Alesis RA 100 电路图.pdf

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1、 ALESIS RA-100 Reference Manual RadioFans.CN 收音机爱 好者资料库 CHAPTER 1 GETTING TO KNOW THE RA-100 1.1 INTRODUCTION.1 Principal Features.1 Unpacking and Inspection.3 About This Manual.4 CHAPTER 2 INSTALLATION 2.1 REAR PANEL CONNECTIONS.5 2.2 POWER CONSIDERATIONS.5 Fuse.5 The AC Cord.5 Electrical Service t

2、o the RA-100.6 2.3 OPERATING ENVIRONMENT.6 Thermal Considerations in Rack Mounting.6 Mounting on a Shelf or in a Non-Rack Enclosure.7 Avoiding Electromagnetic Interference.8 2.4 INPUTS.8 Input Jack Characteristics.8 Cables.8 Cable Wiring Tips.9 Adapting the RA-100 to Balanced Lines.9 2.5 OUTPUTS.11

3、Connector Options.11 Output Cables.11 Connecting Cables to Push Connectors.12 The Importance of Speaker Polarity.13 CHAPTER 3 USING THE RA-100 3.1 FRONT PANEL CONTROLS.14 Volume Controls.14 On-Off Switch.14 Mute Switch.15 Clip Indicators.15 3.2 CHECKING FOR PROPER POLARITY.15 3.3 CHOOSING THE CORREC

4、T SPEAKERS.15 3.4 ABOUT GROUND LOOPS.16 CHAPTER 4 TYPICAL APPLICATIONS 4.1 STUDIO MONITOR AMP.18 4.2 SOUND REINFORCEMENT.18 RadioFans.CN 收音机爱 好者资料库 4.3 KEYBOARD AMPLIFICATION SYSTEM.19 4.4 GUITAR AMPLIFICATION SYSTEM.20 4.5 BIAMP SOUND REINFORCEMENT.21 CHAPTER 5 MAINTAINANCE/SERVICE 5.1 GENERAL INFO

5、RMATION.22 Cleaning.22 Maintenance.22 Refer All Servicing to Alesis.22 CHAPTER 6 TROUBLESHOOTING Hum.23 No Volume.23 Distorted or Low Level Sound.23 Thin Sound/Sound that Changes Unpredictably in a Room.23 CHAPTER 7 SPECIFICATIONS DO NOT REMOVE THE RA-100 TOP COVER. THERE ARE NO USER SERVICEABLE PAR

6、TS INSIDE. REFER SERVICING TO A QUALIFIED REPAIR TECHNICIAN. CHAPTER 1: MEET THE RA-100 1.1 INTRODUCTION Principal Features Congratulations on your purchase of the Alesis RA-100 Reference Amplifier. With all the wondrous advances in both analog and digital electronics in the past few years, its easy

7、 to forget that an audio chain is only as good as its weakest link. With low-cost digital devices now offering sound quality unheard of only a few years ago, Alesis has applied its expertise toward creating a sonically accurate, stable, and affordable stereo power amplifier thats suitable for the di

8、gital age. Optimized for studio monitoring applications and moderate-power live performance setups, the amps main features include: 100 watts per channel into 4, 75 watts per channel into 8 Dual clipping indicators alert you of any type of non-linear operation, not just clipping Output short circuit

9、 protection to minimize down time and protect the amplifiers circuitry Massive, conservatively rated, custom-designed extruded heat sinks (individual for each channel) for cool operation No ventilation fan is needed, allowing for quiet operation and reduced ambient noise in the studio Extremely low

10、noise and distortion; suitable for quiet applications such as recording studios, church installations, and museums However, some of the RA-100s most important features are hard to put on a spec sheet. In a quest for a “musical” sounding power amp that can stand up to a tough life on the road as well

11、 as continuous operation in the studio, Alesis has made some changessome minor, and some very significantto the standard power amp. The RA-100 doesnt produce any audio transients during power-up or 1 power-down. Nonetheless, theres a 2-second mute on power-up to compensate for any pieces of equipmen

12、t plugged into the RA-100 that produce transients upon power-up, and receive power at the same time as the RA-100. Also, because the amp doesnt produce power on/off thumps itself, the mute circuit can be pre-power amp. This allows simpler circuitry than what would be required for shutting down the p

13、ower amp stages. The RA-100s power supply has plenty of reserve capacity to handle percussive transients, but if someone kicks the RA-100s plug out of the wall, you want all amplification to cease immediately. Therefore, if the amp senses any loss of power, it instantly mutes the audio. Because powe

14、r-up and -down are noiseless, the on/off switch doubles as a mute or “panic” button. The output stage uses full complementary-symmetry circuitry throughout. Although there are cheaper ways to design an output stage, this time-tested approach is generally considered superior to non-complementary- sym

15、metry types. The output devices are rated at 30 Amps of peak current, and boast a 20 MHz FT (transition frequency) for superior bandwidth. Extremely good stability with reactive loads (e.g., speakers and crossovers). Stable operation is essential when presented with the changing load characteristics

16、 of typical speakers; the RA-100 uses several stabilization techniques to maintain consistent feedback network characteristics. Alesis recognizes that amplifiers will sometimes be driven into clipping even though this is not good practiceduring a recording session or under the pressures of live perf

17、ormance. As a result, a great of deal of research went into creating the best possible clipping entry/recovery characteristics. Amps with lots of overdrive and saturation tend to create overshoot and ringing during the clipping process, which degrades the sound; the RA-100 has been designed so that

18、it exhibits very little saturation, even when overloaded. As a result, it enters and exits clipping very cleanly. Clean clipping allows the RA-100 to be driven harder, which makes the overall perceived sound louder. Monitoring a sine wave being clipped confirms this action. With the RA- 100, the amp

19、 will follow the original input signal as soon as clipping ceases (a). With some conventional amp designs, the signal will “hang” at the clipped level for a while before catching up with the input signal (b. This saturation-caused overshoot can sometimes sound worse than the clipping itself. s 2 No

20、“speaker stress” during shutdown. With traditional protection circuitry, the act of clamping the output devices to a safe value can make the amp unstable with particular notes that interact with the speaker resonance, thus producing oscillation or “motorboating.” This could damage your speakers. The

21、 RA-100 uses an elegant clamping design that observes the load at all times but also integrates the signal characteristics into the clamping action. Thus, the clamping action is gentle and, after clamping to the maximum current encountered in normal operation, will slowly (over 1 to 2 seconds) clamp

22、 based on the load and signal characteristics. If the source of the problem (e.g., a short across the speaker terminals) is removed, the signal recovers instantly. Alesis also recognizes that whatever else, “the show must go on.” As a result, under conditions of extreme abuse (such as ultra-low spea

23、ker impedances or mounting that allows for no ventilation), the RA-100 will limit its signal rather than simply shut down. Taken to an extreme, this will produce distortion but sound will still come out. To acquaint yourself with the RA-100s operation, and to use it properly in various applications,

24、 carefully read this manual. Power amplifiers are high- current devices that are the next-to-last link in the audio chain. Proper attention to cabling, power distribution, ground loops, and other topics covered in this manual is vital to have the RA-100 live up to its full potential. As always, we w

25、elcome your suggestions and comments concerning this product, or any other product in the Alesis line. Unpacking and Inspection Your new Alesis power amplifier was carefully packed at the factory, and the container was designed to protect the unit during shipping. Please retain this container in the

26、 highly unlikely event that you need to return the RA-100 for servicing. Upon receiving the RA-100, carefully examine the shipping carton and its contents for any sign of physical damage that many have occurred in transit. If you detect any damage, do not destroy any of the packing material or the c

27、arton, and immediately notify the carrier of a possible claim for damage. Damage claims must be made by you. If you picked up your amplifier directly from an Alesis dealer, contact the dealer. The shipping carton should contain: This instruction manual 3 Alesis RA-100 power amp with the same serial

28、number as shown on the shipping carton Power cord. Four stick-on rubber feet (for shelf mounting, to prevent the RA-100s bottom surface from scratching the shelf) Alesis warranty card. It is important to register your purchase; if you have not already filled out your warranty card, please do so now.

29、 About This Manual The manual presents information in a logical order. Chapter 2 covers installation, and Chapter 3, how to use the RA-100. Chapter 4 covers several typical applications. The manual closes with information on maintenance/servicing, troubleshooting, and operating specifications. Pleas

30、e remember that a power amplifier is a high-current, high-power device and should be treated with respect and care. Even if you are an audio veteran, we urge you to read the entire manual to make the best use of the RA-100. 4 CHAPTER 2: INSTALLATION 2.1 REAR PANEL CONNECTIONS The following diagram s

31、hows the various rear-panel components. Please refer to this diagram during the procedures described in this chapter. Fuse: 5 Amps (A spare fuse in included in the fuse holder) Right Input Left Input Right Phone Plug Output Left Phone Plug Output Left Push Clip Outputs Right Push Clip Outputs AC Lin

32、e Cord Jack 2.2 POWER CONSIDERATIONS Fuse Replace with a 5 Amp, slow-blow type only; use of any higher amperage value will void the warranty. FUSES ARE FOR YOUR PROTECTION NEVER SUBSTITUTE A FUSE OF A HIGHER RATING, OR BYPASS IT. The AC Cord The RA-100s IEC-spec AC cord (do not substitute any other

33、AC cord) is designed to feed an outlet that includes three pins, with the third, round pin connected to ground. The ground connection is an important safety feature designed to keep the chassis of electronic devices such as the RA-100 at ground potential. DO NOT OPERATE ANY ELECTRICAL EQUIPMENT WITH

34、 UNGROUNDED OUTLETS. PLUGGING THE RA-100 INTO AN UNGROUNDED OUTLET, OR “LIFTING” THE UNIT OFF GROUND WITH 5 A THREE-TO-TWO WIRE ADAPTER, CREATES A HAZARDOUS CONDITION. ALESIS CANNOT BE RESPONSIBLE FOR PROBLEMS CAUSED BY USING THE RA-100 OR ANY ASSOCIATED EQUIPMENT WITH IMPROPER AC WIRING. Electrical

35、 Service to the RA-100 Although the RA-100 has a maximum audio output rating of 200 watts total into 4, this does not represent the total current consumption since there are certain inefficiencies inherent in linear amplifier design. As a result, the fuse is rated at 5 Amps, implying that the maximu

36、m current the RA-100 can draw is around 500 watts. However, in typical studio applications the average power consumption will be much less. However, when multiple devices are plugged into a single AC outlet, the possibility of overheated connections can exist. Electrical standards have taken enormou

37、s strides toward increased safety over the past few decades thanks to circuit breakers, ground fault interrupters, and improved wiring and insulation materials. Unfortunately, some clubs are situated in older buildings whose wiring may not meet current safety standards, or have wiring that has deter

38、iorated over the years. Make sure the circuit supplying power to the RA-100 can supply enough current to run it properly. If the circuit has to supply other high-powered consumption units such as refrigerators, coffee pots, toasters, air conditioning, or stage lighting, plug the RA-100 into a differ

39、ent circuit with a lesser load. 2.3 OPERATING ENVIRONMENT Thermal Considerations in Rack Mounting The RA-100 can be mounted in an equipment rack (taking up 2 rack spaces), placed on a shelf, tucked away in a vocal booth, etc. When you install it, keep in mind that heat is the major enemy of electronic equipment. Fortunately, the RA-100s protection circuitry will not allow the unit to run hot enough to damage any of the circuitry. However, sustained high-temperature operation sufficient to cause limiting will adversely affect the sound quality for as long as the excessive temperature