User Manual
- Remove signal from XLR Input.
- Connect the signal generator to LINE INPUT (RCA socket) and set it at -20 dBu.
- Verify that low amplifier output signal is 28V ±6 Vpp.
NOTE: the low amplifier is designed with a class-D half-bridge self-oscillating amplifier around the
IRS2092 ic, to see in detail how this amplifier works consult IRS2092 data sheet and related application
notes available on International Rectifier website (www.irf.com). The low amplifier oscillating frequency
is in the range of 400-420 KHz. If there is a problem in the nested loop the amplifier doesn’t oscillate:
switch off then check TR6. If the mosfets isn’t fault check the voltage, using the DMM, between –VCC
and pin 3 of IC2 (7812), this is the voltage regulator of low side mosfet driver, if this regulator doesn’t
work the amplifier doesn’t oscillate.
3. COMPRESSOR check of LOW amplifier
- Increase the signal at +10 dBu and check that the output signal remains constant at 40 ±4 Vpp. Check that
the SIGNAL/COMP LED has changed the colour from GREEN to RED.
- Disconnect the 4ohm load resistor from the LOW amplifier output.
6. HIGH amplifier check
- Connect the signal generator to LINE INPUT (XLR/JACK socket) and set it at 10 KHz , 0 dBu.
- Verify that the CH2 (HIGH OUT) signal is symmetrical referring to GND, without detectable distortion and
oscillation.
- Connect the 8 Ω load resistor at LOW OUT and check that the HIGH amplifier output signal is limited to 20
±3 Vpp.
7. X-OVER check.
- Disconnect all resistive loads and set the signal generator to -10 dBu.
- Sweep the frequency and check that the LOW amplifier power out signal level is as the 1a plot and HIGH
frequency amplifier power signal level is as 1b plot.
- Set the
NEARFIELD/MIDFIELD button in MIDFIELD position.
- Sweep again the frequency and check that the LOW amplifier power out signal level is as the 2a plot and
HIGH frequency amplifier power signal level is as 2b plot.
1a
1b
2