CONTENTS |
|
SCENARIO |
1 |
INTRODUCTION |
3 |
UNPACKING |
3 |
VISUAL INSPECTION |
3 |
SPECIFIC POINTS |
3 |
IMPORTANT SAFETY INSTRUCTIONS |
5 |
POWERING |
6 |
TECHNICAL SPECIFICATION |
8 |
EQUALISATION CURVES |
11 |
BLOCK DIAGRAM |
12 |
CONNECTOR PANEL |
13 |
CONNECTIONS |
14 |
INPUT MODULE |
16 |
OUTPUT MODULE |
19 |
ADJUSTMENTS AND CALIBRATIONS |
|
22 |
|
AD100-015 POWER SUPPLY UNIT |
24 |
CUSTOMER NOTES AND FACTORY MODIFICATIONS |
25 |
TECHNICAL LIBRARY |
26 |
SCENARIO
Time was when it became necessary to update the ubiquitous AD145 PICO mixer. Our survey showed two main requirements: as well as Audio Developments' build and audio qualities, narrower and shorter modules were required, and the simple but effective equaliser from PICO had to be retained. By this time, 4-track recording equipment had begun to trickle into the marketplace (Nagra D etc), so we decided to give the new mixer four outputs. Because of the lower noise-floor of modern digital recorders, the level of input signals may be reduced. We have taken advantage of this fact and lowered the slope ratio of the limiters to 7:1. By so doing, not only is signal distortion greatly reduced, but also the artefacts associated with limiters become much less noticeable or objectionable. Also, sixty years after the event, sound engineers have come to realise the potential of Blumlein's M-S techniques; to this end, facilities have been incorporated to take advantage of these techniques. The result is AD146 - a four-output mixer.
This was followed by AD148 - edit mixer. Based on AD146, two comprehensive left and right monitor modules have been added for editing purposes. If a mic/line module is included for commentary or voice-over purposes, its input-gain switch can be changed to a potentiometer, and its gain structure changed to ensure consistent level matching with a fixed, mechanical point of reference. Unfortunately, this way of working does reduce headroom and also compromises a mixer's noise performance.
After AD146/AD148 it was back to the drawing board. Our customers were still demanding a two-output mixer - as a true replacement for the PICO, and with the PICO's simplicity. Despite past assurances to the contrary, T powering is still required. And could we incorporate auxiliaries? And could we possibly bring it to market at 'entry level'? We have, and we have and that's MERCURY (AD147).
AD149 completes the 140 series of mixers, and has a repertoire of party tricks not to be found in any other mixer - not even for 'ready money'. The design team took, as its starting point, our list of all the ideas and suggestions presented to us over the past few years. Many of these requests came from film-sound recordists - a sub-set of recordists we have unintentionally neglected in the past.
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Being latter-day converts, we have included circuitry to take full advantage of all M-S techniques - even shuffling - in both production and post-production.
AD149 is Audio Developments' tribute to, and celebration of the genius of Alan Blumlein.
Well - we HAD every intention that AD149 would complete the 140 series.
We'd reckoned, however, without the persistence - nay, insistence - of our customers for a mains-operated version of the AD146 with four auxiliaries ...
we've called it AD144.
Radical change and PICO have proved to be uneasy bedfellows: never a matinée idol and denied its dulce et decorum death, AD145 has now been repackaged in the 140 series metalwork - thereby reducing its size and weight. Facilities remain largely unchanged: internally, the microphone amplifier has been replaced with the one designed for AD146 and externally, the mono return is now in stereo form. Now designated AD245, shall we have PICO - like the poor - always with us?
With the advent of multi-track recording and its general acceptance as a useful tool in drama and film location; our market research has indicated a need for a sound mixer with facilities similar to AD245 but with multi-track features. The addition of direct outputs from each input and two auxiliary busses make up the main extra features over those of AD 245. The analogue meters have been replaced by two LCD displays to enable the signal levels of the two main outputs, two auxiliaries and an input module to be monitored simultaneously.
2
INTRODUCTION
Unpacking
If there are any signs of damage to the outside of the carton, please notify us or your supplier immediately, regardless of the unit's apparent physical condition. This is in case a claim has to be made at a later date because of previously undetected transit damage. The packaging material should not be discarded until the mixer has been acceptance tested and a suitable transit/storage case is available for secure, safe storage.
Visual Inspection
Identification - please make a separate note of the serial number for your own capital equipment records. Ensure that it agrees with the number on the invoice/packing note. The serial number label is on the back cover, adjacent to the battery compartment.
Temperature - check the meter glasses for condensation. If the package has been in transit during cold weather, leave the mixer for at least 12 hours to allow it to return to normal room temperature. Any measurements or subjective tests then made, will be to a known temperature reference.
Specific Points
Battery compartment - the mixer has an integral battery compartment to accept 8
size-C cells, and is formed as part of the bottom transversal extrusion. This helps to lower the centre of gravity, as well as adding to the rigidity of the frame.
DC-DC converter - is mounted on the top side of the battery housing and is underneath the fader section of the modules.
In order to facilitate the testing and calibration of all modules, a set of two extender modules is available from the factory.
Connectors - for convenience, the connector panel is labelled for reading from above. All connectors are in line with their corresponding module.
3
Fuses - to protect the mixer and internal power supply are mounted on the power supply/converter board. Access is gained by removing the output module. 20mm, 1A ANTI-SURGE HRC fuses are used - one for the internal battery power supply and one for the external DC supply.
Limiter threshold - is set at the factory at +8dBu (PPM 6), but an internal preset potentiometer allows adjustment to any other level above 0dBu. The limiters are to be found on the output module printed circuit board.
Microphone powering - the mixer will remain unconditionally stable if the powering on unterminated input channels is switched off - this also improves the noise performance and crosstalk. Powering - 48V phantom or 12V tonader - may be selected before or after the microphone is connected to the module.
Module fix screws - Hexagon head screws are used to fix the modules and back cover. The size being 1.5mm HEX A/F with a 2.5M thread.
If it becomes necessary to remove modules or back cover it is strongly advised using a good quality hexagonal head driver.
Use of a screwdriver, however desperate, is not recommended.
We wish you many trouble-free hours of use from your mixer. As a company, we are fully committed to BS EN ISO 9001. Should you have any problems or require any further information, please do not hesitate to contact us on:- tel 01922 457007 or by fax on 01922 457008.
4
WARNING
IMPORTANT SAFETY INSTRUCTIONS
The user of electrical products must be familiar with their potential dangers, and fundamental precautions must always be taken. Please read the following text carefully.
Power supply units manufactured or supplied by Audio Developments Ltd are not user serviceable. There are no user-serviceable parts associated with any such power supply unit.
THE OUTER COVERS MUST NOT BE REMOVED
Such a power supply unit is solely for use with audio mixers and sound processors - hereafter called the equipment - manufactured by Audio Developments Ltd.
Always use a cord set accepted by a National Approved Body.
EARTHING/GROUNDING: When using an external power supply unit that is connected to the mains supply to drive the mixer it must be CONNECTED TO EARTH.
In certain types of malfunction or breakdown, earthing provides a path of least resistance for electric current and considerably reduces the risk of electric shock.
DANGER: Incorrect connection of the equipment grounding/earthing conductor can result in the risk of electric shock. Where possible obtain a pre-wired mains lead from a reputable supplier with the correctly fitted mains connector for the type of mains outlet in use; otherwise, one correctly wired and checked by a qualified electrical engineer. If your mains lead is not suitable for the mains outlet, have the correct plug fitted by qualified personnel.
The MAINS PLUG of this equipment is the primary disconnect device. Therefore, in the final application, ensure it remains close to the equipment and easily accessible.
5
POWERING
The mixer may be powered from either internal cells or an external DC power source.
The integral battery compartment requires a total of 8 size-C cells. Access is gained via a captive lid which is retained by two, 90-degree-turn buckles. The lid hinges outwards 45 degrees from the back panel. When installing new cells, the row nearest the hinge should be fitted first.
Either conventional dry or rechargeable nickel-cadmium cells may be used. NI-CADs may be recharged in situ through the 4-pin POWER IN connector. (The circuit for recharging is already incorporated within the mixer.) A voltage in the range +15V to +24V DC @ 250mA is required on PIN 2 of the POWER IN XLR.
When driving the mixer from an external power source, PIN 1 is the 0V connection and a voltage in the range +12V to +15V DC should be supplied to PIN 4. The power source should be capable of delivering approximately 500mA - allowing some capacity for phantom powering.
If an external power supply unit (PSU) is to drive the mixer and simultaneously charge a set of NI-CADs, a current capability of at least 750mA is required. It is poor practice to run a PSU at its limit, therefore we recommend a minimum of 1A.
A suitable unit is PSU Model No AEH24US15 supplied by Audio Developments. (AD Part No 94-100-015)
WARNING: When NOT using the PSU (AD 94-100-015) supplied for the mixer, ensure your 4-pin XLR is correctly wired to match the POWER IN connector. Failure to do so may result in the breakdown of the internal DC-DC converter. Make this check even if using a PSU which may have been supplied to you in the past, eg AD100-06.
AD100-05 PSU is NOT suitable for use with an AD255 mixer and must not be used.
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7
TECHNICAL SPECIFICATION - ELECTRICAL
REFERENCE 0dB=775mV at 1kHz unless otherwise stated.
MAX GAIN |
MIC |
80dB |
|
|
|
LINE |
50dB |
|
|
MAX INPUT LEVEL |
MIC @ MAX GAIN -44dB |
@ MIN GAIN + 6dB |
||
|
LINE @ MAX GAIN -14dB |
@ MIN GAIN +20dB |
||
|
STEREO-RETURN +18dB |
|
||
|
TB RETURN |
+18dB |
|
|
INPUT IMPEDANCE |
MIC |
|
|
>2k5R |
|
LINE |
|
|
>6k5R |
|
STEREO-RETURN |
>100kR |
||
|
TB RETURN |
|
|
>20kR |
MIC POWERING |
48V PHANTOM & 12V TONADER |
|||
MAX OUTPUT |
+23dBm |
L-R TRANSFORMER BAL (600R LOAD) |
||
|
|
MONO TRANSFORMER BAL (600R LOAD) |
||
|
+18dBm |
DIRECT OUT UNBALANCED (600R LOAD) |
||
|
|
H’PHONE |
|
UNBALANCED (600R LOAD) |
|
|
TB SEND |
|
UNBALANCED (600R LOAD) |
OUTPUT IMPEDANCE |
<60R |
L-R & MONO |
|
|
|
<20R |
DIRECT OUT & MONITOR |
||
|
<20R |
TB SEND |
|
|
FREQUENCY RESPONSE |
0: -1dB |
L-R & MONO |
|
0: -1.5dB |
MONITOR PATHS |
HARMONIC DISTORTION |
<0.05% @ 1kHz @ 0dBm OUTPUT |
|
|
<0.15% @ 40Hz to 15kHz @ +15dBm OUTPUT |
|
OVERLOAD INDICATOR |
ILLUMINATES @ +15dBu at the PRE-FADER POINT |
|
CROSSTALK |
<-70dB 40Hz to 15kHz |
|
|
INTERGROUP & INTERCHANNEL |
|
NOISE |
MIC <-126dB EIN 20Hz to 20kHz; 200R SOURCE |
|
|
LINE <77dB SNR 20Hz to 20kHz 0dBu IN & OUT |
|
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