have time to discharge before enter-
ing the unit.
Care needs to be taken during
this procedure in order to prevent
damage by static electricity to the
VTPH-2 internal components. Use
of a grounding wrist strap is
highly recommended.
The original tubes should provide
many years of good performance,
due to the conservative plate voltage
and current operating requirements
of the Herron Audio Phono
Preamplifier.
If tube replacement is required,
channel-to-channel gain matching
can be done using the left and right
gain controls on the printed circuit
board.
Tube Locations
Tube Recommendations
Units RIAA passively compensated
for 4 12AX7s, and 1 12AT7,
the following tubes are
recommended:
V1 and V3 (first gain stage) EI 12AX7
V2 and V4 (2nd gain stage) EI 12AX7
V5 (output stage) EI 12AT7
Units RIAA passively compensated
for 2 12AX7s, and 3 12AT7s,
the following tubes are
recommended:
V1 and V3 (first gain stage)
Svetlana 12AX7
V2 and V4 (2nd gain stage)
Electro-harmonix 12AT7
V5 (output stage) EI 12AT7
Other current production or NOS
tubes may be preferred with experi-
mentation.
Tube locations as marked on the
printed circuit board
Install the grounding lug
under the top screw at the rear
of the chassis when reinstalling
the cover.
Owner’s Manual
eleven
Please read the Owner’s Manual completely BEFORE operating the unit.
Power Line Polarity
Set the power line polarity switch to
the “A” position. With the volume
control at its lowest position, place
the line stage input selector in the
position to select the VTPH-2 phono
preamplifier.
Increase the volume to a normal
listening level and check for hum.
Reduce the volume to a lower posi-
tion and play a record. Gradually
increase the volume control to the
desired level and listen closely to the
quality of the reproduction. This will
be used as a baseline for determining
AC polarity.
Place the line stage input selector
to an unused position and change
the AC polarity of the VTPH-2
phono preamplifier by switching the
power line polarity switch to the “B”
position. Repeat the process, listen-
ing to the same recording. Place the
AC polarity switch in the position
that sounds best.
Optimum Performance
With higher definition and detail
available in the musical signal, more
careful attention to the set-up of
other components will yield greater
benefits. We have found that the
best place to start is with the
turntable set-up. Adjustments of
the vertical tracking angle will be
easy to resolve using the Herron
Phono Preamplifier. Users may gain
improved performance by making
fine adjustments. Slight changes in
cartridge tracking force can improve
tracking and position the coils in a
cartridge at the correct position
relative to the magnets.
This can dramatically improve
performance. We recommend that
the VTPH-2 be used with a line
stage having an input impedance of
50,000 Ohms or higher for optimum
performance. Depending on the
cartridge output rating, the line
stage may require an input capacity
of as high as 15 volts rms.
We recommend the use of high
quality interconnecting cables
between the turntable and the
phono stage and between the
phono stage and line stage. It is
very important for achieving best
performance from the VTPH-2 that
the cables between the phono stage
and the line stage be a low capaci-
tance type.
Changing Tubes
When changing tubes, the VTPH-2
should be unplugged and left off for
a minimum of 30 minutes prior to
opening the unit, to insure that haz-
ardous voltages in the power supply
VTPH-2 Herron Audio Vacuum Tube Phono Preamplifier
ten
When changing tubes, the phono stage should be unplugged and left
off for a minimum of 30 minutes prior to opening the unit, to insure that
hazardous voltages in the power supply have time to discharge before
entering the unit.
CAUTION CAUTION CAUTION CAUTION CAUTION CAUTION
