Please search Queenway PRE-501TU for trial videos
Technical specifications:
*Electronic tube: 4*ECC82/12AU7,
*Gain high(H)/low(L)display,
*2.4inch LCD display,
*Volume knob and Gain H/L switch (press it), Volume progress bar (white line),
*IR Remote Sensor,
*Input Selector，
*Input: 2sets RCA,
*1set XLR (Each channel setting has a separate memory),
*Output: 1set*RCA, 1set*XLR ,
*Frequency response: 20Hz-30KHz,
*Rated harmonic distortion:<0.06%(maximum) @ 1KHz,
*Signal to noise ratio: High gain mode:90dB,
*Low gain mode: 110dB High gain mode: 100dB,
*Maximum output voltage: 12V
*Input impedance: 100KΩ @ RCA input, 50KΩ+50KΩ @ XLR input,
*Volume attenuation: 30 step relay array volume attenuation circuit ,
*Gain: Low gain mode -6dBHigh gain mode:12dB,
*Transformer input switch (only fit for input2-3),
*LCD brightness adjustment, 1.2.3.4 level brightness,
*Phase 0°/180° switch, P=0°, N=180°,
*Transformer ON/OFF.
*Power supply: AC 110V or 220V 50-60Hz *Power consumption: 40W
*Size: 430mm(wide)*430mm(high)*120mm(deep)
*Net weight 12.5Kg
Note: This video is a bit compressed, you can view the video in the link
https://youtu.be/QCchXaxGq58
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1.It is carefully designed in all directions, and the interior of the machine is designed with an integrated and ultra-high degree of integration.It brings together the difficult technical design of weak-signal analog amplifier circuit, digital logic circuit, vacuum tube high-voltage amplifier circuit, low-signal transmission circuit, and stabilized power supply circuit.
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2.The volume attenuation method adopts the highest fever specification design-purely mechanical switching of signals.All use original imported Japanese OMRON ultra-low signal special relays, and only a single relay is strobe for each level of volume to ensure that the audio signal loss is minimized.This effect is far better than the common carbon film sliding potentiometer or multi-resistance sliding potentiometer volume attenuation method, which can be said to be a world of difference!
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3.The shell panel is simple and generous, with a remote control and LCD screen display, and the interface is friendly.Each channel can set and store parameters separately, and has functions such as fast switching of input channels, loading selection of input channels, adjustable output positive and negative phase, adjustable display brightness, and silent boot protection delay.
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4.Use 4 12AU7/ECC82 tubes with strictly matched parameters to ensure that the vacuum tube amplifier circuit keeps working in the best condition.
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5.The CPU processor core running the embedded software system uses the enhanced high-performance ST ST's ARM Cortex-M3 STM32F103VET6 to ensure sufficient processing performance.
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6.The AC input terminal uses a high-purity oxygen-free copper OFC-wound conjugated filter inductor to isolate clutter interference from the external power grid and improve the audio effect.
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7.Each phase of the power supply is all supplied by a high-precision regulated power supply to ensure that the voltage ripple is minimized and the audio characteristics are optimal.In addition, each digital circuit and each analog circuit are completely separated from the transformer coil power supply, minimizing the crosstalk of various circuits to achieve the ultimate performance effect.
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Internal detail circuit board
1.CPU logic control circuit：
2.DC2DC regulated power supply Separeted power supply for filament and digital logic module：
3.The First and Second section tube amplifier! power supply circuit：
4.Main differential balance tube amplifier circuit：
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5.30 levels relay array volume attenuation circuit：
6.Input source select and transformer translated circuit:
Frequency response 1
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Frequency response 2 (20Hz -30kHz ± 0.3dB)
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THD+N total harmonic distortion
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SNR signal-to-noise ratio (A-weighted)
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Maximum output voltage 12V
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Usage scenario diagram:
Silver 
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