Rane_Sound_System_Interconnection 电路图 维修手册.pdf

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1、Interconnection-1 Introduction This note, originally written in 1985, continues to be one of our most useful references. Its popularity stems from the continual and perpetual difficulty of hooking up audio equipment without suffering through all sorts of bizarre noises, hums, buzzes, whistles, etc.

2、not to mention the extreme financial, physical and psychological price. As tech- nology progresses it is inevitable that electronic equipment and its wiring should be subject to constant improvement. Many things have improved in the audio industry since 1985, but unfortunately wiring isnt one of the

3、m. However, finally the Audio Engineering Society (AES) has issued a standards document for interconnection of pro audio equip- ment. It is AES48, titled “AES48-2005: AES standard on interconnections Grounding and EMC practices Shields of connectors in audio equipment containing active circuitry.” R

4、anes policy is to accommodate rather than dictate. However, this document contains suggestions for external wiring changes that should ideally only be implemented by trained technical personnel. Safety regulations require that all original grounding means provided from the factory be left intact for

5、 safe operation. No guarantee of responsibility for incidental or consequential damages can be provided. (In other words, dont modify cables, or try your own version of grounding unless you really understand exactly what type of output and input you have to connect.) Rane Technical Staff RaneNote 11

6、0 1985, 1995, 2006, 2007, 2011, 2015 Rane Corporation Sound System Interconnection Cause effect- loops and insert-points on consoles; signal processing boxes; semi-pro digital and analog tape recorders; computer cards; mixing consoles; et cetera. The next several pages give tips on how to successful

7、ly address hooking up unbalanced equipment. Unbalanced equipment when “blindly” connected with fully balanced units starts a pattern of hum and undesirable operation, requiring extra measures to correct the situation. Figure 1b. Recommmended practice. CASE (+) () COMMON (WRONG) PRACTICERECOMMENDED P

8、RACTICE () (+) OPTIONAL CASE 1 2 33 1 2 CHASSIS GROUND SIGNAL GROUND CHASSIS GROUND CHASSIS GROUND The Next Best Right Way To Do It The quickest, quietest and most foolproof method to con- nect balanced and unbalanced is to transformer isolate all unbalanced connections. See Figure 2. Many manufactu

9、rers provide several tools for this task, including Rane. Consult your audio dealer to explore the options available. The goal of these adaptors is to allow the use of standard cables. With these transformer isolation boxes, modification of cable assemblies is unnecessary. Virtually any two pieces o

10、f audio equipment can be successfully interfaced without risk of unwanted hum and noise. Another way to create the necessary isolation is to use a direct box. Originally named for its use to convert the high impedance, high level output of an electric guitar to the low impedance, low level input of

11、a recording console, it allowed the player to plug “directly” into the console. Now this term is commonly used to describe any box used to convert un- balanced lines to balanced lines. The Last Best Right Way To Do It If transformer isolation is not an option, special cable assemblies are a last res

12、ort. The key here is to prevent the shield currents from flowing into a unit whose grounding scheme creates ground loops (hum) in the audio path (i.e., most audio equipment). It is true that connecting both ends of the shield is theo- retically the best way to interconnect equipment though this assu

13、mes the interconnected equipment is internally grounded properly. Since most equipment is not internally grounded properly, connecting both ends of the shield is not often practiced, since doing so usually creates noisy interconnections. A common solution to these noisy hum and buzz prob- lems invol

14、ves disconnecting one end of the shield, even though one can not buy off-the-shelf cables with the shield disconnected at one end. The best end to disconnect is the receiving end. If one end of the shield is disconnected, the noisy hum current stops flowing and away goes the hum but only at low freq

15、uencies. A ground-sending-end-only shield connection minimizes the possibility of high fre- quency (radio) interference since it prevents the shield from acting as an antenna to the next input. Many reduce this potential RF interference by providing an RF path through Figure 2. Transformer Isolation

16、 NOT CONNECTED AT CHASSIS (PLASTIC JACK) EARTH GROUNDED METAL ENCLOSURE CHASSIS IS GROUNDED TO PIN 1 1/4” TIP-SLEEVE CASE LUG MAY CONNECT TO CHASSIS (NOT REQUIRED) TRANSFORMER UNBALANCEDBALANCED 3 1 2 RadioFans.CN 收音机爱 好者资料库 Interconnection-4 a small capacitor (0.1 or 0.01 microfarad ceramic disc) c

17、on- nected from the lifted end of the shield to the chassis. (This is referred to as the “hybrid shield termination” where the sending end is bonded to the chassis and the receiving end is capacitively coupled. See Neutriks EMC-XLR for example.) The fact that many modern day installers still follow

18、this one-end-only rule with consistent success indicates this and other acceptable solutions to RF issues exist, though the increasing use of digital and wireless technology greatly increases the possibility of future RF problems. If youve truly isolated your hum problem to a specific unit, chances

19、are, even though the documentation indicates proper chassis grounded shields, the suspect unit is not in- ternally grounded properly. Here is where special test cable assemblies, shown in Figure 3, really come in handy. These assemblies allow you to connect the shield to chassis ground at the point

20、of entry, or to pin 1, or to lift one end of the shield. The task becomes more difficult when the unit youve isolated has multiple inputs and outputs. On a suspect unit with multiple cables, try various configurations on each con- nection to find out if special cable assemblies are needed at more th

21、an one point. See Figure 4 for suggested cable assemblies for your par- ticular interconnection needs. Find the appropriate output configuration (down the left side) and then match this with the correct input configuration (across the top of the page.) Then refer to the following pages for a recomme

22、nded wiring diagram. Ground Lifts Many units come equipped with ground lift switches. In only a few cases can it be shown that a ground lift switch improves ground related noise. (Has a ground lift switch ever really worked for you?) In reality, the presence of a ground lift switch greatly reduces a

23、 units ability to be “properly” grounded and therefore immune to ground loop hums and buzzes. Ground lifts are simply another Band-Aid to try in case of grounding problems. It is true that an entire system of properly grounded equipment, without ground lift switches, is guaranteed (yes guaranteed) t

24、o be hum free. The problem is most equipment is not (both internally and externally, AC system wise) grounded properly. Most units with ground lifts are shipped so the unit is “grounded” meaning the chassis is connected to audio signal ground. (This should be the best and is the “safest” position fo

25、r a ground lift switch.) If after hooking up your system it exhibits excessive hum or buzzing, there is an incompatibility somewhere in the systems grounding con- figuration. In addition to these special cable assemblies that may help, here are some more things to try: 1. Try combinations of lifting

26、 grounds on units supplied with lift switches (or links). It is wise to do this with the power off! 2. If you have an entirely balanced system, verify all chassis are tied to a good earth ground, for safetys sake and hum protection. Completely unbalanced systems never earth ground anything (except c

27、able TV, often a ground loop source). If you have a mixed balanced and unbalanced system, do yourself a favor and use isolation transform- ers or, if you cant do that, try the special cable assemblies described here and expect it to take many hours to get things quiet. May the Force be with you. 3.

28、Balanced units with outboard power supplies (wall warts or “bumps” in the line cord) do not ground the chassis through the line cord. Make sure such units are solidly grounded by tying the chassis to an earth ground using a star washer for a reliable contact. (Rane always provides this chassis point

29、 as an external screw with a toothed washer.) Any device with a 3-prong AC plug, such as an amplifier, may serve as an earth ground point. Rack rails may or may not serve this purpose depending on screw locations and paint jobs. Figure 3. Test cable TEST WIRE GROUND CLIP FEMALEMALE 1 C 2 3 1 2 3 RED

30、 BLACK SHIELD RED BLACK SHIELD 2-CONDUCTOR SHIELDED CABLE Interconnection-5 Floating, Pseudo, and Quasi-Balancing During inspection, you may run across a output called floating unbalanced, sometimes also called psuedo-balanced or quasi-balanced. In this configuration, the sleeve of the output stage

31、is not connected inside the unit and the ring is connected (usually through a small resistor) to the audio signal ground. This allows the tip and ring to “appear” as an equal impedance, not-quite balanced output stage, even though the output circuitry is unbalanced. Floating unbalanced often works t

32、o drive either a bal- anced or unbalanced input, depending if a TS or TRS stan- dard cable is plugged into it. When it hums, a special cable is required. See drawings #11 and #12, and do not make the cross-coupled modification of tying the ring and sleeve together. Winning the Wiring Wars Use balanc

33、ed connections whenever possible, with the shield bonded to the metal chassis at both ends. Transformer isolate all unbalanced connections from bal- anced connections. Use special cable assemblies when unbalanced lines can- not be transformer isolated. Any unbalanced cable must be kept under 10 feet

34、 (3 m) in length. Lengths longer than this will amplify all the nasty side effects of unbalanced circuitrys ground loops. Summary If you are unable to do things correctly (i.e. use fully bal- anced wiring with shields tied to the chassis at both ends, or transformer isolate all unbalanced signals fr

35、om balanced signals) then there is no guarantee that a hum-free intercon- nect can be achieved, nor is there a definite scheme that will assure noise-free operation in all configurations. References 1. Neil A. Muncy, “Noise Susceptibility in Analog and Digi- tal Signal Processing Systems,” presented

36、 at the 97th AES Convention of Audio Engineering Society in San Fran- cisco, CA, Nov. 1994. 2. Grounding, Shielding, and Interconnections in Analog Workshops designed and presented by Neil Muncy and Cal Perkins, at the 97th AES Convention of Audio Engineering Society in San Francisco, CA, Nov. 1994.

37、 3. The entire June 1995 AES Journal, Vol. 43, No. 6, available $6 members, $11 nonmembers from the Audio Engineer- ing Society, 60 E. 42nd St., New York, NY, 10165-2520. 4. Phillip Giddings, Audio System Design and Installation (SAMS, Indiana, 1990). 5. Ralph Morrison, Noise and Other Interfering S

38、ignals (Wi- ley, New York, 1992). 6. Henry W. Ott, Noise Reduction Techniques in Electronic Systems, 2nd Edition (Wiley, New York, 1988). 7. Cal Perkins, “Measurement Techniques for Debugging Electronic Systems and Their Instrumentation,” The Pro- ceedings of the 11th International AES Conference: A

39、udio Test & Measurement, Portland, OR, May 1992, pp. 82-92 (Audio Engineering Society, New York, 1992). 8. Macatee, RaneNote: “Grounding and Shielding Audio Devices,” Rane Corporation, 1994. 9. Philip Giddings, “Grounding and Shielding for Sound and Video,” S&VC, Sept. 20th, 1995. 10. AES48-2005: AE

40、S standard on interconnections Grounding and EMC practices Shields of connectors in audio equipment containing active circuitry (Audio Engineering Society, New York, 2005). Band-Aid is a registered trademark of Johnson & Johnson Interconnection-6 Figure 4. Interconnect chart for locating correct cab

41、le assemblies on the following pages. Note: (A) This configuration uses an “off-the-shelf” cable. Note: (B) This configuration causes a 6 dB signal loss. Compensate by “turning the system up” 6 dB. To Input MALE BALANCED XLR BALANCED TRS (TIP-RING-SLEEVE) OR 3.5mm UNBALANCED TS (TIP-SLEEVE) UNBALANC

42、ED RCABALANCED EUROBLOCK From Output 1234 6521 10987 121187 12112221 1623 23 151413 20 2424 191817 BB BB AA AA AA FEMALE BALANCED XLR (NOT A TRANSFORMER, NOR A CROSS-COUPLED OUTPUT STAGE) FEMALE BALANCED XLR (EITHER A TRANSFORMER OR A CROSS-COUPLED OUTPUT STAGE) ” BALANCED TRS (NOT A TRANSFORMER, NO

43、R A CROSS-COUPLED OUTPUT STAGE) ” BALANCED TRS (EITHER A TRANSFORMER OR A CROSS-COUPLED OUTPUT STAGE) ” FLOATING UNBALANCED TRS (TIP-RING-SLEEVE) (SLEEVE IN UNIT = NC) ” OR 3.5 mm UNBALANCED TS (TIP-SLEEVE) UNBALANCED RCA (TIP-SLEEVE) CABLE CONNECTORS BALANCED EUROBLOCK + to + to SHIELD ONLY TO XLR

44、PIN 1 + to + to SHIELD NC + to + to SHIELD NC + to + to SHIELD ONLY TO EUROBLOCK + to + to SHIELD NC + to + to SHIELD ONLY TO TRS SLEEVE + to + to GROUND to GROUND + to + to GROUND to GROUND Interconnection-7 10 9 S=SHIELD R=NC T=RED S=SHIELD R=NC T=RED 8 7 S=SHIELD R=BLACK T=RED S=SHIELD R=BLACK T=

45、RED MALE 6 5 3=BLACK BLACK 4 3 3=NC 2=RED 1=SHIELD SHIELD SHIELD 2 FEMALE 1 3=BLACK 2=RED 1=SHIELD MALE B B B B S=NC R=BLACK T=RED S=SHIELD R=BLACK T=RED 11 CROSS-COUPLED OUTPUT ONLY: CONNECT PIN 1 TO PIN 3 AT THIS END AND SET GROUND LIFT SWITCH TO GROUNDED (IF PRESENT). CROSS-COUPLED OUTPUT ONLY: C

46、ONNECT PIN 1 TO PIN 3 AT THIS END AND SET GROUND LIFT SWITCH TO GROUNDED (IF PRESENT). CROSS-COUPLED OUTPUT ONLY: CONNECT RING TO SLEEVE AT THIS END AND SET GROUND LIFT SWITCH TO GROUNDED (IF PRESENT). 1 3 2 3 1 C 2 3 1 C 2 3 1 C 2 3 1 C 2 3 1 C 2 3 1 C 2 1 3 2 To Input From Output RED BLACK RED BLA

47、CK SHIELD RED BLACK BLACK FEMALE FEMALE 3=BLACK 2=RED 1=SHIELDRED RED SHIELD RED SHIELD SHIELD RED RED BLACK N/C N/C N/C RED BLACK RED SHIELDN/C BLACK RED BLACK RED 3=NC 2=RED 1=SHIELD 2=RED 1=SHIELD 3=BLACK 2=RED 1=NC 3=BLACK 2=RED 1=NC 3=BLACK 2=RED 1=SHIELD SHIELD FEMALE FEMALE FEMALE RED SHIELD

48、RED BLACK SHIELD SHIELD RED BLACK RED BLACK BLACK RED RED SHIELD RED SHIELD RED SHIELD RED SHIELD RED BLACK 2-CONDUCTOR SHIELDED CABLE 2-CONDUCTOR SHIELDED CABLE 2-CONDUCTOR SHIELDED CABLE 2-CONDUCTOR SHIELDED CABLE 2-CONDUCTOR SHIELDED CABLE 2-CONDUCTOR SHIELDED CABLE 2-CONDUCTOR SHIELDED CABLE 1-C

49、ONDUCTOR SHIELDED CABLE 1-CONDUCTOR SHIELDED CABLE 1-CONDUCTOR SHIELDED CABLE 1-CONDUCTOR SHIELDED CABLE S=NC R=BLACK T=RED S=SHIELD T=RED S=SHIELD T=RED S=SHIELD T=RED S=BLACK T=RED S=BLACK T=RED S=BLACK T=RED S=BLACK T=RED 12 S=SHIELD R=BLACK T=RED S=BLACK T=RED CROSS-COUPLED OUTPUT ONLY: CONNECT RING TO SLEEVE AT THIS END AND SET GROUND LIFT SWITCH TO GROUNDED (IF PRESENT). BLACK SHIELD RED BLACK RED 2-CONDUCTOR SHIELDED CABLE Interconnection-8 DOC 102907 Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5000 USA TEL 425-355-6000 FAX 425-347-7