STAX DMA-X2

Commentary

A monaural power amplifier developed with the aim of expanding the input electric signal without adding anything or losing anything.

The DMA-X2 circuit consists of two class A amplifier circuits and a dynamic push-pull power supply. The output terminals are BTL connected to each other to form one amplifier. There are also two driver stages, each driving two output stages.

For the output stage, we have adopted an A-class amplifier using a swing power source based on the concept of a new-age A-class amplifier which combines the good sound of A-class with the low power consumption of AB-class.
The use of a NON-NFB circuit prevents the back electromotive force generated by the speaker from returning to the input section through the NFB circuit, resulting in an output waveform different from the input waveform.

Class A amplifier and differential input circuit are used in the driver stage.
By adopting a low-noise dual-FET differential amplifier circuit and applying NFB in an orthodox way, a flat frequency characteristic is obtained over a wide band. In addition, the driver stage is amplified against earth in order to suppress external noise coming through the power cord.

The power supply consists of a 1,500 va ultra-large cut-core power transformer, 33,000 μ Fx4 and 68,000 μ Fx4 Ultra High Volume electrolytic capacitors with a total capacity of 404,000 μ F, and a Schottky barrier diode to reduce noise generation.

We prevent adverse effects from the power supply to peripheral circuits by taking into consideration the layout of parts and the routing of circuits.

A PC limiter circuit is mounted as a protection circuit to protect the output stage of the amplifier from destruction even if the + and - terminals of the speaker terminals are shorted by mistake. In addition, an excess input protection circuit is mounted to suppress the input of an abnormally high voltage, and a temperature protection circuit is mounted to shut down the power supply to prevent thermal runaway when the output stage becomes abnormally high temperature.
In addition, a speaker protection circuit is mounted to prevent damage to the speakers by automatically turning off the power of the amplifier when DC or abnormal pulse is input from the preceding stage (preamp, etc.), or when abnormal DC of ± 5 V or more is generated at the output terminal due to damage to the amplifier itself.

Equipped with two input terminals, balanced and unbalanced.
Unbalanced terminals also have subsonic cut (AC) terminals.

Equipped with a gain selector switch, two levels of 30dB/36dB can be selected.

The speaker terminal uses Stacks original GBP-2.

Input ON/OFF terminal is mounted.

Model Rating

Type	Monaural power amplifier
Circuit system	Fully balanced input, balanced output Voltage amplification stage : complimentary service FET differential-input all-stage to earth amplification Power amplifier stage : NON-NFB dynamic power supply class A amplifier
Maximum power output	600W (8 Ω)
Frequency characteristic	At DC Input : 0.8 Hz ~ 220 kHz (at 10W Output) At AC Input : 15 Hz ~ 220 kHz (at 10W Output)
Total harmonic distortion factor	0.1% or Less (20 Hz to 20 kHz, 0.03W to 600W, 8 Ω)
Signal-to-noise ratio	116 dB or more (using IHF-A Network)
Residual level	100 μ V or Less (Using IHF-A Network)
Input level	Lo:2V Hi:1V
Input impedance	Balance : 64k Ω RCA : 32k Ω
Amplification factor	Lo:30dB Hi:36dB
Load impedance	2 Ω or More (Music Playback) 6 Ω or more (at test signal input)
Damping factor	100 or More (10 Hz to 20 kHz)
Output voltage drift	± 10 mv or less
Speaker protection operating voltage	+ / - 4 V (DC)
Other	Input ON/OFF switch Sensitivity (Hi/Lo) selector switch Balance/RCA input selector switch With Subsonic cut (AC) input
Power consumption	390W (No Signal)
External dimensions	Width 430x Height 227x Depth 546 mm
Weight	47kg