A representative preamplifier equipped with NFB type equalizer is the MARANTZ Model: 7. This is a 3-step amplification NF equalizer based on 12AX7, which applies NFB from the 3rd stage cathode to the 1st stage cathode.(so-called “K-K type”). The advantage of the NFB type is that it does not require a high gain level and is not very sensitive to tube quality. However, the impedance of NFB at high frequency range becomes very low and results in a negative effect – the sound becomes hard and dry. The NFB type is usually used as it is an easier way to attain a good signal-to-noise ratio. As for the CR type, a masterpiece preamplifier equipped with the CR type equalizer is the vintage Harman-Kardon Model: “Citation IV”.