Imitation AURA-VA50 amplifier

VA50 is a famous product of AURA company. It has been produced since about 1989 (from this we can see that AURA company
has a very short history). As soon as the machine was launched, it attracted the attention of enthusiasts all over the world, and the style was determined by this.
It has been retained in subsequent VA series amplifiers produced by AURA . From the appearance, it is difficult to tell the difference between the current VA80SE VA100 and
the early VA50.
    The biggest feature of VA50 is simplicity (in line with the fever principle of "simplicity first"), which is not only reflected in its appearance,
but also in In terms of its internal circuit, the most distinctive feature of its circuit is the high-amplification power amplifier. Since the amplification factor
is as high as loo times (40dB), the preamplifier can be omitted, so its interior is actually a one-step power amplifier.
rate amplifier. In addition, in order to cater for those LP enthusiasts, it also has an RIAA equalization
amplifier with NE5532 as the core. However, for the vast majority of domestic enthusiasts, it may be difficult to use this function.
    The main amplifier circuit of AURA is shown in Figure 7-38. This circuit is actually very similar to Bada DCf 211B. Since the output
uses MOSFET, the power push stage can be omitted, making the whole circuit more concise. Except for the beam chrysalis,
which uses Japanese field-effect power pairs, the entire original circuit of the amplifier is made of ordinary materials. Because the circuit is very simple, it is very convenient and easy to copy
. In order to save costs, the RIAA function that is already used by most domestic enthusiasts is omitted when copying.
Based on years of experience, the input stage <VT1, VT2) was replaced with Toshiba's input twin pair tube ZSA1349, the two constant current tubes (VT3,
VT4) were replaced with Toshiba 's ZSA970, and the voltage amplification stage (VT5) was replaced with Hitachi 's famous low-power Fever tube 2SC2856 (this tube
is usually paired with 2SA1191 and has excellent linearity when the operating current is not greater than 10mA); in addition, the electrolytic capacitor is best
to use Japan's ELNA SILMIC capacitor t, while the small capacitance capacitor uses Panasonic's five-color ring Non-inductive capacitor. After such
adjustments, the overall effect can be improved to a higher level.