Academy Audio Hi-End MUSES VCM Podręcznik użytkownika - Strona 9
Przeglądaj online lub pobierz pdf Podręcznik użytkownika dla Jednostka sterująca Academy Audio Hi-End MUSES VCM. Academy Audio Hi-End MUSES VCM 12 stron. Mini electronic volume controls
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+15V
GND
+15V
IN_L
COM_L
IN_R
COM_R
Figure 6. Potentiometer Type Single Ended Volume Control Application.
Unlike previous examples, this circuit is heavily dependent on the loading of the downstream audio
circuitry. The table of Figure 7 shows an error magnitude depending on the value of the loading
impedance.
It is obvious that higher impedance loads provide lower volume control errors. It is recommended to
use a buffer or a high input impedance amplifier at the output of the volume control. For buffers and
amplifiers having a bipolar input, resistors R3 and R5 provide a current pass for their input bias currents,
and capacitors C2 and C4 block DC current from reaching resistive elements of the MUSES chip. Resistor
values shall be selected between 100kOhm and 470kOhm for optimal performance. Capacitors' values
shall be high enough to pass low frequencies of the audio band. For JFET based buffers and amplifiers,
or when the circuit is used as a passive outboard Volume control feeding a power amplifier with a DC
insensitive input, the DC blocking networks C2R3 and C4R5 may be omitted.
Figure 8 demonstrates a balanced application of the potentiometer type volume control.
VCM Board
J3
J4
CON16
J5
J7
C3
J9
J10
47uFx35V NP
C5
J12
J14
47uFx35V NP
R_load,
0dB to -32dB
kOhm
10
20
47
100
200
1000
Figure 7. Volume Control Error.
OPTIONAL
(SEE TEXT)
R6
MUTE
6.8K
R7
C2
C4
Volume Control Position
-32dB to -112dB
Error, dB
Error, dB
-4.08
-2.28
-2.28
-1.21
-1.04
-0.54
-0.51
-0.26
-0.26
-0.13
-0.05
-0.03
Page 9 of 11
TO MUTING RELAY
Q1
2N2222A
22K
J6
OUT_L
R3
J8
COM_L
J11
OUT_R
R5
J13
COM_R