U47 - U87 series
with Neumann's "Famous" U47
U47 microphone is found with various different
badges on it's housing, other then that of the
manufacturer, Neumann. Sometimes found with
Telefunken or Seimens badges. In the early days,
Neumann was a small company with little marketing
outlets. Therefore, like other small companies,
Neumann distributed the microphone through other
big named companies. These companies then placed their
own badges on that product.
letter U, designated the use of a
"Plug-in" type of valve.. Neumann also
used other letters, M being used for microphones
with wire ended valves e.g. MSC2 or AC701k types.
Being soldered into place, as seen in the M49 and KM54 for example. With the letter K, standing for
the case of the U47 microphone, it would be the famous Telefunken
valve, which was originally designed for use in
portable radio receivers. Early versions, of the
U47, had the output matching
transformer mounted "up-right", rather
then "laying flat" as on all the later
versions. Sometime after the change in transformer
mounting, the housing tubes were shortened. Hence
the long and short models we now find. The U47 had
just 2 polar patterns i.e. Cardioid and Omni. The
U48 microphone, was basically the same as the U47,
with Cardioid and Fig'8 polar patterns.
the later years of production, the VF14 valve
became increasing hard to find. Neumann decided to
use a "Nuvistor" type of valve, i.e.13CW4, a "Triode", in it's place. A
modification to the PSU was required, as the 13CW4
required a greater filament current. Together with
an adaptor socket for the 13CW4, with additional
components, to fit into the original valve socket.
Unfortunately, the 13CW4 "Nuvistor"
version would never find the popularity of it's
VF14 based predecessor. The sound between
the VF14 and 13CW4 versions, is quite different.
Both types having their own followers.
"Retro" modification is available, that
converts a 13CW4 working microphone / PSU
combination, back to the "Original" VF14 (RV-14m)
working. For further information please see "Modification".
"Replacement Valve" for the VF14m
have serviced many U47's over the past 25 years or
In that time, I have tried to find a suitable
replacement for the VF14 valve, with no joy. Some
U47's have come through for servicing, fitted with
a whole variety of different valves. You can
"Get by" using an EF14 or UF14, with
suitable PSU modifications, but the VF14 will
always sound the best of the bunch. Even
"Good" examples of the EF14 and UF14 are
becoming difficult to find.
you own a U47/48, then surly you expect to obtain
the "Original" sound qualities from it.
Therefore, with the VF14 being "Obsolete", I decided to produce a
"Replacement", namely the RV-14m.
Thankfully, the sound of the U47 should be here
for many years to come.
Feedback", for comments on the sound
quality of the RV-14m valve.
information on the RV-14m, please refer to the "Replacement
phantom powered version of the U47 was introduced
in the early the 1970's. Known as the U47fet.
There were two models, one being the U47fet, with
"Tuchel" (Din) type connector, and
the other being the U47fet i, with "Switchcraft"
(Cannon) type connector. The circuit/electronics were quite complicated,
using some 7 transistors, one being an FET. Sounding quite different
to it's older valve counterpart, the U47fet found
many applications, especially in broadcast
circles. The U47fet is now becoming almost as
collectable/sought after, as it's valve predecessor.
modern day, valve version, of the U47 was to
emerge in the late 1990's. To be known as the M147. Alas, the
are of a hybrid design and therefore the M147 sounds very
different to the U47 we all know so well. Using
the same miniature "selected" VHF double
triode, type 6111WA, as found in the Neumann M149.
The use of an output matching transformer has been dropped,
in favor of a modern electronically balanced output stage.
happened to the U57
never manufactured a U57 microphone. Maybe due to the
fact that Neumann Gefell, the other half of
Neumann and yet another story, produced the UM57. The choice of valve,
would be the 6AB4/EC92 miniature
"Triode". The UM57, used the
same M7 capsule as the U47, and provided the user
with 3 remotely controlled polar patterns i.e.
Omni, cardioid and fig'8. Therefore, the sound is closely related to that
of the U47, other then the tonal qualities
generated by the different valve and, slightly
modification is available, that allows the UM57 to
operate as a U47, together with the benefits of
remote polar pattern control. For further information
please see "Modification".
microphone that should not be forgotten, is the
small U64 "Pencil" microphone. The
circuit/electronics being based around the 7586
"Nuvistor" type valve. The U64 maybe not the
most memorable microphone that Neumann manufactured,
however, it's acoustic qualities are useful for
1960, we saw the introduction of the U67. Just
like the U47, the circuit/electronics
of the U67 utilized a "Pentode"
type valve. This time, however, using a modern
"Miniature" plug-in EF86. Through the
production years of the U67, the EF86 was to be superceded
by the EF806S,
a low-noise and low microphonic version of the EF86..
Together with a new
capsule design, namely the KK67, the U67 would
have a sound all of it's own. The new components
that formed the U67, were all mounted in a
new look housing assembly, this would be used for
many years and models to follow. We would also see
the use of various
connectors used for the range of microphones
using this new housing..
limited number, of the U67, were re-issued in the
mid' 1990's. Using the same circuit/electronics
, with modern day components. It was good to see
an genuine re-issue, and not a modern day
"Modified/Re-designed" version of an old
classic, such as the AKG C12VR.
semiconductor era was upon us, but alas there was
nothing available to replace the high input
resistance of a valve, for some years to come.
However, when the FET (Field effect transistor)
finally arrived, Neumann were quick to utilize
it's electrical properties. The U77
was to be
Neumann's first, large capsule, transistor based
microphone and would still use the
"Proven" KK67 capsule from the U67 era.
utilised the ever popular 2N3819 or 2N4302, for
impedance conversion. Designed to work on external
power and/or built in battery (9
volt type). Enabling the microphone to be used
with portable equipment or with desks/mixers that
did not have a suitable power source. During this time, the mid' 1960's,
microphone powering was that of the
"Modulation Lead" type. More commonly
known as AB or "T" powered format.
Whereby, the 12v dc supply required by the
microphone, is supplied through the Send/Hot
(+12v) and Return/Cold (0v) wires of the balanced
audio cable. The screen being purely, a screen and
not the zero volt return path, as it is on the
"Phantom" power principle of to-day.
Running at such low voltage, the microphone used a
DC to DC converter, to generate the polarizing
voltages (+/- 60 volts) require by the capsule.
Previously, in the U67 for example, the polarizing
voltage was derived from the microphone's HT supply. Through the principle of design and
operation, when using "Modulation Lead"
powering, there is no need for an output
transformer. The audio signal is simply
"Filtered off" at the power supply end
of the cable. In the case of the Neumann design,
this was carried out via capacitors, some
manufactures used a capacitor coupled transformer
arrangement. The sound quality of the U77, is
somewhat "Dry" and "Clinical",
when compared to that of the U87. A typical character
to that obtained from other microphones powered in
this fashion. A sound, not so far away from that
found in modern day transformer-less designs.
the late 1960's we saw the introduction of the
"Famous" U87, designed to work on +48v
phantom power and/or built in batteries (2 x 22.5
volt types). Like the U77, this enabled the microphone to be used
with portable equipment or with desks/mixers that
did not have phantom power. The U87
would use a new, "Double" back-plate,
type of capsule i.e. KK87. Giving improved polar
patterns/frequency response. The circuit/electronics were
based around a single transistor (FET), 2N3819 or
2N4302. The U87 design was straight forward and
simple, with a transformer coupled output. Over
the years, various changes to the electronics took
place. Most of which, to improve the stability of
the internal working voltages. Capsule polarizing
voltages were derided from the +48v phantom
we see the U87a, an improved version of the
original U87. However, like so many discontinued
items, many engineers still prefer the sound of
the original U87 (especially the early ones). One
reason for this, could be that the U87a uses the
KK67 capsule, re U67/U77, thus giving the U87a a
somewhat different sound to the original U87. The
are very similar to that of the
original U87, other then addition of a DC to DC
converter used to generate the higher capsule polarizing
voltages (+/- 60 volts). Thus giving the
microphone a lower noise figure then it's predecessor.
we ever see a U97, and what would the improvements
be, or is the U87a the "end of the line"
of such an historical series
forgetting the U89
would be incorrect for me not to include the U89
microphone in this list. Looking much like a smaller
version of the U87. The
are very similar to that used in the U87a
microphone. However, the U89 microphone uses the
KK89 capsule, which is slightly "Smaller" than that used in the U47/67/77/87 series.
KK89 capsule deviates from Neumann's
normal approach to larger capsule design i.e. the sputtered gold,
used to form a
electrically conductive surface, covers the entire
the diaphragm. Electrical contact with the diaphragm,
is made via
Ring" of the diaphragm mounting, much
like that on the AKG CK12
capsule. Whereas on other large capsules, such as
the KK87 used in the U87, the sputtered gold used
to form a
electrically conductive disc, is somewhat smaller than the
overall diameter of the diaphragm. Therefore leaving an insulated boarder around the
"Working" edge of the diaphragm. The
capsule then requiring a "Centre
Screw" to make electrical contact with the
diaphragm. Other than the difference in
size between the two types of capsule, then the design,
with respect to the electrical
connection, obviously effects the way in which the
diaphragm moves. Thus contributing to the
"Difference" in sound quality between
capsule, and that of the
"Centre Screw" type capsules.
the rest ......
could include the modern TLM range of
"Large" capsule microphones e.g. TLM193,
but for me ..... I am not so sure that the modern
models, will ever have the same type of following
as that received by the majority of the microphones above.
balanced output stages, such as that used in the TLM193,
"Do the job". But ..... what ever has happened to the musical "Signature"
given by the
output matching transformer ...... ?
technology has it's uses, for sure ..... but some
changes are not always such a good move. Sadly, it
is probably all down to how cheap a product can be
produced, rather than how good it
"Could" actually sound.