CONTENTS SCENARIO 1 INTRODUCTION 3 UNPACKING

9 and ambience, whereas recordings made with X-Y techniques can suffer from centre-stage high-frequency deficiency caused by the off-axis degradatio

10 COINCIDENT MICROPHONE TECHNIQUES (Intensity Stereo) A crossed pair of microphones is used with the capsules USUALLY arranged in a v

11 The use of hypercardioid capsules offers a good compromise between crossed pairs of cardioids and crossed pairs of figures-of-eight. The

12 (Note: it is assumed that M=S, ie the microphones have the same sensitivity and that there is the same amount of gain in each of the two signal p

13 M-S / X-Y TRANSFORMATIONS (M=S) FIG 2 (An X-Y pair of cardioid microphones matrixes to a sub-ca

14 SPOT MICROPHONES Very great care must be taken when using highlighting microphones within a stereo sound picture. When directional microph

15 In all circumstances, a camera-mounted stereo microphone is quite inappropriate. When it becomes necessary to employ spot or mono microphones fo

16 NEAR-COINCIDENT MICROPHONE TECHNIQUES These techniques provide good positional information together with a satisfying sense of space as they rel

17 differences. Unlike a dummy-head, this microphone has a flat frontal frequency response and lacks those cues which give fron

18 overall level of the stereo signal. To steer the output of an M-S pair to any position within the final stereo picture, the outputs of t

1 SCENARIO Time was when it became necessary to update the ubiquitous AD145 PICO mixer. Our survey showed two main requirements

19 SHUFFLING This is a fancy name for frequency-conscious width control and based - naturally - on Blumlein's work. By inserting an equalise

20 By increasing the S-signal (over the full frequency range), the stereo image of some recordings can be extended beyond the left and right

21 FURTHER READING British Patent Specification 394,325. A D Blumlein. Improvements in and relating to Sound-transmission, Sound-recording an

22 AD149 AUDIO MIXER In the new millennium (cliché), it is noticeable that sound recordists who work away from the controlled environme

23 Our customers know we are totally committed to providing them with facilities for working in the M-S domain. The new monit

24 An addition is the remote stop/start switch for use with suitably equipped tape recorders, eg Nagra IVS and D. Linked with this swi

25 however, a more important rôle: no longer do we have to tolerate the mixer output being limited because of the output from a pa

26 By combining the last two features, AD149 can be configured not only as a four-output mixer but also as two independently-con

27 It is intended that mono line modules shall be fitted in pairs - in odd/even positions within the chassis. Between the pair, a smal

28 TECHNICAL SPECIFICATION - ELECTRICAL REFERENCE 0db=775mV at 1kHz unless otherwise stated MAX GAIN MIC 80dB LINE 45d

2 Being latter-day converts, we have included circuitry to take full advantage of all M-S techniques - even shuffling - in both production and post-

29 NOISE MIC <-126dB EIN 20Hz to 20kHz 200R SOURCE (with respect to the input) LINE

30 TECHNICAL SPECIFICATION - MECHANICAL AD149 is supplied with 6, 8, 10 or 12 input modules. A separate meter bridge fitted with 4 VU or PPM

31 EQUALISATION CURVES AD149 HF and LF EQ Plot-20-15-10-50510152010 100 1000 10000 100000FrequencydBLF BoostLF CutHF CutHF Boost AD149 MF and

32 CONNECTOR PANEL (1) Microphone input (10) Left-Right output/return multiway (2) Line input (11) Left-Right output/return conne

33 All input and output impedances and levels are to be found in the TECHNICAL SPECIFICATION. All inputs to, and outputs from AD149 ar

34 The unbalanced, send outputs have low-impedance with a capability of driving headphones of 25 ohms impedance or greater. (Refer to pag

35 HIROSE connectors (10) → (13) are provided for single-cable connection to the mixer. (10) & (11) and (12) & (13) can be used s

36

37 BLOCK DIAGRAM - PART 1 FIG 4

38 MICROPHONE/LINE MODULE (1) 48V phantom power (2) 12V tonader power (3) Line input (4) Phase change (5) High-pa

3 INTRODUCTION Unpacking If there are any signs of damage to the outside of the carton, please notify us or your supplier immediately, regardles

39 FIG 5

40 The microphone amplifier has been described in detail in the introduction. Switches (1) and (2) select 48v phantom and 12v tonader power fo

41 Following the equaliser is an insert point, accessed via the standard 'A' type jack at the top of the module. Because of lack

42 changing phase of the S-microphone channel will rectify the situation - without having to disturb the microphone. But see, also, M-S NOTES.

43 The routeing switch (16) to the left and right mix busses is, in effect, the channel mute. Panoramic potentiometer - panpot -

44 BOOM Once a module has been assigned to a boom microphone, DIL switch 1 mounted on the module's sub-board will route the signal to

45 LIMITER CALIBRATION Refer to page 61, #1 for use of external test equipment. Switch off the limiter and set the presets for Release,

46 THIS PAGE IS BLANK

47 MONO LINE MODULE (1) EQ split (2) Matrix 1 (3) Line-input 2 (4) Phase change (5) High-pass filter 1 (6) High-pass filter 2 (7) Mid-freq

48 FIG 7

4 Fuses - to protect the mixer and internal power supply are mounted on the power supply/converter board. Access is gained by removin

49 For optimum performance at line level, this module employs a double-balanced, instrumentation-grade input amplifier (3 x ICs) rat

50 These two matrix amplifiers may be inserted across the signal paths to create a 'Blumlein Loop' within which input ga

51 STEREO LINE MODULE (20) Left-path insert jack (21) Right-path insert jack (22) Input-gain control (23) Input-balance control (24) Channel-

52 FIG 9

53 We have already stated our philosophy behind this module and the reason for the omission of limited and limiting equalisation. As w

54 have to apply an HPF to the S-signal only, in order to reduce low-frequency content (with respect to the M-signal). Still within the 'Bl

55 We believe that mono auxiliaries are related to the module’s input signal rather than its output signal, therefore post-fader auxiliaries ar

56 BLOCK DIAGRAM - PART 2 FIG 11

57 OUTPUT MODULE (1) Meter 1 (2) Meter 2 (3) Limiter LEDs (4) L-R output limiters (5) Limiter link (6) L-R output matrix (18) Output fader left (1

58 This module controls all metering of PFL and output signals, and also the level of main and auxiliary output signals. Calibr

5 ABBREVIATIONS PPM peak programme meter VU volume unit VR variable resistor X-Y coincident stereo-microphone A-B spaced-apart s

59 Line-up tone, when selected, replaces the normal signals on the main, L-R output (15) and on the auxiliary outputs (16). The frequency

60 REMOTE REM (22) is a latching switch to start and stop a tape recorder fitted with a remote stop/start function. Via a DI

61 ADJUSTMENTS AND CALIBRATIONS Meters - are to broadcast specification and either a VU or a PPM may be selected. A choice of 3 scales is avai

62 VU meter - there is one preset, on the VU meter PCB, for meter adjustment. Set an input module for a line input and introduce a 1kHz t

63 Main-output limiters - calibration involves two presets per output. Using the 'L' output as the example and referring to FIG 12 …

64 THIS PAGE IS BLANK

65 MONITOR MODULE (20) Return 1 calibration control (21) Return 2 calibration control (22) Split monitor (23) Matrix 1 (24) External 2 level

66 The monitor module is associated with all aural monitoring of input and output signals together with communications between the sound opera

67 CH (1) operates in conjunction with the MON switch on the channels. This MON signal is the same as that which drives the left an

68 may be disabled by DIL switch (3) on the left-hand PCB. (Refer to FIG 15) Use of split monitoring makes no change to the meters when rea

6 WARNING IMPORTANT SAFETY INSTRUCTIONS The user of electrical products must be familiar with their potential dangers, and

69 EXTERNAL 1 & 2 AD149 has the capability of sending signals to two outstations - external 1 and external 2. It is suggested t

70 COMMUNICATIONS In order that the sound operator can communicate with any output, the safety switch (Comms Master) ON (29) must be selected: L-R

71 MIXING We have already established that, during post-production, it is desirable for signals to be in the L-R domain at the input to the fader o

72 X-microphones will be panned hard left, and Y-microphones will be panned hard right. Spot microphones will be panned to their correct position

73 MIXER PATHS FIG 17

74 PLAYTIME The following experiments may be performed on the monitor module. Select a couple of L-R recordings; one in natural stereo an

75 DIL SWITCHES MOTHER BOARD Input limiters Link → MIC/LINE MODULE Main PCB Clean f

76 POWER SUPPLY UNIT TYPE AD100-09 The AD100-09 mains POWER SUPPLY UNIT is suitable for driving most of AUDIO DEVELOPMENTS’ range of por

77

78 CUSTOMER NOTES AND FACTORY MODIFICATIONS

7 POWERING The mixer may be powered from either internal cells or an external DC power source. The integral battery compartment requires a total o

79 TECHNICAL LIBRARY

8 M-S NOTES GENERAL BACKGROUND Of the various techniques that have evolved for stereophonic recording, the so-called COINCIDENT, NEAR-COINCIDEN