HP Aikido Stereo 9-Pin B manual Configuring the PCB as a Line Amplifier

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+

R6

C5

C6

R9

R7

C1

out

R4

R8

J8 (J9)

out

R15

C2

in

R3

R10

R1

C11

C12

R12

R13

R14

R16

R2

R5

R11 C3

(input) V2, V3

(output) V1, V4

Typical Part Values () Parentheses denote recommended values

6CG7 & 6DJ8

6CG7 & 6CG7

12AU7 & 12AU7

12AU7 & 12BH7

B+ Voltage =

170V - 250V (200V)

200V - 300V (300V)

200V - 300V (250V)

200V - 300V (300V)

Heater Voltage =

6.3V

6.3V

12.6V

12.6V

R1,5,6,7,12,13,14

=

1M

1M

1M

1M

R2,4

=

270 - 1k (470)*

470 - 2k (870)*

470 - 2k (680)*

470 - 2k (1k)*

R3,9,10

=

100 - 1k (300)*

Same

Same

Same

R8,11

=

200 - 330 (200 10mA)*

270 - 680 (270)*

180 - 470 (200)*

200 - 470 (523)*

R15

=

87.5k

83.2k

80k

79.3k

R16

=

100k

Same

Same

Same

*High-quality resistors essential in this position

All resistors 1/2W or higher

C1

=

0.1 - 4µF* Film

Same

Same

Same

C2

=

0.1 - 4µF* Oil

"

"

"

C3

=

none

"

"

"

C5

=

1 - 10µF* Film or Oil

"

"

"

C6

=

0.1 - 1µF* Film or Oil

"

"

"

C7,8,9,10

=

47µF - 1kµF, 16V

"

"

"

C11,12

=

0.1µF 160V(optional)

Same

None

None

*Voltage rating must equal or exceed B+ voltage

(input) V2, V3 =

6CG7, 6FQ7

6CG7, 6FQ7

12AU7, 5814, 5963,

12AU7, 5814, 5963,

6189, ECC82

6189, ECC82

(output) V1, V4=

6DJ8, 6922,

6CG7, 6FQ7

12AU7, 5814, ECC82

12BH7, ECC99

7308, E88CC