Nexo NXAMP - Manuel (Page 28)

ENGLISH
PAGE
28
AMPLIFIERS (GAIN, POWER)
Gain value
NEXO recommends low gain amplifiers: +26dB is recommended, as it is at the same time adequately
low and quite common. This considerably improves signal to noise ratio and allows all preceding
electronic gear, including the TDcontroller, to operate at optimum level. Remember that using a high gain
amplifier will proportionally raise the noise floor level by the same amount.
Advanced protections
Some high-end amplifiers may have some advanced functions like those found in the NX242
TDcontroller ("loudspeaker offset integration", "limiter", "compressor"...). These functions are not well
adapted to specific system requirements and may interfere with existing protection within the
TDcontroller. NEXO do not recommend using these functions with the NX242 TDcontroller.
Amplifier Latency effects on protection
In order to provide advanced functions (not always relevant for NEXO equipment) some amplifiers use a
digital preamp section where the analogue signal provided at the input of the amplifier is converted to
Digital, treated then converted back to analogue before being send to the power stage.
Such amps are delaying the
signal from the value of the
conversion latency. (This
value reach 1.13ms on the
CROWN ITECH for instance).
When you put such a delay
between the NX242
TDcontroller and the cabinet it
has a strong effect on the
protection by delaying the
effect from the cause…
Lets take for example a peak
limiter limiting a 5kHz signal of
amplitude 1 with attack and
release set to 2ms. You can
easily notice that on the
second axis the effect of
delaying the protection has
massive effects (in fact the
protection doesn’t work
anymore). The higher the frequency, the higher the effect.
0 5 10 15 20
−1
−0.5
0
0.5
1
Peak Limiter no latency
0 5 10 15 20
−1
−0.5
0
0.5
1
Peak limiter with 1.13ms amplifier latency
Time (msec)
All protections dealing with displacement or acceleration of HF drivers and generally speaking all peak
limiter action above 1kHz will be spoiled.
AS A RESULT NEXO STRONGLY RECOMMENDE NOT TO USE AMPS THAT INVOLVE A/D D/A
CONVERSION PROCESS. IT COULD DAMAGE YOUR SPEAKER AND DEGRADE SOUND
QUALITY.
NX242 USER MANUAL LOAD2_22
DATE : 12/3/2004