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Model Variations
Version 1: RCA Single Transformer Finished Unit (Tubes Not Included)
Version 2: RCA Single Transformer with 6Z4 + Psvane Standard Pin Tubes
Version 3: Gold Single Transformer Balanced Finished Unit (Tubes Not Included)
Version 4: Gold Single Transformer Balanced Finished Unit with 6Z4 + Psvane Standard Pin Tubes
Version 5: Gold Dual Transformer Balanced Finished Unit (Tubes Not Included)
Version 6: Gold Dual Transformer Balanced with USA 6X4 + Russian EH Standard Pin Tubes
To address some shortcomings of the traditional Marantz 7 circuit, the Japanese designer Wadamasu made improvements based on the Marantz 7 circuit. The improved circuit is called the Wadamasu Circuit. Its main characteristic is the use of an SRPP circuit to replace the cathode follower of the Marantz 7 circuit. Since the SRPP output stage does not provide any voltage amplification and only acts as a buffer stage, it has a stronger load-driving capability compared to a ordinary cathode follower. In terms of tonal quality, it retains the sweet and lush midrange characteristics of the Marantz 7 circuit, while offering better resolution, high-frequency, and low-frequency response compared to the Marantz 7, along with a relatively higher signal-to-noise ratio. All the vacuum tubes used in this circuit can also be replaced with 12AT7 types.
Years ago, following a special request from a customer, I customized a unit where the high-voltage anode power supply filtering was handled by high-voltage oil-filled capacitors, and the input/output coupling capacitors also used oil-filled capacitors. The result, after completion, was a surprisingly different sound: intoxicatingly beautiful vocals, delicate highs, deep and powerful bass extension, and excellent sound balance! In one word: Perfect!!!
I. High-Voltage Power Supply Section
Utilizes the renowned 6X4 (EZ90) tube for tube rectification + Japanese Kubota-style high-voltage regulation circuit.
The 6X4 (EZ90) rectifier tube slightly outperforms domestic 6Z4 and Russian 6U4N tubes in speed, detail, and resolution.
The Japanese Kubota-style high-voltage regulation circuit uses Hitachi MOSFETs (2SK1170). As is well known, MOSFETs offer advantages like low output impedance, small ripple factor, and sweet sound. This is a distinguishing feature of this circuit compared to other sellers and a major highlight of this unit.
This circuit also includes high-voltage delay and protection against turn-on thumps, helping to protect the lifespan of the amplification section tubes.
Post-regulation is even more remarkable: a three-stage RC filter using (Siemens oil-filled and US "Dragon Label" GE Mexico original) oil-filled capacitors makes the voltage even cleaner.
The high-voltage oil-filled capacitors contribute to the superbly captivating vocals, delicate highs, and pure, thick, powerful lows, resulting in a very comprehensive and balanced sound performance!
II. Amplification Section
The left and right channels are independently separated.
Grounding uses a rational single-point star ground configuration.
Many people worry about noise in the Wadamasu circuit; indeed, it can be hard to overcome. However, there is completely no need to worry about noise in this unit. It has been debugged to an excellent state. Pressing your ear close to the speaker, you only hear a very faint tube thermal background noise. We believe every tube enthusiast can fully accept this level. If this cannot be accepted, then one shouldn't play with tube amplifiers at all.
This unit exclusively uses imported capacitors.
Filter electrolytics are Nichicon, Philips BC, Vishay, etc.
Input and output coupling capacitors are the expensive, imported German MCap (Mundorf) oil-filled capacitors.
The oil-filled capacitors create the intoxicating vocals, delicate highs, and pure, thick, powerful lows, giving the sound its comprehensively balanced character.
III. Chassis & Components
The power transformer spares no cost, using the expensive and rare R-core transformer in the audio world, typically seen only in high-end audio equipment.
The chassis is a high-grade full-aluminum chassis.
Large, solid full-aluminum knob.
Japanese original imported Canare signal cables, etc.
Resistors are imported KOA, Panasonic, Vishay, etc., making the sound purer and more transparent!
IV. Chassis Dimensions:
Width: 430mm * Height: 90mm * Depth: 360mm
V. Tubes Used in This Unit:
6Z4 / 6X4 (Can be switched manually via red jumper caps, allowing use of either 6Z4 or 6X4 tubes without an adapter).
Small signal amplifier tubes: 12AX7 (ECC83, 7025) * 2, 12AU7 (ECC82) * 2, or alternatively 12AT7 (ECC81).
VI. Standard Tube Package Options:
Single Transformer Version: Rectifier Tubes: 6Z4 * 2, Psvane Standard Pin ECC83 * 2, ECC82 * 2.
Dual Transformer Version: USA 6X4 * 2, Russian EH Standard Pin 12AX7 * 2, 12AU7 * 2.
VII. Technical Parameters:
Frequency Response: 5Hz - 30kHz (No Load). Note: The US ATS-AP tester can only measure up to 30kHz; the actual unit likely exceeds 50kHz. 20Hz - 33kHz (with 3.3kΩ load).
Total Harmonic Distortion: 0.0056% (at 1kHz, 1V output).
Amplification Factor: 14 times.
Maximum Output: 14V (with 3.3kΩ load).
Signal-to-Noise Ratio: 92 dBu.
Input Impedance: 100 kΩ.
