Page 2
lower, so that each device is driven only in its low-
power range where linearity is excellent.
A music signal consists of a continuous succession
of pulse waveforms. To prevent clipping on occasional
momentary high-level pulses, the maximum clipping
level of the A-30 is set to 50 watts per channel into 8
ohms (sine wave output).
Current feedback circuit topology assures
excellent phase characteristics in high range
In the A-30, the signal current rather than the more
conventionally used voltage is used for feedback.
Since the impedance at the current feedback point
(current adder in Figure 3) is very low, there is almost
BufferCurrent
adder
I-V
converter
Trans-impedance
amplifier Amplifier Output
Current NFB
network – Input
Buffer + Input
Gain(Large)
(High)
Frequency
no phase shift. Phase compensation
therefore can be kept at a
minimum. A minimal amount of
NFB results in maximum
improvement of circuit
parameters. The result is
excellent transient
response and superb
sonic transparency,coupled with
utterly natural
energy
balance.
Figure 4 shows
frequency
response for
different gain
settings of the
current
feedback amplifier. The graphs demonstrate that
response remains uniform over a wide range.
Robust power supply with large power
transformer and high filtering capacity
In any amplifier, the power supply plays a vital role
since it acts as the original source for the output
delivered to the speaker. The A-30 employs a large
and highly efficient 400 VA power transformer. It ishoused in an
enclosure filled with
a material that
transmits heat and
absorbs vibrations.
This completely
prevents any
adverse influences
on other circuit
parts.
Two aluminum
electrolytic
capacitors rated for
47,000 µF each
serve to smooth out
the pulsating direct
current from the
rectifier, providing
more than ample
filtering capacity.
Fig. 3 Principle of current feedback amplifier
Fig. 4 Frequency response with current feedback(Response remains uniform also when gain changes)
n Power amplifier assembly with three
parallel push-pull power MOS-FET
pairs per channel mounted directly
to large heat sink, MCS+ circuitry,
and current feedback amplifier
