YAC520
s
Realization of system with low residual noise
−
Configuration that uses HGVC1
−
HGVC1
+
+
-
16dB to -
1µ
Vrms
+30dB
30µ
Vrm
0
Vrm
-
+16dB
1µ
Vrms
+30dB
30µ
Vrm
−
Conventional configuration
−
Volume+PreAMP
MainAMP
Volume
PreAMP
MainAMP
General audio amplifiers are designed with the input sensitivity of approximately 150mV, and has gain
of approximately 16 dB at PreAMP section, and approximately 30 dB at Power AMP section.
For passive volume, they are given configuration of “Volume”−”PreAMP”−”MainAMP” as shown in the
above right figure. System with very small residual noise can be made by giving HGVC1 also the
function of “PreAMP” because HGVC1 has the positive side gain (max : 32 dB).
Since the residual noise of HGVC1 (gain=- ) is 1
µVrms(typ),
the noise level at the speaker end becomes
30
µVrms
if the noise of MainAMP is neglected. On the other hand, when conventional configuration is
used, the noise at the speaker end becomes very large because the noise produced by the initial stage of
PreAMP is amplified approximately by 46 dB (200 times) even if the level of noise produced by the
volume section during mute is zero.
To achieve the noise level at the speaker end that is equivalent to the one obtained with configuration
using HGVC1, the level of the noise converted to that of input of PreAMP is required to be approximately
0.16
µVrms
(-136 dBV), which is very difficult to achieve.
As described above, HGVC1 provides advantage of making the residual noise very small because it has
built-in amplifiers.
6
YAMAHA [ YAMAHA CORPORATION ]
