QES Labs SMP-2 User manual

SMP-2
Stereo Microphone Preamplifier
Owner’s Manual
Rev. 1

INTRODUCTION
THANK YOU!...
for choosing the SMP-2 Twin Channel Microphone Preamplifier. This Microphone
Preamplifiers use the best available parts with the shortest, cleanest, signal path
possible. The Preamplifier features an all-tube circuit in the audio path, ZERO
negative feedback, and Mosfet based high-stability “shunt”(parallel) voltage
regulation stage, that has proved to be among the finest amplification circuits for
demanding audio professionals.
It combines flat frequency response, very high headroom, low noise and low
distortion.
The Preamplifier also has the Input Attenuator (PAD) before any tube stage so that it
can easily accomodate any reasonable signal level.
There is also a rotary LEVEL switch which helps to change the preamplifiers
operating characteristics to suit a wide variety of microphones.
This is done via an 11-step rotary switch connected to a multi-tap (total 20-tap) state
of the art mu-metal core audio transformer pair, so that you will get a consistent
sound through each step, without losing any signal information as conventional
potentiometers can do.
The design is fully “differential”(balanced), from microphone input to output,
so that the preamplifier can interface with virtually anything without hassle.
Standard 48V Phantom power is provided.
Thank you again, and please enjoy!

GENERAL NOTES
LOCATION & VENTILATION
The SMP-2 Microphone Preamplifier must be installed in a stable location with
ample ventilation. It is recommended, if this unit is rack mounted, that you allow
enough clearance on the top and bottom of the preamp such that a constant flow of air
can flow through the ventilation holes.
WATER AND MOISTURE
As with any electrical equipment, this preamplifier should not be used near water or
moisture. If liquid enters the preamplifier, it must be immediately returned to your
dealer for servicing.
SERVICING
The user should not attempt to service the preamplifier beyond that described in the
owner's manual.
Refer all servicing other than tube replacement to QES Labs.
MAINS CONNECTIONS
IMPORTANT:
DO NOT CONNECT/SWITCH ON THE MAINS SUPPLY UNTIL ALL
OTHER CONNECTIONS HAVE BEEN MADE.
Your preamplifier has been factory set to the correct mains voltage for your country.
The voltage setting is marked on the serial badge, located on the rear panel. Check
that this complies with your local supply.
The power cord must be earthed- 3-pin type.

Connect the umbilical cable from the external PSU to the main unit following this
scheme:
On front of PSU, connect the RED shrink cable MALE connector to the RED dotted
front panel female connector, and the other cable connector to the adjacent panel
connector, like in the picture below:
Then connect the umbilical cable’s RED shrink female connector to the main unit’s
MALE panel connector with the arrow symbol, then the adjacent connector on cable
to the right connector on the back panel of the main unit, like pictured below:

Gently lock all mating connectors on both PSU and main unit.
When you are sure that all the cables are connected and secured to the respective
devices, you can turn on the unit.
AUDIO CONNECTIONS
The microphone cables should be connected to the FEMALE XLR connectors on the
rear panel of the unit, following the polarity as in the pic below:
The output MALE connectors follow the same pin out:
1 –screen,
2 –HOT, or positive going phase,
3 –COLD, or negative going phase.

OPERATION
SWITCHING ON
Allow this unit a few minutes for the tubes to warm up before use. It is not
recommended that you leave your preamplifier permanently switched on. This only
wastes electricity and tube life. Your preamplifier has solid state rectification and will
reach peak operating condition in approximately 30 minutes.
TUBE LIFE
As with all tubes, their quality degrades with age. This is due to cathode emission, a
natural process found in all tubes. We recommend that you have your preamplifier
checked every 4-5 years, depending on usage, usually the preamplifier will require
re-tubing after this time has elapsed.
Increased noise is usually a sign that the tubes need replacing.
CONTROLS
1. PAD
It’s a -20dB resistive pad, it can accomodate some line level signals to be
amplified by the unit.
2. 48V PHANTOM
Pressing this button, the microphone at the input will be supplied with the
standard 48V Phantom Supply, the mic can easily draw up to 10-15mA of current
without problems. This button MUST remain unswitched if you are using dynamic
and ribbon type microphones. Do not use phantom with unbalanced sources,
damage to the mic or preamp may result. Do not change mics or mic patches with
phantom power on especially if the monitors are up.
3. PHASE REV.
Activating this button, the original phase on the respective input connector will be
reversed.
4. LEVEL
There are 11 steps, 0 being cut-off, 10 being max volume. Each step increases by
approximately 2.5dB .
METERING
The VU meters display the “average”of the output signal, the standard indication
is +8dBu (1.947Vrms) for a 0 VU reading. +4dBu reading is at 50% scale.

REAR PANEL
FUSE HOLDER
In case, replace with “Slow-Blow”(time lag) 5x20mm cartridge fuses, with the
following ratings based on your mains voltage.
100-120V - 4AT
220-240V - 2AT
SPECIFICATIONS
Vacuum tubes (per channel): 2x 12BZ7, 2x 6414
Frequency response: 20Hz –20kHz (±1dB)
Signal to Noise ratio:
96dB or better,
depends on settings and tubes
Max Output Level: +18dBu
Max Input Level: 25mVrms
Max gain: 50dB (±3dB)
Input impedance: 1.2k
optimised for mics with 100 to 600 ohm output impedances
Output impedance: 100 ohms
Suggested load impedance: 10k ohms or higher
Power consumption: 24 Watts

WARRANTY
QES Labs warrants this product to be free of defective parts and
workmanship for a period of one year from the date of original purchase,
except vacuum tubes and light bulbes (60 days).
This warranty excludes the following conditions: normal wear and tear,
misuse, customer negligence, accidental damage, unauthorized repair or
modification, cosmetic damage and damage incurred during shipment.
QES Labs will repair or replace, at its option, any defective parts or repair
defective workmanship without charge, if returned within the warranty
period to our designated service facility.
This warranty is in lieu of all other warranties, expressed or implied,
including, but not limited to, any implied warranty of merchantability or
fitness for a particular purpose.
In no event will QES Labs be liable for lost profits or any other incidental,
consequential or exemplary damages, even if QES Labs is aware of the
possibility of such damages.
In no event will QES Labs’ liability exceed the purchase price of the
product.

DECLARATION OF CONFORMITY
I declare that the model “SMP-2” conforms to the following standards adopted by the
European Community:
EMC (electro magnetic compatibility) 89/336/CEE directive,
LV (low voltage equipment) 73/23/CEE directive on electrical safety (EN61010) and
electromagnetic compatibility (EN61000).
RoHS (Restriction of Hazardous Substances) 2002/95/CEE directive.
QES Labs di Valerio Riccelli
4 Via Ugo Niutta Napoli, NA 80128
Italy.
Data / Date / Datum: 11/09/2009.
Firma / Signature / Signatur / Unterschrift
Direttore tecnico / Technical manager / Directeur technique.