Introduction
WHY A HEAD AMP?
It is in the very nature of a moving coil cartridge,
the way in which it must be made with the limita-
tions imposed by today's materials, that it requires a
head amp. A moving coil cartridge is really an elec-
trical generator. Just like the generators at an elec-
trical generating plant that convert the energy from
falling water, the moving coil cartridge must have a
source of mechanical energy which it can convert to
electrical energy. For the moving coil cartridge the
mechanical energy is supplied by the motion of the
stylus as it follows the music signal impressed on
the record groove walls. The movement of the stylus
corresponding to the musical information is very
small, being measured in only thousandths of an
inch or tens of microns. Such a small mechanical
motion converts into a correspondingly small elec-
trical energy. The output of a moving coil cartridge is
measured in only millionths of a volt. A typical mov-
ing coil cartridge will deliver only two or three hun-
dred millionths of a volt which is equivalent to an
energy output of only a billionth of a watt. The head
amp must amplify this energy and increase its volt-
age level to a few thousandths of a volt in order to
protect the musical content from loss of information
and contamination by interfering electrical fields
which surround everything and everyone of us. Such
contaminating fields would add noise and hum to
the musical signal and decrease its meaning for us.
AN ALTERNATIVE DESIGN
There is another possible means of increasing the
voltage level of the head amp and that is by using an
input transformer. While the transformer can in-
crease the voltage output of the moving coil car-
tridge it can not amplify the energy content of the
musical signal from the moving coil. Hence as the
voltage of the moving coil is increased its cor-
responding current is decreased. The source im-
pedance, the ratio of the moving coil voltage to its
current is increased by the square of the voltage
gain. Thus a voltage gain of say one hundred times
is accompanied by an impedance increase of ten
thousand. The higher the impedance of the output
circuit the more susceptible it is to interfering hum
and noise fields. The head amp can solve this pro-
blem by being designed to have an output im-
pedance of only a few ohms. . .
But there is another problem with transformers
operating at extremely low voltage levels. The ease
with which the magnetic core concentrates lines of
magnetic force varies with voltage level at extremely
small levels. This variation adds distortion to the
music signal at low frequencies. The MCP 1 head
amp solves this problem too. The musical definition
of the MCP 1 is far superior to input transformers
that are many times the weight and size of the MCP 1.
For the highest quality music recovery from your
recordings it is best to locate the head amp close to
the base of the turntable arm. The extremely low
energy levels developed by moving coil cartridges
must be protected from exposure to loss of quality
from long cables to the preamplifier. When the low
voltage signals of the cartridge are amplified by the
head amp, they can then leave for the preamplifier in
robust form, able to survive the passage without
loss of content and be uncontaminated by added
noise or distortion components.
The MCP 1 is powered directly from your 117 volt
line. But an ingenious new development from the
Mcintosh engineering group completely isolates the
MCP 1 from any noise components in the power line.
It is imperative that there be no ground loops
(multiple grounding paths) on the input and output
cables connecting the MCP 1. Each channel of the
MCP 1 has independent ground circuits. The input
cables from the tonearm must have separate
grounds for each channel and these grounds must
not connect to the turntable frame ground. The out-
put cables from the MCP 1 should have independent
ground paths to the preamplifier. If you would like to,
you can test the grounding system using an ohm
meter. When testing the MCP 1 without any connec-
tions to other equipment, the ohm meter should
measure 200 ohms between the left and right chan-
nel grounds and 100 ohms from each channel
ground to the MCP 1 ground terminal.
2
Connect the leads from your turn-
table to the proper impedance for your
cartridge on the MCP 1 input.
Connect the output of the MCP 1
head amplifier to the moving magnet
phono input on the preamplifier.
Connect the turntable ground to the
MCP 1 ground terminal.
Then, connect a ground wire between
the MCP 1 ground terminal and the
ground terminal on the preamplifier.
How To Connect
