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    JD90

    New Concept 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(at 1W into 8Ω) 0dB at 1kHz

    Frequency range:

    8Hz to 62kHz -3db; 0dB=30W1kHz, 8Ω

    6Hz to 60kHz -1db; 0dB=1W 1kHz, 8Ω

    THD+N:

    Less than 0.3% (1W),(20Hz-30kHz,8Ω).typically 0.07% at 1kHz

    Less than 3% (30W),(23Hz-30kHz,8Ω).typically ≤3% at 1kHz

    Circuit Mode: Current-Mode A Mode

    Bias adjustment: Auto Biased

    The amount of negative feedback: 6dB

    Input impedance: 100kΩ

    Input sensitivity:

    Max 1.4Vrms at 1kHz for 30W

    SNR:

    95dB at rated output,A-Weighted

    Rated output impedance:

    4Ω OR 8Ω

    Input Channel Isolation:

    More than 85dB below 20kHz

    Channel Separation:

    More than 85dB below 20kHz

    Tubes Used:

    4pcs KT90;2pcs 6922

    Machine size:

    17(W) x 14(D) x 9.6(H) inches

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

    Weight:

    78 lbs (33kg) N.W. 86 lbs(39 kg )G.W.

    Fuse:
    230 VAC/50HZ,T3.15A. 110VAC/60HZ,T6.3A
    Maximum Power:
    Not more than 300VA
  • FRE-1W

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    FRE-15W

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    FRE-30W

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    THD-1W

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    THD-15W

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    THD-30W

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    SNR-L

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    SNR-R

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    Sensitivity

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    Channel Seperation

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    Channel Isolation

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  • List of Tubes Used

    This machine uses two 6922 vacuum tubes and four 6SN7 vacuum tubes for the front stage of amplification. The rear stage uses four Russian KT88 vacuum tubes for push-pull amplification.

    TF* is Tube Fidelity Company's special pure thickness sound processing Tube, which has the effect of pure thickness and pure sound, eliminating noise, and improving sound quality.

    Vacuum tube model for this machine

    6922EH

    SVKT90

    Alternative vacuum tube options

    E88CC