SENSOR 2 MkII
MC / MM PHONO PREAMP
The SENSOR 2 MkII is a phono preamplifier that builds upon the concept of the “first” Sensor. It is the result of our experience and efforts to improve the performance of such a demanding device as a phono preamplifier. The design was conceived and built according to the principle of making the most of available resources and technology. At the same time, all components used in this project are the result of practical experience, which has allowed us to implement an optimal configuration while maintaining an affordable price.
Just like the first version, the SENSOR 2 MkII stands out from other phono preamps thanks to its high output signal level. Our experience shows that, to achieve optimal sound quality, this value should not be less than 1 volt. This is due to many factors, such as the fact that current input stage designs favor sources with a high signal level. Ideally, the output level should be 2 volts—the same as in a standard CD player. This approach places very high demands on the entire system, since with an MC cartridge having an output level of 0.3 mV, the signal must be amplified by approximately 76 dB—that is, more than 6,300 times.
Like its predecessor, the SENSOR 2 MkII, of course, allows you to select the input mode, which can operate in either balanced or single-ended mode. The signal from the phono cartridge is balanced, so with the proper input configuration, it’s possible to achieve a higher signal-to-noise ratio and a wider dynamic range. Why give up something that works so well?
The input load is adjusted using switches located on the rear panel. The “2” model features an eight-position switch, which allows for more settings and, consequently, a more precise selection of the input load. Switches are also located in the same place to set the appropriate gain and select the input circuit’s operating mode—balanced or single-ended.
Signal amplification is handled by carefully selected integrated circuits, while RIAA equalization is implemented as a two-stage passive circuit that uses low-noise resistors and polypropylene capacitors. To ensure accurate signal correction, each filter component is measured and selected by hand, resulting in a deviation from the ideal response of less than 0.3 dB in the 20 Hz to 20 kHz frequency range.
Power supply is a crucial element in achieving complete success. The SENSOR 2 MkII is equipped with a balanced power supply, and its design incorporates solutions aimed at minimizing interference. Great emphasis was placed on the proper selection of capacitance in the filtering circuit and on reducing the power supply’s output impedance. The separation of the transformer from the rest of the circuit and its placement in a separate enclosure also plays a significant role in the final result. The changes implemented in this part of the unit include the main power supply as well as the power supply circuitry around the operational amplifiers. The first section houses the transformer, the rectifier circuit, and the first stage of voltage regulation. The second stage is located in the preamplifier’s main chassis.
The preamplifier and power supply enclosure is constructed from rectangular-section tubing, which has significantly improved its rigidity. All components are made of non-magnetic materials.
These extensive changes have improved dynamics, reduced noise levels, and created a soundstage with much greater breadth. Listeners familiar with the Sensor Prelude will be impressed by the improvements offered by the SENSOR 2 MkII, and its new owners will be able to enjoy an unparalleled listening experience with vinyl records.
The MkII version is an upgraded version of the base Sensor 2. The printed circuit boards and some electronic components have been modified, and the RCA jacks have been replaced with the excellent Furutech FT-903R terminals.
Technical Specifications
| Input sensitivity: | 0,3 – 5 mV (adjustable) |
| Sensitivity adjustment: | 0,3 – 0,4 – 0,6 – 0,9 – 1,4 – 2,5 – 5 mV |
| Reinforcement: | 52 – 76 dB (2 V rms exit) |
| Input impedance: | 20 ohm – 47 000 ohm |
| Impedance adjustment: | 20 – 30 – 50 – 100 – 200 – 400 – 1000 – 47 000 ohm |
| Input capacity: | 100 pF |
| Input operating mode: | symmetric – asymmetric |
| Entry: | RCA |
| THD: | 0,01% |
| S/N: | 85 dB |
| RIAA Linearity: | +/- 0,3 dB (20 Hz – 20 kHz) |
| Output impedance: | 70 ohm |
| Output: | XLR, RCA |
| Nominal output level: | 2 V rms |
| Maximum output level: | 8 V rms |
| Dimensions: | 245 x 227 x 110 mm – preamplifier 122 x 230 x 70 mm – power supply |
| Weight: | 3,5 kg – preamplifier 1,7 kg – power supply |
| Recruitment: | max 17 W |
