JD90

JD90

CURRENT-MODE Tube Power Amplifier

Introduction to the Characteristics of Products

1. The current-mode circuit architecture eliminates the intermodulation distortion inherent in traditional long-tail phase-split driving circuits, which is the primary factor degrading sound quality.
2. The current-mode circuit features a wide frequency bandwidth, high slew rate, and unlimited voltage swing, offering a large dynamic range.
3. The minimal use of vacuum tubes in the amplification path significantly reduces phase distortion.
4. The adaptive constant-current and constant-voltage hybrid biasing of the JD90 power tubes ensures push-pull arm current balance, minimizing DC magnetization of the output transformer.
5. The independent balanced feedback structure guarantees stability across the entire frequency spectrum and dynamic range.
6. The low-noise DC-regulated power supply for the driver stage achieves high power supply noise rejection and stable driving capability for the power tubes, overcoming the influence of Miller capacitance on the slew rate and delivering sharp dynamic performance.
7. The application of power tube temperature equalization and high-efficiency flat heat pipes significantly reduces the operating temperature of the vacuum tubes. The temperature of the power tube glass envelope decreases by over 100°C, greatly improving the lifespan and reliability of the vacuum tubes while achieving ultra-low background noise. The overall system achieves a signal-to-noise ratio (SNR) of 95dB or higher.

Amplifier technical specification

Stereo Output Power:  

30w per channel at 8 Ω, 8Hz to 62kHz, -3dB

Frequency Range:

 6Hz to 60kHz -1db; 0dB=1W 1kHz, 8Ω

 8Hz to 62kHz -3db; 0dB=30W1kHz, 8Ω 

THD+N:

Less than 0.3% at 1W output,20Hz to 30kHz,8Ω,typically 0.07% at 1kHz

Less than 3% at 30w output,23Hz to 30kHz,8Ω,typically ≤3% at 1kHz

Circuit Mode:    Current-Mode,Class A

Bias Adjustment:  Auto Biased

The amount of negative feedback:   6dB

Input Impedance:   100kΩ

Input Sensitivity:     Maximum 1.4Vrms at 1kHz for 30W

SNR:    100dB at rated output,A-Weighted

Rated Output Impedance:   4Ω or 8Ω

Input Channel Isolation:     More than 85dB below 20kHz

Channel Separation:     More than 70dB below 20kHz

Tubes Used:  4 x KT90；2 x 6922

Machine size:  17 width x 14 depth x 9.7 height (inches)

                     43.6 (W) x 36.4 (D) x 24.5 (H)  cm

Machine size:   Not more than 33kg Net,39 kg Packaged

Fuse:     230 VAC/50HZ,T3.15A. 110VAC/60HZ,T6.3A

Maximum Power:   Up to 300VA