24V Aikido --> 6GM8 with Buffer

[lordearl]

I'm going to build this as a first tube project:

http://www.tubecad.com/2006/06/blog0067.htm

See the BUF634 section.

So far, I haven't come across anyone who has built this schematic yet.

Question is, do I just build the entire amp as per:

http://www.tubecad.com/2006/04/blog0059.htm

And then add the buffer section?

Or can I ignore the orginal 6GM8 pre amp schematic altogether? It seems like a lot of capacitors, etc, will be missing if it's built as per the schematic with the buffer.

Cheers for any tips.

 

[MRupp]

Well, the output caps from the standard Aikido have been moved behind the buffer stage, other than that I do not see a major difference. The "standard" schematics has caps from the tube's internal shielding to ground , they were omitted in the buffered version, I believe, to simplify the diagram and show the fundamental circuit. So build the buffered version and consider including the caps for the shielding.

 

[lordearl]

Okay that makes a little more sense.

As far as I can tell;

R1 on buffer schematic = R7 on the original 6GM8 preamp schematic
R2 " = R12 "

But just above R1 on the buffer schematic, there's a capacitor which isn't on the Aikido board.

How would I wire this into the circuit?

 

[MRupp]

R1 on buffer schematic = R7 on the original 6GM8 preamp schematic

No, look again! And better still, read thru the wole set of articles and try to understand in more detail how the Aikido works.

 

[lordearl]

hahah back to the drawing board I think -- time to understand first how my electric toothbrush works......

 

[lordearl]

Is there any particular reason Broskie recommends *only* using the T0-220 package (ie. BUF634T)?

 

[MRupp]

Do you mean this sentence "Be sure to get the TO-220 package and put a good heatsink on it." ???

 

[lordearl]

Yeah - I've noticed that particular BUF634 is very rare. Also, a lot of posts on this buffer find people not using heatsinks at all.

ie. one could probably use any BUF634 (P,U,T) without a heatsink?

 

[MRupp]

Depends whether you really bias it into class A as indicated and on how much power your headhpone will need but I would say it is a risk not to use the T0220 version with heatsinks.

 

[lordearl]

Cheers mate!