Audio-GD - HE1 LE – Linear Power Balanced Pre-amplifier (RCA, XLR, ACSS)

HE-1 LE (Linear Power Supply Balanced Pre-amplifier)

The first generation HE-1 was released in 2015.

Since 2016, there have been questions about a new version.

The design of the analog circuits is developing more slowly than the digital designs. Especially the analogue designs at Audio-GD which are already very good. Completely discrete and HE series matched transistors.

Since the first generation Master-1 was released, we have not changed the design, we always wanted to upgrade the design, but the possibilities did not lend themselves to it. After 9 years of testing and trying we have released a new test version and now we are releasing the new version. It adopts the perfect layout technology, the sound quality improves greatly. Better detail and dynamic reproduction, the sound is even less harsh.

Functional changes have also been made such as:

1. Two gain modes to support a wider range and better matching of power amplifiers

2. Double volume control which can match well with the different output level sources.

3. The new design applies the exact same design of left and right channels. so not mirrored, so that there can be no difference in left and right channel to guarantee consistency.

HE-1 LE and HE-1 MK2 DIFFERENCE

HE-1 MK2 has built in regenerate power supply that can filter all power line noise and provide the pre-amplifier the cleanest power to the analog boards .

The HE-1 LE has built in the linear power supply , benefit from the built in pure class A PSU that can offer very clean power to the analog boards.

Both HE-1 and HE1 mk2 share exactly same analogue circuits and functions.

SUMMERY

Fully balanced class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.

Non- feedback ACSS analog output stage.

Uses three R-core transformers (In total 145W ) and more than36,000uf audio grade NOVER capacitors are used to ensure ample and smooth power delivery.

4 group class A PSUs power supply for Left and Right audio signal amps .

Four-channel 100 steps digitally controlled relay-based volume control avoids channel imbalance and improves sound quality.

Four-channel 9 steps digital controller relay-based pre-volume control can control the source input level from 0DB (Bypass) to -8DB.

Two gain modes, high gain has 16DB and low gain has 6DB, which is more flexibility for the different gain power amp .

5 analog inputs: RCA X2, XLR X2, ACSS X1 ( Even with RCA or XLR inputs, the output still had ACSS aviable)

3 outputs: XLR / RCA / ACSS (ACSS and XLR/RCA have the separate output circuit design so they can connect 3 units power amp simultaneously)

Unique non-feedback ACSS technology

HE-1 LE is a true balanced design applying the newest ACSS design which can improve the XLR connection to sound as good as the ACSS connection. The HE-1 LE seem complex , but in fact they are the most simple design the world has ever had , their a lot components to process the power supply. The simplest and shortest signal journey brings out the most neutral and least colored sound.

HE-1 LE applies ultra-low distortion single stage ACSS amplifier , an OPA already had built in two stages amplifier. they are soldered directly on the motherboard.

The ACSS is a non-feedback technology made with discrete amplifiers. Most people know the global feedback design can offer better specs in test measurements, and non-feedback can’t do well in test measurements but can offer better sound for the human’s ears. Here is a conflict of the classic circuits.

But the ACSS opens a new field, it can offer a least coloration sound which is more neutral with very low distortion and high linearity. So it can retain the dynamics, detail and neutral sound but not sound bright or harsh.

All signal gain is in current area, all transistors work in class A mode and applies class A power supplies.

HE-1 LE has all components of four channels exactly matched before installation.

Uses three R-core transformers (In total 145W ) and more than36,000uf audio grade NOVER capacitors are used to ensure ample and smooth power delivery.

4 group class A PSUs power supply for Left and Right audio signal amps .

conversion volume control technology

The volume control is also different from conventional technology. Conventional volume control technology is the volume control implement in the analog amp input stage through a volume pot to reduce the signal . The volume pots quality effect the sound quality direct , the low quality volume pot cause lost the detail and channels imbalance cause the soundstage distortion . Even the high performance volume pot ,in the attenuation then gain the signal mode ,still cause the detail lose and cause the S/N worst .

In the HE-1 LE, we applied the I/V conversion volume control , the volume control just a variable passive I/V conversion place at the ACSS amp output , where the output is the current signal, not the voltage signal. The volume control is I/V conversion, and the volume depends on the current (I) conversion to the voltage (V). (Like R-2R D/A chips output passive I/V conversion) It can keep the signal frequency band flat and not lost any detail. It can’t degrade on sound quality in every volume level . After the volume , there are four groups FET non-feedback buffer output stages offer the very low output impedance .

The volume control quality is much important in the real balance gear . It must guarantee the four channels signal control exact to achieve the performance of the real balance gear . If the cool and hot of the balance signal can’t guarantee exact, the balance output will has large distortion cause the sound quality and performance even much worst than a single end gear , waste the balance gear design and the cost.

In HE-1 LE is applied a four channels digital control relays based volume control, through changing the tolerance 0.05% resistors to control the volume for avoid channels imbalanced ,achieve the best performance and sound quality of the gear.

HE-1 LE have 100 steps volume control, applied Supper Exponential Volume Characteristic, easy match the volume with different power amp and speaker .While change the volume, the different relays break or close, it may had slightly switch sound on output and disappear while stop change the volume.