RCM Audio Sensor 2 User manual

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THE SENSOR 2
Thank you for purchasing the RCM Sensor 2 phono preamplifier. We are certain you will be delighted with the
performance when partnered with your favorite turntable and cartridge.
Please read this manual carefully before connecting the Sensor 2 to your system.
illustration 1
DESCRIPTION
Unlike the output from a CD player the raw signal from a phono cartridge suffers frequency distortion
because the output at 20 Hz is 1000 times lower than that at 20 kHz. This is deliberately implemented during
the recording process to enable the signal to be cut into the vinyl of the record. The phono preamplifier must
restore the frequencies to their correct balance using an RIAA equalization curve. The Sensor 2 uses passive
equalization in two stages to achieve this.

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In addition the phono preamplifier must amplify the low level signal to line level to match other sources. CD
players have an output of 2 volts whereas MM (moving magnet) cartridges typically output just 2 mV.
Therefore, the MM signal needs to be amplified 1000 times. MC (moving coil) cartridges can have outputs as
low as 0.1 mV and thus require amplification more than 6000 times. Doing this with low noise is a very
difficult task and one which the Sensor 2 achieves with precision and excellence. Most commercial phono
amplifiers struggle to do this and only provide 1 volt output. Our tests prove that 2 volts is optimum, the same
as a CD player. Therefore, the Sensor 2 is capable of providing 76dB of gain and an output of 2 volts.
CONNECTION
We recommend placing your Sensor 2 on a clean, dry, stable, vibration free surface, as close
as possible to your turntable. The power supply can be located some distance away for
convenience and to minimize noise. If you hear any hum or noise please move the preamplifier
around until the noise goes away. Because of the very high amplification factor it can pic up
stray hum fields from other pieces of equipment.
Connect the power supply chassis to the Sensor 2 amplifier chassis with the umbilical cable
provided (i.1 pos.14).
Connect your turntable to the RCA input soc ets (i.1 pos.4 and 11). The inputs are RCA only
but the output from a phono cartridge is inherently balanced. The Sensor 2 ta es full
advantage of this by virtue of the fact that it is a balanced circuit inside. Both Balanced XLR
(i.1 pos.1 and 8) and Unbalanced RCA (i.1 pos.2 and 9) outputs are provided so if your
integrated amplifier or preamplifier is XLR equipped you can you can ta e full advantage of this
feature. No switching is necessary to use this feature.
ADJUSTMENTS
To ensure optimal cartridge matching the Sensor 2 has both LOAD and GAIN adjustment via
DIP switches accessible on the rear.

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The GAIN (i.1 pos.3 and 10) switches enable the user to adjust the output of the preamplifier
to match the other sources in the system. Start with all the switches in the OFF position and
successively switch each one in and out until you reach the desired level to match other
sources.
0,3 mV 0,4 mV 0,6 mV 0,9 mV
1,4 mV 2,5 mV 5,0 mV

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The LOAD (i.1 pos.5 and 12) switch allows you to adjust the input impedance that the
cartridge sees. With all switches OFF the load impedance is 47 ohms. This is suitable for MM
cartridges. MC cartridges generally li e to see higher impedance and the manufacturer will
usually state the optimum in the cartridge specifications. However it is best to adjust this by
ear. You can progressively switch the DIP switches ON to increase the impedance. As you do so
the sound will become progressively tighter and cleaner. As you pass the optimum position
the sound will become slow and dull. Therefore you will want to settle on a position where the
cartridge sounds lively but controlled. This will generally be just before it starts to slow down in
perceived sound.
47 kohm 1 000 ohm 400 ohm 200 ohm
100 ohm 50 ohm 30 ohm 20 ohm

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Balanced or unbalanced mode connection
RCM recommends that you wire your phono cable as per the diagram below if you wish to ta e
advantage of the fully balanced operation mode. This will give your system the lowest noise
floor and best sound quality.
In ut mode
Wiring diagram for balanced and unbalanced input using RCA connection
Great care has been exercised in manufacturing this product for your enjoyment.
If you have any questions please feel free to contact us for advice.
We wish you many hours of happy listening.
RCM Audio

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Technical data
Input: RCA – Balanced and Unbalanced (selectable via switch)
Output: 1 pair Balanced XLR, 1 pair Unbalanced RCA (single ended)
Input sensitivity: 0.3 – 5 mV (selectable in 7 steps)
Gain: 52 – 76 dB (2 V rms output at 1 Hz)
Input impedance: 20 Ohm – 47 Ohm (selectable in 8 steps)
Input capacitance: 150 pF
THD: 0.01 % (1 Hz)
S/N: 85 dB (lowest gain settings)
RIAA linearity: +/- 0.3 dB (20 Hz – 20 Hz)
Output impedance: 50 ohm
Nominal output: 2 V rms
Maximum output: 8 V rms
Power consuption: 17 W
Dimensions: Preamplifier W 245 x D 227 x H 110 mm, 3.5 gs.
Power Supply W 122 x D 230 x H 70 mm, 1.7 gs.