2
Nominal load impedances
100V output
70V output
25V output
DPA 4245
28,5
Ω
Ω
14
Ω
Ω
1,8
Ω
Ω
DPA 4260
20
Ω
Ω
9,8
Ω
Ω
1,25
Ω
Ω
1. Operation voltage:
U(B) = 230V / 50Hz ... 60Hz
2. Deviation limit of the operation voltage:
-30% .... +10%
3. Power consumption (both channels driven via the 100V output, f = 1kHz)
DPA 4245
DPA 4260
idling condition power consumption
30-60W
40-80W
nominal power consumption (nominal load)
1580W
1950W
standard power consumption (nominal load)
470W
620W
maximum power consumption (nominal load)
1680W
2180W
power consumption at 1/8 of the maximum output capacity
600W
870W
4. Settings
4.1. IDLING CURRENT ADJUSTMENT
Connect the DC-volt meter at the BIAS measuring points (refer to service connectors) and adjust the idling
current via the trim potentiometer VR101/VR301 (located on the Main PCB). Adjust both channels of the power
amplifier A&B to U(DC) = 7.5mV. Adjusting the idling current has to be performed at normal room
temperature. In case the power amplifier had previously been operated, it has to be given several hours to regain
its normal temperature.
4.2. VCA - OFFSET
Rhythmically open and short-circuit CNS2.1 and CNS2.2 for channel A as well as CNS2.3 and CNS2.2 for
channel B. The switches are located on the Main PCB. Using VR100 or VR300 respectively to adjust the power
amplifier's
Direct Output
to its minimum offset (with oscilloscope to minimal peak value or to the audible
minimal volume of the interfering pulse).
5. Functioning test
5.1. OUTPUT - offset voltage
DC-voltage measuring at the
Direct Output A/B
with U(DC) 10mV.
5.2. LIMITER
5.2.1. Voltage limiter
Both channels separately driven without load via the Direct Output with a 1 kHz signal up to U(A) = 38V.
Increase the input voltage by 10 dB. The LIMITER LED lights and the output voltage ascents by approx. 1.5 dB
or 2.5 dB respectively to approx. 44V or 52V, respectively. The distortion rate of the limited signal should not
ascent above 0.8%.
5.2.2. Distortion limiter
Both channels separately driven via the Direct Output at 2
Ω
with a 1 kHz signal up to U(A) = 20V or U(A) =
25V, respectively. Increase the input voltage by 5 dB. The LIMITER LED lights and the output voltage ascents
by approx. 1.5dB to approx. 25V or 29V respectively and it is slightly clipping. The distortion rate of the limited
signal is approx. THD = 2 ... 3%. Further increasing the input signal by +10dB should not result in a remarkably
higher clipping of the output signal.
