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GlassWare Audio Design 7
Configuring the PCB as a Line Amplifier
The Aikido topology makes a
perfect line amplifier, as it offers low distortion, low
output impedance, and excellent power-supply noise rejection—
all without a global
feedback loop. The key points are not to use capacitor C3
. For guidance on part
values, look at the page
12, which lists several line-
amplifier design examples.
Calculating R15’s value is easy; it equals R16 against [(mu -2)/(mu + 2)].
For example,
a triode with a mu of 20 results in R15 = 100k x (20 – 2)/(20 + 2) = 81.8k (82k)
B+ Voltage =
Heater Voltage =
R1,5,6,7,12,13,14 =
R2,4 =
R3,9,10 =
R8,11 =
R15 =
R16 =
6CG7 & 6DJ8 6CG7 & 6CG7 12AU7 & 12AU7 12AU7 & 12BH7
170V - 250V (200V) 200V - 300V (300V) 200V - 300V (250V) 200V - 300V (300V)
6.3V 6.3V 12.6V 12.6V
1M 1M 1M 1M
270 - 1k (470)* 470 - 2k (870)* 470 - 2k (680)* 470 - 2k (1k)*
100 - 1k (300)* Same Same Same
200 - 330 (200 10mA)* 270 - 680 (270)* 180 - 470 (200)* 200 - 470 (523)*
87.5k 83.2k 80k 79.3k
100k Same Same Same
C1 =
C2 =
C3 =
C5 =
C6 =
C7,8,9,10 =
C11,12 =
0.1 - 4µF* Film Same Same Same
0.1 - 4µF* Oil " " "
none " " "
1 - 10µF* Film or Oil " " "
0.1 - 1µF* Film or Oil " " "
47µF - 1kµF, 16V " " "
0.1µF 160V(optional) Same None None
*Voltage rating must equal or exceed B+ voltage
(input) V2, V3 =
(output) V1, V4=
6CG7, 6FQ7 6CG7, 6FQ7 12AU7, 5814, 5963, 12AU7, 5814, 5963,
6189, ECC82 6189, ECC82
6DJ8, 6922, 6CG7, 6FQ7 12AU7, 5814, ECC82 12BH7, ECC99
7308, E88CC
*High-quality resistors essential in this position
All resistors 1/2W or higher
Typical Part Values
() Parentheses denote recommended values
R4
R2
in
out
R8
R11
R3
R9
R1
C11
R5
R6
R7
C2
C12
B+
C1 out
R15
C6C5
R10
R16R12 R13 R14
J8 (J9)
C3
(input) V2, V3 (output) V1, V4