BALANCED PREAMPLIFIER WITH ACSS CONNECTIONS

Fully balanced Class A design built from discrete analog stages with no OPA or coupling caps in the signal channels.

ACSS analog output stage without feedback.

It uses three R-core transformers (total 145W) and audio-grade NOVER capacitors of over 36,000 uf are used to ensure wide and smooth power delivery.

4 PSU class A power supplies for left and right audio signal amplifiers.

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

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

Two gain modes, the high one has 16DB and the low one has 6DB, for more flexibility.

5 analog inputs: RCA X2, XLR X2, ACSS X1 (also with RCA or XLR inputs, ACSS output available)

3 Outputs: XLR / RCA / ACSS (ACSS and XLR / RCA have separate output circuit design so you can connect 3 power amplifiers at the same time).

Unique ACSS technology without feedback

HE-1 LE balanced applies the brand new ACSS design. It sounds complex, but it actually represents the simplest design the Hi-Fi world has ever had. The HE-1 LE integrated amplifier has a single "voltage" gain stage to process signals, but operates in ACSS mode, so in effect it is a current gain stage instead of voltage, while normal OPA chips do already include two or three stages. The simpler and shorter signal travel brings out the more neutral and less colorful sound.

HE-1 LE applies a very low distortion single-stage ACSS amplifier soldered directly to the motherboard. The gain stages and the diamond cross output stage work in pure class A state.

ACSS is a feedback-free technology built with fully discrete amplifiers. Most people know that global feedback design can offer better specs in test measurements while non-feedback can't work well in measurements, however it can offer better sound for human ears. ACSS offers a new field, as it can deliver a sound with minimal colouration, more neutral and with very low distortion and high linearity. So it can keep dynamics, details and neutral sound without sounding bright or harsh.

All the signal gain is current, obtained from the unique and superb open loop multiple output current mirror. The result is an incomparably precise and ultra-low distortion of the gain signal. The signal path is fully balanced and all transistors operate in class A mode.

Volume control

The volume control is also different from conventional technology. Conventional volume control technology involves volume control in the analog amplifier input stage via a potentiometer to reduce the signal. This way the quality of the pots directly affects the sound quality, a low quality volume pot causes loss of detail and channel imbalance causes sound distortion. Even the high-performance volume pot still causes loss of detail.

In our project, we applied the I / V conversion volume control, the volume control has a variable passive I / V conversion position at the output of the ACSS amplifier, where the output is the current signal and not voltage .

Volume control with I / V conversion, can keep the signal frequency band flat and not miss any detail. It cannot degrade on the sound quality in every volume level. After the loudness, there are four groups of non-feedback buffer stages that offer very low output impedance.

The quality of the volume control is very important in balanced design. The volume control must ensure the signal control of the four channels exactly to achieve the performance of the balanced design. If cold and hot the balanced signal cannot guarantee the exact balance, the balanced output will have a great distortion, since the quality and performance of the sound are even worse than those of a single final stage.

A four-channel digitally controlled relay based volume control is applied in our project. This machine has four total channels and uses DALE resistors to control the volume to avoid unbalanced channels.

The volume control has 100 steps, the control range reaches 90DB, a very easy control range on the first 50 steps, cooperate with a gain and evato of 20DB, so it can easily adjust the volume for headphones and speakers both high and low.

Components

S/N Ratio	>130DB
THD	<0.0005 %
THD+N	<0.0025%
Frequency Band (XLR input)	20Hz - 100KHz (<4DB )
Volume characteristic	100 steps Supper Exponential Volume Characteristic
Gain	High gain :+16DB Low gain : +6DB
Output Level (Max)	9.5V @ RCA  19V @ XLR 6MA @ ACSS
Output Impedance	10 ohm @ XLR >10M ohm @ ACSS
Input Impedance	94K ohm @ XLR <5 ohm @ ACSS
Channels cross	< -130DB
Channels imbalance	< 0.01DB
Power Requirement	1 Version  100-120V  AC 50/60 Hz 2 Version  220-240V  AC 50/60 Hz
Power Consumption	35W Class A  @230V or 120V
Transformer Power	145W (3 unit transformers)
Package Weight	Approximately 18KG
Dimensions	W430 X L485 X H123 (MM, Fully aluminium )
Accessories	Power cord  X1