Aikido Stereo 9-Pin PCB Revision C USER GUIDE Introduction Overview Schematics Recommended Configurations Tube Lists Assembly Instructions 05/29/2008 GlassWare AUDIO DESIGN Copyright 2006-2008© All Rights Reserved
GlassWare Audio Design A Warning! @ This PCB is for use with a high-voltage power supply; thus, a real shock hazard exists. Once the power supply is attached, be cautious at all times. In fact, always assume that capacitors will have retained their charge even after the power supply is disconnected or shut down. If you are not an experienced electrical practitioner, before applying the B-plus voltage have someone who is experienced review your work.
GlassWare Audio Design 2 Introduction to the Aikido The Aikido amplifier delivers the sonic goods. It offers low distortion, low output impedance, a great PSRR figure, and feedback- free amplification. The secret to its superb performance— in spite not using global feedback— lies in its internal symmetry, which balances imperfections with imperfections. As a result, the Aikido circuit works at least a magnitude better than the equivalent SRPP or grounded-cathode amplifier.
GlassWare Audio Design 3 Remember, tubes are not yardsticks that never change, being more like car tires— they wear out. Just as a tire’s weight and diameter decrease over time, so too the tube’s conductance. So the fresh 6DJ8 is not the same as that same 6DJ8 after 2,000 hours of use.
4 GlassWare Audio Design Heater Issues The board assumes that a DC 12V power supply will be used for the heaters, so that 6.3V heater tubes (like the 6FQ7 and 6DJ8) or 12.6V tubes (like the 12AU7 or 12AX 7) can be used. Both types can be used exclusively, or simultaneously; for example 6GC7 for the input tube and a 12BH7 for the output tube. For example, if the input tube (V2 and V3) is a 12AX 7 and the output tube is a 6H30 (V1 and V4), then use jumpers J1, J5 and J6.
GlassWare Audio Design 5 B+ DC Heater PS B+ 300k 2W 300k 2W AC B+ 4 0.1µF 250V B+ 4 0.1µF 250V 100k 1/2W 100k 1/2W 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.
6 GlassWare Audio Design Jumper J7 connects the PCB’s ground to the chassis through the top centermost mounting hole. If you wish to float the chassis or capacitor couple the chassis to ground, then either leave jumper J7 out or replace it with a small-valued capacitor (0.01 to 0.1µF). Warning: if rubber O-rings are used with PCB standoffs, then the ground connection to the chassis is not likely to be made. Tube Selection Unlike 99.
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)].
GlassWare Audio Design 8 Configuring the PCB as a Headphone Amplifier The standard Aikido is a thoroughly single-ended affair, nothing pulls while something else pushes. Unfortunately, wonderful as single-ended mode is sonically, it cannot provide the larger voltage and current swings that a push-pull output stage can.
GlassWare Audio Design Typical Part Values 9 () Parentheses denote recommended values 6CG7 & 6DJ8 6CG7 & 6CG7 12AU7 & 6H30 B+ Voltage = Heater Voltage = 170V - 250V (250V) 6.3V or 12.6V 200V - 300V (300V) 6.3V or 12.6V 200V - 300V (150V) 12.6V R1,5,6,7,12,13 = R2,4 = R3,9,10 = R8,11 = R15 = R16 = 1M 270 - 1k (640 5mA)* 100 - 1k (300)* 200 - 330 (291 10mA)* 87.3k 100k 1M 470 - 2k (640 5mA)* 100 - 1k (300)* 200 - 470 (240 10mA)* 83.
R1 in 9 7 C11 R3 V3 R2 6 8 R4 R5 R9 C12 9 V4 R11 1 R8 8 3 C3 R10 out out out out R15 C6 J7 R14 J8 C2 C1 C3 R10 R7 7 9-Pin Aikido Schematic (Rev.
.25" 2.00" 1.00" .50" .25" .125R, 4 PLCS 7 8 9 1 2.00" V1 6 5 4 8 MOUNTING HOLE LOCATIONS 2 3 2.30" 7 9 V2 2.75" 1 2 3 7 9 V3 2.75" 8 1 6 5 4 2 3 2.30" OVERALL PC BOARD DIMENSIONS: 4.00" x 10.0" 1.60" Top Side PCB Mechanical Layout 8 6 5 4 1.60" 4 VACUUM TUBE LOCATIONS 7 9 V4 2.00" 8 1 6 5 4 2 3 .25" 0.
GlassWare Audio Design 12 Tube 6AQ8 6BK7 6BQ7 6BS8 6CG7 6CG7 6CG7 6CG7 6CG7 6CG7 6CG7 6DJ8 6DJ8 6DJ8 6DJ8 6DJ8 6DJ8 6DJ8 6FQ7 6GM8 6H30 6H30 6H30 6H30 6H30 6N1P 6N1P 6N1P 6N27P 9AQ8 12AT7 12AU7 12AU7 12AU7 12AU7 12AU7 12AV7 12AV7 12AZ7 12AX7 12AX7 12BH7 12BH7 12BH7 12BH7 12BH7 12BZ7 12DJ8 12FQ7 5687 5687 5687 5687 5751 5963 5965 6072 7119 ECC81 ECC82 ECC83 ECC85 ECC86 B+ Ik(mA) mu 300V 10.0 57.0 300V 10.0 43.0 300V 10.0 38.0 300V 10.0 36.0 150V 3.0 20.5 200V 5.0 21.1 250V 5.0 21.0 300V 4.5 20.8 300V 7.