L-Acoustics V-DOSC, Operator'S Manual

Page: 38 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 38 of 158
1.6 POWERING V-DOSC
The L-ACOUSTICS LA48a power amplifier is specified for use with V-DOSC. For full technical details
please see the LA48a user manual (available for download on:
www.l-acoustics.com ). A brief summary
of important specifications follows:
INPUT SENSITIVITY 2.30 Vrms (+9.5 dBu)
GAIN 32 dB (specified amplifier gain for V-DOSC)
Table 1: L-ACOUSTICS LA48a power amplifier ratings
MLS SWITCH SETTING
LOAD CONFIGURATION -5 dB -4 dB -2 dB 0 dB
16 ohms Stereo (2 channel) 220 260 410 650
8 ohms Stereo (2 channel) 430 520 820 1300
4 ohms Stereo (2 channel) 830 1000 1600 2300
2.7 ohms Stereo (2 channel) 1380 1665 2130 2700
2 ohms Stereo (2 channel) 1660 2000 2400 2900
When powering V-DOSC, two amplifier channels power the low section (since 15'' components are
wired separately internally), one channel powers the mid section and one channel powers the high
section. If we consider half an RK124a amplifier rack loaded with 4 x LA48a amplifiers (numbered 1-4
from top to bottom), nominal impedance loads and amplifier channel assignments when powering a
single V-DOSC cabinet are:
1 x 16 ohms for the high-frequency channel (Amplifier #1 – Channel A)
1 x 8 ohms for the mid-frequency channel (Amplifier #2 – Channel A)
2 x 8 ohms for both low-frequency channels (Amplifiers #3, #4 – Channel A)
When powering subwoofers, one SB218 is powered per amplifier channel at a 4 ohm load. Multiple
cabinet impedance loads and power ratings are summarized in Table 2.
Fully equipped, the L-ACOUSTICS RK124a rack contains 4 L-ACOUSTICS LA48a amplifiers and can
power 1+1, 2+2, or 3+3 V-DOSC, 4+4 SB218 subwoofers, 6+6 dV-DOSC or 6+6 ARCS. When
powering V-DOSC, 2 enclosures in parallel is the optimum load while 3 is more cost-effective.
Powering 3+3 V-DOSC enclosures is safe for the amplifiers, but does not provide the same standard
of sonic quality due to reduced headroom - particularly for the mid and high sections (see Table 2
below). Powering 4+4 V-DOSC in parallel is not recommended for normal operation but it is possible
to do so in emergency situations.