A-1 :

True balanced current transfer, completely feedback-free post-amplifier

XLR and CAST inputs

Dual transformers for separate power supply to left and right channels

8 pcs total 1200W output tubes

125W @ 8 ohms output power.

Overview:

The gain and pre-output stages operate in pure Class A condition, with no OPA or coupling capacitors used for the signal channels,

Diamond-shaped crossover output stage design avoids switching distortion and gives the same performance as a Class A amplifier,

Fully negative feedback-free CAST circuit,

2 sets of inputs: XLR / CAST,

Uses 8 high power transistors with a total power of 1200W. With 125W X2 (8 Ohms) output.

Separate power supply for left and right channels using two high quality ring bulbs with 80,000 UF filter capacitors,

All high quality audio components are used, including Vishay and KOA resistors, WIMA capacitors, and NOVER (UK brand) capacitors as per our requirements. All triodes for the four balanced channels are precisely paired and mounted.

The core:

The A1 is a truly balanced design post-amp that uses the latest CAST technology to push the XLR input to sound as good as CAST, with an all-transistor design (the OPA op-amp is a DC servo circuit).

The A1 may look complex, but it is actually the simplest design in the world, with many of the components used for power supply processing. The A1 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 and minimal sound colouration.

The A1 uses a single stage CAST amplifier circuit with extremely low distortion and is mounted directly on the motherboard for better sound quality.

The CAST circuit is a transistorised amplifier with no feedback at all. Many audiophiles know that a negative feedback design provides better test specs, 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 operates in current mode, using a unique set of open-loop current mirrors for extremely low distortion amplification. All devices in the signal section are in Class A operation.

All components of the A1'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 eight high-power transistors. The filtering capacity is up to 80,000 UF and two power supply transformers provide independent power to the left and right channels.

Inputs:

The A1 accepts XLR signals as well as CAST current transfer inputs. Either way, the A1 is gain amplified in CAST mode.

Components:

The A1's balanced four channel transistors are all precisely matched.

Notes on use:

Power ON: The signal source must be powered on with the preamp before turning A1 on in each case.

Power OFF: The A1 must be switched off in each case before the rest of the system is switched off.

Input selector button on the rear panel: Press in for CAST input. Pressing it out is the XLR input. Must be operated with A1 switched off.

To operate the input and output lines, the A1 must be switched off.

The A1 will be aged for 100 hours before shipment, but an additional 300 hours of aging is still recommended. We recommend that the A1 is switched off when not listening to music.

The A1 is a balanced bridge design and cannot be bridged to increase power. However, two units can be purchased in Bi-Amp mode to increase power and improve sound quality. To use the Bi-Amp mode, the user must ensure that the tweeter and woofer of the speaker have separate terminals.

It is recommended to use with a fully balanced preamp with a gain greater than 10DB.