Audia Flight PRE MK3
The new reference quality Audia Flight PRE MK3 is designed for complete neutrality, allowing all the nuances and ambience in the music to shine through. Audia Flight PRE MK3 preamplifier is the perfect interface between source component and the power amplifier. Incorporating the excellent Audia Flight circuit design, highest quality volume control, and cabinet interior layout with isolation between key stages, the Audia Flight PRE MK3 exhibits complete transparency and lowest possible noise. The high current, Class A output stage, separate power supply for each channel and one for the logic control, the high quality input selector and constant impedance volume control, provides an extended frequency response, tonal accuracy and wide soundstage. Audia Flight PRE MK3 combines the merits of AUDIA FLIGHT circuit design based on the local feedback and the trans-conductance amplification, the use of a constant impedance attenuator with 0.5 dB steps and a chassis designed to get an a total separation among every stages, still keeping a single cabinet.
Cabinet
The cabinet plays a fundamental role in the realization of a preamplifier since its structure (and the corresponding placement of the boards) helps to fix the degree on immunity against external noises and of interaction among different internal stages.
In a preamplifier is also very important the shielding of audio boards with respect to transformers, since the stray flux could be “detected” and amplified by sensitive stages.
Audia Flight PRE MK3 is a single cabinet unit (the hypothesis of designing a “two chassis” unit has been left out for two main reasons: the problems connected with installation and encumbrance and the question of the alimentation cable that could have reached “worrying” length), however the internal volume is strategically divided to suppress interference, with the horizontal partition placed at half height. In the lower section are placed the three toroidal transformers into a secondary shield metal box and the main supply board, whereas in the upper section is placed the main audio board.
A massive sheet of damping material is stuck under the upper cover plate.
Since the Audia Flight PRE MK3 is microprocessor controlled, the control board is placed behind the front panel and it is closed in its proper volume in a metallic shell.
The cabinet is completely made of aluminium and has been made exclusively by means of Numerical Control (NC) units and laser machines; the front panel is realized starting from an aluminium ingot 25 mm – thick and worked out by means of NC micro millers.
Input selector
The input selector allows to choose four unbalanced inputs and two balanced ones by means of sealed relays in inert atmosphere and with golden terminations.
Only the selected input is connected to ground.
Supply stage
The main supply stage of Audia Flight PRE MK3 is placed in the lower part of the cabinet. Here, in fact, there are two toroidal 50VA transformers (one for each channel) and a third 15 VA one to feed the control logic.
All transformer are explicitly made for audio applications, that is designed to have the least stray flux but, at the same time, with a great driving ability. The 10.000 Gauss core plate is autoclave resin sealed and dried in oven. The coils are realized with automatic machine-tools assuring the appropriate wire tension.
The three toroidal transformers are close into a secondary shield metal box.
The high-current supply stages for the audio sections are realized exploiting, in each channel, four “Ultra Fast Recovery” diodes with bypass capacitance to eliminate possible commutation noises of the diodes. There are eight filtering capacitors by 3.300µF 63 V (52.800µF total) with high discharge velocity (low internal impedance) and discrete stages stabilizer , for a stabilized output tension of 50 + 50 V.
The third supply stage, the one for the control logic, uses EMI filters and an integrated stabilizer.
Moreover, on the amplification board are inserted four more dual discrete stages stabilized supply units per channel, that provide the alimentation of the various section of the amplification board, drastically reducing interference among different stages in the preamplifier.
In practice, Audia Flight PRE MK3 is endowed of a whole 18 stabilization circuits just for the audio stages supply, each designed as a discrete stage.
Attenuation control (volume)
Achilles’ heel of many preamplifiers is represented by the volume-control since usually this introduces a variable impedance element as a function of the attenuation value (that is of the position of the potentiometer).
The result is that the frequency response, the slew-rate and even the internal impedance couplings among different stages are not fixed but are function of the attenuation value (volume).
This is a problem which affects above all the potentiometers; using instead integrated attenuators (I.C. dedicated to volume control or the use of D/A converters) solves the problem of variable impedance, but not that of the frequency response and of the absolute velocity response.
For this reason, AUDIA FLIGHT developed a constant impedance attenuator, realized with discrete components (low-noise metallic film resistors), which provides a gain range as high as 127 dB, with constant steps of 0.5 dB.
The result obtained probably overcome the wall of standard performance, since Audia Flight PRE MK3 grants an extremely extended frequency response (3Hz / 1MHz –3 dB) and the high value of slew rate (> 250V/µs in all the gain range (-90 / +10 dB).
As the volume is micro controlled one, all interconnections between the analog stage and digital stage are insulated using hi-speed fotocoupler
Gain stage
The gain stage of the preamplifier is realized using AUDIA FLIGHT technique, that is using a current-feedback circuitry, entirely A – class biased and realized with discrete components.
As sketched in the section about “alimentation” is fed by four stabilized independent stages per each channel: one for the input buffer, one for the input stages for the signal amplification, one for the current mirror and the last for the output stage.
The high-current low-noise output stage, made of audio-use transistors, A-class biased, is not closed in the feedback ring.
Control logic
The hearth of this section is based on the use of an 8 bit micro-controller endowed with a 16 Kbyte ROM.
The control of peripherals is given to two PIO devices, to get the control of the 40 characters fluorescent alphanumeric display, of the infrared receiver, of the custom optical encoder, the buttons and the relays.
Remote control
The remote control too, as the front panel, is realized starting from an aluminum ingot later milled.
The surface is firstly completely brushed, then anodized.
Technical Data
Input: 2 balanced XLR / 4 unbalanced RCA
Gain range: -90 dB / +10 dB
Gain resolution: 0.5 dB
Frequency response (1W rms -3dB): 3 Hz ÷ 1 MHz
Slew-Rate (on 8 ohm): > 200 V/μS
THD: < 0,05 %
S/N Ratio: 95 dB
Input impedance: 680pF Unbalanced 51 Kohm
Balanced: 30 Kohm
Output impedance: Unbalanced 12 ohm
Balanced: 50 ohm
Main voltage AC (50/60Hz): 100, 110-115, 220-230,240 V
Power consumption: 60 W
Dimensions (W x H x D): 420 x 113 x 380 mm
Weigth: 12 Kg
Shipping dimensions and weigth 570x270x540mm (wxhxd) - 15 Kg
