Предусилители — Kondo Audio Note Japan G-70i

The G-70i is a stereo valve line preamplifier from Kondo Audio Note Japan and the revised form of the G-70, which was introduced in late 2010 at USD 33,968. At that time the G-70 was presented as a smaller version of the M1000MkII preamplifier, and it shares its chassis width and height with the GE-1 phono amplifier that was designed alongside it. Kondo describes the aim of the design as combining the qualities of classic valve circuits with modern measured performance.

Key specs that matter

There are four single-ended RCA inputs with a 50 kohm impedance, together with two RCA output pairs meant for loads above 20 kohm. Gain is 25 dB. Frequency response runs from 10 Hz to 240 kHz within 0 and -3 dB, measured into a 100 kohm load, and residual noise is below 0.15 mV. The valve complement is two 6072 twin triodes for the audio circuit and one 6X4 rectifier. Power consumption is 21 W. The case measures 303 mm wide, 160 mm high and 408 mm deep, and the weight is 17.5 kg.

Engineering and use context

Each channel uses a plate follower directly coupled to a cathode follower, so there is no coupling capacitor between the two halves of the 6072, and the cathode follower gives the stage a low output impedance for driving cables and power amplifiers. Parts are wired straight to one another on module boards to keep signal paths short and less open to interference, and every channel has its own decoupling capacitors so that the signal loop stays small. The supply rectifies with the 6X4 valve and uses a transformer made to Kondo's own design with measures against vibration. Each channel has 700 uF of reservoir capacity, built from three capacitor types in parallel of 600 uF, 100 uF and 0.47 uF. Construction relies on silk-covered silver wire, Kondo silver foil capacitors, resistors with silver leads, metal film resistors, the company's own RCA jacks and a copper chassis, all chosen through extended listening. On the earlier G-70, volume was handled by an Alps HQPro control and the transformers and chokes came from ISO Tango.

Pairing

There is no phono section, so records need a separate phono amplifier such as the GE-1. With two outputs, one pair can go to the main power amplifier while the other drives a second amplifier or a subwoofer, as long as each input is above 20 kohm, which most valve and transistor power amplifiers meet. All connections are single-ended.

Alternatives

The Kondo G-72i is a line preamplifier with four 6072 valves, a 6CA4 rectifier and two XLR inputs next to three RCA pairs.