Technical data

JFET differential input stage (available in PRE ON confi guration).
Selectable two level input gain structure adjusted (available in PRE ON confi guration).
Balanced output buffer for control unit (available in PRE ON confi guration).
Thermally stabilized (available in PRE ON confi guration).
Control Unit:
Allows the amplifi er to be properly confi gured and adjusted.
- Sensitivity.
Adjusted using the IN SET switch and ADJUST control.
IN SET allows you to adjust the amplifi er’s sensitivity in 2 levels by changing the pre-amplifi er’s gain.
The fi rst level is used for input gain from 1÷6 V (0 dB Gain), while the second is used for input gain from 0.25÷1.5 V
(13 dB Gain).
The ADJUST control allows adjustment within the indicated values.
- L/R alignment.
Used to increase L or R channels level up to +3dB.
This is useful to balance the output of the two channels.
- IN Mode.
Used to select balanced or unbalanced input mode.
- Out Mode.
It allows the amplifi er to operate in stereo or mono confi guration (R input).
Unlike what occurs with all amplifi ers that have one channel out of phase channel, the HV venti has in phase channels
for perfect symmetry.
Pressing the Out Mode control to confi gure the amplifi er in mono, a phase inversion is activated.
When using in the mono mode, the loudspeaker has to be connected to the positive lead of each terminal. In the mono
mode, if the optional crossover module is installed, the Lo Pass 24 dB confi guration is automatically activated.
When control unit is bypassed (PRE switch on OFF), IN MODE and OUT MODE are the only enabled switches.
b) Crossover
Factory optional module.
In order to insert the module, you have to remove a small bypass module. The crossover module itself contains all the
electronics needed to allow proper adjustment.
The crossover was designed in this way so that, in case of passive systems or the use of external processors, there would
be no extra components for the signal to pass through, degrading the signal.
Available adjustments are Hi Pass /Lo Pass 12 dB and Lo Pass 24 dB mono.
Four cut-off frequencies are selectable for the fi lter (45; 55; 65; 80 Hz). Adjustment can be made by removing and rotating
a small module that is on the crossover.
Although this solution is limiting compared to a continuously adjustable cut-off, fi lter linearity is drastically improved and
long signal paths are avoided.
You can install the crossover module both in the PRE ON and the PRE OFF confi guration.
c) Driver
150 V separate power supply.
Thermally stabilized.
Class A biasing.
Balanced input (available in both PRE ON and PRE OFF confi gurations).
First stage, complementary JFET differential.
Second stage, complementary BJT differential.
Cascode voltage amplifi er.
Output buffer to drive output stage.
d) Output power stage
The output power stage is based on an innovative topology similar to IGBT (Insulated Gate Bipolar Transistor) but
employing discrete devices.
The circuit is made from a complementary pair of Hitachi DMOS drivers, usually used as output stage devices (such as
in HR100), which drive two pairs of SANKEN power BJT transistors providing each with 30 A peak current capability and
200 W dissipation.
This solution allowed the use of only two pairs of output devices, thus permitting bias currents to be reduced which
necessarily have to be shared according to the number of output devices in parallel; therefore increasing the bias
current
- 5 -
DESCRIPTION
INTRODUCTION
2