when relatively short 1/4" cable patches are made to this input from various outputs on this amplifier, or from other equipment that shares the same rack with this amplifier. The quasi-balanced circuitry is “automatic” and virtually “invisible” in normal usage. This feature can be defeated with a jumper on the barrier strip from the “-” input terminal of that channel to the ground terminal.
(15)LOW CUT SWITCH
This switch is used to activate the LOW CUT filter for the corresponding channel. It is again a push- push type switch, requiring a small “tool” to activate. The IN position routes the input signals through the 40 Hz LOW CUT filter, while the OUT position bypasses the filter. This filter will cut extremely low frequencies, protecting speakers from the possibility of over-excursion. The filter low-frequency rolloff is 12 dB per octave. The LOW CUT filter for each channel will function independently of the crossover function to be discussed next.
(16)CROSSOVER SWITCH (150 Hz XOVER)
This switch is used to activate the 150 Hz crossover for the corresponding channel. It is also a push- push type switch and requires a small “tool” to activate. The PV® offers two 150 Hz crossovers. These are specially designed features that enhance the response of most loudspeakers in a typical bi-amped application. Rather than just having a flat output curve, these crossovers use special filters to tailor the response and provide a flat acoustical output. This type of crossover “sounds” more natural than conventional “state-variable” type crossovers.
With the switch IN, the input signals are routed through the crossover, and the low frequencies are automatically sent to the corresponding channel. At the same time, the high frequencies are sent to the HIGH OUT (18) jack and must then be patched to INPUT of the other channel of this amplifier or to another amplifier input to complete the bi-amped system. Additionally, the low frequencies are sent to the THRU/LOW OUT (17) jack, and can be patched to other amplifier inputs to permit even larger systems. With the switch OUT the crossover is defeated, and the input signal is routed directly to the respective power amp channel. The crossover frequency is fixed at 150 Hz and cannot be changed. The crossover configuration is a 4-pole Linkwitz-Riley approximation.
(17)THRU/LOW OUT JACKS
As per previous crossover discussion, this 1/4" jack supplies low-frequency out signals from the activated crossover for patching to additional power amplifier inputs, providing added flexibility in larger bi-amped systems. When the crossover function is not activated, this jack converts to a THRU function, where the output of the electronically balanced input circuitry is supplied to this jack. The THRU function provides the means to patch a full range input signal to the other input of this amplifier (parallel mode), or to other amp inputs in the same rack. This function allows one balanced mixer feed to be connected to the amp via the desired balanced input connector (XLR, 1/4", Barrier), and then further distributed locally. Regardless of the crossover switch position, this 1/4" jack provides an unbalanced (tip/sleeve) output to be patched with single conductor shielded cables.
(18)HIGH OUT JACKS
Again, as per previous crossover discussion, this 1/4" jack supplies high frequency out signals from the activated crossover for patching to this amplifier and/or additional power amplifier inputs. Unlike the low-frequency crossover output, that is automatically routed to the associated channel, the high- frequency output signal must be patched to some suitable input in order to complete the bi- amped system. This 1/4" jack also provides an unbalanced (tip/sleeve) output to be patched with single-conductor shielded cables.
INDUSTRIAL AND COMMERCIAL INSTALLATIONS
For commercial and other installations where sustained high-power operation is required, the amplifiers should be mounted in a standard 19" rack. It is not necessary to leave a rack space between each amplifier in the stack since each fan pulls air in from the rear and exhausts the hot air out the front. However, an adequate cool air supply must be provided for the amplifier when rack mounted. The internal fan must have a source of air that is not preheated by other equipment. The amplifier will start up in low speed fan operation and will normally stay at low speed unless sustained
