The BasX A2m is a flexible stereo amplifier that combines excellent audio performance with several unique and extremely useful features. The A2m can be used as the foundation of a great small stereo system – with or without a separate preamp. Its small size makes it the ideal solution for situations where space is limited or where multiple two-channel amplifiers will be used to power multiple different zones or sets of surround or height speakers. The A2m also features unique headphone output circuitry which is able to deliver great sound quality from a wide variety of both normal and difficult to drive headphones.

The BasX A2m is a two channel power amplifier that delivers 50 watts / channel into 8 Ohms, and 90 watts / channel into 4 Ohms, with a rated THD+N of < 0.1%, and an A-weighted S/N ratio of 112 dB. The BasX A2m features the same high-quality Class A/B amplification and full-sized five way speaker binding posts as our other BasX power amplifiers, but utilizes an advanced switch mode power supply, which contributes to its compact form factor and efficient power utilization.

The A2m has several additional features that make it uniquely flexible. A rear-panel switch allows the A2m to be used either as a power amplifier, with a fixed gain, or as an integrated amplifier, with higher gain, and a convenient front panel Volume control. This allows the A2m to be used with a single line level stereo analog source without the need for a separate preamp. Another switch allows the A2m to be configured to turn on automatically when it detects either a standard Trigger input, or an incoming audio signal.

The front panel of the A2m includes a full-sized ¼” headphone jack driven by some very special headphone circuitry. Like the headphone outputs on highly-prized vintage gear, the headphone output on the A2m is powered directly from the main output amplifiers, through a pair of precision dropping resistors. This enables the A2m to power both regular low impedance headphones and demanding high impedance headphones with ease; a special internal jumper option allows you to route the main output power directly to the headphone output in order to drive low impedance planar headphones.

Circuit Topology

• The BasX A2m is a stereo power amplifier, with unbalanced RCA analog inputs, a high powered headphone output, and the option of either fixed or variable gain. The A2m combines classical audiophile amplifier architecture, including a carefully designed high current short signal path Class A/B output stage, with advanced microprocessor-controlled monitoring and protection circuitry, and an advanced switch mode power supply, to deliver superb sound quality at a truly reasonable price.

Audio Specifications

• Power Output: 
  (Two Channels Driven) 
  50 watts RMS per channel; 20 Hz – 20 kHz; THD < 0.1%; into 8 Ohms. 
  90 watts RMS per channel; 1 kHz; THD < 1%; into 4 Ohms.

• Power Output (headphone output; normal mode):

8 Ohms: 60 mW / channel

33 Ohms:  200 mW / channel

47 Ohms:  250 mW / channel

150 Ohms: 430 mW / channel

300 Ohms: 440 mW / channel

600 Ohms: 350 mW / channel

• Power Output (headphone output; direct drive mode - requires internal jumper; USE WITH CAUTION):

8 Ohms:  50 watts / channel

33 Ohms:  12 watts / channel

47 Ohms:  8.5 watts / channel

150 Ohms:  2.6 watts / channel

300 Ohms:  1.3 watts / channel

600 Ohms:  0.6 watts / channel

• Power Bandwidth (at rated power; 8 Ohm load): 20 Hz to 20 kHz (+ / – 0.07 dB)

• Broad Band Frequency Response: 10 Hz to 80 kHz +0/-1.8 dB

• THD + noise: < 0.02% (A-weighted); ref rated power.

• Signal to Noise Ratio (8 Ohm load): 
> 112 dB; ref rated power; (A-weighted)

• Minimum Recommended Load Impedance (per channel): 4 Ohms (equals one 4 Ohm load or two paralleled 8 Ohm loads)

• Damping Factor (8 Ohm load): > 500

• Input Sensitivity and Gain (for rated power; 8 Ohm load): 

Fixed gain mode: 0.7 V / 29 dB. 

Variable gain mode: 0.5 V / up to 32 dB.

• Input Impedance: 27 kOhms

Input and Output Connections

• Input Connections: Unbalanced (RCA); one each per channel.

• Speaker Output Connections: Audiophile grade 5-way binding posts.

• Headphone output (front panel): Full sized ¼” stereo headphone jack.

• Trigger: 

Trigger Input: 5 – 12 V (AC or DC); <10 mA input current required. 

Trigger Output: 12 VDC; can drive any load up to 120 mA.

Power Requirements

• 115 - 230 VAC @ 50 / 60 Hz (automatically detected).

Front Panel Controls and Indicators

• Standby: push button.

• Status LEDs: one per channel; blue.

• Status LEDs change to red to indicate a fault condition

• Standby LED: amber

Rear Panel Controls

• AC Power switch: slide switch selects between On and Auto-On modes.

• Gain switch: slide switch selects between Variable Gain and Fixed Gain modes.

Internal Settings

• One pair of internal jumpers which can be used to bypass the series dropping resistors to enable full output power to be routed directly to the headphone output (shipped with jumpers OFF).

Protection

• The BasX A2m is protected against excessive operating temperature, shorted speaker connections, ground faults, and other common fault conditions.

Mechanical

• Dimensions: 

8-1/4” wide x 3” high x 14-1/4” deep (not including connectors).

• Weight: 

7.5 lbs (unboxed) 

10.5 (boxed)

Downloads

Download Product Manual