The basic structure of the amplifier Maestro MONOBLOCK is the same used in the precision balanced amplifier used in the laboratories. It is made of three different amplifiers. The first two must amplify in tension the balanced signal and the third one must supply the necessary current amplification to drive the speakers. This kind of structure has two important benefits: the first one is a high immunity to the disturbs, while the second one is the possibility to improve each amplification stage. The separation between the gain in tension and of the gain in current permits to realize class A tension amplifiers made with low power components, so to obtain a frequency response up to about 500kHz. Such frequency extention gives the possibility to mantain the phase errors to a very low level. The power section has been designed to obtain a high gain in current and not in tension. Thanks to this solution, it is possible to keep the frequency response at full power around at 200kHz. Also the bass frequency extention has been realised with care applying an off-set recover circuit able to go down to 3Hz. Due to its two stages configuration, the amplifier Maestro Monoblock does not have a global feedback between inputs and outputs.
Available colors
Technical description
POWER STAGE The Maestro Monoblock’s nominal output power is of 200W on a 8OHM impedance. This power goes up to 800W@2ohms. The protections starts to work at around 1000W with a load of 1ohm(if your house system can support it!) To obtain these kind of power levels the supply section has been overdimensioned. In fact, have been used two toroidal transformers for a total of 1406W. Each power branch is rectified from a diode’s bridge, with 50A components and the filter section contains 8 electrolytic 15000F capacitors for a total of 120000 F. Furthermore, also the supply of the low power section has been realized one bridge for each branch and filtrated with two 15000F capacitors. To maintain a low output impedance has been realised 10 pairs of bipolar transistors whom low distortion level are guaranteed by the producer. Their polarization current permits to get a class A working up to about 10W. The current pass trough some copper bars. Each earth converges to a sole junction (star configuration) realised with a copper plate half a millimetre thick that has also a shielding function. Obviously, such big quantity of different parts is used to supply only one channel of your stereo system! PROTECTIONS An amplifier able to supply more than 30 ampere must be well protected. The amplifier Maestro Monoblock has a section exclusively dedicated to this function. At the moment of the switching on, the filter capacitors are loaded trough two power resistors to limit the power comsumption. Once the supply voltage has passed the critical phase, the resistors are excluded by two 40A relè. These relay are able to stop the supply of the power amplifier and have been used to replace the fuses. The only existing fuse on the Maestro Mono is used to protect the control board and hasn’t any effect to the audio signal. There are also others protections that are used to control the presence of DC power on the speakers, the AC power voltage drop and the current absorbtion surplus.
Technical features
Input impedance
47 KOhm
Power on 8Ω load
Power on 4Ω load
Power on 2Ω load
THD + N (1W, 8Ohm 1 KHz)
0,01 %
Slew Rate
50 V/μs
Frequency Response(Att. 0dB, -3dB band)
2 Hz - 100 KHz
Input Noise(Band limits 0Hz-80kHz/A-weighted)
-130 dB
> 100 dB
225 x 445 x 470 mm
61.5 Kg
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La società AF Group SRL, CF 03352850139, ha ricevuto nel corso dell’esercizio 2020 aiuti di Stato di cui all’art. 52, Legge n. 234/2012 oggetto di obbligo di pubblicazione nel Registro Nazionale degli Aiuti di Stato che sono ivi indicati nella sezione trasparenza a cui si rinvia.
AF Group SRL
Via Cesare Battisti 126G
51015 Monsummano Terme
Tel. +39 0572 030964
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