Amplifier A21


Natural, precise, powerful

With its 100 W output power per channel, the A21 is the most powerful Audial amplifier so far. And it is physically the biggest too.

But there is more to it than meets the eye. It is also a reference, in the original meaning of this word. Something to confide in. A solid ground, you can build the highest class system upon.

€ 2,300

Balanced and linear.
In every way.

Which brings not only sonic benefits of its own but also four times more power, with the same supply voltage. So, more power, keeping the operating points of its opamps based output stage in the sweet spot.

Still, with its fully differential input stage, which is a unique, highest performance discrete circuit without global feedback, the A21 normally accepts also unbalanced sources.

And, the A21 keeps about every feature you have seen in the A20. Five inputs in sum, friendly input impedance, and a digitally controlled resistive network potentiometer chip, with 63 steps of 1 dB, easily adjusting listening levels in different systems.

Copper binding posts,
copper heatsink.

We have been using the pure copper connectors for a decade, and now, in the A21, we also use the copper for the output opamps’ heatsink.

And, the copper heatsink does not only improve heat dissipation, but due to its mechanical and RF properties, it also improves the sonic performance.

A21 copper heatsink

A21 also employs:

• A 10 Ampere capable, power opamps based output stage
• Three RCA and two “Combo” (XLR / phone jack) inputs
• JFET buffered line pre-out (RCA)
• Six discrete, zero-feedback regulated supplies for line-level circuits, and one more separate supply for logic circuits and display
• Separate transformer secondary windings for each output stage channel, so the output stage practically operates as dual-mono
• Mains DC blocker
• High-quality parts, including National / Texas Instruments, Toshiba and Zetex semiconductors, Panasonic, Nichicon, and Elna capacitors, and Vishay carbon resistors
• No-compromise layout, with the shortest possible signal path
• Tinned copper (RoHS compliant) printed circuit board (no nickel here)
• Volume and balance control and input selection are simply operated by a single knob
• A21 can also be operated by the optional remote control.

Quiet and powerful.

The A21 includes a mains DC blocker, and two carefully designed toroidal transformers, with tweaked core flux. The bigger transformer, rated 500 VA, feeds the output, and the smaller 50 VA unit feeds the line stage.

The A21 thus ensures both substantial output power and perfectly quiet operation, even in the presence of significant DC offset in the mains.

3 x RCA
2 x Neutrik “Combo” – accept balanced XLR, or balanced (TRS) or unbalanced (TS) phone jack 6.3 mm
Input voltage
Min 0.5 V RMS for full power
Max 4.5 V RMS (input overload)
Input impedance
@ unbalanced inputs
38 kOhm
@ balanced inputs
38 kOhm from each pole to ground
76 kOhm between poles
Output power
2 x 100 W RMS @ 8 Ohm
2 x 150 W RMS @ 4 Ohm

Maximum output current
10 A
Output DC offset
Less than 1 mV, from each pole to ground or between poles
Frequency response
20 Hz – 100 kHz, ±0.5 dB
Harmonic distortion
0.06%, across the audio band (worst case), @ 4 Ohm, full power
Intermodulation distortion
0.02% (SMPTE), @ 4 Ohm, full power
Output noise
35 uV (-98 dB @ 1 W)
68.9x (36.7 dB)
(max gain between the input and speakers out)
Ratio between pre-out and speakers output
34.4x (30.7 dB)
Pre-out gain
1.1x (0.8 dB), at volume max
Pre-out impedance
130 Ohm
Absolute phase
Correct, for both the loudspeakers and pre-out
Mains voltage
220-240 VAC, or 110-120 VAC, or 100 VAC
50-60 Hz
Idle power consumption
18 W
Allowed DC on the mains
1.3 V max
Size (W x D x H)
467 x 330 x 112 mm, including feet, but excluding the knob and connectors
12 kg

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