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Old 16th May 2012, 01:31 PM   #1
Einric is offline Einric  United States
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Default Aikido Power Amp.....Possible??

Just wondering here, reading through the TubeCAD Aikido pages I find it interesting that Mr. Broskie states a 300B can be made to work in an Aikido topology.
This makes me wonder some more.
Would it be possible to make an Aikido Power Amp?
The specific tubes used I don't think matter so long as they are the same in the follower as the input.

Has this been done before?
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Old 16th May 2012, 03:15 PM   #2
nazaroo is offline nazaroo  Canada
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The Aikido comedy might be worth avoiding, to instead follow a better design.
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Old 16th May 2012, 03:18 PM   #3
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Choosing proper tubes, bias and drivers, I donīt why it will not work.
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Old 16th May 2012, 03:25 PM   #4
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Quote:
Originally Posted by nazaroo View Post
The Aikido comedy might be worth avoiding, to instead follow a better design.
Easy critics.... then come up yourself with a better design, or at least (try to, but I am not very optimistic) point out why the Aikido is "comedy"
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Old 16th May 2012, 03:36 PM   #5
DF96 is offline DF96  England
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What is the point of an Aikido? It is to reduce PSU noise into low level signals (such as a line stage) and to reduce the signal currents sent back to the PSU.

The first point is much less needed in high level stages such as outputs. The second point can be done approximately by normal push-pull, or very wastefully by SE Aikido. Remember that the Aikido is only balanced when it has no load - fine for a line stage, no good for an output. You would need to arrange things so that for every watt sent to the speaker you sent another watt to a power resistor, so efficiency (already low for Class A) is halved.

I would not call an attempted output Aikido "comedy", just misguided?
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Old 16th May 2012, 03:40 PM   #6
SY is offline SY  United States
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I was about to reply, then saw that DF96 nailed the points I was going to make.
I should note that in practice, the noise rejection isn't that fabulous anyway.

The linearity is as good as a conventional stage if you use very high B+, which is fine in a preamp, not so fine in a power amp.
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Old 16th May 2012, 07:14 PM   #7
Einric is offline Einric  United States
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Thank You all very much.
You have answered my question fully.
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Old 16th May 2012, 09:59 PM   #8
nazaroo is offline nazaroo  Canada
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Originally Posted by pieter t View Post
Easy critics.... then come up yourself with a better design, or at least (try to, but I am not very optimistic) point out why the Aikido is "comedy"
The comedy is in this:

It effectively cancels power supply noise when there is no signal.

When there is an actual signal, it no longer cancels power supply noise!

Its the perfect comedy, because the louder your music, the more it drowns out the power supply noise.

Effectively, you have what is called 'masking',
and it works very well.

To understand the comedy fully, go here,

Ace Ventura - Shikaka! - YouTube

and watch from 1:50 to 2:22 minutes into skit.

THIS is Aikido in action re: noise rejection,
demonstrated visually.

Think of the chief as the Aikido method of noise rejection,
and Ace Ventura as the power supply noise.

Last edited by nazaroo; 16th May 2012 at 10:04 PM.
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Old 16th May 2012, 10:44 PM   #9
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Quote:
Originally Posted by pieter t View Post
Easy critics.... then come up yourself with a better design, or at least (try to, but I am not very optimistic) point out why the Aikido is "comedy"
Do you mean Aikido comedy is the best design and nobody can offer nothing better?

Come on...

Please provide any proof before demanding such things.
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Old 17th May 2012, 10:11 AM   #10
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The Aikido makes a good line stage. The output impedance is low by line stage standards. As a power amp there are designs with much lower output impedance. As far as PSRR goes the feed foreword noise cancellation can use some tuning. John Broskie offers one formula to calculate the voltage divider for the full on the Aikido and another for the standalone Aikido output stage the Aikido Cathode Follower.

I run the Aikido as a headphone amplifier with a para feed style output transformer to drop the output impedance. I tuned the voltage divider to minimize idle noise with the cans on my head (it is dead quiet). The noise cancellation is a plus. It is my feeling that power supplies have a sound they contribute from voltage sag or whatever the cause. The out of phase noise injection helps. I also run this Aikido with a regulated voltage supply to help minimize the contribution of the power supply.

John Broskie has written several times regarding cathode follower Power amplifiers, see his current blog.

To speak of the Aikido Comedy requires perhaps too much Drama.

DT
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