AIKIDO - Low-volage with buffer version

Mrpong · 11th September 2007, 12:59 PM

Hi

According the Aikido blog0067 here : http://www.tubecad.com/2006/06/blog0067.htm, I'm interested in building a low-volage Aikido version with buffer. This will be my headphone amp project, and there are some points I woud like to understand.

In the first schematic, it is only the solid state buffer. Right? It has R 47K at the input. Then comes to the second schematic which is the combination of the low-voltage AIKIDO and the solid state buffer. In this second schematic, this 47K was removed. What happen if we keep the 47K resistor?

I asked this question because I separated the low-voltage AIKIDO and the solid state buffer to two PCBs. One PCB is for Aikido. The other one is for the solid state buffer which includes R47K.

Many Thanks!!!

kevinkr · 11th September 2007, 01:10 PM

The 47K isn't required because the low voltage aikido output stage provides a path for the transistor base current. The resistor also creates an additional ac and dc load on the output of the aikido circuit, which given the low operating voltages and currents may result in increased distortion. (Conjecture on my part as I have neither built nor analyzed the performance of this circuit.)

One other comment - I have used a very similar buffer circuit, and I would recommend placing the 100 ohm base resistors very close to the output transistors. (MJE200/210) Note that the transistors connected across the 6.8 ohm emitter resistors in the output stage are to provide short circuit protection, and I think in an application like this can be safely omitted.

Mrpong · 11th September 2007, 01:27 PM

Thank a lot Kevin!!!!

- If I use the solid-state buffer for other schematics (not for Aikido)? do we need R47K?
- May I know the reason why we need to place R100 close to MJE200/210 as much as possible?

protos · 11th September 2007, 03:49 PM

well the other major difference obviously is the first buffer schematic uses a bipolar supply which does away with the big electrolytics at the output.
Those base transistors are there for suppresing parasitic oscillations and need to be on/next to the pins.

11th September 2007, 12:59 PM	#1
Mrpong diyAudio Member Join Date: Aug 2004 Location: Bangkok	AIKIDO - Low-volage with buffer version Hi According the Aikido blog0067 here : http://www.tubecad.com/2006/06/blog0067.htm, I'm interested in building a low-volage Aikido version with buffer. This will be my headphone amp project, and there are some points I woud like to understand. In the first schematic, it is only the solid state buffer. Right? It has R 47K at the input. Then comes to the second schematic which is the combination of the low-voltage AIKIDO and the solid state buffer. In this second schematic, this 47K was removed. What happen if we keep the 47K resistor? I asked this question because I separated the low-voltage AIKIDO and the solid state buffer to two PCBs. One PCB is for Aikido. The other one is for the solid state buffer which includes R47K. Many Thanks!!!

11th September 2007, 01:10 PM	#2
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	The 47K isn't required because the low voltage aikido output stage provides a path for the transistor base current. The resistor also creates an additional ac and dc load on the output of the aikido circuit, which given the low operating voltages and currents may result in increased distortion. (Conjecture on my part as I have neither built nor analyzed the performance of this circuit.) One other comment - I have used a very similar buffer circuit, and I would recommend placing the 100 ohm base resistors very close to the output transistors. (MJE200/210) Note that the transistors connected across the 6.8 ohm emitter resistors in the output stage are to provide short circuit protection, and I think in an application like this can be safely omitted. __________________ www.kta-hifi.net

11th September 2007, 03:49 PM	#4
protos diyAudio Member Join Date: Mar 2002 Location: Athens+Addis Ababa	well the other major difference obviously is the first buffer schematic uses a bipolar supply which does away with the big electrolytics at the output. Those base transistors are there for suppresing parasitic oscillations and need to be on/next to the pins. __________________ ``The author always assumes that when power is applied , the amplifier will explode or ,at the very least, catch fire.´´ Morgan Jones, Building Valve Amplifiers.

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11th September 2007, 01:27 PM	#3
Mrpong diyAudio Member Join Date: Aug 2004 Location: Bangkok	Thank a lot Kevin!!!! - If I use the solid-state buffer for other schematics (not for Aikido)? do we need R47K? - May I know the reason why we need to place R100 close to MJE200/210 as much as possible?

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