplifier in the IN position, or from the output of the input amplifier stage in the BYPASS position. The Equalizer LEVEL Control (3) provides adjustment of the Equalizer output level over the range of 2 1 5 dB relative to its zero setting. Reduction in output is accom- plished by attenuating the signal input to the input ampli- fier. An increase in output is produced by changing the gain in the output amplifier. The LEVEL Control operates only when the EQUALIZER INIBYPASS switch is set to the IN position. I -10 z U - 5 g 0 P $ - 5 -10 u 2 0 100 K O 0 IOPOO 20,000 FREWENCY IN HERTZ FIGURE 5A- E m FILTER AT 7.5 dB BOOST OR CUT t 2 0 + I 5 t 1 0 1 5 U H O p -5 u : -I0 g -I5 -20 2 4 6 8 1 2 4 6 8 1 2 4 6 8 1 2 2 0 100 1000 IO.WO 20.000 FREWENCV IN HERTZ FIGURE50 -EACH FILTER AT MAXIMUM BOOST OR CUT FIGURE 5. TYPICAL FILTER CHARACTERISTICS The output amplifier has a gain of 5 to 20 dB depend- ing on the setting of the LEVEL Control, and is capable of delivering + 18 dBm through the output transformer to a 600-ohm load at either of the balanced LlNE OUTPUT Connectors (9, 11). The three-pin male OUTPUT Con- nector may be switched from balanced line level to low- impedance microphone level output (50 dB below line level) by means of the MIC/LINE Slide Switch (10) which selects one of two secondary windings on the output transformer. The AUX OUTPUT Phone Jack (8) is sup- plied with an output signal that is 20 dB below that of the LlNE OUTPUT. This is obtained from an attenuator net- work at the output of the output amplifier. The AUX OUT- PUT can be used to feed the link input of an audio console or mixer so equipped. An LED driver stage connected to the output amplifier illuminates the front panel OVERLOAD LED (4) when the audio signal approaches the output clipping level. The OVERLOAD Indicator operates in both the EQUALIZER IN and BYPASS modes. Input and Output Connections Two LlNE INPUT Connectors are located on the rear panel of the SR107. A professional, three-pin female audio connector (13) provides a balanced connection from the audio console or mixer-preamplifier. A standard 1/4 in. three-conductor (stereo) phone jack (14) provides either a balanced or unbalanced input connection de- pending upon the phone plug (three-conductor or two- conductor) used. The gain of the SR107 can be adjusted by means of the back panel GAlN Control from UNITY to +20 dB in either the EQUALIZER IN or BYPASS modes. The 20 dB gain capability may be used in hi-fi or Link applications to maintain desired signal-to-noise performance through the SR107. It also allows the Equalizer to accommodate a variety of normal input and output levels while maintain- ing an adequate operating signal-to-noise ratio. Three output connectors are provided on the rear panel. A professional three-pin male audio OUTPUT con- nector provides a balanced low-impedance output at either microphone or line level depending upon the setting of the associated MIC/LINE Slide Switch. The LlNE OUTPUT Connector is a standard 1/4 in. three- conductor (stereo) phone jack which provides a low- impedance line level output that can be either balanced or unbalanced. The AUX OUTPUT Connector is a stand- ard 1/4 in. two-conductor phone jack providing a low- impedance unbalanced output suitable for connection to a hi-fi power amplifier or the link input of a mixer or audio console. The LINE, microphone level and AUX out- puts are isolated and may be used simultaneously. APPLICATIONS The primary applications for the SR107 Audio Equal- izer are as follows: 1. Feedback Control -Adjustment of sound system frequency response to provide maximum gain be- fore feedback and improved sound quality in a variety of live performance situations. The SR107 is equally adaptable to feedback control functions in either a house sound system or stage monitor (foldback) system. 2. Playback Equalization -Adjustment of audio play- back system frequency response to compensate for any variations in electrical or acoustical response that may alter the natural sound of the recorded material. 3. Live Performance Equalization - Adjustment of sound system frequency response to provide a tonal balance appropriate to the performance and to reduce the tendency for feedback. The following sections present procedures and recom- mendations for the use of the SR107 in each of these applications. Also included is a section discussing acous- tic measurement instrumentation and its use with the SR107. Feedback Control In many live performance sound reinforcement applica- tions, feedback is often the limiting factor in achieving

Audio Equalizer provides the means for selective sup- pression of those octave frequency bands in the audio spectrum where feedback is likely to occur. These fre- quency bands differ from one installation to another depending upon the acoustics of the room, equipment used, and speaker and microphone placement. The range of control of both frequency and amplitude provided in the SR107 is sufficient to accomplish significant feedback suppression without noticeable loss of program material. Proper adjustment of the Equalizer for feedback control is a matter of some experimentation; a general procedure is described here. These procedures for both house and stage monitor live performance sound reinforcement sys- tems assume that the system speakers have a consistent phase relationship and that all microphones used are also wired for consistent phase operation. If necessary, the phase of any balanced microphone line equipped with professional 3-pin connectors can be reversed using a plug-in Shure Model Al5PR Phase Reverser. House System 1. Refer to General Operating Instructions for initial connections and setup. 2. Adjust individual mixer volume control for each per- former's microphone to level slightly below feed- back threshold. If console or mixer is equipped with output phase reversal switch, set to position giving highest gain without feedback. If necessary, reduce setting of master volume control slightly and return to feedback point for each switch position to evaluate switch effect. Operation of this switch will usually affect only low-frequency feedback. 3, Increase LEVEL setting until feedback squeal or ringing is heard. If feedback appears to be high- pitched, one of five mid-to high-frequency Filter Controls (1 thru 16 kHz) will be most effective in eliminating feedback. Each Filter Control should be turned down (counterclockwise) and back to "0" position slowly to determine which is most effective. Control which stops feedback with the least rota- tion should be turned down only so far as necessary to eliminate feedback. 4. If feedback frequency happens to fall between bands covered by two adjacent controls, it may be necessary to turn down both controls slightly to obtain desired feedback suppression. 5. If feedback sound first noted in step 3 was low- pitched, adjustment procedure should be started using low-frequency (31 to 500 Hz) Filter Controls. 6. Having eliminated first feedback condition, increase gain by clockwise rotation of LEVEL Control until feedback is again noted. Repeat steps 3, 4, and 5 to eliminate new feedback condition. This may re- quire adjustment of different Filter Control or a further decrease in control or controls previously turned down. 7. Repeat step 6 until either: (a) volume level of sound system before feedback is sufficient for perform- ance involved, (b) feedback becomes a combination of sounds of various frequencies, or (c) any one Filter Control has been turned all the way down (-15). Adjust LEVEL Control to slightly below point at which final feedback sound occurred. 8. Conduct voice test using each live microphone in sequence. As each microphone is used, listen for ringing. If ringing is noted, attempt to eliminate it by further decrease in appropriate Filter Control or slight decrease in LEVEL Control setting. 9. Perform critical listening check in audience area during talk test or live performance to determine if additional equalization adjustments are necessary to improve sound quality (boost of frequency bands in the 1 kHz to 4 kHz region to improve presence and intelligibility, etc.). Refer to Live Performance Equalization for additional information. Stage Monitor System In a stage monitor system the SR107 is connected be- tween the audio console monitor line output (line level) or the line level output of a monitor mixer and the line level input of the power amplifier used to drive the stage monitor loudspeakers. With this exception the initial set- up of the stage monitor system is the same as that given in General Operating Instructions. The number, type and arrangement of microphones and speakers should be the same as used in the performance. 1. If more than one performer's microphone is in- volved, select lead performer or center stage micro- phone for use in feedback equalization procedure. NOTE: During this procedure a person must stand in front of or hold the microphone being equalized in a manner similar to that of the performer. 2. Roll off low frequency response of system by ad- justing 31 Hz Filter Control to - 15, 63 Hz to - 10, 125 Hz to -5. This will reduce low frequency noise pickup without affecting intelligibility. 3. Equalize stage monitor system following House System procedure, Steps 2 through 7. 4. Conduct voice test for each of remaining micro- phone positions in sequence using same channel gain setting as for first microphone. (This assumes that all microphones used have essentially the same sensitivity and response.) If feedback or ringing is encountered at any microphone location, try elim- inating it by adjustment of nearest speaker position or microphone distance. While performing voice test, check intelligibility of sound from monitor speakers. Intelligibility can usually be improved by boosting frequencies in 1 kHz to 4 kHz range, pro- vided that the feedback threshold is not affected. 5. Check operation of stage monitor system with all performer microphones on (preferably with some- one standing in front of or holding each micro- phone) to determine maximum gain settings before feedback for individual channel and master volume controls. 6. Operate stage monitor system and house system simultaneously at desired volume levels to verify satisfactory performance. If house system console or mixer is equipped with output phase reversal switch, operate switch and check for any improve- ment in gain before feedback in either house or stage monitor system. Playback Equalization The SR107 Equalizer may be used to adjust the overall frequency response, octave by octave, of an audio play- back system to compensate for any electrical or acousti- cal response deficiencies of the system and to provide more natural sound reproduction. Assuming that good engineering practice has been followed in selecting and installing the loudspeakers for uniform sound coverage, it is necessary to subjectively evaluate the sound quality and to equalize for reasonable audio spectral balance. While no specific procedure can be offered for this type of equalization, the following recommendations should be helpful:

tions and setup. Use typical program source and program material. Locate listening position in main audience area so that what is heard is typical of what most of the audience will hear. If practical, the SR107 should be at this location (temporarily) for ease of ad- justment. As Filter Control adjustments are made, adjust LEVEL Control to maintain initial volume level, using EQUALIZER INIBYPASS Switch to compare equal- ized to unequalized sound level and quality. Bass guitar, string bass or kick bass drum sounds are most affected by 63 Hz and (to a lesser degree) 125 Hz Filter Controls. Avoid excessive boost of these frequencies or low-frequency overload may occur. Power supply hum (60 Hz) and certain types of turntable rumble may be suppressed using 63 Hz Filter Control. The 31 Hz Control may also be help- ful for very low frequency turntable sounds. The 8 kHz Filter Control is most effective in con- trolling "brightness" of the sound, especially affect- ing speech sibilance and cymbal sounds. The 8 kHz and 16 kHz Filter Controls may also be used to reduce record noise and tape hiss. Vocal performer sound is affected most by varia- tions in the Filter Controls covering the 1 kHz to 4 kHz range. If room resonance is encountered where frequen- cies in a certain band are accentuated, some ad- justment of speaker positions may correct the condition. If this is not practical, experiment with attenuation of the octave bands in the suspect fre- quency region. The low-frequency octaves (32 through 250 Hz) are often affected by room char- acteristics. A typical subjective effect is that of a "boomy bass" sound. Use tone controls on the console or mixer (if so equipped) for broadband adjustment of the high or low end of the audio spectrum. Live Performance Equalization Equalization of a sound reinforcement system for live entertainment applications is similar to that described in Playback Equalization except that microphones and per- formers constitute the sound source. Utilize this section where applicable in live performance equalization. In most indoor sound system installations, the SR107 Audio Equalizer is adjusted first for feedback control as previously described. Additional adjustments may then be made to improve sound quality. This second level of adjustment is usually performed during a rehearsal where the performers and musicians are present and the sound aspects of the total performance can be evaluated. It is important to note that this secondary equalization process can affect the feedback threshold previously achieved and should therefore be performed with caution. If the SR107 was not previously connected to the sound system, refer to General Operating lnstructions for con- nection and setup instructions. Preliminary adjustment of the Equalizer can be made using recorded program material typical of the live performance. The recommendations given in Playback Equalization should be considered along with the following: 1. While judgements of sound quality should be made in the main audience area, it is advisable to check a number of locations throughout the area for significant variations in response. If such are en- countered, speaker location and aiming should be reviewed. 2. Any increase in Filter Control setting (clockwise rotation) previously adjusted for feedback suppres- sion should be done with care. In the case of a reverberant room where an audience would signifi- cantly increase the sound absorption, this may be possible. 3. Intelligibility and presence for vocal performances may be improved by slight increases of system response in the 1 kHz to 4 kHz region. 4. Adjustment of the response of a particular micro- phone must be made through the use of the console or mixer tone controls for that particular channel. If an individual channel exhibits a "hollow" or un- natural sound, the gain of that channel may be near feedback threshold and should be reduced. 5. If the room is acoustically "dead" (carpeted, up- holstered seats, acoustic wall treatment), the sound system output may seem deficient in the lower mid- range frequency region. In this case, slight boosting of the frequency bands in the range of 1 kHz to 4 kHz is appropriate. If the room is "live" or rever- berant, the sound may seem excessively "bright" and some attenuation of the octave bands at 8 kHz and 16 kHz may provide a more uniform response. In outdoor applications, attenuation of both low and high frequencies may be experienced. Boosting octave bands 125 Hz and below, 8 kHz, and 16 kHz may be helpful but must be performed carefully to avoid excessive amplifier and speaker drive levels. 6. Occasionally a combination of program material and room resonance produces a "boomy" sound in which some low frequencies are accentuated. At- tenuation of the 63, 125 or 250 Hz Filter Controls will suppress this characteristic. Equalization Instrumentation While the final measure of any equalization effort is a subjective judgement of the quality of the sound delivered to the audience, acoustic measurement instrumentation is available which can be of considerable assistance in more efficient and consistent equalization procedures. The equipment consists of a pink noise generator (equal sound energy per octave), an equalization analyzer and an omnidirectional analyzer microphone with a known frequency response. The analyzer generally pro- vides a display of input signal amplitude versus frequency in either octave or 1/3 octave bands for the complete audio spectrum. In general, equalization analyzer equipment is used to measure sound system performance instead of perform- ing the subjective evaluations previously discussed. Con- nection, setup and operation of the SR107 remains the same. Recommendations regarding various equalization objectives are also generally applicable. Operation of the analyzer equipment is in accordance with the manufac- turer's instructions. Usually, the analyzer equipment is used first to estab- lish the desired house curve or preferred sound system response characteristic. For playback equalization, the analyzer microphone is located in the main audience area and connected to the equalization analyzer input. The noise generator is connected to the audio console or mixer input and the volume adjusted to provide a sound level sufficiently above the room ambient noise level. The analyzer should be placed close to the SR107 so that as Equalizer adjustments are made, the results are easily observed. Adjustment for a flat response in the

overly bright sound. Common practice is to adjust for 3 dB per octave rolloff of the high frequencies starting at about 1 kHz. Frequency response is then checked in other locations in the audience area and, if necessary, the Equalizer is readjusted slightly to improve the aver- age response for the entire audience area. Final equaliza- tion adjustments are based on listening tests using typical program material. Equalization of a sound reinforcement system using instrumentation is similar to playback equalization. The sound system is equalized initially to produce the desired house curve with all microphones turned off. The individ- ual microphone volume controls are then increased to the approximate use settings, slightly below the feed- back threshold. The SR107 LEVEL Control is then in- creased slowly while observing the equalization analyzer. As the feedback threshold is approached the analyzer will show a prominent increase in amplitude of the fre- quency band where feedback is about to occur. The appropriate SR107 Filter Control setting is then reduced until the amplitude increase disappears. This process is continued until the major feedback tendencies have been suppressed and a reasonable sound volume level is being produced. A talk or performance test of each open mi- crophone is then conducted and the quality of the sound produced is sampled by listening in various locations throughout the audience area. Additional equalization ad- justments are made based on the listening evaluation and taking care to avoid any significant reduction in the feedback threshold previously achieved. Equalization of a stage monitor system using analyzer equipment is similar to playback or house system equal- ization except measurements and evaluation are confined to the performer's stage area. The pink noise generator is connected to the mixer input and the mixer volume adjusted to provide an output from the monitor speakers significantly above the ambient noise level. A person is placed in front of the lead performer's microphone (to simulate performance conditions) and the analyzer mi- crophone is placed next to the person at ear level to sample the sound field in that area. The analyzer micro- phone output is viewed on the equalization analyzer and initial response adjustments, such as low frequency roll- off, are made. The mixer volume control for the per- former's microphone is then set to a stable point slightly below the feedback threshold. The SR107 LEVEL Control is gradually increased until an obvious increase in am- plitude over a narrow frequency band is noted on the equalization analyzer. This is the onset of feedback and the appropriate SR107 Filter Control is used to reduce the system response in this area. This process is con- tinued until satisfactory gain before feedback and a desired response is achieved. A voice test of each per- former microphone position is made to determine if a similar feedback threshold is attainable. Final adjustment of the SR107 and/or individual channel tone controls (if available) is made to improve quality or intelligibility of the sound presented to the performers. Connecting a VU Meter An external VU meter may be connected to the LlNE OUTPUT of the SR107 with a series resistor (see Figure 6). Use a true VU meter (such as Simpson 1349) and a resistor connected as shown. The resistor should be Yz-watt carbon 5%. With a 600-ohm load zero VU is $ 4 dBm. / TIP WIRE 3 6 0 0 5% I I TO LlNE LEVEL OUTPUT PHONE JACK NOTE I NO CONNECTION TO SLEEVE REQUIRED. FIGURE 6. EXTERNAL VU METER SERVICE INSTRUCTIONS Service The SR107 Audio Equalizer uses components of the highest quality, operating well within their respective ratings to assure long life. WARNING Voltages in this equipment are hazardous to life. Refer servicing to qualified service personnel. Replacement Parts Parts that are readily available through local electronic parts distributors are not shown on the accompanying Parts List. Their values are shown on the Circuit Diagram (Figure 11). Commercial parts not readily available and unique parts are shown on the Parts List and may be ordered directly from the factory. The commercial alternates shown on the Parts List are not necessarily equivalents, but are electrically and me- chanically similar, and may be used in the event that direct factory replacements are not immediately avail- able. To maintain the highest possible performance and reliability, Shure factory replacement parts should be used. When ordering replacement parts, specify the Shure Replacement Kit Number, description, product model number and serial number. Cover Removal To service components inside the chassis, the pro- tective top cover must be removed. This is done by removing eight screws from the top surface and lifting the cover off. Fuse Replacement The Equalizer is provided with a wired-in main power fuse F1 which is rated at 1/16A, 250V, Slo-Blo for the SR107 and 1/8A, 250V, Slo-Blo for the SR107-2E. If re- placement becomes necessary, replace with identical fuse. Insulating tubing should be used on the fuse leads and to cover the metal end caps of the fuse. Knob Replacement All front panel rotary control knobs are pull-off types and are interchangeable. Ferrite Beads Ferrite beads are used on the signal leads to all input and output connectors except the AUX OUTPUT. Be sure to replace the ferrite beads wherever they have been removed during servicing. Printed Circuit Board Removal The SR107 chassis contains two printed circuit board assemblies, the Amplifier Board and the Equalizer Board identified as A1 and A2 in Figure 7. The foil side of board A1 may be made accessible for servicing by disconnect-

ing the leads from the push-on board terminals S and R, and removing the four Phillips head screws securing the board. The rear edge of the board (side nearest the back panel) can then be raised, tilting the board toward the front panel until it is in an upright position. The foil side of board A2 may be made accessible in a similar manner by disconnecting the lead from the push- on board terminal A and removing a total of six Phillips head screws securing the board. Replacement board assemblies are supplied with a number of the interconnecting wires already cut to length and soldered to board terminals. If either of the two boards in the SR107 are to be replaced, the new board assembly should be examined first to determine which leads are already soldered in place. Those leads which are duplicated on the new board assembly should be un- soldered at the point of origin and removed from the chassis along with the board. Note the lead colors and points of connection before unsoldering to avoid con- fusion when installing the new board. Refer to the Circuit Diagram, Figure 11 for lead identification. Transistor, Diode and LED Removal All transistors and diode rectifiers used in the SR107 are mechanically supported by their leads. When replac- ing these devices, proper lead configurations must be followed. Minimum soldering heat (preferably with a low- wattage soldering iron) should be used to avoid damage to the device. Transistor lead codes are included in the Notes to Circuit Diagram (Figure 8). To replace light-emitting diode (LED) D6, mounted on the front panel, use a long-nose pliers to remove the mounting ring from the rear of the LED. Press against the front-panel projection of the LED lens to force it out the back through the mounting clip. Disconnect the gray and orange leads from push-on terminals G and E, respectively, on printed circuit board A1 and remove the defective assembly. To install the new assembly, insert the LED in the mounting collar in the front panel. Slide the mounting ring over the leads and push it firmly onto the mounting collar, securing the LED in the panel. The Shure replacement LED is supplied with gray and orange leads attached. Thread the leads through the grommet in the shield separating the power supply from the signal circuit components. Connect the gray lead to terminal G and the orange lead to terminal E on board Al. Active Component Checking Defective transistors and diode rectifiers may be lo- cated by use of a standard ohmmeter such as a Simpson 260. Polarity of the ohmmeter must be verified before these checks are made. With a known diode orientation, measure the diode resistance in the forward and reverse directions. The lowest meter reading will establish the "minus" probe while the other probe will be "plus." Some ohmmeters are not polarized in this manner with relation to "volts plus probe" and "volts minus probe." With the ohm- meter "plus" probe on the anode end of a diode and the "minus" probe on the cathode end, the ohmmeter should read approximately 2000 ohms or less. With the meter probes reversed, a reading of about 10,000 ohms or more should be obtained. If either of these conditions is not met, the diode should be replaced. To check transistors, the ohmmeter should be set to the 100- or 1,000-ohm scale. Transistors and diodes must be removed from the circuit before testing. If all condi- tions in the following table are met, the transistor may be considered free of any major defect; if any of the following conditions are not met, the transistor should be replaced. See Notes to Circuit Diagram (Figure 8) for transistor lead codes.

- ~ - ~ ~ - - ~ - ~ - - ~ - NPN PNP lead (gray lead still grounded). he *LED should light when power is applied to the Equalizer. If it does not "Plus" Lead "Minus" Lead Transistor Transistor light it should be replaced. N O ~ E : D~ not check LED^ Collector Emitter High High with an ohmmeter; the ohmmeter may damage the LED Emitter Collector High High or give erroneous readings. Collector Base ~ i g h Low Emitter Base Low Service Illustrations Base Collector Low High The parts location photo (Figure 7) used in conjunction Base Emitter Low * with the overall Circuit Diagram (Figure 11) provides identification of all chassis-mounted assemblies and com- * NO^ a s ~ g n ~ f ~ c a n t measurement ponents. Reference to the overall Circuit Diagram and the Printed Circuit Board Parts Location drawings (Fig- To check the LED OVERLOAD indicator disconnect the ures 9 and 10) provides the means for quickly locating orange LED lead from terminal E of the amplifier printed board-mounted components. Foil circuit paths are shown circuit board A1 and connect a 1, 1.5, or 2.2 kilohm as shaded areas in Figures 9 and 10. REPLACEMENT PARTS LIST (See Figures 7, 9, 10 and 11) - - CHASSIS-MOUNTED PARTS AND ASSEMBLIES Commercial Alternate * Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is shown will be shipped in RKC quantities. 10 Reference Designation Replacement Kit No. * Replacement Kit Consists Of: 90A2236 90A2239 866628 8611628 86B632 86J628 86A404 90A1989 80A297 80A322 90R2600 95A482 95A198 Printed Circuit Board Assembly (Amplifier) Printed Circuit Board Assembly (Equalizer) Capacitor, Electrolytic, 400 ,F, 15V Capacitor, Electrolytic, 250 ,F, 40V Capacitor, Electrolytic, 1000 ,F, 40V Capacitor, Electrolytic, 47 or 50 pF, 35V min. Silicon Rectifier, 100V, 112A Diode Assembly, Light-Emitting Fuse, AC, 1 /16A, 250V, Slo-Blo, Pigtail (SR107) Fuse, AC, 1 /8A, 250V, Slo-Blo, Pigtail (SR107-2E) Connector, Phone Jack, 3-Conductor, Open Circuit, LlNE INPUT and LlNE OUTPUT Connector, Female, 3-Pin Audio, LlNE INPUT Connector, Male, 3-Pin Audio, OUTPUT A1 A2 C3 C4 C5 C6 D l -D5 D6 F1 F1 J1, J4 J2 J3 Description Qty. None None Sprague WH11 D407G016K CDE BR250-50 Sprague TVA 1316 Sprague 30D-TE1200; CDE NLW 50-50 Motorola 1 N4002 Monsanto MV5023 Littelfuse 31 5.062 Littelfuse 31 5.125 Switchcraft 128 Switchcraft C3F Switchcraft C3M Part No. - - - - - - RKC21 RKC133 - - - RKl19P RK122P - - - - - - 4 1 - - - 1 1

* Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is shown will be shipped in RKC quantities. Commercial Alternate Switchcraft 11 None None Stackpole 57-0180; Ferronics 21-030J None Leecraft 36N1311-6 None None None Cutler-Hammer 7501 K13 None Switchcraft 46206LR Switchcraft 46206LR None None None None None Belden 17408 None Reference Designation J 5 J6-J7 J8 L1 -L8 MP1 P L1 R1 R2-R11 R12 SI S 1 S2 S3 S4 T I T2 T2 T3 W1 W1 Replacement Kit No. * RKC68 RKC105 - RKC45 - - - - A - - A A - - - - - Replacement Kit Consists Of: Description Connector, Phone Jack, 2-Conductor, Open Circuit, AUX OUTPUT DC Receptacle, Red and Black Connector, 3-Pin, AC (MAINS) POWER (SR107-2E) Ferrite Bead Ring Knob Assembly, White, Filter Controls and LEVEL Lamp, Indicator Potentiometer, Center Tapped, Special Taper, 20K, LEVEL Potentiometer, Special Taper, 250K, Filter Controls Potentiometer, Screwdriver Adjust, Modified Log Taper, 10K, GAIN Switch, Toggle, SPST, POWER ON-OFF (SR107) Switch, Toggle, SPST, POWER ON-OFF (SRI 07-2E) Switch, Slide, DPDT, EQUALIZER IN-BYPASS Switch, Slide, DPDT, MIC-LINE Switch, Slide, DPDT, VOLTAGE SELECTOR (SR107-2E) Transformer and Shield Assembly, Line Level Input Transformer, Power (SR107) Transformer, Power (SR107-2E) Transformer, Line and Microphone Level Output Line Cord and 3-Conductor Ac Plug Assembly (SR107) Line Cord and 3-Conductor Ac Female Connector Assembly (SRl07-2E) Qty. 1 1 ea. - A - 1 - - - - - - - - - - - A - - Part No. 958446 95A226 958226 95A689 80A253 90A2594 80A79 46A057 46A76 46A058 9082600 90D2600 5581 19 55C119 55A116 90C2150 51A263 51 A270 51A235 95A632 90A1888

AMPLIFIER (BOARD Al) Reference Designation EQUALIZER (BOARD A2) Replacement Kit No. * C101, (2103- C104 C102, C108 C106 C109 D l 01-Dl 03 Q101, Q103, Q108-Q110 Q102, Q104, Q107 Q105 Q106 * Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is shown will be shipped in RKC quantities. *' Cornell-Dubilier alternate part has *lo% tolerance; select to 55% if possible. C201 -C202 C203 C204, C222, C223 C205 C206 C207, C211 C208, C210 C209, C213 Commercial Alternate Replacement Kit Consists Of: - - - - - - - RKC65 RKC66 Qty. 86A630 868629 86A646 86F628 86A415 86A350 86A348 86A334 86A335 - - - - - - 1 1 - - - - - - - - Part No. Capacitor, Electrolytic, 4.7 or 5 ,F, 35V Capacitor, Electrolytic, 22 ,F, 35V Capacitor, Electrolytic, 100 ,F, 25V Capacitor, Electrolytic, 400 ,F, 25V Diode, Silicon, Computer, 75V Transistor, Silicon, NPN Transistor, Silicon, Low Power, PNP Transistor, Silicon, NPN Transistor, Silicon, PNP - - - - - - - - Description Sprague 30D-TE- 1303; CDE NLW-5-50 Sprague 502D- 226G050CE10; Mallory MTV-25CD35 CDE NLW-100-25; Sprague TE-1211 Sprague TVA-1209 TI or GE 1 N4148 Motorola 2N5210 Motorola or Fairchild 2N5087 TI TIS92 TI TIS93 86A630 50XA330A 50XA271A 50WA122 50WA472 50WA183 50WA102 50WA683 Capacitor, Electrolytic, 4.7 or 5 pF, 35V Capacitor, Mica, 33 pF, 50V Capacitor, Mica, 270 pF, +5%, 50V Capacitor, Mylar, .0012 ,F, f 5%, lOOV Capacitor, Mylar, .0047 ,F, &5%, lOOV Capacitor, Mylar, .018 ,F, +5%, 100V Capacitor, Mylar, .001 ,F, k 5 % , 10OV Capacitor, Mylar, .068 ,F, +5%, 1OOV Sprague 30D-TE- 1303; CDE NLW-5-50 CDE ED330J03 CDE ED271 J03 CDE WMC08D12** CDE WMC08D47* * CDE MFP-05S18** CDE WMC08D1* * CDE MFP-05S68* *

Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is shown will be shipped in RKC quantities. * * Cornell-Dubilier alterhate part has *lo% tolerance; select to *5% if possible. Commercial Alternate CDE MFP-05S1*' CDE MFD-05S33* * CDE MFP-05P27* * CDE MFP-05P22'* CDE MFP-O5Wl * * CDE MFP-05P68' * CDE MFP-05W5** CDE ED-1 51 J03 CDE ED-331 J03 CDE WMC-08D22* * CDE MFP-05S39" * CDE MFP-05P15** CDE MFP-05P47 CDE MFP-05W2** CDE-N LW-75-25 TI or GE 1 N4148 Motorola 2N5210 Motorola or Fairchild 2N5087 Reference Designation C212, C225, C227 C214, C226 C215 C216 C217 C218, C232 C219 C220 C221 C224 C228 C229-C230 C231 C233 C245 D201 Q2014203, Q205-(2208, (2210, Q216-Q220, Q226-Q230 (2204, (2209, Q211 -Q215, Q221-Q225 Replacement Kit No. - - - - - - - - - - - - - - - - - Kit Consists Of: Description Capacitor, Mylar, .01 ,F, +5%, lOOV Capacitor, Mylar, ,033 ,F, *5%, lOOV Capacitor, Mylar, .27 ,F, f 5%, 50V Capacitor, Mylar, .22 ,F, +5%, 1OOV Capacitor, Mylar, 1.0 ,F, +5%, 50V Capacitor, Mylar, .68 ,F, +5%, 50V Capacitor, Mylar, 5.0 ,F, +5%, 1 OOV Capacitor, Mica, 150 pF, +5%, 50V Capacitor, Mica, 330 pF, 1 5 % , 50V Capacitor, Mylar, .0022 ,F, +55,1OOV Capacitor, Mylar, .039 ,F, a s % , IOOV Capacitor, Mylar, .15pF, +5%, 1OOV Capacitor, Mylar, .47 ,F, +5%, 50V Capacitor, Mylar, 2.0 ,F, *5%, 50V Capacitor, Electrolytic, 80 ,F, 25V Diode, Silicon, Computer, 75V Transistor, Silicon, NPN Transistor, Silicon, Low Power, PNP Qty. - - - - - - - - - - - - - - - - - Replacement Part No. 50WA103 50WA333 50WA274 50WA224 50WA105 50WA684 50WA505 50XA151A 50XA331A 50WA222 50WA393 50WA154 50WA474 50WA205 86H628 86A415 86A350 86A348

General Shure part numbers are not shown in the Parts List ac- companying the Circuit Diagram (Figure 11) if parts are readily available through local electronics parts suppliers. In these instances, the Circuit Diagram shows only the reference designation and value of the standard parts. All capacitor values are shown in microfarads unless otherwise designated. All non-electrolytic capacitors are 100 working volts dc or more unless otherwise specified. Electrolytic capacitors are shown in microfarads x volts. All resistor values are shown in ohms (k=1000). Re- sistors are '/!-watt, 10% tolerance unless otherwise specified. Transistor lead codes are shown in Figure 8. Accept- able replacements are shown in the Parts List. The following ground symbols denote: Chassis Ground /f7 Circuit Ground 1 - - Printed Circuit Board Ground (7 Troubleshooting A general troubleshooting process is as follows: If the SR107 is completely "dead," check the ac power source, fuse and power supply output (30 Vdc at pin V or T of printed circuit board Al). If the Power Indicator Lamp is on but the output is distorted, low or not present, apply an input signal as described under Ac Voltage Measure- ments below and determine that the input and output voltage for each board assembly is correct. If an incor- rect ac voltage is found at either board output, perform Dc Voltage Measurements as described below to isolate the problem area. AC Voltage Measurements The numbers within rectangular symbols on the Circuit Diagram denote the ac voltage at that point under the following test conditions: 1. Voltage measured with respect to chassis unless otherwise indicated. 2. Line Voltage: 120V, 50160 Hz (SR107) or 230V, 50160 Hz with VOLTAGE SELECTOR Switch in 220V position (SR107-2E). 3. All front panel Filter Controls at zero except 1 kHz Control at - 15. LEVEL Control at zero; EQUALIZER Switch set to IN. GAIN Control at UNITY. 4. Input 1 volt at 1 kHz through 600 ohms. LINE OUT- PUT terminated in 600 ohms. AUX OUTPUT not loaded. 5. Measurements made with ac VTVM of 1 megohm or greater input impedance. NOTE: Measurements of voltage (*) at collector of Q203 and Q208 made with 22 kilohm isola- tion resistor at tip of VTVM probe. 6. Ac voltage measurements may vary %20% from values shown. DC Voltage Measurements The number within elliptical symbols 0 on the Circuit Diagram denotes the dc voltage at that point under the following test conditions: 1. Voltages measured with respect to chassis unless otherwise indicated. 2. Line voltage: 120V, 50160 Hz (SR107) or 230V, 50160 Hz with VOLTAGE SELECTOR Switch in 220V position (SR107-2E). 3. No input signal applied. 4. Dc voltage measurements may vary f 20% from values shown. 5. Measurements made with VTVM of 10 megohms or greater input impedance. NOTE: Measurements of voltage at collector Q208 made with 22 kilohm isolation resistor at tip of VTVM probe. Resistance Measurements With the ac line cord disconnected from the ac source and the POWER ON-OFF Switch in the OFF position, the following ohmmeter measurements may be made. 1. Transformers may be checked for continuity of each winding. 2. To test transistors, diodes or the LED, see Active Component Checking. FIGURE 8. TRANSISTOR LEAD CODES

PARTS LOCATION FIGURE 10. EQUALIZER CIRCUIT BOARD PARTS LOCATION

rf7 FIGURE 11. SR107 AUDIO EQUALIZER CIRCUIT DIAGRAM - - - - - POWER 5 I 2 RED h GflN SR107.2E POWER SUPPLY

I EQUALIZER BOARD ( ~ a i NOTES : I, SPECIFIED. ALL RESISTORS l/4 WATT, 10% UNLESS OTHERWISE rt/ CHASSIS GROUND .$. CIRCUIT BOARD GROUND 0 D.C. VOLTAGE 1-1 A.C VOLTAGE 4. VOLTAGE MEASUREMENTS TO BE MADE WlTH ALL FRONT PANEL CONTROLS AT CENTER ROTATION EXCEPT I KHz CONTROL AT -15, AND REAR PANEL GAIN CONTROL AT FULL CCW RDTATION. ALL MEASURE- MENTS TO BE TAKEN USING A 10 MEGOHM VTVM. A.C. LINE - I20 V.A.C., 60 Hz. ALL VOLTAGES SHOWN ARE *20Z A.C. VOLTAGES MEASURED WlTH I VOLT, l KHz INPUT THROUGH 600a LINE OUTPUT W A D W WlTH 600n. D.C. VOLTAGES M~ASURED WITH ZERO SIGNAL APPLIED. 5. f TAKEN WlTH 22 KOHM ISOLATION RESISTOR AT TIP OF PROBE. FIGURE 11. SR107 AUDIO EQUALIZER CIRCUIT DIAGRAM

50/60 Hz line-operated all silicon transistor active audio frequency equalizer for use as a component of a sound system to adjust the overall system frequency response. The Equalizer shall contain a total of ten octave band, minimum phase, combining type filters extending over the frequency range of 31 Hz to 16 kHz. Each shall be adjustable for approximately 15 dB of boost or attenua- tion. The equalized output shall be adjustable over a 2 1 5 dB range. The Equalizer shall include a switch to disconnect the equalization circuitry and permit operation in a bypass mode. Gain in either the equalizer in or the bypass mode shall be adjustable from unity to approximately 20 dB through the use of a rear-panel control. The Equalizer shall be equipped with a peak-respond- ing overload indicator to provide a visual indication approximately 3 dB before output clipping occurs in either equalizer in or bypass operation. The overload indicator shall be a light-emitting diode (LED) mounted in the front panel. * All specifications apply to Model SR107-2E except for the operating voltage range which is 105-125 or 210-250 volts, 50/60 Hz ac for this model. The Equalizer shall have a high-impedance balanced input suitable for operation from a line level source of 10 kilohms or less. Two parallel-wired LlNE INPUT connect- ors, a three-pin female professional audio type and a three-conductor %-inch phone jack, shall be provided. Outputs shall include: a three-pin male profesional audio OUTPUT connector switchable by means of a MIC/LINE slide switch to line level or microphone level output, a LlNE OUTPUT three-conductor %-inch phone jack, and an AUX OUTPUT two conductor %-inch phone jack. The microphone and line level outputs shall be balanced and low impedance. The auxiliary output shall be unbalanced and low impedance. A POWER ON-OFF Switch and power-on indicator lamp shall be provided on the front panel. The Equalizer shall be enclosed in a metal housing de- signed for rack-mounting in a standard 19-inch (483 mm) audio equipment rack, or mounting in an accessory vinyl-covered wood portable case. Overall dimensions shall be 44.4.mm (1-3/4 inch) in height, 483 mm (19 inch) in width, and 218 mm (8-9116 inch) in depth. The weight shall be no more than 3.5 kg (7 Ib, 12 oz). Any Equalizer not meeting all of the above specifica- tions shall be deemed unacceptable under this specifica- tion. The Audio Equalizer shall be a Shure Model SR107. GUARANTEE This Shure product is guaranteed in normal use to be free from electrical and mechanical defects for a period of one year from date of purchase. Please retain proof of purchase date. This guarantee includes all parts and labor. This guarantee is in lieu of any and all other guarantees or warranties, express or implied, and there shall be no recovery for any consequential or incidental damages. SHIPPING INSTRUCTIONS Carefully repack the unit and return it prepaid to: Shure Brothers Incorporated Attention: Service Department 1501 West Shure Drive Arlington Heights, Illinois 60004 If outside the United States, return the unit to your dealer or Authorized Shure Service Center for repair. The unit will be returned to you prepaid.