INTRODUCTION

There are two main types of RIAA equalization systems, one is the NFB (Negative Feedback) type and the other is the CR type. A representative preamplifier equipped with NFB type equalization is the MARANTZ Model: 7. This is a two-stage NFB equalization based on 12AX7, which applies NFB from the cathode of the 3rd stage to the cathode of the 1st stage.

The advantage of the NFB type is that it does not require a high level of gain and is not very sensitive to the quality of the tubes. However, the resistance of the NFB at high frequencies becomes very low and has a negative effect – the sound becomes harsh and dry. The NFB type is commonly used as it is easier to achieve a good signal-to-noise ratio.

Regarding the CR type, a masterpiece preamplifier equipped with CR type equalization is the old Harman-Kardon Model: Citation IV. CR type equalization requires a high level of gain and is much more sensitive to the quality of the tubes. Since the quality of the tubes is directly amplified, the best possible tubes are required for this type of equalization. Additionally, proper implementation is more difficult. However, the CR type is much superior sonically to the NFB type, is very stable in the high-frequency range, and can reproduce very high-quality sound, especially when high-quality tubes are used.

VICTORY HISTORY

Country Publications Award Name France Revue du Son 5-STARS (July/August 2006)

The RS-28CX is equipped with CR type equalization based on GE (General Electric/USA) 12AT7, authorized by the J.A.N. (Joint Army & Navy) specification of the US Army, and can reproduce very high-quality and clear sound without adding NFB. To avoid degradation of sound quality, one of the solutions we implemented to fully protect the sensitive CR type equalization from negative effects was the development of a separate power supply unit. Similarly, some of the best available high-quality audio components were selected for the RS28C in order to maintain the RIAA curve deviation within +/-0.3%.

Of course, the phono preamplifier is only one of the advantages of the RS28C. Another notable feature is the very strong output voltage created by the Dual-Triode 6CG7 tube from General Electric (USA), used for the line stage. Leben further selected the best tubes from these and built a powerful SRPP type amplification that can provide power amplifiers with a maximum clean output signal of 80V. Considering that the output voltage of a typical preamplifier is roughly 40V, the RS28C can output about twice that voltage, which will drive power amplifiers with very low input sensitivity. Similarly, for using the RS28C with a powerful amplifier, there is a 5-step attenuator to eliminate residual noise from the speakers. Leben also includes two outputs (one fixed and one variable) to meet the requirements for adding a subwoofer.

RS-28CX SPECIFICATIONS

• Tube Complement: 2 x 6CG7 (G.E.)
• 2 x 12AT7 (G.E.)
• 1 x 5Y3WGT
• Phono Preamplifier Gain: 20.2dB
• RIAA Curve: Less than ±0.3dB.
• Maximum Input: 400mV (2KHz.)
• Line Amplifier Gain: 25.2dB
• Maximum Output: 80V (Variable) & 80V (Fixed)
• Output Impedance: 580 Ohms
• Residual Noise: 0.03mV
• WEIGHT: Main Unit: 7.0 Kg
• Power Supply: 6.5 Kg
• DIMENSIONS: Main Unit: 352(W) x 240(D) x 175(H) mm
• Power Supply: 233(W) x 240(D) x 175(H) mm

ACCESSORIES: AC Power Cable, Power Connection Cable.