XIANGSHENG 728A tube preamp Shigeru Wada circuit pre-amplifier

You can get the version Come WITH key to Adjust bass and treble like following too



 

Xiangsheng 728A Vacuum Tube Pre-Amplifier Upgraded Version 2015

The preamplifier has been improved many times on base of the third generation 728A tube preamplifier. Appearance elegant and dignified, extraordinary taste. Retain all its advantages and add the following advantages:

1. New 728A is designed with a circuit board, and the interior layout is more reasonable, clean and beautiful.

2. the front panel adopts Silver 6mm thick aluminum alloy plating drawing process panel, blue power indicator tube, and increased the unique electron tube to display the big window, the background uses the warm red orange, the grade, the grade is higher.

3. advanced sand blasting paint, thin steel plate case, high light metal knob, honeycomb type big machine foot.

4. signal input 4 groups of stereo switching, the use of traditional rotary switching switch control advanced full sealed relay to achieve signal conversion, to avoid switching noise, long life.

5. signal output adopts the relay delay, when the large tube is put into the stable working state, the relay takes in the output signal to avoid the unpleasant noise caused by the preheating process of the electronic tube.

6. output signal provides two sets of outputs and can play dual power amplifier systems.

7. input interface is made of gold-plated RCA lotus seat, which reduces contact resistance.

8. the power supply line adopts three plug socket, which is easy to replace and upgrade the power cord.

9. a network filter and purification circuit is designed, which can filter out the interference of clutter and the DC component in the grid.

10. It is using an antique oil capacitor, as well as imports of WIMA and other polypropylene capacitor coupling.

11. the transformer with the best performance in the transformer R power supply, but also the most expensive transformers (ring and square transformers, magnetic leakage, large radiation noise, low efficiency, while the efficiency of R cattle up to 90%, magnetic leakage minimal).

12 high voltage using electronic tube rectifier, 2 parallel, providing sufficient current.

13.2 large reservoirs, filter capacitor and inductance filter, constitute the best filtering CLC filter circuit, which suppresses the residual noise.

14. electronic tube filament AC power supply, compared with DC power supply, moist, listening, will not lead to sound hardening, extending the life of the electron tube. And ensure the interference of the filament to a minimum.


Specification:
Input Impedance：100K
Output Impedance：600 ohm
Total Hamonic Distortion： less than 0.01%
Frequeney Responses： 10Hz-30KHz
Signal to Noise Ratio： 90dB
Input Jack： 4 groups
Output Jack：2 groups
Input Power Voltage: AC 100V to 240V 60Hz/50Hz (100V, 110V ,120V,230V,240V,version will take 3-14 work days to order). 220v is in stock.
Size: 430mm(Width )×90mm(Height )×290mm(Depth )
tubes: 12AT7×2、12AU7×2、6Z4×2
Working environment: Temperature:5℃—40℃
Humidity：35%—80%
Weight：about 8.5 Kg
Gross weight: 9.5kg