Level setting:
To set the output level or signal gain,
the up and down buttons are used,
marked ”UP” and “DOWN”. Pushing
once will induce a 1 dB level step.
Holding down the button will make
the level scroll up or down. The level
setting is indicated by red LEDs in the
display, in dB, marked ”dB”.
When 0 dB is indicated a very low to no (zero) output signal is given. When 60 dB is in-
dicated the maximum amplification is reached. Depending on the selected signal the
amplifier may reach its maximum output voltage before reaching the 60 dB setting.
Selecting a signal:
The right led in the display will indicate which type of signal is active. And a letter L/A
shows the equalization setting for Qohm.
To select a signal press the button on the top right, marked “signal”. The output signal will
toggle between:
pink noise
L. linear output between 45-20000 Hz*
pink noise
A. shaped spectrum 45-16000 Hz* equalizing the source
pink noise
E. shaped spectrum 45-16000 Hz, with low frequency tuning
white noise
L. linear output between 45-20000 Hz*
white noise
A. shaped spectrum 45-16000 Hz* equalizing the source
white noise
E. shaped spectrum 45--16000 Hz, with low frequency tuning per octave band.
external signal** L. linear output spectrum 20-20000 Hz
external signal** A. shaped spectrum 45-16000 Hz* equalizing the source
external signal E. shaped spectrum 45--20000 Hz, with low freq. tuning per third octave
In each case the letter for the equalization is displayed and the LED bar on the far right
will point to the type of signal as printed next to the LED bar. The level of output
power/noise will vary significantly when going from L to A and E filtering.
* The frequency range depend on the selected and pre-programmed product (sound source or other) the
shown numbers are valid for the Qohm, Qohm2 or Qm products.
** For linear amplification the external signal is limited to 0.35 V sspk or 0.7V pk-pk.
Selecting interrupted mode:
Short depression of the mode button will make the amplifier run in interrupted mode. It
will put the amplifier is stand-by mode for 20s, automatically followed by 20s activity,
followed by standby, etc. To de-activate this mode just briefly push the mode button
again.
Central LED meaning:
Four red warning LEDs are located in the middle of the display.
The top one will clearly light up when the amplifier reaches saturation and goes into a
non-linear mode. In this mode the peak voltages are limited to a + 75V and -75V maxim-
um. It is well possible to let the amplifier work in this non-linear range. But it may not be
safe for the source or speaker or shaker, because the amount of electric power going
into the speaker is increasing even if the peak voltage is limited.
The second LED down indicates an overheating of the amplifier. This may occur after
long periods of stand-by in warm environments or when the amplifier is covered by an
other object hampering the normal cooling. The amplifier will restart automatically when
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