D-28 (ES9038Pro):

Discrete true balanced DAC + true balanced headphone/preamp

Features XLR / RCA analogue inputs and four digital inputs

Uses Sabre ES9038Pro top-of-the-line chip

USB / HDMI support for DXD and DSD Native 512, 32Bit /384KHz

Extremely sophisticated 10-group dual regulated power supply

1500 mW @ 100 ohm (per channel) pure Class A output power, sufficient to drive most headphones

Up to 9500 mW @ 25 ohm (per channel) with two gain levels, driving 80+ DB sensitivity headphones is a breeze

All filter settings can be controlled via the panel, no need to open the case.

28 Standard Edition: ES9028 PRO

38 Standard Edition : ES9038PRO

38 Upgrade: ES9038PRO, Accusilicon femtosecond clock and USB interface to upgrade two Crystek femtosecond clocks

Complimentary Mini remote control:

Upgraded version using Accusilicon clocks and USB interface Crystek clocks:

Product Overview:

True balanced all-transistor feedback-free CAST amplifier circuit and zero-distortion diamond output stage circuit

The ES9038PRO is powered by a 10-group regulated power supply and the digital circuitry is powered by a dual regulated power supply using seven high-speed regulated power supplies.

Two sets of ultra-low noise transistor servo power supplies supply the ES9038PRO's internal DACs with separate left and right supplies, maximising the ES9038PRO's performance

Analogue circuitry using two fully transistorised regulated power supplies

Four-channel digitally controlled relay I/V-converted 100-step volume control to avoid channel imbalance and sound degradation

Volume board uses 0.1% accuracy resistors in parallel to achieve 0.05% accuracy

High power, high performance R-type transformer

Panel-settable digital filter operating mode makes changing the tone a breeze

High and low gain modes, low gain for driving normal sensitivity high and low resistance headphones, high gain for driving ultra low sensitivity headphones

Multiple internal shielded isolation panels to separate the power input socket, transformer, power supply regulator, digital and analogue circuits to avoid interference between the different sections

4 digital inputs : USB / I2S / Coaxial / Optical

2 analogue inputs : XLR / RCA

DAC and preamp outputs : XLR / RCA / CAST

Headphone output : 4-pin XLR / 6.3MM SE

Best sound quality for short signal transmission：

The D-28 uses the latest ESS top-of-the-range Sabre32 DA chip ES9038Pro, which supports up to 32Bit/768KHz.

The CAST circuit is inherently current mode, and we designed the CAST circuit with balanced inputs to transfer the current signal from the ES9038Pro to the output for I and V conversion, which requires only one CAST circuit for one channel. The ES9038Pro is designed to process signals through a single stage.

This extremely short signal transfer design provides optimum detail and dynamic reproduction with virtually no tonal colouration, allowing the true sonic timbre of the ES9038Pro to be fully realized.

The CAST circuit is a completely feedback-free circuit consisting of all transistors. As many enthusiasts are aware, loop feedback makes for better test metrics, while no feedback makes for poorer but more pleasing sound. CAST technology opens up a whole other dimension, with a more pleasing sound and high metrics, with very little tonal colouration and plenty of dynamic detail without sounding cold and hard.

Zero Distortion Diamond Output Stage:

The D-28 is designed with four zero-distortion diamond output stages acting as balanced output drivers, each cleverly designed to achieve zero distortion without further human adjustment.

This pair of diamond-shaped output stages uses four pairs of 15W transistors to enhance the output drive, while the balanced drivers increase the output power by four times compared to unbalanced drivers with the same power supply, driving even high or low resistance headphones to a snug fit.

For better reproduction of musical details and flavours, the unit is designed with a considerable amount of pure Class A output power (1500mW @ 100 ohms, 9500mW @ 25 ohms). Most headphones can be connected to work in pure Class A.

The balanced drive cancels out noise and distortion at the output, resulting in a more tranquil soundstage and clearer detail.

The performance of this unit is excellent even when used as a simple headphone amplifier or preamp, connected to an external DAC.

Separate power supply from multiple power sources is key to ensuring sound quality:

The D-28 uses an R-type transformer made from imported materials and uses 10 groups of regulated power supplies to power the whole unit.

Seven of these high-speed regulated power supplies form a double voltage regulator to separate the power supply to the digital circuits.

The DAs in the ES9038PRO are very sensitive to the power supply, so two ultra-low ripple transistor servo power supplies are designed to provide separate power supplies for the left and right DAs, increasing the dynamic range and distortion by at least 15DB compared to common ultra-low noise regulator ICs, bringing the ES9038PRO's performance to the limit. The separate power supply for the left and right DAs allows the sound to be virtually crosstalk-free and the soundstage to be wider.

The D-28's analogue section is powered by a discrete, high-speed linear power supply. Although the circuitry is much more complex than the three-terminal regulated power supplies used in some other products, the positive improvement in sound quality is worthwhile and necessary, resulting in a higher signal-to-noise ratio and better dynamic and transient response with a strong analogue flavour.

The I/V switchable volume control does not degrade the sound quality:

There are two common types of control used for DAC + headphone/preamp.

One is controlled in the digital section of the circuit, but every 6DB reduction in volume costs the DA one bit of accuracy, and even with a 32-bit DA chip, you may actually get less than 16 bits of accuracy if you listen at low volumes.

Another option is to use a volume control at the input of the headphone, but the quality of the volume potentiometer has a direct impact on the sound quality, causing loss of detail and channel imbalance that affects the soundstage. Even a high quality potentiometer will result in a loss of detail.

Both ways can degrade the sound quality.

In the D-28, we use an I/V converter volume control, which acts like a variable passive I/V resistor converter, operating on a current signal rather than a voltage signal. The volume control simply converts the current signal from the CAST circuit into a voltage signal, which (like the passive I/V converter from the R-2R's DA chip) results in a wider and flatter frequency response without loss of detail, and no deterioration in sound quality at any volume level. This is followed by four zero-distortion diamond feedback-free output stages.

To achieve the lowest possible channel imbalance, the resistors on each of the four 100-stage volume controls used in this unit are all reconnected in parallel with 0.1% resistors to achieve 0.05% accuracy.

As the user adjusts the volume, the different relays switch the resistors, so the output may have a slight relay switching sound, which will disappear once the volume is stopped.

Shielding to avoid interference：

The D-28 has multiple shielded isolation panels inside to separate the transformer, the power supply regulator, the digital circuitry and the analogue circuitry to avoid interference between the different parts. Even the power input IEC socket is shielded with a copper shield.

Instructions for use:

Input mode:

Press the "Input" button to select the input signal source.

Input 1: USB input

Input 2: HDMI-IIS input

Input 3: Optical input

Input 4: Coaxial input

Input 5: RCA Analogue Input

Input 6: XLR Analogue Input

Gain mode:

Press the "Gain" button and the display will alternate between "L, H" .

"L" means that the machine is operating in low gain mode (10DB) for normal sensitivity headphones.

"H" means the machine is in high gain mode (20DB) for low sensitivity headphones such as the HE-6 or low output level sources.

With our new gain control technology, no in-line switches, relays or amplifier parameters are changed when switching between gains, so the sound quality is exactly the same at different gains, the user just needs to select the right mode to make the volume control more convenient for personal adjustment.

Output mode:

Press the "DAC/HP" button and the display will show "P , H" in turn.

"P" means that the signal is output from the XLR / RCA / ACSS on the back of the machine. Each group of outputs can be connected to several amplifiers at the same time.

"H" means that the signal is output from the headphones on the front of the machine.

"d" is displayed when the switch on the back of the unit is pressed and the panel is switched to the original "P" state, at which point the volume cannot be adjusted and the unit will be used as a pure DAC output (if using the unit as a preamp). (If using the unit as a preamp, be sure not to set the unit to DAC output). The headphone output will always have a volume control function.

The I2S input supports DSD/PCM:

The D-28 automatically detects the signal from the I2S input and filters out the POP noise during song selection if it is a DSD signal.