Please note.

This is a 100W pure Class A amplifier and will operate at a temperature of approximately 50°C. Do not place in a poorly ventilated cabinet.

Overview:

The fully negative feedback-free CAST circuit gain stage operates in a pure Class A state, with no OPA or coupling capacitors used in the signal path

Completely feedback-free output stage with linear fax technology, avoiding switching distortion and providing excellent linearity

2 inputs: XLR / ACSS, even with XLR inputs, the signal is amplified by the CAST amplifier

Uses 80 ON Semiconductor high power transistors. 100W X2 (8 ohms) pure Class A output power and 150W X2 (8 ohms), 600W X2 (8 ohms) maximum output

Two high quality ring bulbs and two R bulbs for a total of 4 transformers with a total power of 1800W, 260,000 UF filter capacitors for separate power supply to the left and right channels

Four pure Class A parallel regulated power supplies

All high quality audio components are used, including DALE resistors, WIMA, NOVER (UK brand) capacitors and audio grade input and output sockets as per our requirements, gold plated RA power sockets

All components of the four balanced channels are precisely matched for installation

The graphs below show the distortion curves for this machine.

The main purpose of negative feedback technology is to reduce distortion.

Some people believe that while negative feedback reduces distortion, it also makes the sound unnatural.

Although negative feedback designs have a low distortion rate when tested with static loads, once an inductive load such as a real loudspeaker is connected, the electrical potential of the loudspeaker operation is fed back into the amplifier input from the feedback loop and the resulting distortion increases significantly and has a significant impact on the sound quality. A completely feedback-free design avoids this disadvantage completely.

Negative feedback techniques reduce distortion, but distortion increases as the output power increases. This makes it easy for some of the larger dynamics to fly off the speakers during listening and come crashing down on you with a sense of dissonance.

Distortion is usually higher and less controllable in designs without feedback. This is especially true for output stages operating at high currents.

The gain amplifier in this unit is a completely feedback-free amplifier using CAST technology, which, due to its technical advantages, can be made to have very low distortion.

The output stage uses Rexchip's linear fax technology completely feedback-free technology.

The whole machine is working in a completely negative feedback-free state. However, as you can see from the graph below, the distortion level at 20Hz to 5KHz stays fairly flat and straight, ensuring a consistent sound when various instruments are played.

The distortion in the higher frequency range from 5KHz drops dramatically and is even lower than that of an amplifier that relies on negative feedback, fully demonstrating that Rexchip's Linear Fax technology has brought the amplifier's linearity to the ultimate level.

For example, the distortion of a $70,000 amplifier mentioned above is 0.018% at 20KHz, while the distortion of this amplifier is less than 0.002%.

The completely feedback-free, ultra-low distortion in the high frequency range, which relies on the excellent linearity of the line itself without the need for negative feedback, makes the sound particularly clear and detailed.

In addition, the output power of the unit varies from small to large, with less distortion, and the soundstage is very stable with a consistent, clear and rounded sound regardless of the size of the signal. The soundstage is very stable. Of course, the sound does not become rough and unpleasant when the volume and output power are high.

Noise + distortion at 8 ohms 10W output

Noise + distortion at 8 ohms 25W output

Noise + distortion at 8 ohms 50W output

Core:

The Master-2A is a truly balanced design post-amp that uses the latest CAST technology to push the sound quality of the XLR input as far as CAST, with an all-transistor design (the OPA op-amp is a DC servo circuit).

The Master-2A may look complex, but it is in fact the simplest design in the world, with many of the components used for power processing. The Master-2H applies only a single "voltage" gain stage (operating in the CAST current transfer state is actually a current gain stage) to handle the gain of the signal (whereas an ordinary OPA op-amp already contains two or three voltage gain stages). The simple and short signal processing channel results in a significant improvement in sound quality with minimal sound coloration.

The Master-2A uses a single stage CAST amplifier circuit with extremely low distortion and is mounted directly on the motherboard for better sound quality, and uses a Class A power supply.

The CAST circuit is a transistorised amplifier with no feedback at all. Many audiophiles know that a negative feedback design provides better test metrics, but a feedback-free design provides better listening. This is a contradiction between traditional circuits. But the CAST circuit breaks new ground by offering extremely low tone coloration, a very neutral and natural sound with very low distortion and excellent linearity. As a result, it reproduces dynamics and detail without sounding rough and dry.

The gain of the signal works in current mode, using a unique set of open-loop current mirrors for extremely low distortion amplification. All devices in the signal section operate in Class A.

The CAST section uses four high performance all-transistor Class A parallel regulated power supplies to form a dual regulated supply.

The Class A parallel regulated power supplies have very high input impedance and very low output impedance, effectively isolating the audio circuitry from the power supply to avoid power supply interference entering the audio circuitry, providing a clean and fast power supply to the circuitry.

All components of the Master-2A's balanced four channels are precisely paired and mounted.

Driver:

The powerful high power components and power reserves ensure that the output can drive most loudspeakers. The four-channel feedback-free diamond-shaped output stage uses 80 ON Semiconductor high-power transistors. The filtering capacity is up to 260,000 UF and the four power supply transformers have a total power of 1800 W.

Inputs:

The Master-2A accepts XLR signals as well as CAST current transfer inputs. Either way, the Master-2A is gain amplified in CAST mode.

Isolation:

The Master-2A uses a heavy, all-aluminium chassis to avoid transformer eddy currents being transmitted through the chassis to the circuit board. The signal gain board, output board and transformer are completely isolated using thick aluminium plates. The power cable is also connected from the rear of the unit to the front power switch via a special copper shielded channel.

Components:

All high quality audio components are used, including DALE resistors, WIMA and SOLEN capacitors, special NOVER (UK brand) capacitors as per our requirements and audio stage input and output sockets, gold plated RA power sockets. The output stage uses 80 ON Semiconductor high power transistors and all components of the Master-2A's balanced four channels are precisely paired and mounted.

CAST and XLR input options:

How to connect a preamp with RCA outputs:

The Master 2A is a true balanced design amplifier, so even if an unbalanced preamp with only RCA outputs is connected, it can be converted to balanced outputs within the amplifier without any additional design, and the improvement in sound quality is noticeable compared to some bridge amplifiers that are not true balanced designs.

When connecting an unbalanced preamp, the best way to connect it is to use the signal cable connection as shown below. Changing the RCA input on the Master 2A or using an RCA-XLR adaptor will introduce more noise.