ATI Technologies M100 Operating instructions

AudioTechnologiesInc.|154CooperRoad#902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
© Copyright 2008, Audio Technologies Incorporated - Printed in USA
M100
MICROPHONE AMPLIFIER
OPERATING AND MAINTENANCE MANUAL

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
GENERAL
The ULTIMIKE M100 Microphone Amplifier is designed specifically to provide the
ultimate in no-compromise audio performance. A rugged, small AC line powered
amplifier, it may be placed close to the mike on the stage, in the pulpit or in the overhead
lighting structures to shorten sensitive low-level mike lines. Replacing your long runs of
low-level mike cable with high level feeds will greatly reduce your susceptibility to RF,
hash and hum pickup. In addition, the M100 is itself very well protected from both
radiated and conducted interference and has unmatched broadband common made
rejection to cancel microphone hum and RF pickup. A unique distortion-free transformer
coupled output provides total isolation of ground loops and ground voltage differentials
while simultaneously providing a low driving impedance to minimize high frequency
rolloffs due to excess cable capacitance.
To allow you to install the M100 close to the mike when necessary in what may be a
remote or poorly accessible location, we have designed the preamp to accept a very wide
range of input levels (up to 0 dBu) without input overload and we have incorporated a
switchable slow acting (but very low distortion) 24 dB limiter to turn down the output
level pot when you can’t reach it.
In addition to all these modern conveniences, the ULTIMIKE is a superb performer with
ruler flat response, no ringing, excellent CMR, exceptionally low input noise, and trivial
distortion.
The ULTIMIKE amplifier is packed in a rugged, compact steel enclosure. All controls
and connecters are recessed for protection. Identification markings are printed on the
protected reverse side of a heavy duty polycarbonate overlay. All power supply
components are well shielded by the steel chassis.
Input mike level audio to the ULTIMIKE must run a gauntlet of ferrite suppressors,
bypass capacitors, DC blocking capacitors, and protection diodes designed to block the
trash, and transistors (Q1 and Q2) in an instrumentation amplifier configuration provide a
very low noise input gain stage. The balanced feedback network R12, R13, R20, and R
21 is driven from the outputs of A1A and A2A to eliminate any input loading that might
degrade common mode hum rejection and to allow use of low valued feedback resistors
for minim noise generation. Dual constant current stages (Q3 and Q4) sink DC emitter
current from Q1 and Q2 and allow complete servo cancellation of input offsets via
integrator A3A to maximize input stage headroom at A2B. A differential amplifier and
limiter are formed by A1BA2B. Common mode input signals are nulled out by R27 and
an LDR (light dependant resistor) in A2B’s feedback loop reduces the input stage gain in
response to limiter levels. Even without limiting, the input stage will handle input levels
up to 0 dBm (gain – HI switch) or +20 dBm (gain –20 dB).
A3B forms a variable gain stage with a smooth logarithmic adjustment range of +37 to
–19 dB. R30, the level potentiometer, is screwdriver-adjustable through the front of the
amplifier. When rack mounted, the level adjustment is accessible through the panel.

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
A4A makes a switchable, unity gain high pass filter with two-pole response of -3dB at
150 Hz and rolling off 40 dB at 15 Hz. The filter is switched in or out of the circuit with
S4.
The output line driver A4B and output transformer T2 provide 16 dB of gain and the total
isolation, faraday shielding, RF immunity and ease of use of a true transformer coupled
balanced output. A unique feedback technique totally avoids the transformer’s
characteristic limitations of high distortion, poor response and hum pickup. Typical
output distortion measurements made at both peak (+22 dBm) and nominal (+4 dBm)
levels barely exceed generator residuals from 20 to 20,000 Hz. Hum pickup from the
power supply is well below the noise level and low frequency response is greatly
extended. The output is protected from short circuits but will drive over one-half mile of
shielded cable with less than 1 dB of signal rolloff at 20,000 Hz.
We deliberately omit the output connector pin 1 ground lift jumper (W4). If you insist on
setting up loops by grounding your cable shields at both ends, you can connect the shield
to the output connector plug shell.
A5A and A5B make an active full wave rectifier and filter to drive the limiter. R5 sets a
limiting threshold corresponding to an output level of +14 dBm. The limiter has a soft
knee and a gentle slope of about 4:1 so that continued peaks greater that 10 dB above the
nominal output will cause a slow reduction in gain. If the limiter switch is off, the front
yellow LED will light on sustained peaks to tell you to use the limiter or to reduce the
gain. With the limiter on, an occasional flash will indicate normal operation but
sustained illumination is an indication that you are reaching the end of the gain reduction
range.
Q5 is a constant current driver for the limiter LDR, which can be controlled by an
external 10 Kohm potentiometer plugged into the phono jack type connector. The remote
gain control has an adjustment range of 0 to –15 dB and does not interact with the limiter
except that both share the 24 dB total gain reduction range of the LDR. The remote gain
control is DC operated and can be located a considerable distance from the M100 without
noise pickup.
A5C and A5D form a 40 kHz DC-to-DC converter to efficiently generate the +48 VDC
microphone phantom power.
Your M100 operates from an internal, double-filtered bipolar 16 VDC supply, which uses
a couple of unique regulated devices called zener diodes. In contrast to fancy three
terminal regulators, these devices will live through power line trash and transients and
simultaneously protect your valuable circuitry. The supply is designed for minimum
susceptibility to power line conducted RF and hash with bypassed ferrite beads, RC
primary side bypasses and a mu-metal shielded, non-concentric wound, semi-toroidal
power transformer. A large board mounted 1/2A AC line fuse protects your M100 but
can make taking off the cover with the AC line still connected into a very exciting
adventure.

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
Different types of attachment plugs or line cords may be required for connection to
alternate supply voltages.
INSTALLATION
MOUNTING
The M100 can mount to any flat surface with the included angle brackets, which should
be mounted to opposite small faces of the M100 by the cover screws. The M100 can be
rack mounted either singly or in pairs in only 1-¾” using accessory Front Panel Kit, P/N
20273-501.
GROUNDING
The M100 includes an output transformer, a beaded, bypassed and clipped input network,
a triple protected AC input, a double ground plane PC board and a well shielded magnetic
enclosure. However, in a difficult broadcast application, RF levels may require a better
ground path for the RF bypass networks than can be provided by the third wire AC
ground. In difficult cases, a separate low inductance studio ground bus tied to the chassis
may be necessary.
The power line ground could cause a loop with a separate studio ground. If you are sure
your studio ground will provide adequate protection to your personnel in case of an
accidental AC short to the chassis, a 3-to-2 adapter can be used to isolate the power line
ground. We strongly recommend that the adapter be removed and the power line ground
be reconnected prior to any service work requiring removal of the studio ground from the
chassis.
INPUT AND OUTPUT CABLES
The female XLR type input connector is wired conventionally with pin 2 HI and pin 1
and the connector housing grounded. +48 VDC phantom power is applied to both pins 2
and 3 with reference to ground on pin 1.
The male XLR type output cable connector is wired with pin 2 HI, pin 3 LO and pin 1
floating. The connector housing is grounded to the chassis. Pin 1 is left ungrounded to
prevent large loop currents from circulating through the cable shield if inadvertently
grounded at both ends. The shield should be grounded at the receiving end of the signal.
If it is absolutely necessary to ground pin 1, ground lift jumper W4 can be inserted into
the circuit board.

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
NOTE
Output transformers which block RF and interrupt ground loops MUST be properly
loaded in order to provide flat response and minimum overshoot. Always be sure that the
output sees a 600 ohm load across pins 2 and 3. An occasional double load (300 ohms) is
better than no load.
REMOTE GAIN TRIM CONTROL
A 10 Kohm linear potentiometer can be connected across a single conductor shielded
cable with a standard RCA type phono plug at the M100 end. Connect the wiper and one
end of the pot together and to the shield, connect the other end of the pot to the center
conductor. Decreasing resistance will cause decreasing gain to a limit of approximately
-15 dB change. If you use a pot of lower value than 10 K, you will be unable to achieve
full gain at maximum resistance. The maximum length you can run the remote gain
control cable is somewhere between three feet and one mile.
MAINTENANCE
There is no routine maintenance required by your ULTIMIKE amplifier. If you have a
problem while using the M100, eliminate by substituting the microphone, cables,
connectors, load, and AC power and switch positions as possible causes before attacking
the M100.
DISASSEMBLY
1. Remove AC power.
2. Remove nine Philips head screws.
3. Pull off switch protector bracket.
4. Unlock both XLR connector PC board mounted center inserts from their cover
mounted outer shells using an .090 wide screwdriver placed into an access hole
located above the three terminals in each insert. Give each 1/8 turn CCW to
unlock; slot is horizontal when locked. DO NOT FORCE.
5. With your thumbs on the connector inserts and your fingertips on the sides of the
cover, gently slide the cover forward until the connector shells clear the inserts.
Lift the cover clear and pull the line cord grommet clear of the cover.
6. Reassembly is the reverse of the above. Don’t forget the grommet.
ADJUSTMENTS
Avoid the temptation to adjust the internal trimpots R27 and R40 just to see what affects
they cause. Both are sharp null type settings, which are greatly degraded by even slight
misadjustment. Replacement of any semiconductor in the unit should not require pot
readjustment.

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
COMMON MODE REJECTION
Replacement of R6, R7, R8, R9, R62, C11, or C12 will require readjustment of R27 to
maintain maximum common mode rejection (CMR). To set R27, apply 10 Vrms at 60
Hz between ground pin 1, pin 2, and pin 3 (tied together) of XLR input J1. Measure
output (at J2 pins 2 to 3) and adjust R27 for null. A 90 dB CMR is attainable but may be
difficult to measure without a tuned voltmeter.
DISTORTION
Replacement of R36, R37 R38, R39, and R40 or output transformer T2 will require
readjustment of R40. Apply sufficient 20 Hz signal to the input with the gain switch at
–20 dB and the gain control set to 12 o‘clock to drive the loaded output to +20 dBm.
Measure Total Harmonic Distortion (THD) at the output and adjust R40 for the best null.
If you cannot detect a good null, your audio generator may well have more internal
distortion at 20 Hz than even the untrimmed contribution of the M100, which is typically
less than .25%. When properly set, using superior test equipment such as Amber or
Audio Precision, distortion measurements should be limited only by residual white noise
to levels of .03% across the audible band.
GENERAL
Power supply voltages are + and – 16 VDC nominal. IC output DC voltages under no
signal, shorted input conditions should read 0 VDC at A1 and A2, pins 1 and 7, A3-7,
A4-1 and 7 and A5, pin 1 and 6. A3 pin 1 should read within the range of + to –10 VDC
and a 28 Vp-p square wave should be visible with an oscilloscope at A5, pins 8 and 14.
Deviations of more than .1 VDC from the 0 VDC nominal is an indication of IC or circuit
problems. Ten years from now, we recommend replacing all aluminum electrolytic
capacitors. Keep 250 Watt soldering guns out of the M100.
MODIFICATIONS
230 VAC OPERATION
The M100 is wired for 115 VAC, 50/60 Hz operation unless otherwise requested at the
time of ordering. It can be modified for 230 VAC use by removing W1 and W3 and
inserting a jumper wire in W2.

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
TECHNICAL SPECIFICATIONS
GAIN 54 dB nominal, adjustable 0 to 74 dB
NOMINAL POWER -50 dBm / 150 ohms available input power
+4 dBm / 600 ohms output
PEAK LEVELS -32 dBu in, +22 dBm out
MAXIMUM INPUT 0 dBu- HI gain switch, +20 dBu- LO gain
switch
NOISE OUTPUT -70 dBm, 20 to 20,000 Hz measurement
bandwidth
HUM OUTPUT -80 dBm, 60, 120, and 80 Hz
DYNAMIC RANGE 92 dB, peak output to noise
HARMONIC DISTORTION .10% THD maximum at peak level
20 to 20,000 Hz .03% THD maximum at nominal level
INTERMOD DISTORION .005% maximum SMPTE 7K / 60 Hz 4:1
FREQUENCY REPONSE +0, -.25 dB
20 to 20,000 Hz -3 dB at 1 Hz and 65 kHz
HIGH PASS FILTER -3 dB at 150 Hz nominal, -40 dB at 15 Hz
INPUT HUM REJECTION 90 dB minimum CMR, internal adjustment
INPUT IMPEDANCE 40 kohms, balanced
OUPUT IMPEDANCE Transformer balanced, 40 ohms source
impedance, 600 ohms +/- 10% load
impedance
OUTPUT RISE TIME 6 uSec symmetric rise and fall times,
typical
OUTPUT OVERSHOOT 5% maximum
PHASE SHIFT 30 degrees maximum input to output, 20
to 20,000 Hz
COMPRESSOR THRESHOLD +14 dBm out +/- 1 dB

AudioTechnologiesInc. | 154 Cooper Road #902|West Berlin, NJ 08091 |Voice 856-719-9900 |Fax [phone]| www. audio.com
COMPRESSOR SLOPE 4 : 1 maximum
COMPRESSOR TIMING 100 mSec attack and recovery
COMPRESSOR RANGE 20 dB gain reduction minimum
REMOTE GAIN TRIMMER 10 kohm linear external pot, user supplied
DC control, 0 to –15 dB range
PHANTOM POWER +48 VDC at 4 ma. through paralleled 6.8
Kohms resistors
AC POWER 115 – 230 VAC +/- 10%, 47 to 63 Hz, 4
VA
DIMENSIONS 1.5” H by 8.5” W by 5.5” D (9.75” W with
mtg brackets); 3lbs. Net, 5lbs. Shipping
weight
ENCLOSURE Plated steel wraparound with reverse
printed graphics overlay and rugged
switch protector
MOUNTING Keyhole slot #8 screws on 9-1/8” centers
accessory rack mount
CONNECTORS Mike input, XLR Type, three terminal,
female; Line output, XLR type, three
terminal, male; Remote Gain Trimmer,
RCA type Phone Jack