Neumann M149 Amplifier Tube Microphone Operating Instructions

: June 13, 2024
: Neumann

Table of Contents

Neumann M149 Amplifier Tube Microphone
Description
Getting Started
Microphone Cables
Technical Specifications
Frequency Responses and Polar Patterns
Accessories
FAQs
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Neumann M149 Amplifier Tube Microphone

Neumann-M149-Amplifier-Tube-Microphone-product

Description

The M 149 Tube is a large diaphragm studio condenser microphone with nine switchable polar patterns: omnidirectional, wide-angle-cardioid,cardioid, hyper-cardioid, figure-8, with an additional the intermediate pattern between each of the aforementioned standard patterns. The input stage is a vacuum tube (valve) with the sound properties unique to this type of device.

The M 149 Tube is characterized by

very low inherent self-noise and a wide dynamic range
a newly developed circuit design with a vacuum tube input stage and a transformerless output stage
the full, rich, and warm sound of a tube microphone.

The microphone has a balanced transformerless output and is powered by the included power supply unit. The front of the microphone is designated by the Neumann logo. On the back is a seven-stage highpass filter switch whose cut- off frequencies can be selected in half-octave steps between 20 Hz and 160 Hz.

The M 149 Tube Condenser Microphone

The M 149 Tube is a switchable pattern condenser microphone. It is equipped with the legendary dual-diaphragm capsule made famous in the U 47 and M 49 microphones (“M 7 capsule”). The M 149 Tube can be switched to nine different pick-up patterns and can thus accommodate a very large range of recording situations. It is, like its predecessors, especially suited to speech and vocal recording. This is not only due to its capsule design but also because of the extremely low inherent self-noise level.

A vacuum tube is used as the input stage of the M 149 Tube. Unlike earlier tube microphones which needed a transformer-coupled output stage, the M 149 Tube uses a transformerless output stage. This circuit design – proved to be effective in the “TLM” series of microphones – is especially insensitive to capacitive (cable) loads. The microphone can therefore be connected to long cables without the risk of high-frequency distortion. Also due to the transformerless circuit design the sound of the medium and lower frequencies is entirely determined by the capsule and the tube. Earlier tube microphones used a transformer which affected the sound quality depending on the volume, the frequency, and the load. The transformerless circuit design of the M 149 Tube provides a very good common mode rejection factor just like a transformer. It effectively attenuates signals influencing the balanced audio signal.

In addition to the polar pattern switch, the microphone features a seven-step high-pass switch for altering the cut-off frequency (–3 dB) in half-octave steps between 20 Hz and 160 Hz. Thus, impact noise or noise from air- conditioning systems is effectively muted. Moreover, this switch allows to finely vary the characteristics of the audio signal, e. g. when close-miking a voice (proximity effect).

The M 149 Tube has a sensitivity of approx. 50 mV/Pa. Due to the 10 dB amplification of the capsule signal by the tube, it delivers an output signal that is 10 … 15 dB higher than that of conventional studio microphones. Thus, the sound of the M 149 Tube is exclusively determined by these components, not by the following filter and output stage. Despite the microphone‘s high sensitivity, its inherent self-noise is exceptionally low: the noise level is 3 … 5 dB lower than that of comparable tube microphones. The head grille of the M 149 Tube has the same shape as that of the M 49, but it is acoustically more transparent and thus achieves a more neutral sound. A dome underneath the capsule defl ects away sound from the upper hemisphere to avoid any interference with the direct sound caused by internal reflections. The capsule is elastically mounted to protect it against handling and structure-borne noise.

Additional Information on the M 149 Tube Circuit Design

In contrast to other tube microphones, the M 149 Tube uses a combination of a specially selected triode and state-of-the-art circuitry. The developers‘ aim was both to utilize the advantageous properties of a vacuum tube for amplifying the capsule signal and to exclude any interference from other parts of the circuitry when the amplified signal is fed to the microphone output. This is why the M 149 Tube – unlike conventional tube microphones – does not use an output transformer but an integrated amplifier to drive the different output loads. This special audio amplifier features an extremely low, low self-noise and high current capacity.

Thus, the vacuum tube is entirely decoupled from the microphone output, and the typical tube characteristic can be used for processing the highest input signal levels. In contrast to conventional tube microphones, the high output current of the M 149 Tube allows cable lengths of up to 300 m without risking a deterioration of signal quality. The tube amplifies the capsule voltage by about 10 dB to exclude any remaining impact of the electronics on the microphone signal. Despite this amplification, the dynamic range of the M 149 Tube remains very wide as the microphone delivers a peak output voltage of ± 10 V at 20 mA. During its entire life, the operating point of the tube is kept stable. This refers both to the anode current and to the heater voltage which is stabilized by a control loop in the power supply unit. Cable losses of up to 4 V DC – which corresponds to a cable length of approx. 100 m between the microphone and the power supply unit – are detected and compensated for by a sensor line. A breakdown of this line due to a short-circuit or an open circuit is not dangerous as the heater voltage would automatically be reduced and all other voltages switched off . To ensure a long life, the tube is heated very gently by current limiting with foldback characteristics.

The operating voltages for the M 149 Tube are delivered by the power supply unit using a switching regulator. Analog pre-controlling and two-stage active filtering at the switching regulator‘s output ensure high-quality operating voltages with a minimum of unwanted interfering voltages. The AF output of the power supply unit is provided with special protective circuitry so that the microphone can be connected to audio inputs with 48 V phantom powering without any problems. The load on the phantom source will be approx. 1 mA.

Getting Started

The M 149 Tube comes complete with KT 8 eight-core microphone cable, power supply unit, and elastic suspension EA 170 in an aluminium case. The stand connector of the elastic suspension EA 170 has a 5/8″-27 internal (female) thread and comes complete with an adaptor to convert to 1/2″ and 3/8″ threads. A cloth dust cover is included to protect the microphone capsule. This provides breathable, effective protection against contamination if the microphone goes unused for long periods. When hooking up the microphone, the order in which the cables are connected does not matter. A sensor in the power supply ensures that the operating voltages are not run up until the microphone is connected properly. The LED on the power supply then changes from a low glow to shine brightly. Within a few minutes, at the latest, the tube in the M 149 Tube reaches its stable operating condition and then evidences its particularly low residual noise level.

When switching the directional characteristic, an elevated noise floor can be noticed for 30 s max. This is due to the reloading of the capsule to the appropriate polarization voltage. External phantom power, if present, does not detract from the performance of the M 149 Tube. If an external phantom power source is switched on or off , only a short, slight rise in the residual noise level will result. The on/off switch of the power supply functions as a secondary voltage interrupt for the feeds from the built-in mains unit. To save energy, the power supply should be unplugged from the wall outlet if it goes unused for an extended period. To protect the microphone in close miking applications we recommend using a pop-screen PS 15 or PS 20 a. For details, see the topic “Accessories”.

Type and Confi guration of the Microphone and Power Supply Outputs
The following versions of the M 149 Tube microphone are available:

M 149 Tube (EU) …….ni ………..Cat. No. 08390
M 149 Tube (US) …….ni ………..Cat. No. 08399
- M 149 Tube (UK) …….ni ………..Cat. No. 08403

The microphone is finished in matt nickel. The 8-pin connector of the microphone and the corresponding connector of the power supply unit have the following confi guration:

Pin 1: –70 V
Pin 2: +5 V
Pin 3: audio signal (+phase)
Pin 4: +70 V
Pin 5: sensor line
Pin 6: ground
Pin 7: +32 V
Pin 8: audio signal (–phase)

The included eight-core cable connects the microphone to the power supply unit. At the power supply unit, the audio signal is available at a 3-pin XLR socket which requires an XLR 3 F connector. The microphone is wired as per DIN EN 60268-12 or IEC 60268-12: An increase in sound pressure at the microphone‘s front diaphragm produces a positive voltage at pin 2.

Microphone Cables

The following cables are available for the M 149 Tube:

KT 8 (10 m) ……….. blk …………..Cat. No. 08407
(included in the supply schedule)

Cable for M 147/149/150 Tube, with a double twist (double helix) braiding as shield. Ø 5 mm, length 10 m. DIN 8 connectors.

IC 3 mt ……………. blk …………..Cat. No. 06543

Microphone cable with a double twist (double helix) braiding as a shield. Ø 5 mm, length 10 m. XLR 3 connectors, matte black.

Custom-made cables are available on request. The microphone is especially insensitive to capacitive loads. Even the use of long cables does not cause TIM or frequency response distortions. Thus, the audio signal cable can have a length of up to approx. 300 m, the 8-core connecting cable between the microphone and the power supply unit can be as long as approx. 100 m.

Power Supply Unit
The N 149 A power supply unit is available in the following versions:

N 149 A EU ……… blk …………..Cat. No. 08447
N 149 A US ………. blk …………..Cat. No. 08446
N 149 A UK ………. blk …………..Cat. No. 08448

(included in the supply schedule)

The three available versions of the N 149 A just differ in their enclosed main power cable.

Operation with Unbalanced Inputs
At the power supply unit, the audio signal is available at a balanced XLR 3 output. The microphone is wired as per DIN EN 60268-12 or IEC 60268-12:

Pin 1: 0 V/ground
Pin 2: audio signal (+phase)
Pin 3: audio signal (–phase)

So pin 2 is the “hot phase”, pin 3 must be connected to the ground when used with unbalanced inputs

Technical Specifications

Acoustical op. principle ………..Pressure gradient transducer
Polar pattern ………….Omni/wide-angle cardioid/ cardioid/hyper-cardioid/fi gure-8 and 4 additional intermediate patterns
Frequency response ………………… 20 Hz…20 kHz
Sensitivity1) ………………………..34/47/62 mV/Pa2)
Nominal impedance ………………………….50 ohms
Nominal load impedance ……………… 1000 ohms
Signal-to-noise ratio3),
- CCIR4) ……………………………………66/69/71 dB2)
Signal-to-noise ratio3),
- A-weighted4) …………………………..78/81/83 dB2)
Equivalent noise level,
- CCIR4) ……………………………………28/25/23 dB2)
Equivalent noise level,
- A-weighted4) ………………………..16/13/11 dB-A2) Max. SPL (tube characteristic)5)
for THD < 0.5 % …………………………………120 dB
for THD < 5 % ……………………………………136 dB

The dynamic range of the amplifier (cardioid) A-weighted5)

for THD < 0.5 % …………………………………101 dB
for THD < 5 % ……………………………………121 dB
Max. output voltage ……………………………18 dBu
Power supply ……………………………… N 149 (A/V)

Required connectors:

Microphone ……………..Binder 8-pin (DIN 45326)
Power supply unit ……………………………… XLR 3F
Weight…………………………………….approx. 730 g
Dimensions …………………….. Ø 70 mm x 201 mm

94 dB SPL 1 Pa = 10 μbar 0 dB 20 μPa

at 1 kHz into 1 ohm rated load impedance.
Polar patterns: omni/cardioid/figure-8
re 94 dB SPL
according to IEC 60268-1;
- CCIR-weighting according to CCIR 468-3, quasi-peak;
- A-weighting according to IEC 61672-1, RMS
THD of the microphone amplifier at an input voltage equivalent to the capsule output at the specified SPL.

Frequency Responses and Polar Patterns

Neumann-M149-Amplifier-Tube-Microphone-fig-2

Hints on Microphone Maintenance

Use a dust cover: Microphones not in use should not be left on the stand gathering dust. This can be prevented by the use of a non-fluffy dust cover. When not in use for a longer period, the microphone should be sealed against dust and stored under standard climatic conditions. Use a pop screen: A pop screen not only prevents the occurrence of plosive pop noises in vocal recordings but also efficiently prevents unwanted particles, from respiratory moisture to food remnants, from settling on the diaphragm. Avoid the use of old windshields: As the foam material of a windshield ages, it can become brittle and crumbly. Instead of protecting the microphone, an old windshield can thus lead to the soiling of the microphone capsule.

Therefore please dispose of worn-out wind shields. Function testing: Although modern condenser microphones are not harmed by high sound pressure levels, one should under no circumstances use a pop-test to check whether the microphone is connected and the channel on the mixing console is pulled up, since this can result in sound pressure levels of over 140 dB! Normal speech is quite sufficient for function testing. Do-it-yourself repairs can be expensive! Unfortunately, do-it-yourself repairs sometimes do more harm than good

. Cleaning soiled capsules in particular requires considerable experience and an expert touch. The protective lacquer on circuit boards indicates, among other things, places that must not be soldered. Certain components are specially selected and cannot be replaced by standard parts. To avoid unnecessary expense, we recommend sending defective microphones to us or our representatives for servicing. Regular inspections: Sending in microphones regularly for inspection, as practiced by some theaters and broadcasting corporations, can aid in the early detection of damage. Slight soiling can be removed much more easily than a nicotine layer inextricably bonded to the diaphragm. Regular inspections are particularly recommended for microphones that are rented or are used in dusty or smoky environments since the costs are low in comparison with the cost of a major overhaul

Accessories

Table and Floor Stands
MF 3 ………………… blk …………..Cat. No. 07321
The MF 3 is a table stand with an iron base, 1.6 kg in weight, and 110 mm in diameter. It has a black matte finish. The bottom is fitted with a non-slip rubber disk. The stand comes with a reversible stud and an adapter for 1/2″ and 3/8″ threads.

MF 4 ………………… blk …………..Cat. No. 07337
Floor stand with grey cast iron base. The floor stand has a matt black finish and rests on a nonskid rubber disk attached to the bottom. A reversible stud and a reducer for 1/2″ and 3/8″ threads are also supplied. Weight 2.6 kg, Ø 160 mm.

MF 5 ………………… gr …………….Cat. No. 08489
Floor stand with grey soft-touch powder coating. It has a non-skid sound- absorbing rubber disk attached to the bottom. The stand connection has a 3/8″ thread. Weight 2.7 kg, Ø 250 mm.

Stand Extensions

STV 4 ……………….. blk …………..Cat. No. 06190
STV 20 ……………… blk …………..Cat. No. 06187
STV 40 …………….. blk …………..Cat. No. 06188
STV 60 …………….. blk …………..Cat. No. 06189

The STV… stand extensions are screwed between microphone stands (for example MF 4, MF 5) and swivel mounts (for example SG 21/17 mt). Length 40, 200, 400 or 600 mm. Ø 19 mm.

Elastic Suspension

EA 170 …………….. ni …………….Cat. No. 07271
EA 170 mt ………… blk …………..Cat. No. 07273

(included in the supply schedule)
The EA 170 is designed for the TLM 170 (R) and M 149 Tube microphones. It has a swivel mount with a 5/8″-27 female thread, plus a thread adapter to connect to 1/2″- and 3/8″ stands.

Auditorium Hangers

MNV 87 ……………. ni …………….Cat. No. 06804
MNV 87 mt ………… blk …………..Cat. No. 06806

The auditorium hanger consists of a cable suspension and a rotating 1/2″ threaded stud, to connect to e. g. swivel mounts. The stud is screwed into the threaded coupling of the swivel mount. Then the microphone can be tilted while it is suspended from its own cable.

Pop Screen
Pop screens provide excellent suppression of so-called pop noise. They consist of a round, thin frame covered with black gauze on both sides. A gooseneck of about 30 cm (12″) in length is mounted at the popshield. It will be attached to microphone stands by means of a clamp with a knurled screw.

PS 15 ……………… blk …………..Cat. No. 08472
- The frame is 15 cm in diameter.
PS 20 a ……………. blk …………..Cat. No. 08488
- The frame is 20 cm in diameter.

Further articles are described in the catalog “Accessories”.

Neumann-M149-Amplifier-Tube-Microphone-fig-3

Limitation of Liability
Georg Neumann GmbH shall not be liable for consequences of an inappropriate use of the product not being in compliance with the technical allowance in the user manual such as handling errors, mechanical spoiling, false voltage and using other than the recommended correspondence devices. Any liability of Georg Neumann GmbH for any damages including indirect, consequential, special, incidental, and punitive damages based on the user’s non-compliance with the user manual or unreasonable utilization of the product is hereby excluded as to the extent permitted by law. This limitation of liability on damages is not applicable for the liability under European product liability codes or for users in a state or country where such damages cannot be limited.

Declaration of Conformity
Georg Neumann GmbH hereby declares that this device conforms to the applicable CE standards and regulations. Neumann is a registered trademark of Georg Neumann GmbH in certain countries.