|
The function of the M63 can be described by the icon on it's
faceplate, which symbolizes small (unamplified) music entering
the grid of a vacuum tube and exiting as large (amplified)
music. Similarly, the tiny AC signal generated by the capsule
or ribbon of a microphone enters the M63 and exits at line-level,
suitable for recording to a magnetic tape or hard-disk recorder.
The preamplifier can also be used to boost an instrument-level
signal such as that from an electric bass or other instrument
using a standard pickup. The ventilation holes on the top
and bottom covers were carefully designed to provide adequate
and uniform ventilation throughout the entire chassis, while
maintaining a strong visual aesthetic. The pattern is based
on the sunflower, which uses "golden" or equiangular spirals
in opposite directions for the arrangement of its seeds. This
pattern provides a natural beauty, while perfectly satisfying
its purpose. The "M63" name is taken from the name of a galaxy
35 million light years away, whose spiral arms form a similar
shape to the sunflower seed pattern and is therefore nicknamed
"The Sunflower Galaxy".
Chassis
The housing of the entire unit is a custom made enclosure
designed by Electronaut. The face plate is a .1875" thick
anodized 5052-H32 aluminum panel, with silk-screened lettering.
The body is also made from 5052-H32 aluminum, but has an alodine
coating for excellent RFI / EMI shielding, as well as excellent
electrical conductivity for good grounding. The ventilation
holes on the top and bottom plates provide adequate airflow
inside the unit for convection cooling.
Power Supply
The power supply in the M63 consists of three main sections,
all fed from a custom made electromagnetically shielded toroidal
power transformer. The three sections are high voltage, filament
voltage, and phantom power voltage. These sections are described
below.
High Voltage - Each channel of the M63 is powered
by a dedicated high voltage power supply consisting of a 12X4
indirectly heated vacuum tube rectifier. The rectified DC
voltage is filtered and smoothed by several high-value computer-grade
electrolytic capacitors, resulting in a very clean and steady
DC voltage with an enormous reserve. Indirectly heated rectifiers
exhibit a very slow warm-up time, which results in very gentle
treatment of the amplifier tubes, thereby helping to prolong
the life of the audio tubes. Having separate power supplies
for each channel isolates the channels from each other.
Low Voltage - The low voltage supply consists
of a regulated 12V DC power supply, which supplies power to the tube heaters, the switching relays, and the pilot and meter lamps.
Phantom Power Voltage - The phantom power supply consists
of a solid-state, regulated circuit which provides well-filtered
DC voltage for condenser microphones or other microphones
requiring a DC voltage, such as active ribbon microphones.
The +48 volts is available at pins 2 and 3 of the input XLR
connector, and is supplied through two perfectly matched resistors,
resulting in zero net voltage between the + and - sides and
at the input transformer primary winding.
Signal Transformers
Both the input and output transformers are made by Lundahl
Transformers in Sweden. Lundahl makes some of the best quality,
best sounding audio transformers in the world, and Electronaut
is very pleased to use them in the M63. The input transformer
is made up of two coils, each with two primary and one secondary
winding separated by electrostatic shields. The core is a
high permeability mu metal lamination core. The output transformer
also consists of the two-coil structure, and both are magnetically
shielded by a mu metal case, resulting in high magnetic noise
immunity. The input transformer is capable of an amazing +16
dBU input, and the output transformer can produce up to +30
dBU @ 50 Hz without distortion.
Connectors
The balanced microphone input and line output connectors are
NeutrikŪ types with gold plated pins. The unbalanced 1/4"
instrument input is a locking 1/4" NeutrikŪ connector with
silver plated contacts.
VU Meters
The British made VU meters are illuminated, high-quality
audio level meters which can be switched out of the circuit
for protection from intentional overdrive. When switching
a meter out of the circuit, the illumination is also switched
off to provide a natural, visual indicator. The standard meters
used in the M63 do not fully conform to the full VU meter
specification, but are in fact slower by approximately .03
seconds. Electronaut believes that because meters should be
used only as a general reference, and because the ears make
a far more reliable indicator of sound quality, the performance
of these meters is more than adequate. However, the M63 can
be ordered with optional full-specification VU meters at an
additional cost.
Switches
All the switches on the front panel of the M63 are heavy-duty,
overrated toggle switches which control high-quality, sealed
relays for audio switching. This makes possible the use of
a rock-solid switch with excellent tactile feedback, without
passing sensitive audio signals through the switch. This also
reduces the number of times the audio signal is routed up
to the front panel for control. The phantom power switch is
a heavy-duty, locking toggle switch. This was chosen to reduce
the possibility of the accidental application of phantom power
to microphones that can be harmed by it, such as vintage ribbon
microphones.
Tube Sockets and Tubes
All the tube sockets in the M63 are ceramic, and the 9-pin
sockets for the audio amplifiers have gold plated pins. The
tube used in the first stage of the amplifier circuit is a
6072A dual triode, and the tube used in the second stage is
a 5687 dual triode. Each tube is tested in house by Electronaut
for low noise and excellent performance. NOTE: The 5687 tube
has a "9H" pinout, which is different than the standard "9A"
pinout used in the 6072A, and in other standard preamp tubes
like the 12AX7, etc.. It is therefore INCOMPATIBLE with these
other tubes -- in other words, don't stick a 5687 tube in
a guitar amp designed for a 12AX7, and don't stick a 12AX7
in the 5687 socket in the M63.
Signal Capacitors
All signal coupling capacitors are excellent quality polypropylene
capacitors, which are made using a technology originally developed
by the European Space Agency for very high pulse current power
electronics. The manufacturer describes these capacitors as
follows: "These capacitors exhibit near-zero losses, they
reduce linear, nonlinear distortion and phase distortion to
unmeasurable level, showing an almost unbelievable ideal capacitance
reactance curve which gives the highest level of signal resolution."
Potentiometers
All the potentiometers used in the M63 are sealed, conductive
plastic types for low noise and maintenance-free operation.
Features:
-
Phase reverse switch (switches at output)
-
+48 Vdc phantom power with locking toggle switch
-
Input switch (selects between 0, -20 dB pad, or instrument)
-
Balanced microphone input and line output through XLR
connectors with gold-plated pins
-
Unbalanced instrument input through locking 1/4" connector
-
Illuminated VU meters with separate isolated meter amplifiers
-
Meter switch (removes the meter from the signal path
to protect it from intentional overdrive)
Downloadable specification sheet coming soon!
All handmade preamplifiers are built to order and take 6-8
weeks for delivery. Please contact Electronaut
for details.
|
