Anthem Audio Pre 1P Operating Manual - page 4
Most phono cartridges are designed with a particular elec-
trical load in mind to yield a smooth, overall flat frequency
response.
If the cartridge is incorrectly terminated into its intended
load, frequency response errors of up to +/- 5 dB or more
may arise, causing a clearly audible effect.
This potential interface problem can be averted only by
proper termination of the cartridge into its intended load.
The optimum load must be supplied by the combination of
tone arm wiring, interconnect cabling and input resistance
and capacitance of the phono stage.
Most cartridge manufacturers provide the recommended
load values for their products on the data sheet included
with the cartridge or should be contacted directly for this
information. Likewise, tone arm and interconnect cable
manufacturers supply similar information.
The Pre 1P provides convenient solder pads designated
Cload1 and Cload2 and Rload1 and Rload2 on the main
printed circuit board facilitating installation of appropriate
resistors and capacitors, thus enabling the user to tailor
the phono stage’s input loading characteristic to match
the cartridge. These additional components may be
installed by anyone with reasonable soldering skills, your
dealer or a qualified audio repair technician.
The required values for these added components may be
computed as in the following example:
A typical Moving Magnet phono cartridge requires a load
resistance of 33,000 Ohms and a load capacitance of
470pF (Pico Farads) for optimum performance.
A typical tone arm and its interconnect wiring have a
specified combined capacitance of 100pF. The wiring
resistance is usually so very small it may be ignored as its
effect is negligible.
The Anthem Pre 1P’s input load capacitance is specified as
100pF in parallel with 47,000 Ohms of resistance for each
channel.
To calculate the additional capacitance required on each
channel, we add the 100pF value of the tone arm / inter-
connect capacitance to the 100pf value of the Pre 1P’s
input capacitance, then, subtract the sum from the
required 470pF optimum cartridge load value, giving 270pF
as the value of capacitor to be installed for Cload1 and
Cload2.
Cload = 470pF - (100pF + 100pF)
.
.
.Cload = 270pF
Suitable capacitor types for Cload include 5% tolerance or
better, polystyrene or polypropylene dielectric types, of the
closest standard value, 63 volts or higher.
To calculate additional resistance values required to be
added to each channel, the reciprocal value of the 47,000
Ohm phono stage load resistance is subtracted from the
reciprocal value of the 33,000 Ohm desired load resis-
tance. Then take the reciprocal of the difference value giv-
ing 110,785 Ohms as the resistor value for Rload1 and
Rload2.
Rload =
.
.
.Rload = 110785
Ω
The Rload resistors should be selected as the nearest
value 1/4 Watt 1% metal film types. For the above example
the closest 1% standard value from the E96 range would
be 110,000 Ohms or 110k.
O P T I O N A L P H O N O C A R T R I D G E L O A D I N G
1
1
1
3 3 0 0 0
Ω
4 7 0 0 0
Ω
-
After the insertion of the tubes, replace the cover and fas-
ten it with the screws provided. The Pre 1P is now ready
for operation. For further information on tube replacement,
contact your dealer, a Sonic Frontiers Customer Service
Representative or The Parts Connection, a division of
Sonic Frontiers.
O P E R A T I O N
Before plugging in the Pre 1P, check to see that the unit is
configured for the correct AC line voltage for country of
use. The operating AC line voltage is indicated on the side
of the shipping box. If the Pre 1P is set incorrectly for the
country in which it is to be operated, contact the dealer or
distributor in your area. If the unit is configured properly,
continue with operation.
Connect the Detachable Power Cord to the Pre 1P chassis
rear (see Figure 3). Plug your Pre 1P into the AC power
source.
Note: Never unplug your Pre 1P during operation.
First shut off your Pre/Power Amplifier, then
remove AC power by pressing and releasing Power
Switch (B).
All connections to external equipment are made with
unbalanced audio interconnect, terminated with RCA
plugs. Connect the turntable to the Inputs of the Pre 1P
(E); left channel to left channel and right channel to right
channel.
The Pre 1P’s outputs connect to the unbalanced line level
inputs of other units such as preamplifiers, integrated
amplifiers or receivers; connect left channel to left channel
and right channel to right channel.
The Pre 1P is now ready for turn-on. Power the Pre 1P by
placing the On-Off button (B) in the ON position. The
Power Indicator LED (A) will illuminate. During this time,
the Main Outputs are muted while the tubes are warming
up and stabilizing. After 45 seconds warmup, the muting
relay will engage, enabling operation.
Figure 3 - Alignment of the AC power connector and detachable cord.