Introduction:

● B22 (beta 22) is a high-end, reference-quality DIY stereo amplifier for dynamic headphones. It could also be built as a power amplifier for speakers (18Wrms into 8Ω unbalanced, or 50Wrms into 8Ω fully-balanced), or as a preamplifier.

 

● The all-discrete (no integrated circuits), fully complementary and cascoded topology, high-current MOSFET output stage, full class A operation and carefully tuned operating points provide vanishingly low distortion, high speed, wide bandwidth, low output impedance, and high output power. All elements of the design were critically examined to create an amplifier that performs as well on the test bench as it does with music.

 

● The B22 is the result of a community service project for the audiophile hobbyist. The schematic diagram is open source. The circuit design, as well as the printed circuit board layout are the work of AMB with participation from the DIY community. It is designed to be relatively easy to build, but it is not recommended as a first-time project for the beginner.

 

● The B22 project is primarily centered around the main amplifier board. Each PCB supports one channel.

 

● The B22 amplifier board does not include a power supply (PSU). It needs a separate dual-rail DC supply to provide power to the circuit.

 

● The current draw from the β22 board is approximately 200mA per board as a headphone amplifier, depending on its quiescent current (bias) adjustment settings. As a speaker amplifier, the current draw could have peaks of over 5A per β22 board, while it idles at the same 200mA. It is a good idea to use a power supply with some headroom above the maximum draw.

 

● Always measure the actual output voltage of the power supply before connecting it to the amplifier for the first time, to make sure its output voltage is as expected.

 

● The recommended configuration for the β22 is to use an outboard power supply. This allows the power transformer and other AC components to be located far away from the sensitive amplification circuitry for minimum induced hum and noise. You may instead use a large chassis and put all β22 amplifier boards and the power supply in it, but be sure to position the power transformer and other AC components as far from the amplifier boards as possible. A toroidal power transformer is recommended in this setup for its lower magnetic field leakage.

 

Main Ingredients:

● Full aluminum chassis.

● Original Nichicon KG series 10000uF 50V main filter capacitor.

● Pure copper custom OFC toroidal transformer.

● Japanese ALPS 27 type potentiometer+canare pure copper signal wire.

● HIFI sandblasting gold plating RCA.

 

Input voltage: AC115V or AC230V (For choose)

External dimensions: 227mm*72mm*260mm (W*H*D)

Weight: About 4.5KG

Input impedance: 47.6KΩ

Output impedance: 0.01Ω, 20Hz - 20KHz

Maximum output voltage: 43Vp-p (15.2Vrms) load, 38Vp-p (13.4Vrms) 32Ω

Output Power: 0.75Wrms into 300Ω, 5.6Wrms into 32Ω, 18Wrms into 8.

 

Package includes:

B22 Class A headphone amplifier                       X1

NOTE: We do not provide any cables.