18
C Series
Quick Start Guide
19
NOTE:
When bridging two channels, you must add +6 dB to the input sensitivity to achieve maximum output voltage due to the automatic -6 dB gain compensation
inserted by the amplifier.
Audio Input and Output connections, setup and features
Balanced / Unbalanced Input connection
Two electronically balanced Phoenix-type inputs are available. Follow the +,– and Ground labels when connecting the input signal.
If an unbalanced connection is desired this can be achieved by summing the minus (“COLD”) and Ground terminals and using the + terminal as the “HOT” signal.
For the best possible performance, the summing of ground and minus wires should be done at the source unit end of the cable (e.g. a CD player).
Four connectors are supplied for attaching cables to the inputs. The type of connector used is: Phoenix Contacts, Part number MSTB 2,5/3-STZ-5,08.
NOTE:
When linking the same source signal to several input channels, be aware that there is a limit to the number of channels an output source can “drive”. A typical
output source (e.g. a DSP crossover unit) can drive up to four amplifier channels before external line-drivers might be required to buffer the signal.
Output operation and connection
Screw-terminal connectors with + and – poles are provided at each channel
output for connection of the speakers.
Make sure that the speaker cables are connected correctly and tightly, and that
accurate polarity is maintained to all speakers in the system.
As the amplifier outputs produce high voltage, do not connect or
disconnect speaker cables when the mains power is on. Also, attach
the safety cover on the speaker terminals for safe operation and to
comply with electrical product approvals.
Output bridge mode
It is possible to bridge channels in pairs of two (A+B and C+D for example).
When bridged, the input source must be connected to input A (A+B) or C (C+D)
respectively. Output speaker cables must be connected to the plus pole on
channel A or C and the minus pole on B or D.
The main benefit of bridging the output is a doubling of output voltage. Bridging
can be used to turn the amplifier into a three-channel amplifier with, for
example, 2 x 1200 W and 1 x 2400 W at 4 ohms utilizing the C 48:4, or simply to
achieve an impressive 200 Vrms supply per channel.
Most power amplifier designs, when bridged, automatically introduce a +6 dB
input gain boost which can lead the user to conclude that said amplifier delivers
“more than double the power” when in bridge mode. This is clearly not the case,
as the gain boost artificially enhances perceived power at the cost of headroom.
The C Series amplifiers work on globally set constant gain, and automatically
compensate the input gain by -6 dB. For example, if the amplifier is configured in
a three-channel mode, then the selected gain is maintained from input to output
on all channels.
Amplifier Input Gain
All C Series amplifiers feature adjustable input gain. This versatility enables the
amplifier to accommodate a multitude of system configurations with various
input sources and speaker layouts.
Amplifier gain is set globally for all four channels. The range is +23 dB to +44 dB
in 3 dB steps. Individual channel fine level adjustment is available using the
potentiometers on the front panel.
The unique adjustable input gain feature of the C Series makes it easier to attain
the optimum balance between headroom and signal-to-noise ratio in the signal
path. A weak signal at the input might require the gain to be raised in order to
achieve maximum output power with the lowest signal-to-noise ratio. A “hot”
input signal, however, would require a lowering of the gain to avoid sending the
amplifier into Voltage or Current clipping.
See Appendix to review the table containing Gain versus VPL setting implications
for input sensitivity and output power.
NOTE:
Bridge mode operation automatically compensates by -6 dB, keeping all
channels at the same gain.
Channel gain/level (front-panel pots)
Individual channel gain (level) may be adjusted using the potentiometers
located on the front-panel behind the dust filter cover. Range is from 0 dB to
-infinity in 21 steps. The attenuation is logarithmic, with the 12 o’clock position
indicating -10 dB.
Use your fingers or a screwdriver to adjust the potentiometers.
NOTE:
If the level control is used to attenuate to a lower level than the headroom
relative to input sensitivity AND the amplifier input is driven into clip, there is a
danger of clipping the input stage before the current or voltage peak limiters are
activated.
Amplifier sensitivity
Sensitivity is defined as how many volts (rms) or dBu (referred to 0.775 Vrms) are
required to achieve full (maximum) output power. As the output power varies
with the load impedance, 4 ohms is usually the common reference.
Since C Series amplifiers are capable of providing multiple maximum output
power levels through use of the VPL feature, many sensitivity calculations may be
required for a single amplifier. We recommend use of the DeviceControl software
to simplify this process. DeviceControl’s Device View page, used in combination
with the DIP-switch settings display, will automatically produce a sensitivity
calculation from the given data (VPL, Gain and load).
Output Voltage Peak Limiter (VPL)
The Voltage Peak Limiter (VPL) is a unique feature in C Series amplifiers. It is used
to select the maximum power available on each output channel. Four levels can
be set using the DIP-switches on the amplifier’s rear panel.
V peak
Vrms
141
100
118
84
100
70
85
60
71
50
59
42
50
35
42
30
The values for VPL are displayed as maximum Voltage Peak. To translate Voltage
Peak into Vrms, you must divide the Voltage Peak values by 1.41 (see table).
The VPL allows you to set the correct maximum output peak power for optimum
performance with the connected speakers. The correct setting depends on the
system type (low or high impedance) and the specific load connected to the
channel. Since each channel can be configured to deliver either very high voltage
peak power OR high current draw at low impedances, it is important to set the
VPL correctly.
To configure an individual output channel for a constant voltage system, you
simply adjust the DIP-switches to the desired voltage. However, when using
an output for a low-impedance system ( 4, 8 or 16 ohms), then you may need
to adjust the VPL to a lower setting to avoid either delivering excessively high
continuous power to the speaker or overheating of the output channel through
high current draw. For example, with a very “hot” continuous output signal, the
temperature could rise to a critical level and activate Temp warning or even Temp
Mute. Lowering the VPL setting usually will solve this situation.
If the Current Peak Limiter is active or indicates low impedance, lowering the VPL
setting can rectify this situation as well.