Audial A21 User manual

A21
STEREO AMPLIFIER
USER MANUAL
Revision 0, May 2023

IMPORTANT!
1. This manual is a guide only.
2. Do not expose this device to rain or moisture, excessive heat, or mechanical force.
3. Use this device exclusively with specified voltages.
4. Unplug the device from the wall outlet during a lightning storm.
This manual comprises introducing information on the use and performance of this device.
For more information, please visit https://www.audialonline.com/a21/, or send your questions to
[email protected].
WARRANTY
Audial claims the proper operation of this product for two years. Audial is obliged to correct for
any malfunction within this period, at no charge, either by the competent repair service, or by
swapping the sold unit with the new one.
For the units sold directly by Audial, the invoice is also a guarantee certificate. Audial however
maintains its database of directly sold units, so the original buyers will not usually need it. Warranty
is also fully transferrable from the original to the subsequent owner(s), however in this case we will
probably ask for the invoice.
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Audial A21

!
The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the
user to the presence of uninsulated “dangerous voltage” within the product’s enclosure that may
be of sufficient magnitude to constitute a risk of electric shock to persons.
The exclamation point within an equilateral triangle is intended to alert the user to the presence of
important operating and maintenance (servicing) instructions in the literature accompanying the
product.
Copyright © 2023, Audial d.o.o.
www.audialonline.com
4Audial A21

STARTING WITH THE A21
The A21 stereo amplifier is relatively simple to use and,
provided it is used within its limits, it requires no special
care in everyday operation.
It achieves claimed specifications right from the start,
even though it still needs 5-7 days of burning in to
perform its best in the subjective audio terms.
Afterward, it is generally enough to leave it powered
on for half an hour before the critical listening.
It is not harmful if A21 is left constantly powered up,
however a general recommendation to turn such
devices off whenever out of home applies regardless.
Also, it is important not to block the opening holes at
the bottom, back, and top plate, as they provide air
circulation into and from the unit interior, and thus
ensure proper cooling.
CONNECTIONS
The A21 mains connector is standard IEC C14 and is
located at the back panel. Every unit is produced to
match the mains voltage in the customer’s country.
The A21 is a balanced amplifier, however it sports both
unbalanced and balanced inputs. Thus, on its back
panel, there are three unbalanced RCA and two
"Combo" connectors. These Combo connectors can
accept both balanced (XLR or 6.3 mm "TRS" phone
jack) and unbalanced sources (6.3 mm "TS" phone
jack). The input impedance is 38 kOhm for unbalanced
inputs and from each balanced pole to the ground,
and 76 kOhm between the poles of the balanced
inputs, so the A21 is a friendly load for the majority of
sources.
The A21 employs also a buffered pre-out, which can be
useful for bi-amping, or to connect the active
subwoofer. This output is provided as an unbalanced
RCA connection only.
The output loudspeaker connectors are Audial made
pure copper binding posts, which accept the usual 6.3
mm spades or 4 mm banana plugs.
The A21 does not invert polarity (absolute phase).
Hence with the source which also does not invert
polarity, the speakers should be wired in phase.
The A21 also sports the ground connector. This ground
is the chassis ground and can be used for cable
shielding, or as a system earth connection. This
connection should not be used as an audio ground /
return path.
IMPORTANT: The A21 is a balanced amplifier, so both
the positive and negative loudspeakers output
connectors carry audio signals. Please, DO NOT
connect the negative output to the ground!
USING THE A21
Apart from the mains switch, the A21 has only one
control knob, which is both the volume and balance
control, and the input switch. The amplifier settings are
shown on the display.
Normally, the volume is set by rotating the knob. The
volume is set in 1 dB steps, and has the "mute", and 63
steps between the 0 dB and maximum position.
The inputs are selected by pressing the knob.
By long pressing the knob (for 2 seconds), the amplifier
enters the balance menu. The display, instead of the
volume position, in its second row then shows the
balance position. The balance can be set in 1 dB steps
(from "Center" to 31 dB left or right). By another long
pressing of the knob (again for 2 seconds), or by its
inactivity for 5 seconds, it will go back to the regular
volume control operation. If the balance is set out of
the center, the appropriate reminder will remain on the
right side of the upper row of the display.
The volume and balance positions and input selection
are non-volatile after the power off, that is, the same
setting will apply on the next power-up. This however
applies to the volume setting only if it was set for at
least 5 seconds before the power off, to the balance
setting only after exiting the balance menu, and to the
input setting it applies unconditionally.
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Audial A21

6Audial A21
A21 back plate
From left to right:
Pre-out, line inputs and ground connector above, loudspeakers outputs, mains connector with fuse.
A21 front plate
From left to right:
Power switch, IR sensor, display, control knob.

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Audial A21
SPECIFICATIONS
INPUTS:
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 the ground, 76 kOhm between poles
OUTPUT POWER: 100 W RMS @ 8 Ohm, 150 W RMS @ 4 Ohm
MAXIMUM OUTPUT CURRENT: 10 A
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 LEVEL: 35 uV (-98 dB @ 1 W)
GAIN
Max gain between the input and speakers out: 68.9x (36.7 dB)
The 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
DIMENSIONS (W x D x H): 467 x 330 x 112 mm, including feet, but excluding the knob and connectors
WEIGHT: 12 kg

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