IBF-Akustik IBF-MP1r User manual

IBF-MP1r Microphone Preamplifier
User Guide
IBF-MP1r
microphone preamplifier
User Guide
Draft 1, June 2002
(C) Wolfgang Frank
Ingenieurbuero f. Akustik, Elektronik, Messtechnik
Alexanderstr. 66
68519 Viernheim
Germany
Tel. [phone]
Fax. [phone]
[e-mail]
www.ibf-akustik.de
Design and Specifications are subject to change without notice. Ask factory for technical specifications before
purchase and/or use. Whenever a doubt about safety issues arises from this product, please inform us
immediately for technical consultation.

Contents
ÀQuick Guide to using the MIC-Amp
ÀIntroduction
ÀGeneral Description
ÀInstallation
ÀLocating the unit
ÀSignal connections
ÀOperational Notes
ÀPower Switch
ÀBias Supply
ÀClipping Indicator
ÀAcoustic Calibration Procedure
ÀPower Output
ÀBatteries and external Voltage supplies
À
ÀAppendices
ÀControls, Connectors and Indicators
ÀGAIN Control
ÀMIC IN / LINE IN
ÀLINE OUT
ÀPower Out
ÀPOWER LED
ÀLow Battery Indicator
ÀCLIPPING INDICATOR LED
À94dBspl-LED
À-10dBV-LED
ÀPOWER Switch
ÀBias Supply Coding
ÀBATTERY Compartment
ÀSpecification
ÀCE Conformity Statement
ÀLimited Warranty
ÀSafety Clause And Unauthorized Applications

Quick Guide to using the MIC-Amp
All of us get in a hurry to use a new device. We want you to fully understand how to
use the mic amp and avoiding user faults.
Step 1
Open the batterie compartment and connect the batterie, accumulator or external voltage supply unit.
Note: The mic-amp has a build in reverse polarity protection avoiding damages caused by voltage supplies
with wrong configurated ouput voltage polarity
Step 2
Check the power switch position and make sure it is in the off state. The power switch is part of the
potentiometer function..
Step 3
Set the gain potentiometer to mid gain.
Step 4
Using shielded microphone cable, connect a microphone to the microphone input channel on the front panel.
Step 5
Connect the line output to the line input of the next device.
Step 6
Be Careful!
Turning power switch on or off, can produce a voltage spike in the line and/or power output. Protect your
ears, speakers and equipment by being careful while the mic-amp line output is connected to the next device.
Step 7
Adjust the gain control with signal going into the microphone to give the desired output level. The indicator
LED‘s can provide help in setting the right level. See section „amplitude calibration procedure“ in this manual.
The Clip-LED has a characteristic somewhat between that of a peak and VU control (short attack and
enlarged release time). It is a quasi reference and should force you into a lower gain setting if necessary.
Step 9
Be Careful and watch the gain setting! Is it realistic!
Most equipment connected to the mic-amp will clip before the mic-amp will. Your soundcard may be
distorting on peak signals even though the mic-amp isn't. This is because the soundcard line inputs being
overloaded with too much signal coming from the mic amp's line output. Turn down the mic-amps gain
control until distortion stops.

Introduction
General Description
The IBF-MP1r is a portable, battery-powered microphone preamplifier with bias supply for electret
microphones and designed for 20Hz to 20kHz audio bandwidth. This quality mic pre is ideal for audio
recording and acoustic measurement purposes such as speaker and roomacoustic measurements.
With its rugged mechanical and electrical construction, compact size and high-quality components, the IBF-
MP1r is extremely durable and easy to use. This highly reliable mic preamp will provide years of superb audio
performance under regular conditions.
Installation
Locating the unit
Keep the mic-amp physically separated from other electronic equipment that produce electrical fields. As a
high gain device, hum and noise pickup is possible through chassis and associated cable. Placing the unit
away from transformers, power amplifiers, etc. will help to avoid pickup of those unwanted signals.
Signal and supply connections
All necessary connections on the mic-amp are made via RF phono jacks. Both the microphone input
connectors and line output connectors are female. In addition a power output (3.5mm jack) and an DC-IN
(1.3mm connector) jack can be found on the right side of the device.
Operational Notes
Power Switch
The power switch is a built in function of the gain potentiometer. When power is switched on or off, high level
audio "pops" on the output connectors are likely.
This is a function of DC voltage turning on or off to the circuitry and can also be seen on the indicator LED's.
Care must be taken to ensure that these "pops" do not damage equipment or ears associated with the mic
preamp ouputs. It is a good idea to lower the sound level of the associated equipment.
Clipping Indicator
The Mic-Amp has a build in clipping indicator that can provide assistance in setting the gain control.
It has a characteristic somewhat between that of a peak and VU control (short attack and long release time).
It is a quasi reference and should force you into a lower gain setting if necessary.
Acoustic calibration procedure (94dBspl-LED and -10dBV-LED)
Place the microphone near to your speaker (approx. 10“ away).Playback a 1kHz Signal from a testsignal CD
or playback a 1kHz-wav-file through your computer-soundcard (connection soundcard – stereo assumed).
Increase loudness until you get the green 94dBspl-LED signal. From this point: vary loudness until the LED
indicates with full itensity. SPL setting is done.
Now you have to set the preamplifier gain.
Increase gain from lowest value until the yellow –10dBV LED glows with full itensity.
Calibration is done: Now you know, that 94dBspl gives you a –10dBV output signal.
You can now continue with your measurement software settings/calibration.
Note: The LED-signal is low pass filtered (500Hz-3dB). Therfore calibration must be done with a 1kHz signal.

Power output
Both 3.5mm mono or stereo plugs can be used. Signal is applied to the tip, gnd to the sleeve. No signal is
applied to the ring-contact when using a 3.5mm stereo plug.
Batteries and external Voltage supplies
The IBF-MP1r is designed to operate on one 9 V battery or accumulator or external 9V power supply (It
contains a reverse polarity protection device). Due to the power consumption of approximately 20 mA and
supply by battery power dictates applying power only as required or using a plug-in power supply.
We recommend using plug-in power supplies with a stabilized output voltage. Types without that feature
normally have a higher voltage output at low current consumption. This can damage the preamp or parts of it.
Using „unstabilized“ plug-in power supplies also can cause additional noise in the signal path. Use a
connector with a 1.3mm hole.
Hole: +9V
Sleeve: gnd
Note: The audio performance, respectively the maximum output voltage swing doesn‘t depend on the batterie
voltage which drops down during it's life-time.

Appendices
Controls, Connectors and Indicators
GAIN CONTROL (built in rotary power switch)
Selects the amount of gain from input to output.
MIC IN
unbalanced MIC-Input accepts microphone level signals, Both input channels use RF Phono jacks
recommended for semi permanent connections in audio applications.
LINE OUT
unbalanced line level signals via RF Phono jacks. Minimal Load resistance 2kOhms
POWER OUT
Unbalanced. Has low impedance drive capabilities. Lower output level compared to Line out.
POWER LED / Low Batt indicator
LED illuminates green when the unit is powered. Same LED flashes when Battery voltage is too low for
regular operation.
CLIPPING INDICATOR LED
LED illuminates red at clipping
94dBspl-LED
LED indicates green when a 94dBspl signal was fed to the related microphone (Amplifier is factory set for
accurate level control).
LED-off : signal < approx 93dBspl
LED-on : signal approx 93 to 95dBspl (corresponding itensity varies low-high-low. A high itensity signals „near 94dBspl“)
LED-weak : signal > approx 95dBspl

-10dBV-LED
LED indicates yellow when the amplifier output gives you a –10dBV consumer level
LED-off : signal < approx -12dB
LED-on : signal approx -12 to -8dBV (corresponding itensity varies low-high-low. A high itensity signals „near –10dBV“ )
LED-weak : signal > approx -8dB
Note: (0dBV=1Vrms / -10dBV=0,316Vrms
POWER Switch
Is part of the gain control potentiometer. Powers the unit when the switch is moved from the marked OFF-
position.
BATTERY Compartment
Requires one 9V battery, accumulator or plug-in power supply for operation. Due to the 20 mA Power
requirements we recommend the use of a accumulator instead of a battery.
Note: Plug-in power supply. Use a type which can give you an electronically stabilized 9V supply voltage
(Unstabilized Power supply can cause damages and/or hum and noise).
Specification
CE Conformity Statement
I declare under my sole responsibility, that the product microphone preamplifier "IBF-MP1r" combined with
the microphone "IBF-EMM8" is in conformity with the following european standard: EMC Directive no. 89/336
EEC.
This is documented by accordance with the following standards:
EN 50081-1
EN 50082-1
EN 55011 (CISPR 11)
EN 55022 (CISPR 22)
Viernheim/Germany , 10 . 06 . 2002
(This decalaration of conformity is suitable to the European Standard EN 45014,
"General criteria for suppliers declaration of conformity")
Number of preamplifier channels - 1 Mic
Connectors - RF phono jacks for both inputs and outputs
Input - unbalanced, capacitor coupled, input impedance
>2kOhm
Output - unbalanced, capacitor coupled, min load
2kOhm, short circuit protected, guaranteed output level
without clipping +3dBV (full battery) Note: 0dBV=1Vrms
Power output – 3.5mm connector , low impedance drive
capability (ideal for driving long cables and
head/earphone), reduced output level -5dB
Gain Range - up to 52 dB input to output
Frequency Response - 20 Hz - 20 kHz, +-0.2 dB
(relative to 1 kHz)
Output Clipping Level - 4Vpp (2 k• load)
Clipping indicator LED - Red indicates clipping short
attack time, long release time. Bipolar detection
THD < 0,02% , THD & Noise < 0.04% , SNR > 70 dB
Bias Supply - typ. 2.5V coupled via 2.7kOhm resistor
Power - 1x 9V batterie, plug-in power supply connector
Power LED - Green indicates power ON, blinking LED
indicates low batt. (Vbatt < 7V)
Acoustic REF LED - 94dB acoustic reference LED
(off / bright / weak indicates < = > 941 dBspl)
-10 dBV LED – Consumer Level reference LED (off /
bright / weak indicates < = > 102 dBV)
Polarity - Mic input to line output is non-inverting.
Operating Temperature Range
0 to 40 degrees Celsius (32 to 104 degrees F)
Power up delay – approx. 10 sec
Dimensions
34 mm x 68 mm x 120 mm (h x w x d) (1 11/32" x 2
11/16" x 4 23/32")
Weight (unit only)
120 grams (4 1/8 oz.) battery removed

Limited Warranty
IBF (engineering office Wolfgang Frank) warrants the IBF-MP1r preamplifier against defects in material and
workmanship under normal use and service for a period of 2 years from date of original purchase. We will
repair or replace the product at no charge provided that the product is returned, shipping prepaid, to the
manufacturer.
This warranty does not apply if, in our opinion, the product has been damaged due to abuse, misuse,
misapplication, accident or as a result of service and modification by other than an authorized dealer.
For all service, including warranty repair, please send the IBF-MP1r, along with proof of purchase date to:
Safety clause and unauthorized applications
Products manufactured and/or sold (abrreviated products) by Ingenieurbüro Frank, Germany (abbreviated
ibf-akustik) are not designed for use as a component in any life support, life safety, or other comparable
application. Our products should not be used in any application where the failure or faulty performance of the
product might create a risk of personal injury or death. Buyer assumes all risk of loss, damage or injury
alleged to arise from the failure or faulty performance of a ibf-akustik product in any unauthorized application.
Buyer agrees to indemnify and hold harmless ibf-akustik, and its directors, employees, agents,
representatives and sales partners, from and against any and all claims, costs, damages, losses and
expenses including attorney fees which arise from or are elleged to have been caused by any claim for
personal injury or death connected with buyer's use of a ibf-akustik product in any unauthorized application,
including claims which allege that ibf-akustik has been negligent in connection with the design or
manufacture of the product.
Ingenieurbüro Frank (ibf-akustik) (28.02.02)