amplifiers without this provision.
Adjust the GAIN TRIM for proper channel balance. Some minor adjustment is
sometimes required as the MP-1 is a zero feedback design. The Gain Trim
controls are a volume control system employing a shunt-style control- the
controls themselves are not in series with the audio signal. Set them so that
the Master control is easy to use.
Due to the low impedance operation of the MP-1, cable quality between the
preamplifier and power amplifier is considerably less important. You may hear
differences in the cables, but they will be minor compared to the differences
you may be used to hearing in single-ended cables. Thus we have no
recommendation for cables to be used between the preamplifier and power
amplifier. On the other hand, the
input
cables may be
very
critical, depending
on the source. Atma-Sphere offers a variety of interconnect cables for this
purpose. Contact your dealer or Atma-Sphere for details.
PHONOGRAPH HOOKUP
All phonograph cartridges with four signal pins are a balanced source. Thus
the MP-1 allows you to set up your turntable as a fully balanced source, with
considerable sonic advantage. For best results, follow the connection scheme
outlined below:
1) Use a cable that has two signal conductors PLUS a shield for each channel.
The two conductors are for the plus and minus outputs of the cartridge, and
the shield connection becomes the tone arm/turntable ground connection and is
common to BOTH channels.
2) Pin number one of any XLR connection should always be ground as per
industry standard.
3) Pin two of the XLR phono input corresponds to the "+" or non-inverting
output of the cartridge, and pin three is the "-" or inverting output of the
cartridge (absolute system phase can be corrected from the front panel).
4) There is no need for an independent ground wire from the arm to the preamp.
If you set up the cable correctly, there will be NO hum whatsoever. Many tone
arms use a five pin connector that plugs into the tonearm. If you have such an
arm, you may order a tone arm cable with the right connections from almost any
cable manufacturer. Sometimes a copy of this page sent to the cable
manufacturer is helpful. If your arm has RCA connectors at the output, an
adapter cable can be made that will work. The shield connection of the RCA
becomes the connection to pin 3 of the XLR connector, and the tone arm ground
connection should be made as described above. ON NO ACCOUNT should you allow
the shield connection of the RCA to become the shield for the cable, as this
will result in a loud hum.
The cartridge loading is accomplished by installing resistors on the loading
terminal above the phono connectors on the rear panel. A screwdriver is all
that is needed for attachment. You will find that the MP-1 is relatively
insensitive to loading of low output moving coil cartridges. This is because
the MP-1 is very RFI immune and loading of low output moving coil cartridges
has most of its effect at Radio Frequencies. If using a high output cartridge,
things are different and loading can be quite critical as the load affects the
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