Creek Audio OBH-15 User manual

The function of the OBH-15 is to boost the level and correct the frequency response
of a low level signal coming from a phono pick-up on a conventional turntable. The
signal required by most modern amplifiers is described as being 'LINE' level, which
is, in technical terms, between 200 and 500 milli-Volts with a flat frequency response.
Unless your amplifier has a specific 'Phono' or Disc input, the level will be too low
and the frequency response will be wrong. The OBH-15 is designed to boost the sig-
nal and introduce an R.I.A.A. frequency response characteristic.
INPUT AND OUTPUT CONNECTION
The output from the turntable is normally terminated on
two 'Phono' plugs or RCA jacks. The level is dependent
on the type of cartridge used, and in the case of moving
magnet will normally be around 2 - 5 milli-Volts and for
moving coil - 200 - 500 micro-Volts.
Most MM or high output MC cartridges will be properly
matched by using the OBH-15. By plugging the signal
leads from your turntable into the OBH-15 input, the sig-
nal will be boosted to 'LINE' level at its output. To pre-
vent hum pick-up, it may be necessary to join the
turntable's earth lead to the OBH-15 ground terminal.
The output from the OBH-15 can be connected to most
integrated amplifier’s and pre-amplifier's line inputs via
a regular Phono to Phono (RCA to RCA) stereo inter-
connect lead.
CREEK OBH-15 SPECIFICATION
MM MC
GAIN 37 dB 56 dB
FREQUENCY RESPONSE 20 Hz to 20 kHz ± 0.25 dB
SIGNAL TO NOISE RATIO - 83 dB - 75 dB
TOTAL HARMONIC DISTORTION < 0.03% < 0.05%
R1AA DEVIATION ± 0.5% ± 0.5%
OUTPUT 250 mV 250 mV
OUTPUT IMPEDANCE <100 ΩΩ<100 ΩΩ
INPUT SENSITIVITY / IMPEDANCE 3.5 mV/ 47 KΩΩ/ 220 pF
INPUT SENSITIVITY / IMPEDANCE 0.5 mV/ 1000 ΩΩ/ 3300 pF
OVERLOAD MARGIN 22 dB 20 dB
MATES WELL WITH MM CARTRIDGES 2.5 mV - 5 mV output
MATES WELL WITH MC CARTRIDGES 0.5 mV - 1 mV output
DIMENSIONS 150 x 100 x 66 mm
POWER SUPPLY VOLTAGE 24V DC 30 mA
Supplied with an OBH-2 High Grade Regulated Power Supply,
220-240V 50Hz or 110-120V 60Hz
Creek Audio Ltd reserves the right to change or modify the specification
of its products without prior warning.
Creek OBH-15
Creek Audio Ltd
12 Avebury Court, Mark Road, Hemel Hempstead HP2 7TA England
Tel: + 44 (0) 1442 260146 Fax: + 44 (0) 1442 243766
E-mail: [email protected] Internet: www.creekaudio.co.uk
Designed and made in the UK.
Operating
Instructions

POWER SUPPLY REQUIREMENTS WIRING THE OBH-15
Note 1. The OBH-15 should be placed away from power supply hum
fields for the lowest noise operation.
Note 2. It is necessary for the OBH-15 to be 'burned-in' for at least 24
hours before its full sound quality potential can be realised.
CONNECTIONS
With its enhanced drive capability coupled with lower output impedance, the
OBH-15 phono pre-amplifier can now drive longer cables than its predeces-
sors, the OBH-8 and OBH-9.
It has combined the gain stages of the OBH-8 and OBH-9 and caters for
both moving magnet and moving coil cartridges, selectable via a simple
external switch on the rear panel. It also allows for the connection of two
turntables.
SWITCHING
To change from moving manet to moving coil, you will find the switch locat-
ed on the rear panel.
CAUTION
When switching between MM and MC always be sure to reduce the volume
to zero for several seconds - or better still switch the power off until after the
change has been made, to avoid loud noises.
In common with all electrical appliances, the OBH-15 requires a power
source.
The requirement for the OBH-15 is for 24 Volts DC at 30 milli-Amps current,
minimum. A Creek OBH-2 high grade power supply, dedicated for the local
voltage and plug type, has been provided. It has a thin cable exiting from it,
with a 2.1mm positive centre pin DC power jack fitted on the other end. It
should be connected to the Phono amp via the DC inlet on its rear panel.
To operate the phono amp it is necessary to switch-on the unit by pushing
the power button on the rear panel. It may be left switched on permanently
as it draws very little power.
N.B. Due to the inherent muting circuitry in the OBH-15 the signal will
take a few seconds to be heard after the power is switched on.
Keep the main amp’s volume control at minimum to avoid hear-
ing any unpleasant noises during the on/off phase.
OUTPUT
The output impedance of the OBH-15 is < 100 Ω, therefore it can be used
to drive long interconnects, without loss, provided they are not high
capacitance types.