Version Description:
Version 1: Silver panel with remote, VU meter, tone control, balanced ports, full aluminum
Version 2: Silver panel with remote, tone control, balanced ports, full aluminum
Version 3: Black panel with remote, tone control, balanced ports, full aluminum
Version 4: Silver panel with remote, tone control, full aluminum chassis
Version 5: Black panel with remote, tone control, full aluminum chassis
Version 6: Silver panel with remote, tone control, steel chassis
Version 7: Black panel with remote, tone control, steel chassis
Version 8: Silver panel with VU meter, tone control
Version 9: Black panel with VU meter, tone control
Version 10: Silver panel, no tone control, Standard Edition
Version 11: Black panel, no tone control, Standard Edition
Version 12: Silver panel, no tone control, Economy Edition
Version 13: Black panel, no tone control, Economy Edition
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In response to numerous requests from audiophiles, we are now introducing remote-controlled models with balanced input and output: featuring a full aluminum alloy chassis, 4 imported permalloy transformers for true transformer-balanced input/output ports, using genuine ALPS imported motorized volume potentiometers, and premium components such as DALE resistors (USA), Panasonic resistors, military-grade "Big Red Robe" resistors, vintage oil-filled capacitors, German WIMA, German ERO, Siemens "Thousand-Layer Cake" polypropylene capacitors, and Teflon internal signal wiring.
The Japanese ALPS motorized potentiometer uses a motor to drive a traditional potentiometer for volume adjustment, ensuring no impact on sound quality. It is fully sealed, has a long lifespan, and is free from interference. It does not use electronic chips for volume control, as electronic volume controls can affect sound quality.
Standard and Remote-controlled Editions are equipped with the following tubes: 2x Psvane ECC81 or Shuguang 12AT7, 2x Psvane ECC82, and 2x Shuguang or Yunguang J-grade 6Z4.
Economy Edition is equipped with: 2x Beijing 6N2, 2x Beijing 6N1, and 2x Shuguang or Yunguang J-grade 6Z4.
Please contact me if you require a Bluetooth module to be installed.
The 728A has been in production and sales for over a decade, with multiple improvements. It utilizes 4 vintage oil-filled capacitors for coupling, combined with high-resolution German WIMA, ERO capacitors, Siemens capacitors, and other polypropylene capacitors, resulting in a warm,detail sound without sacrificing detail!
(Note: As the oil-filled capacitors were produced by old military factories many years ago and are from stock, batches may vary in appearance and condition. Please be aware of this before ordering to avoid disappointment.)
The internal signal wiring uses imported Teflon silver-plated wire, which helps enhance signal detail, reduce signal loss, and minimize induced noise. The circuit parameters have also been adjusted for modern high-level audio sources, ensuring large signals pass through easily without clipping.
This unit has absolutely no background noise! If noise occurs, please check if your signal cables are shielded, if a ground loop exists, or if there is a ground potential difference!
The circuit, originally introduced by Japan's Wada Shigeru in the early 1960s, offers excellent performance. It retains the deep & rich and musical character of the Marantz 7 while surpassing it in dynamics, transients, frequency response (high and low), resolution, and signal-to-noise ratio. In terms of soundstage and transport, it is on par with the Marantz 7.
The improved 728A tube preamplifier is one of our company's most highly praised and recommended products by customers and dealers alike. It features mature design, outstanding sound quality, stable performance, and a excellent reputation, selling well both domestically and internationally. This unit can be connected to a pure power amplifier or used with an integrated amplifier as a tone controller to further enhance sound quality. The actual sound quality of an audio system depends on the source, pre/power amplifiers, and speakers. If other components in your system are well-matched, this unit will not disappoint. Please consult our online constom service before purchase for objective advice for reference.
I. Product Introduction:
This unit is based on multiple improvements over the third-generation 728 tube preamp. Compared to the original, it features a more elegant, dignified, and tasteful exterior design. While retaining all its advantages, it adds the following:
Utilizes a printed circuit board design for a more rational, neat, and aesthetically pleasing internal layout. The front panel is made of 6mm thick silver aluminum with an electroplated brushed finish, featuring a blue power indicator and a unique large display window for the tubes with a warm red-orange background light, enhancing its grade and taste level (see pictures below).
High-quality sandblasted paint finish on a thin steel chassis, high-gloss metal knobs, and honeycomb-style large feet.
4 sets of stereo input switching, using a traditional rotary switch to control high-grade, fully sealed relays for signal switching, avoiding switching noise and ensuring long life. Signal output uses relay delay; the relay engages after the amplification tubes have stabilized, avoiding unpleasant noise during the tube warm-up process.
Provides two sets of signal outputs for bi-amplification systems. (Note: The manual may label them as High and Low level, but current production units have identical outputs. Please refer to the actual unit.)
Both input and output interfaces use gold-plated RCA connectors to reduce contact resistance.
Power inlet uses a standard 3-pin socket for easy power cable upgrades.
Includes a power line filtering circuit to remove interference from noise and stray signals and DC components from the mains.
Utilizes vintage oil-filled capacitors and imported WIMA polypropylene capacitors for coupling.
Standard Edition uses a high-performance R-core transformer, while Remote Edition uses a high-performance toroidal transformer (EI-core transformers have higher noise, lower efficiency, and greater magnetic leakage, making them unsuitable for small-signal amplification).
High-voltage section uses tube rectification with 2 tubes in parallel, providing sufficient current.
Two large filter capacitors combined with an inductor form an effective CLC filter circuit, suppressing residual noise.
Tube filaments are powered by AC, which yields a warmer, more pleasant and listenable sound compared to DC, prevents the sound from becoming hard or harsh, and extends tube life while minimizing filament interference.
II. Performance Parameters:
Dimensions: 435x90x290mm
Input Impedance: 100K ohms; Output Impedance: 600 ohms
Signal-to-Noise Ratio: 90dB
Frequency Response: 20Hz - 30KHz (±1dB)
THD: 0.01%
Internal Tubes: 12AT7 (ECC81) x2, 12AU7 (ECC82) x2, 6Z4 x2
Net Weight: approx. 5.6kg; Gross Weight (with packaging): approx. 8kg
III. Product Images:
728 with dual VU meters (custom imported meter movement, high magnetic steel, backlit, Japanese professional driver chip, excellent needle transient performance and accurate indication, not the type with erratic needle movement):
As the oil-filled capacitors were produced by old military factories many years ago and are from stock, each batch may use capacitors with different appearances and shapes, but we guarantee their parameters are not lower than the original specifications. Please do not order if this is a concern.
