Creek Audio OBH-21mk2 User manual

Rev 1.0
OBH-21mk2
Headphone Amplifier
Instruction Manual

Page: 1
Thank you for purchasing the OBH-21mk2 Headphone Amplier.
You are now in possession of a State of the Art product. The oper-
ation of the OBH-21mk2 is extremely simple, however, the follow-
ing notes are provided to explain all aspects of its design and use.
OVERVIEW
The OBH-21mk2 is a very high quality miniature integrated ampli-
er, designed specically to drive one or two pairs of low impedance
headphones simultaneously from a line level source. To do this, it
has very low output impedance and high output current capability.
It is also possible to use it as an active pre-amp, with a single input
and variable output.
The OBH-21mk2 will amplify any line-level analogue signal. For
example: a CD player, DAC, or many other signal sources can
also be connected directly to the OBH-21mk2’s input. It can also
be used in conjunction with a stand-alone pre-amplier or integrat-
ed amplier which has a xed line level output (Tape). If used as a
pre-amp it must be connected to a separate power amplier.
Output level is controlled by the high-quality ALPS 27mm Blue Vel-
vet volume control on the front panel.
N.B. The OBH-21mk2 cannot drive loud speakers directly and it doesn’t
have any digital inputs.

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INPUT AND OUTPUT CONNECTIONS
The OBH-21mk2 has three pairs of stereo RCA sockets on the
rear panel. The rst pair on the left is the ‘Input’ from any line level
source, direct from the source or via the tape output of an amplier.
The second pair of sockets, marked ‘Loop-Out’, are to chain-link
the signal into the next component in the system. Therefore, the
OBH-21mk2 can accept a signal from the Tape Output of an am-
plier and series link it to the Tape recorder input.
The third pair of sockets marked Pre-Out, is to enable the OBH-
21mk2 to be used as a pre-amplier in a full stereo system. There
is a 2.1mm DC power jack, with centre positive pin, for connection
to a custom Creek OBH-Uni type power supply adaptor.
On the front panel there two 6.3mm (1/4 inch) sockets for plugging
in the headphones.
INSTALLATION AND OPERATION
Connect the OBH-Uni power supply adaptor to the mains sock-
et. Find a suitable place for the OBH-21mk2 and plug the DC
power lead into the rear panel DC jack socket. Connect a pair of
high-quality interconnect cables from the output of the source to
the input sockets on the rear of the OBH-21mk2.
Plug your headphones into a socket on the front panel. If you are
using the OBH-21mk2 with two headphones, the output from each
socket will be identical.
Push the On/Off button on the rear to power-up the OBH-21mk2.
The small LED on the front panel will light when it is ready for use.
The front panel volume control should be set to the desired signal
level.

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GAIN ADJUSTMENTS
As higher impedance headphones require more gain and vice-
verse, it is important to be able to match these gain requirements
with the OBH-21mk2. A simple set of miniature switches are posi-
tioned under the headphone amp and with the easy-to-read table
on the base, it is possible to select the most suitable match for
your requirements.
Operating as a pre-amp it is likely to require less gain, so a sepa-
rate setting is provided to allow the user to attenuate the pre-amp
output only, while allowing the headphone output to remain higher.
POWER SUPPLY REQUIREMENTS
In common with all electrical appliances, the OBH-21mk2 needs
a power source (24 Volts DC @ 500 mA). A Creek OBH-Uni cus-
tom power supply is included to run it, which must be connected
to the unit via the DC inlet (2.1mm positive centre pin power jack)
on the rear panel. The OBH-Uni power supply adaptor should be
plugged into a suitable mains socket which should be matched
for the voltage of the country of use. The OBH-Uni comes with
3 different connectors, for UK, North America and central Eu-
rope regions. Before you can use it, a suitable connection head
should be clipped-on to the adapter.
Note 1: When new, it is necessary for the OBH-21mk2 to be
‘burned-in’ for at least 24 Hours before its full sound quality po-
tential can be realised.
Note 2: Listening to high sound pressure levels for long periods of
time can permanently damage your hearing. Be careful and enjoy
the music.

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TECHNICAL SPECIFICATION
POWER OUTPUT > 100mW / 8 Ohms
> 160mW / 16 Ohms
> 200mW / 33 Ohms
> 210mW / 68 Ohms
HEADPHONE IMPEDANCE RANGE 8 to 1k Ohms
OUTPUT IMPEDANCE 1 Ohm
INPUT IMPEDANCE < 20K Ohm
FREQUENCY RESPONSE 10 Hz to 50 kHz
THD < 0.002% - 20 Hz to 20 kHz
0.5V into 68 Ohms
PRE-AMP THD < 0006% - 20 Hz to 20 kHz
SNR 116dBA ref 1V
107dBA at > 12.5dB gain
CROSSTALK < -80dB 10Hz - 20 kHz Line out
< 60dB headphone out - 33 Ohm
GAIN SETTINGS 0dB, 6dB, 10dB and 12.5dB
PRE-AMP ATTENUATION SETTINGS 0dB and -6dB
POWER CONSUMPTION < 6 Watts at max power
OBH-UNI POWER SUPPLY 24V DC 12 Watts max
< 0.5 Watts standby
SIZE (including knob and sockets) 180mm x 95mm x 60mm
7” x 3.75” x 2.25 inches
WEIGHT (NET) 630g - 22 ounces

Creek Audio Ltd
12 Avebury Court, Mark Road, Hemel Hempstead, Hertfordshire, HP2 7TA England
www.creekaudio.com - [email protected] - [phone]