Curio's
- Calrec,
some "Old Favourites" and more !
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The
mid' 1960's
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Times
were changing and technology had moved away from
the use of valves, to that of the modern semiconductor.
With the emergence of the new "Field Effect Transistors"
(FET's), then the very Hi-Impedance input stage of
a condenser microphone,
could now be designed around an FET, rather than
the traditional valve.
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In
1965, tests were being carried out by Calrec, into
the use of FET's
in their microphone designs.
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Calrec
had finally arrived in the modern world of
semiconductors, saying a fond farewell to the
"Calrec" valve years.
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The
Calrec CM652, from the 600 series microphones.
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Let
us not forget .....
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Prior
to the FET range of microphones, manufactured by Calrec, there was the relatively
less well known CM450
"Dynamic" microphone. Very similar in
size and appearance to the Calrec CM650. Maybe the
CM450 was not the best dynamic microphone ever
made, but one that was very suitable for PA and
general Studio use.
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In
the case of the CM450, then the "4"
stands for the 400 series, using the "Dynamic"
principle of operation. The "50"
standing for "Cardioid" polar pattern,
as is the code used on their capacitor capsules
e.g CC50 being a Cardioid capsule with a flat
frequency response. It is worth noting, to avoid confusion,
that although the dynamic capsule element of the CM450 is
fitted inside a metal windscreen, it has a
"Flat" frequency response. Unlike the
later "CC56" capacitor type capsules
that incorporate a bass roll-off.
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Introduction
of the FET condenser (Capacitor) type
microphones
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The
first
FET microphones manufactured by Calrec, would be the very popular "Fi-Cord"
600 and 650 microphones. These microphones,
together with the 700, 800 and 900 series, were
all designed and manufactured by Calrec, but
originally distributed by "Fi-Cord"
and therefore labeled as "Fi-Cord"
microphones. The design and technical
specification of the microphones, catered for
most demands required by the "Potential"
end user. Also, the variation in designs, allowed the various
models to work on the many different powering
arrangements available at that time.
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The
Capsules used in the Calrec/Fi-Cord FET
microphones, would be a smaller diameter than that
used in their valve models i.e. The capsules
employed in the C41, FC1200 valve microphone etc,
were somewhat larger in diameter than that used in
the 600 series and all other Calrec/Fi-Cord FET
type microphones. Of course, this would mean a
change in tonal quality, but the FET microphones
would still retaining that familiar Calrec sound.
The design of the capsules would still be of the
same general principle, only on a slightly
smaller scale.
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Note
- See "Calrec
- The Valve Years" for more information
about Fi-Cord.
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600 series
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Designed with the "Amateur" and "Semi-professional" user in
mind, the 600 series offered microphones with
fixed capsules. Capsule types available were, Omni,
Cardioid, and Cardioid with bass roll-off, the
later mounted
in a wire mesh windshield. Despite the fact that
only 3 capsule types were available, this would prove
more than sufficient
for most uses. Throughout the many years since
their introduction during the mid' 1960's, the 600 series
gathered very many fans and followers. Indeed,
many examples are still in use today.
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From
a service engineers point of view, the Calrec 600
series is a nightmare. The Hi-Impedance areas of
the PCB, being totally encapsulated in epoxy
resin. Therefore, should any component fail within
that area, then the PCB was rendered
un-serviceable, and a replacement PCB would be
required. That would not have presented a problem
when the microphones were still in production, as
the PCB's were readily available. However, in the
current day, it is not financially justifiable to
have new PCB's produced and
"Populated" with the required
components, to enable these microphones to be
serviced. Having said that, not all faults are in
this part of the circuitry, and should a fault lay
outside of the "Encapsulated" area, then
the PCB/microphone can still be serviced/repaired.
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The
method of construction was also to cause problems
during servicing (See Later paragraph's - "Construction
Problems").
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One
of the disadvantages with the 600 series, is
that of the powering arrangement and the type of audio output,
used by the
microphones. The "Professional" type
3-pin connector, similar to that of the
"Din" family, carries the common
"Earth/0v", +48v power and an
"Un-Balanced" audio output. The +48v
feed not being Phantom derived, but a single rail
supply. This would not have presented any problem
back in the 1960's, as the microphone used it's
own PSU and "Phantom" powered
systems were only just coming into being. Now
however, those engineers who still use the 600
series microphones, would probably like to use
them on "Phantom" powered systems.
Without the disadvantage of an
"Un-balanced" audio output and the
requirement of having to use Calrec's "Special"
power supply units.
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There
are various methods of over coming this problem of
powering the 600 series microphones. I
manufacture a "Conversion
Lead", a nominal length of 4 Mtr's, to
overcome this problem. This then allows any 600
series microphone to be connected to a
"Standard" +48v phantom powered microphone
input. If required, the lead can then be extended
up to a maximum of 50 Mtr's, by the use of any
"Balanced" cannon to cannon microphone
lead.
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A
new PCB, using the same "Front-end" as
in the 600 series microphones, but with
conventional "Balanced" output, thus
allowing the microphone to work on
"Standard" phantom powered microphone is
currently under design. This will then be retro
fitted into the 600 series microphone's that
require such modification.
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Note
- All semi-conductor "Calrec"
microphones used the Suffix "C" or
"D" to donate the type of connector used
i.e. "C" for "Cannon" type and
"D" for "Din" (Touchal) types.
Alas, some models with "Cannon" types of
connectors, such as the 600 series for example,
might not be wired to the "Standard" one
expects to find. Always check first !!!
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The
"Ferrograph" C651 microphone ?
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A
Calrec
microphone that never made it into production, was
the C651. This microphone was specifically
designed for use, with Ferrograph series seven
tape recorders, thus being sold under the
"Ferrograph" name. The circuit, was
based around the CM600 series, with a few minor
modifications to the power rail and output
level/impedance matching. As any
"Ferrograph" series seven and
"Super" seven, owner is
aware, there is a Octal multi-way "Auxiliary"
connector on the connector panel of the recorder.
This provides the +48v supply required by the
"Ferrograph" C651 design.
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The idea of
the "Ferrograph" C651 microphone, all fitted
nicely into place ..... Ferrograph were sent 3
samples for evaluation. But sadly, the project never got
beyond that stage. Why, who knows ?
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However, user's of "Ferrograph"
series 7 and super seven machines, could/can still
use the Calrec 600 series microphones, with a few
small modifications etc.
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The
"Orange Hypercon" microphone
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This
microphone, manufactured by Calrec, was
designed for stage/vocalist use. Manufactured for
the "Orange Music" company, based in
London. A company known for the famous
"Orange" PA amplifiers of the 60's/70's.
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Cosmetically
and mechanically, the "Orange
Hypercon" was very similar to the Calrec
CM656, but used a "Tighter" Cardioid capsule.
The polar pattern almost being a hyper cardioid,
hence the name "Hypercon".
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Judging
from the amount of these microphones that I have received
for servicing, sales of the microphone must have
been quite good.
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Note
- The "Orange" amplifiers, designed by
Matthew Mathias, were made by Cliff Cooper in
Huddesfield (Gt. Britain), a town very close to
that of Hebden Bridge, home to Calrec microphones.
It's a small world !
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A
"Simms-Watts" microphone
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Yet
another microphone manufactured by Calrec, was
designed for the famous "Simms-Watts"
London based music company. Alas, I have little
information on this product and as yet, I have
never had the pleasure of seeing one "In the
flesh". However I do have a picture,
showing a typical example.
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700
series
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Lesser
well known, is the 700
series of "Self contained" battery
powered "True" capacitor microphones.
Rather than the "Electret" types so
often found today. The 700 series microphones,
were based around the two different
"Pre-amplifiers". One being the CB7C,
with a "Cannon" type connector, the other being the
CB7D, with a "Din" type connector. Both types used in conjunction
with the CC75* series of inter-changeable capsules i.e. Omni,
Cardioid, and Cardioid with bass roll-off, the
later being mounted
in a wire mesh windshield. Thus
offering great versatility and making the 700
series ideal for use with
portable recording equipment.
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The
battery consisted of 6 x 625 type
"Button" cells, giving a total of 7.5v.
For ease of use, these could be
"Stacked" together and fitted inside the
case of an old AA size battery. This would then
fit neatly into
the microphone.
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As
the power source was only 7.5 volts, then some
form of "Step-up" system was required,
to give around 50volts, to "Polarize"
the capsule. A minature DC to DC converter would
be used for this application. Much of the design work,
for the DC to DC
converters, was assisted by Peter Baxendall.
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Although
the 700 series was an excellent design,
"Battery" powered microphones were not
so eagerly accepted by the potential end user's,
as Calrec had anticipated. Sales of the 700
series, would prove to be very disappointing.
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Note
- External powering of the 700 series is possible,
but involves the fitting of a "Shorting
Link" in the place of the normal battery. The
microphone is then powered from an external
source, much like the 600 series. In the case of
the 700 series,
"Earth/0v", - 7.5v power and an
"Un-Balanced" audio output.
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800
series
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Very
similar to the 600 series microphones i.e. Using
the same, fixed capsule design. The important difference,
with the 800 series, being the use of a transformer
coupled "Balanced" audio output, therefore
allowing the microphones to work on +48v
"Phantom" power. Making these
microphones ideal for use in Radio, TV and
Recording Studios.
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900
series
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The 900 series is
also very
similar to the 600 series microphones i.e. Using
the same, fixed capsule design. However, the 900 series
was designed for use on "Modulation
Lead" powering. (DIN 45 595 standard), also known as
"AB" or "T" powering.
Whereby the nominal 12volt supply is feed directly
to the send/hot and return/cold wires of the
"Balanced" output of the microphone.
This being a system of powering used by many of
the "European" countries at this time. This method was
employed by many other microphone manufacturers e.g. Neumann's KM70 series and
some of the Sennheiser models. The 900 series microphones
would be ideal for use in "European" Radio, TV and Recording Studios. Not forgetting
the compatibility with portable recording
equipment, from companies such as "Nagra".
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The 900 series,
was manufactured between 1973 - 1980 . Just
like the 700 series, sales of the 900 series,
would also prove to be a disappointment.
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1000
series
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There
are 2 "Versions" of the 1000 series
microphones i.e. The "Original" types,
with detachable capsules, and the "Later"
models, with fixed capsules.
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"Original" 1000
series
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The
"Professional" 1000
series, was to
replace the older "Fi-Cord" (Calrec)
FC1200, FC1200a and the "Original"
Calrec CM1050, which were all valve (Nuvistor)
type microphones. The design of the 1000 series, employees a separate
body (Pre-amplifier) together with a detachable
Capsule. The body i.e. CB1000, contained the Impedance
converter/Pre-amplifier for the associated
Capsule. This PCB, being held in place by locking
screws mounted in the cannon socket assembly. The microphone worked on
"Phantom" power and therefore the audio
feed was in "Balanced" form. The output
connector being of the now "Standard"
cannon type, as opposed to the
"Professional" Din type used on the 600
series..
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A
choice of Capsules were
available for use with the CB1000 body e.g.
CC1050, cardioid type.
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Again,
from a service engineers view, these
"Early" examples of the 1000 series,
used the best "Construction" design/technique,
employed throughout the entire history of Calrec
microphones. The microphone being very easy to
dismantle i.e. By simply undoing 3 small screws around
the socket end of the microphone. Somewhat
different to other Calrec microphones produced throughout
the years, whereby a special jig is required to
"Break" the glued seal, used to hold the
assembly together. All of the
components, mounted on the 1000 series PCB, are easily
accessible for service purposes. Access to the capsule is quite straight
forward, to allow for cleaning etc. A great design
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"Later"
models of the 1000
series and "Construction
Problems"
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In
an attempt to keep costs down, the later models
of the 1000 series were to utilize, fixed
capsules. There were 3 different models available;
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CM1001
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Hand
Held Omni i.e. Built in Pop Filter
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CM1050
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Cardioid
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CM1051
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Bass
Roll-off Cardioid
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Alas,
later models of the 1000 series, along with the majority
of the other models, were to use the "Glued
Together" method of construction (A service engineers complete
nightmare), rather than the screwed together
method of the "Early" 1000 series. It proves
to be so easy to damage the housing tube, when dismantling the
"Later" 1000 series microphones. Therefore
requiring a new housing tube to be fitted during
reassembly after repair/servicing. Not only was
the case "Glued Together", but ..... an expanding brass "Locking Ring",
holding the PCB and Capsule in place, was
also glued into
the microphone housing tube. The glue needs to be completely
removed from the expanding ring, to allow
access to the locking "Grub Screw",
which often proves very difficult to undo.
So, when the housing tube and lock ring are
completely free of any traces of glue, the PCB can
finally be withdrawn
from the housing tube, to enable the required work
to take place. All of this "Messing
About" being very "Time Consuming"
and not very cost effective, but it still has to
be done !
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When
a microphone of this type is serviced, then during
"Final" reassembly of the socket to the housing tube, a
modification is carried out. This involves drilling and tapping a hole in the socket
assembly, together with a locating hole in the
housing tube. Then using a small grub screw, to
hold the microphone parts securely
together. Thus,
if required, the unit can be easily dismantled for
future servicing etc.
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The
internal assembly of the microphone i.e. PCB and
Capsule, is "Pushed" together and held
under tension via a "Brass" expanding
ring. This "Brass" expanding ring, used
on many of the various PCB's
used in Calrec microphones, expands sufficiently via the
grub screw insert, therefore not to warrant being
re-glued back in place.
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Finally,
the 2000
and 2100 series
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Like
the "Original" 1000 series, these
microphones used separate bodies (Pre-amplifiers)
and capsules. Alas, the PCB was not held in place
by screws, but rather by being "Glued"
in place like the "Later" 1000 series. A choice of two bodies were
available, both being "Phantom" powered.
One being the CB20, designed specifically for +48v
working, and the other being the CB21, designed to work on
supplies between 7.5 v < 52v. The circuit (PCB) of
the CB21, employing a DC to DC oscillator, to
provide "Constant" HT potentials within
the microphone, over a very wide supply voltage
range.
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A
choice of no less than 5 different capsules were
available for use with the CB20 and 21 bodies;
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CC01
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Hand
Held Omni i.e. Built in Pop Filter
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CC03
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Studio
Omni
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CC50
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Cardioid
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CC51
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Bass
Roll-off Cardioid
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CC56
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Bass
Roll-off Cardioid mounted in a Wire Mesh
Windshield
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Many
of these microphones, were to be purchased by the
BBC. A excellent recommendation, if ever
there was !
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"Valve"
version of the 2000 and 2100 series
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The
FET CB20 and CB21 microphone bodies work very
well. However ..... a "Valve" version
would be a very welcome addition. Therefore, after
spending many hours designing, and carrying out an
apparent endless amount of listening tests, a
"Valve" version of the CB20 and CB21
microphone bodies, is now available.
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For
more information on the RMB-2021, please refer to
the "Replacement
Microphone Body" page.
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Other "Calrec" Microphones - "Talkback" and "Test and
Measurement"
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During
the many years of microphone production, Calrec
also manufactured
"Talkback" and "Test and
Measurement" microphones.
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Below
is a list of some of "Talkback" microphones,
and the CM15 "Test and Measurement"
microphone, that Calrec manufactured. The later
being used by Klark Teknik, known as the AT1, for
use with there excellent spectrum analyzer unit.
The list also gives details of the respective
powering requirements and other information.
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CM10
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+7.5 to +52 volt "Phantom" / Also known as the
AT780 / Uses 2100 series PCB
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CM11
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+7.5 to +52 volt "Phantom" / Uses 2100 series
PCB
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CM12
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+48 volt
(Not Phantom) / Uses 600 series PCB
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CM15
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+9
to +24 volt "Phantom" / Also known as
the Klark
Teknik AT1
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CM16
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Powering
requirements are unknown / Mini-mixer Microphone
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CM17
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+7.5
to +52 volt "Phantom" / Uses 2100
series PCB
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CM20
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+48 volt
"Phantom" / Cardioid with bass roll-off
/ Mounted on 100mm stem
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CM21
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+48 volt
"Phantom" / Cardioid with bass roll-off
/ Mounted on 200mm stem
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CM22
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+48 volt
"Phantom" / Cardioid with bass roll-off
/ Mounted on 300mm stem
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CM23
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+48
volt "Phantom"
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CM24
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+48 volt
"Phantom" / Cardioid with bass roll-off
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CM25
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+48 volt
"Phantom" / Cardioid with a flat
response
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CM26
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+48
volt "Phantom" / Cardioid with bass
roll-off / Mounted on 450mm stem
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Many
of the above microphones are identical, both
cosmetically and sonically, to their
"Conventional Use" look-a-likes. The
main difference being in the way the microphone is
physically mounted to the associated Mixing
Console.
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The "End
of an Era"
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During
the late 1980's, Calrec discontinued the
manufacture of "Conventional"
microphones. Only to continue production of the
"Soundfield" microphone.
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Production
of the 1000 and 2000/2100 series,
together with the servicing of Calrec/Fi-Cord microphones,
was
taken over by an ex-employee, Keith Ming i.e. "Hebden
Sound". Sadly
Keith passed away in 2002 and production of "Hebden Sound" microphones ceased.
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There
was continued
production of the Calrec designed CM1050 and CM1051 microphones, for a short time, by David Anderson of "Bridge
Microphones".
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My
connection .....
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I
had known Keith for many years, and we would refer
"Clients" to one another, as you do.
Over which time you build up, not only a working
relationship, but a personal friendship.
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Sadly,
Keith
was only too aware of the condition of his health.
He approached me some months before he passed away,
asking if I would be interested in taking over
the servicing of Calrec
microphones. This I willingly accepted.
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I
was to be given many folders of "Documentation",
relating to Calrec microphones e.g. Circuits, together with a
wealth of "Historical" information about
the design and testing of various microphones
throughout Calrec's long history.
Without this vast background of knowledge, I could
not have written the information contained within
the "Calrec" pages of this site.
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