KONDO AUDIO NOTE JAPAN M7 HERITAGE TUBE PREAMPLIFIER IN-DEPTH INFO


There were numerous requests about the Kondo Audio Note Japan M7 Heritage tube preamplifier, so here is my homework being done... The iconic and traditional Audio Note Japan preamplifier "M7" that has been moving along with the history of audio notes. In the late 1980's, it evolved into a vacuum tube preamplifier "M7 TUBE" and gained fame with the power amplifier "ONGAKU" announced at the same time. Especially in Europe, M7 TUBE still has strong fans. M7 Heritage has been refined with current technology while maintaining its dynamic sound image.

The high-quality parts that have been auditioned and the careful circuit configuration have improved basic performance and improved connectivity with modern systems. In addition to sound quality full of life, a wide and stable sound field and low noise level are realized.


Rebuilding tradition with the latest technology, the M7 Heritage will bring fresh pleasure to your audio life.


Characteristics

  • The M7 Heritage has been refined with current technology while maintaining the dynamic sound image of the M7 preamp.
  • In addition to the dynamic sound quality of the M7 preamplifier, a wide and stable sound field feeling and a modern low noise level are realized.
  • The phono circuit added a cathode follower to the two-stage NF circuit of SRPP + plate follower, and made the low impedance output and the RIAA deviation minimal.
  • The line circuit was a plate follower with parallel operation and a cathode follower direct connection system, ensuring the freshness and direct feeling of sound with low impedance output.
  • Equipped with a shunt-type heater circuit adopted in the G-1000, it is also resistant to voltage fluctuations and ensures ideal operating conditions.

Phono amplifier unit

The modularization of the phono amplifier section achieves good hand-wired wiring and a short path equivalent to a printed circuit board. The decoupling capacitors are placed independently on the left and right near the module to minimize the signal loop.


The first stage adopts the SRPP circuit of ECC803S (12AX7), and the 6072 (12AY7) is adopted as the plate follower of the second stage and the cathode follower of the third stage.

Line amplifier unit

The modularization of the line amplifier unit achieves good hand-assembled wiring and a short path equivalent to a printed circuit board. The decoupling capacitors are placed independently on the left and right near the module to minimize the signal loop.


The 6072 (12AY7) plate follower and cathode follower direct connection method achieve an output impedance of 500Ω and a cutoff frequency of 18Hz (at the time of a 20kΩ load), and have a strong driving force.

Power supply circuit, shunt type heater power supply circuit

Rectifier tube adopted EZ81 (6CA4). The original power transformer has been repeatedly listened to and subjected to appropriate vibration suppression processing. In addition, a powerful power supply unit is configured by clearly separating the ripple filter capacitor and decoupling capacitor for circuit design and mounting design. The decoupling capacitor is composed of three types of capacitors, and contributes to a good tone while suppressing the habit of each capacitor.


The shunt-type heater circuit eliminates ripple components with a DC12.6V ignition and a capacitor group of 91,000μF, contributing to the sound field reproduction with no fluctuations. In addition, the shunt-type regulator circuit has no change in the heater voltage within the range of power supply voltage fluctuation ± 5%, and has completed a very stable ideal ignition circuit.

Ultra high quality parts

Including high-grade volume, copper chassis, pure silver foil capacitor, various original parts, electrolytic capacitor, pure silver lead resistance, SSW wiring material, KSL-VzII (pure silver shielded wire), RCA jack, vacuum tube socket, power transformer, choke coil, etc. High quality parts are adopted.


Many of the main components used are produced by skilled techniques based on the accumulation and sharing of know-how over the past 40 years.

In addition, carefully selected parts are effectively placed in various places.

Main specifications

  • Basic configuration: Stereo preamplifier
  • Product name: M7 Heritage
  • Model: M7H
  • Input: terminal / impedance phono 2 system (RCA x2, unbalanced) / 47kΩ
  • Line 4 lines (RCA x3, XLR x1, unbalanced) / 50kΩ
  • 3 output terminals (RCA x2, XLR x1, unbalanced, load 20kΩ or more)
  • RIAA deviation: ± 0.3dB (30Hz-20kHz, excluding low cut)
  • Frequency response: 8Hz to 280kHz (+ 0dB, -3dB / 100kΩ load, unbalanced input)
  • Total harmonic distortion: 0.07% (1kHz, 1V, line section)
  • Residual noise: less than 1.5mV (phono input → line output)
  • Less than 0.15mV (line input → line output)
  • Gain: 63dB (phono input → line output)
  • 25dB (line input → line output)
  • Vacuum tube: ECC803S x2, 6072 x2 (phono section)
  • 6072 x4 (line part)
  • EZ81 x1 (power supply)
  • Power consumption: 38W
  • Dimensions: (excluding protrusions) 438mm (W) 160mm (H) 330mm (D)
  • Weight: 15kg