Then there is a complementary voltage amplifier stage in CASCODE configuration and
realised with BJT transistors.
These circuits have been duly polarised and configured as transconduttance modulators
(HCP - HCN Hyperlinear correction) with filter functions for transient distortions.
The electrical features of the V-AMP 12LV section are: THD distortion at 100 Vpp:
0.04%; Sleaw Rate: 250/
µ
S; Baudwidth: DC
÷
1.5 MHz; S/N: ratio 122 dBA.
Monotonic decreasing distortion spectrum with stop at the harmonic sixth.
The final stage driven by the above mentioned module is a complementary symmetric
inverted triplet configuration and it is supplied with a driver and predriver at low Cob and
five + five transistors amplifiers of 150 W, 15 A with Ft of 30 MHz.
The total reaction rate used in this amplifier is of 4 dB and the global performances
obtained by the whole amplifier stage are: bandwidth 1.5 Hz
÷
180 KHz; THD distortion:
min. 0.1 % at 300 W; Slew Rate: 90 V/
µ
S.
POWER SUPPLY
The switching power supply is composed by a PWM controlled push-pull double power
supply. One of them generates and controls only positive voltages, the other one the
negative voltages. The power supply system functioning logic is directed by a single
circuit, called PWM CONTROLLER, which also attends to the PWM generation in the
positive power supply and operates in a synchronic way with a second circuit called PWM
SERVEUR, which has the task of making the PWM control of the negative power supply.
Synchronism between the two PWM generator clocks avoids the formation of residual
products at low frequency which could be converted into audio disturbance noises by the
amplifier.The particular dynamic control of the audio amplifier voltages allows the
voltage linear levelling and is able to supply energy instantaneously.
This control is active up to the frequency of about 800 Hz; the levelling at upper load
frequencies is given to the transformer capacities which are equal to 19500
µ
F. The
measurable result of such a complex controlling system is to have a "ripple" on the
transformer voltage equal to 300 mV when the
HV trenta
is loaded at the maximum
power on resistive load.
As it regards the sound, the fact that we have a perfectly stabilised power supply voltage
for the final stage allows the correct reproduction of high dynamic content transient
signals, it guarantees details, acoustic precision and very good reconstruction of sound
image.
The power supply delivers three secondary voltages: the first one is for the final power
stage at
±
53 V, the second one for the internal preamplifier at
±
25 V and the third one
at
±
60 V for the final stage driver circuit.
The power supplies are provided with a primary protection which interdicts their
functioning in case of non operative overloading, avoiding circuit damages.
All interactions between power supply and amplifier (secondary voltages control, muting
circuits control and reception of information about the final stage protection) are effected
through optocoupler circuits.
This solution avoids the transfer of the noises coming from the car electric device to the
car radio section.
3
OUTPUTS CONNECTION
THREADED CONNECTORS (
Speaker L-R
). Connect the speakers or the speakers passive
crossover according to polarities.
IMPORTANT: Never connect -R and -L outputs to ground or to each other.
If a crossover filter is used, be sure the two channels don’t have a common ground. An allen key
is provided for the terminals screws.
MONO CONNECTION
Position MONO push-button to ON. Use IN R input. Take the power output from the +L (LEFT)
and -R (RIGHT) terminal.
It’s possible to obtain MONO use just for SUBWOOFER frequencies and to have a STEREO
system for high frequencies using the TRIMODE configuration (pict.1); in this case leave
MONO push-button to OFF position and apply the connection system according to the picture.
Refer to chart for inductance and capacity values relative to the desired crossover frequency.
POWER SUPPLY CONNECTION
THREADED CONNECTORS (
Power
)
±
. The battery positive is connected to the + POWER
terminal inserting a fuse (provided) next to the battery itself.
- POWER terminal must be connected to the battery negative (ground) through the car chassis,
taking care to guarantee an excellent electrical contact on a metallic point not covered with paint
or insulating materials of any kind.
For the electrical connections described, use adequate cables, with a minimum diameter of 6 mm
(3 A.W.G.). An allen key is provided for the terminal screws.
TURN ON CONTROL CONNECTION
THREADED CONNECTORS (
Remote in-out
). Connect the amplifier REMOTE IN input to
the proper head unit output (REMOTE AUX), or to electric antenna control. REMOTE OUT
output is used to turn on another possible device. A green LED ON indicates when the amplifier
is turned on.
MUTING CONTROL CONNECTION
THREADED CONNECTORS (
Mute in-out
). MUTE IN input silences the amplifier.
The device goes into muting when it receives a positive voltage between 3 VDC and 15 VDC,
or when ground (GND) is applied.
MUTE IN can be connected to the proper head unit output (if provided) or to the MUTE output
of a cellular phone; in this case , when there is a phone call, the car system is silenced. When the
conversation is over, the amplifier will automatically play again.
The amplifier MUTE OUT contact must be connected to a second amplifier (if available)
provided with a special MUTE IN output. In this way, the second amplifier becomes dependent
on the first one as far as the car system MUTE functions are concerned.
6