Rob Heaney...
"I surrender, I have found the Holy Grail
of preamps, I'm sorry Neve but you are now #2. This is truly no hipe,
no bullshit, just serious headroom and truth. Finally somebody got it
in a big way and you can quote me on that."
The A-RACK
8+1 is the result of many requests for a multi channel mic preamplifier
system with the same sound as the venerable MA-2.2
True Class A preamp. The A-RACK is a modular design whereby modules
can be removed even with the unit powered and it can currently be equipped
with up to nine MA-1.5 preamp modules.
Hold mouse over to see rear panel.
The standard rack bin is 3 units high and includes the power supply
regulator and monitor module on the right. Due to the high amounts of
heat generated by the True Class A circuitry utilized in this design,
adequate ventilation should be provided and it is suggested that 1/2U
rack space is provided above and below the A-RACK if the unit will be
covered with other equipment. Alternatively, the system can be supplied
in a 4 unit high frame with built in 1/2 unit ventilation areas front
and rear. In addition to the rack mount chassis, the A-RACK can also
be supplied in an attractive 4U ventilated desk top enclosure.
To ensure
best noise performance the power transformer is external, housed in
a robust diecast box with carry handle and fixing points enabling it
to be mounted elsewhere in an equipment rack. The standard power transformer
supplies one A-RACK with a larger version available to power two A-RACKS.
All power cables are fully detachable with heavy duty diecast body "Ceep"
connectors being used for the connection to the frame.
The system includes a Solo buss that can be linked via 1/4" jack
leads to other A-RACKs in a multi rack setup. The Solo monitor section
has a high output headphone amplifier and 43dB range PPM (peak program
meter) for monitoring module output levels. The Solo buss audio is also
available on a balanced XLR output on the rear panel.
As well as direct XLR's, the line output of the first 8 module positions
are internally connected to a DB25 connector at the rear of the monitor
section, wired in accordance to the Protools-HD and DA88 style.
Fully
modular, all modules including the associated rear connector panel can
be easily fitted to or removed from the frame only requiring a small
flat blade screw driver. The handle attached to the front of every module
provides a convenient place for the user to label channel use. TOP
The first module available for the A-RACK 8+1 is the MA-1.5
True Class A Microphone Amplifier. All circuitry is real Class
A discrete transistor using the Buzz Audio BE40
module. There are no transformers in the signal path, high quality film
coupling capacitors are used for DC isolation. The
circuitry is very similar to the MA-2.2 with the addition of the Solo
feature and a Direct Drive Balanced Output circuit
(the DDBO).
There are two main advantages to the DDBO over conventional "transformer
acting" electronic balanced outputs. The first is near perfect
common mode performance on balanced lines ensuring accurate audio signal
transmission over long cables as may be found in remote live recording
situations. The second advantage is an increase of output headroom by
6dB allowing the MA-1.5 to deliver a staggering +32dBu before the onset
of clipping. The only disadvantage of the DDBO is that when driving
an unbalanced load, one of the output amplifiers will be shorted to
ground, which is not desirable. To enable the MA-1.5 to work with unbalanced
loads, the MODE switch converts the output to a pin 2 hot unbalanced
output, which also results in 6dB less gain.
The
MA-1.5 provides real "straight wire with gain" performance
in a modular format, and modules can be purchased as budget permits,
perfect for all multi channel recording situations. TOP
Bal Mode Min Gain
= +22dB (+2dB with pad in)
Bal Mode Max Gain = +70dB
Unbal Mode Min Gain = +16dB (-4dB with pad in)
Unbal Mode Max Gain = +64dB
Maximum Output Level = +32dBu in Bal Mode, +24dBu Unbal
Mode.
Frequency Response = 2Hz to 250kHz @ 20dB gain (-3dB).
= 20Hz to 250kHz @ 65dB gain (-3dB).
Harmonic Distortion = less than 0.008%100Hz to 10kHz.
Slew Rate = typically 140 V/uS, @ +20dBu output level.
EIN = -133.5dB A wtg, 150ohm source Z.
Signal to Noise Ratio = -74dB A wtg, input shorted.
CMNR = 100Hz-80dB, 1kHz -80dB, 10kHz-70dB internal
trims.
Module to Module Crosstalk = below noise.
Input Impedance = 3k ohms/1k2 ohms switchable.
Controls = Gain, Solo, Mode, Mute, Input Impedance,
20dB Pad, Phase Reverse, Phantom pwr.
Indicators = Peak Level @ +18dBu (internally adjustable)
Connectors = In-XLR3F, Out-XLR3M.
Size = DIN 41612 standard 8 HP wide.
Power requirements = Must be fitted into A-RACK module
rack bin. TOP
Specifications are typical of a production
unit and are subject to change without notice.
0dBu reference = 0.775 volts RMS
