
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
FRE-15W
FRE-30W
THD-1W
THD-15W
THD-30W
SNR-L
SNR-R
Sensitivity
Channel Seperation
Channel Isolation
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
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