HP Aikido Stereo 9-Pin B manual Power Supply

GlassWare Audio Design 5

B+

DC	300k	AC
Heater
PS	2W

B+

4

B+

300k

2W

B+

4

0.1µF	100k	0.1µF	100k
250V	1/2W	250V	1/2W

100

100

Alternatively, you might experiment with floating the heater power supply, by “grounding” the heater power supply via only a 0.1µF film or ceramic capacitor. The capacitor will charge up through the leakage current between heater and cathodes. Not only is this method cheap, it is often quite effective in reducing hum.

B+

4

Power Supply

The power supply is external to the Aikido PCB and can be mounted in, or outside, the chassis that houses the PCB. The optimal power supply voltage depends on the tubes used. For example, 6GM8s (ECC86) can be used with a low 24V power supply, while 6FQ7s work better with a 250-300V B-plus voltage. The sky is not the limit here, as the heater-to-cathode voltage sets an upward limit of about 400V.

The genius of the Aikido circuit is found in both its low distortion and great PSRR figure. Nonetheless, a good power supply helps (there is a practical limit to how large a power-supply noise signal can be nulled). I recommend you use at least a solid, choke- filtered tube or fast-diode rectified power supply. If you insist on going the cheap route, try the circuit below, as it yields a lot of performance for little money. FRED rectifiers are expensive, but make an excellent upgrade to the lowly 1N4007.

.01µF	.01µF
1KV	1KV

100mA high-DCR

.01µF	.01µF
1KV	1KV

All Diodes = 1N4007

All Resistors = 1 ohm 1/2W