Test Specification
Fr
equency response
. 8-ohm load
Input set to 1v rms
20Hz – 20kHz = +/- 0.5 dB
.
Distortion
. THD+N 0dBR 4-ohm load.
Input set to 1v rms.
20Hz – 20Khz = <0.02%
M
aximum output
into an 8-ohm load.
Input level set to 1.34 rms 1Khz = 180 watts
di
stortion should be below 0.05%
THD+N
Bias setting notes
The bias
of the P1 is set using an Audio
precision audio analysis package and we
calibrate the power stage for minimum THD the
bench set up procedure follows.
o
Set the input signal to 150mv rms,
frequency to 10kHz. Induce a 4-ohm load
at the speaker output.
o
Rotate preset RV100 clockwise and
observe that the THD falls. Continue to
rotate the preset until the THD falls to a
minimum level and just starts to clime
again.
o
Switch input signal off and allow the
amplifier the Quiesce +30secs
o
Measure the bias level at test point Con
103 (Bias read) and confirm the reading is
below the absolute max of 35mV.
Major component identification.
FMMT 497/597
BC849/BC859
1=Base
2=Emitter
3=Collector
TLO 72
SSM2143
74HC32N
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