Amplification circuit
In broad terms, the amplification stage is made of an input buffer whose output feeds a resistive network in turn linked to the output.
On the resulting node, two currents, that from the buffer and that on the amplifier output, are compared and the eventual error is magnified.
The main advantage consists of getting a very low impedance on the feedback input. This means that the inescapable loss capacitance does not affect anymore the speed and therefore the frequency response of the system.
As already sketched in the section on the "Design concept", this kind of layout provides a bandwidth beyond 1 MHz, a slew-rate higher than 250 V/µS and, at the same time, a strong intrinsic stability allowing to drive the hardest loads. The current feedback amplifier is placed in a resin module to compensate possible thermal drifts.
Layout
The unit is essentially made of three sections, the central one containing the supply stage and the side ones containing the mirror symmetric amplification channels. The three modules are easily removable.
Supply stage
The uneasy task of supply energy to the load is committed to two toroidal 450VA transformers (diameter 140 mm, height 70 mm, weight 3 Kg each), custom made for audio applications. 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 main secondary is produced with multi-wire technology.
The transformers are controlled by a logic stage, which role is to prevent from turn-on extra-currents; in case of high temperature, the same stage puts the amplifier in stand-by.
There are two distinct supply stages per each channel: one which is stabilized feeds all stages up to the drivers; the other provides energy to the power stage.
The dual stabilized supplier is made of, altogether, 8 high-speed ROE, EYS-series capacitors, corresponding as a whole to 26.400µF and is designed in discrete technology with no feedback, since listening tests have shown to be more musical than that with overall feedback.
The supply of the power stage exploits four capacitors, very-low ESR by 22.000µF each, with a 10 µF polypropylene parallel capacitor.
Amplification section
There are two available inputs, balanced and unbalanced.
The selection of the chosen input is made by means of a switch, but the actual commutation between balanced and unbalanced is realized by a relays, insulated in inert atmosphere with golden contact.
The unbalanced input impedance can be adjusted in four steps, by means of dip-switches placed on the rear panel.
The input signal is then applied to the current feedback amplifier supplied by a further stabilizer stage.
The output stage exploits 8 IGBT per channel, made by Toshiba for audio purpose, aged and selected by an automatic process.
In this layout the output stage is able to deliver in principle a continuous amount of current of 80 Ampere and a peak (10mS) of 120 Ampere.
Several capacitors placed near the IGBT co-operates in delivering transient current. To reduce loss resistance, are used 10 mm² OFC copper bars in critical points crossed by huge currents, short, 5.3 mm² section, connecting power cables and circuit boards with a layer of copper of 0.1 mm width!
Due to the high speed of the system, two "Ultra Fast Recovery" diodes protect the IGBT's against inductive loads.
Obviously, every resistor used in this design is of the "metal film" kind with a 1% tolerance, the polystyrene capacitors are from Philips, polypropylene, electrolytic and tantalium ones are by Roedenstein, except those in the supply stage; all transistors are by Motorola; the output stage IGBT's are by Toshiba. All printed boards are made with 70 µm width copper with an additional 30 µm of metal layer for an overall of 100 µm.
The balanced input connectors are by Neutrik; The loudspeakers output connectors are by WBT.
Mechanical realization
The cabinet is completely made of aluminum and has been conceived to easily separate the two amplification stage from the supply stage.
This lead to the design and realization of drawn thermal wasters with a "structural" task and at the same time with a nice looking. The total dissipating surface amounts to 10.000 cm².
The cutting of the metal plates is made by laser machines, whereas for their milling Numerical Control (NC) units were used; the front labels are cut by NC micro miller; the rear labels are not made with serigraphic techniques but with laser cutting.
Selling package
FLIGHT 50 is delivered with a detailed instruction manual and screened alimentation cable 220 Vac with high current delivery. The crate is made of multi-sheeted ply-wood and the unit is contained in a tissue envelope and a second insulated envelope containing silica-gel.
The sound
Useless obviously to say something about what can only be listened to!
Colour Options
The following colour options are available: Black, Silver
