Creek Audio OBH-12 User manual

Thank you for purchasing the OBH-12 Infra-red remote control passive Pre-Amp. You
are now in possession of a State of the Art product. The functions and operation of the
OBH-12 are extremely simple. However, the following notes are provided to explain all
aspects of its design and use.
OVERVIEW
The function of the OBH-12 is to provide input selection
and volume adjustment to your Hi-Fi system from your
armchair, via infra-red remote control.
The unit consists of a motorised volume potentiometer,
and two stereo relays which select the desired input
and tape output, together with a muting relay that can
short the signals to ground. A built-in micro-controller
decodes the infra-red signals transmitted by the hand-
set and translates them into commands which activate
the motorised potentiometer and the muting and input
selection relays. After each operation, the micro-con-
troller turns itself off to avoid any possibility of interfering
with the main music signal. LEDs are used to indicate
the status and mode of operation.
The OBH-12 is purely passive and does not introduce
any gain or distortion into the signal path. It is therefore
suitable to be used as a control Pre-Amp, provided the
sensitivity of the power amp that is being used is high
enough to be driven directly from the source. i.e. CD or
Tuner etc.
CREEK OBH-12 SPECIFICATION
INPUT IMPEDANCE < 50 kΩΩ
OUTPUT IMPEDANCE 0 - 50 kΩΩ
SEPARATION > 80 dB's @ 1kHz
ATTENUATION 0 - 90 dB's
INPUTS 3 Stereo pairs, inc Tape
OUPUTS 2 Stereo pairs, 1 fixed, 1 variable
RELAY MUTING FACTOR > 90dB's
POWER REQUIREMENTS 24v @ 60 mA
POWER CONSUMPTION 2W max
DC CONNECTOR TYPE 2.1 mm female DC jack
INPUT & MUTE INDICATION 2 Tri-colour LED
TAPE MONITOR INDICATION Yellow round LED
SIZE 100 x 130 x 60 mm
4" x 2·4" x 5''
WEIGHT 420 g, 1lb
Creek Audio Ltd reserve the right to change or modify the specification of its products without prior warning.
Creek OBH -12
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Creek Audio Ltd
2 Bellevue Road, Friern Barnet, London N11 3ER, England
Tel: 00 44 + (0)181-361 4133 Fax: 00 44 + (0)181-361 4136
E-mail: [email protected] Internet: www.creekaudio.co.uk
Designed and made in the UK.

The volume control can be operated manually at any time, whether the OBH-12 is
powered or not, but without power only Line 1 can be utilised.
MAINS CONNECTION
When unpacking the module please
keep the packing material in a safe
place for possible future use. In the
pack there is a separate mains
adaptor, prepared for the mains volt-
age supply in the country of use.
The plug at the end of the fixed
cable should be firmly inserted into
the connector on the OBH-12 rear
panel marked DC inlet 24V -
60mA". Remember, do not overload
the mains wall socket with too many
plugs or adaptors. If in doubt,
please contact your supplying dealer or a qualified electrician. The OBH-12 draws
less than 2 Watts of power from the mains under all conditions so it can safely be left
switched on without significantly increasing your electricity bill.
INPUT AND OUTPUT CONNECTIONS
Line 1 and 2 are identical. The output from a CD, Tuner, AV or from an OBH-8 or 9
phono pre-amp can be connected to either of them. For tape machines, use the Tape
input and output - the tape monitor function will allow recordings to be made and
played back. The output from the OBH-12 should be connected to a power amplifier
with suitable sensitivity (gain). Remember, the OBH-12 will not increase the signal
from input to output.
VOLUME LEVEL
The volume control is used to alter the relative level of the sound output from the
amplifier. It is important to realise that the volume control only acts to reduce, or atten-
uate, the incoming signal to the power amplifier stage. The maximum power of an
amplifier is available only if the level of signal available from line level equipment is
sufficient to drive it to clipping, which will be different from one amplifier to another. The
volume control is therefore also used to balance the level from one piece of equipment
to another.
If it is found necessary to have the volume control set to a position which is considered
to be high before the desired level of volume is obtained, it does not necessarily mean
that the amplifier is having to work too hard or "flat-out". Consult your dealer if you
need more advice. Always have the volume control set at minimum (counter-clock-
wise) when switching your amplifier on and off, to avoid thumps or sudden loud noises.
POSITIONING OF THE OBH-12
The OBH-12 needs to be powered from its adaptor to operate the volume, input and
mute functions via the remote control. It will work best if placed on a suitable hard sur-
face or Hi-Fi equipment cabinet. Should it be necessary to place the OBH-12 on the
top of other audio or video equipment, avoid obstructing any ventilation slots that could
cause overheating, or internal mains transformers which might induce hum pick-up.
Very heavy signal interconnects may cause the OBH-12 to tip backwards. There are
two slots on the bottom that could be used to lock it in position. Do not obstruct the IR
sensor on the front panel.
OPERATING THE OBH-12 BY REMOTE CONTROL
The OBH-12 has two line inputs, which can be selected by pressing either button 1 or
2 on the handset. The appropriate LED will light green. By pressing the volume up or
down buttons at the bottom of the Creek remote control handset, the motorised poten-
tiometer will move the control knob and cause the input status LED indicator to flash
yellow. After a second the LED will revert to green indicating that the micro-controller
has gone to sleep until the next operation.
Pressing the Mute button on the handset will cause a relay to cut the signal from the
OBH-12 and change the active LED status indicator to red. To un-mute, press the
Mute button again or the volume up button (volume down will not un-mute the signal).
To un-mute the OBH-12 without the handset, remove the power supply for 10 secs. To
select the tape player or to monitor a tape recording press button 5 Tape 1. The
round yellow LED will light. Press button 5 Tape 1 again to switch this off. All other
buttons on the handset are reserved for other future Creek remote controlled products.
CAUTION
Your OBH-12 amplifier is designed to give you years of reliable use. However, it is
necessary to take care of your possession, so never overheat and only use the recom-
mended Creek OBH power supply.
The OBH-12 is designed to comply with the latest European EMC requirements.
However, it should be noted that it is not possible to guarantee faultless operation of
the equipment if it is used close to the source of high powered radio transmissions,
such as can be found in mobile telephones or CB radio etc. Care should also be taken
to place it away from the source of mains interference caused by mains transformers
in other equipment. Electrical switching noises from domestic or industrial heating sys-
tems, conducted periodically down the mains supply, can sometimes be amplified and
present themselves as a click or a thump through a Hi-Fi system.
If you suspect that a fault has developed, do not remove the cover plate. There are no
user serviceable parts inside. If you are unfortunate enough to need service work car-
ried out on the OBH-12, it should be returned to your dealer for his expert help, in the
original packing material if possible.