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3. INSTALLATION
3.1. Placement, mounting, cooling
All LPA amplifier models are presented in standard 19” rack format and are 2 units high.
It is important that the amplifier, as a heat source, is not placed next to other equipment nor exposed to
high temperatures. Therefore, the ventilation path should be kept free to allow fresh air entering the forced
ventilation tunnel. This system takes air from the unit's backside, bringing it directly to the power amp modules and
distributing it to the transformer and capacitors and then obliging it to pass trough the cooling tunnel to finally blow
out of the front panel. In case of rack mounting, this system avoids heat accumulation inside the unit and thus
increases lifetime of electrolytic capacitors. It is recommended to place power amplifiers on top of other equipment
and not underneath.
3.2. Mains connection
The LPAs are supplied with alternating current at 230 V, 47 / 63 Hz, and include fuses to protect against
possible overloads. In order to protect the power amplifier from eventual power consumption overloads it is
protected by a set of internal fuses. Should a fuse blow, it must be replaced immediately by one with identical
rating. Should it blow again please contact our Technical Service Department. NEVER REPLACE THE FUSE
WITH ANOTHER ONE WITH A HIGHER VALUE.
The mains cables must not be near the shielded cables carrying the audio signal, as this could cause
humming.
3.3. Input signal connections
The input connectors for the balanced signal are of the XLR-3 and ¼” JACK type (11, 13). The assignment is
as follows:
XLR-3
JACK
Hot
or
direct
signal
>
Pin
2
Tip
Cold or phase inverted signal
>
Pin 3
Ring
Ground
>
Pin
1
Sleeve
For an unbalanced connection, short pin 3 to ground (XLR) or the ring to ground (Jack).
The input impedance in balanced mode is 20k
Ω
(10k
Ω
non-balanced). This impedance makes possible to parallel
several amplifiers without losing audio quality. Input sensitivity can be selected via a switch placed on the back
panel (14) Selectable values are 26, 32dB
3.4. Cut filter or crossover
The integrated cut filter has the function of dividing the input signal into two frequency bands. When it is
activated, channel 1 receives and amplifies the frequency band between 20 Hz and 150 Hz, whereas channel 2 does
the same for the frequency band between 150 Hz and 20 kHz. The slope of the cut filter between the two bands, at
150Hz, is 18 dB / octave.
This function is useful for connecting a two-way loudspeaker system to a single LPA amplifier. If the playback
is in stereo, then it will be necessary to use one LPA amplifier for the left signal and another one for the right signal,
whereby each LPA amplifier operates with the low frequencies in channel 1 and the high frequencies in channel 2.
