[12AU7 Balance Pre-Amplifier ]
Analog Metric
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4
•
Do not attempt the measure the voltage by multi-meter with hand after power up. The
probes of the multi-meter should be mounted by some stands to the points of the
measurement before switching on the power supply.
•
Turn off the power supply if you observe any smokes or hear strange sound coming
out from the transformer or board. If there is short circuit, the transformer will be
getting very hot shortly.
PROCEDURES
1.
Hook up all the components according to the schematic, part list, and photos. Notice
to the polarity of the high voltage electrolytic capacitors (C3 and C3B). There are no
polarities of the thin film capacitors.
2.
Apply either one or two 260V DC to P1, one 6.3V DC to P2, and one 12.6V DC to P3.
If you only have one 260V DC supply, connect the two '260V DC' pins together.
3.
Adjust R18 and R18B so that the voltage at PIN #3 and PIN #8 are 7V DC.
4.
Apply input signals (single-end signals: V+, and ground V- and GND; balance
signals: V+, V-, and GND)
5.
Obtain output signals (single-end signals: V+ and GND; balance signals: V+, V-, and
GND)
6.
Enjoy it.
