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Thursday, June 14, 2012

The Aikido Comedy (pt 7): Historical Perspective

..moving along...

Another important historical factor in explaining how and why
this circuit became such a darling of amateur DIYers,
was of course the aggressive promotion of it by John Broskie.

Broskie was careful to hedge his promises, leaving pages of friendly anecdotes,
even create something of an artificial "mystery" surrounding the circuit.

The "Aikido" branding is a perfect example of the technique.
With parts, boards, and prepackaged kits, Broskie's sales hype
was near irresistable to vulnerable DIYers who trusted his analysis.

The best barometer of Broskie's own understanding of tube circuits,
besides his repeated admissions and attempts at a kind of innocent neutrality,
was how he handled the Mu-Follower / Mu-Stage question.

Broskie began back in the early 2000's dismissing the Mu-Follower,
because he did not understand real PSRR, or the effectiveness
of the Mu-Follower circuit in virtually eliminating PS noise.

Its a testament, not to his analytical skills, but to his irrational stubbornness,
that he continued to dismiss the Mu-Follower in favour of his pet (adopted) invention,
i.e., PS noise injection as a solution to PS noise until 2006.

However, unlike some of the posters here,
it is also a testament to John Broskie's self-revelation
that the Mu-Follower after all was the best PSRR circuit.
After nearly 6 years, he incorporated it instead of an SRPP
for the first stage of his preamp,
in the 2005-2006 article, "Aikido meets Mu Follower".

That is, finally Broskie quietly (almost silently!) admitted
that the Mu-Follower was the best solution to PSRR
in a small-signal input stage (better than his first choice).

That Broskie had after 2006 abandoned his early unbridled enthusiasm
for the original Aikido circuit
has been clearly noted by DualTriode:

Originally Posted by Dual Triode
1. John evolved his view from the 50 50 voltage divider to an adjustable division based on the mu of the buffer triodes.

2. The Aikido Cathode Follower circuit has a formula in the instruction manual based on the mu of the installed triodes. This is only the buffer half. The input section is not part of the ACF circuit.

3. The full-on Aikido circuit instruction manual has a different formula for the selection of the buffer divider values. I assume that the different selection formula has to do with the contribution for the first stage. Odd to my way of thinking is that there is no consideration for tube selection or operation point of the input stage.

4. I agree that there should be an adjustment on test to best null the noise output.

5. Considering items 2 and 3 above some of the "if then" conclusions by nazaroo perhaps could be evolved.

6. John has nothing to do with the input stage. The first place I saw this stage is in the post WWII, this is how we did it texts. It was not then and is not now push pull. The top triode acts as a active resistor that can be replaced with a resistor of value rp + (u + 1)Rk, think of this as the DC condition for the AC condition the functional value of the top triode rp varies equally and in opposite direction to the bottom triode providing “cancellation” of harmonics. My simulations show cancellation of both even and odd harmonics. This needs to be confirmed in the real world.

7. Nazaroo lighten up you are battling the Tar Baby left behind by John,he is laughing.

8. Remember most users use well filtered and regulated PS's with the Aikido

I can agree wholeheartedly with DualTriode's observations here.

The Aikido circuit is indeed a 'tar-baby',
as its stubborn defenders have demonstrated,
and it has indeed been significantly modified/abandoned
by Broskie himself, as his updated manual and
own posts on Tubecad show.

In my view, the combination of Broskie's dismissive treatment of the Mu-Follower,
followed by his 6-year refusal to acknowledge its remarkable PSRR features,
along with his shameless self-promotion of his "Aikido" branded line,
show that Broskie is not the "tube-god" many would hype him as.
His analytical skills re: tube circuits have evolved,
but he began in the early 2000's on an amateur level,
and his inability to correctly assess the Mu-Follower
show an incredible density and stubbornness,
not a 'magical' intuitive insight into tube circuits.

Broskie's own opinion of himself is thankfully more modest
than his hysterical defenders.

Nazaroo lighten up you are battling the Tar Baby left behind by John, he is laughing.
He certainly is!

It causes me to recall the famous remark by Liberace,
when someone had tried to humiliate him,
by referencing his sexual orientation and effeminate flamboyancy:
"I'm really hurt by it.
I cried, .........all the way to the bank."

Originally Posted by SY: 
"You have yet to specify what experiment would be appropriate.
Your only suggestions involved changing circuit conditions and looking around inside the circuit rather than where it counts- input versus output in the unmodified circuit. "
One more empty post, no experiments performed, no results posted.
For someone who insists on experiment, you do damn little of it. ...
I would have performed about 30 experiments by now (a night's work),
if I thought experimenting would clarify the circuit operation.
What I don't understand is why a clever and competent experimenter wouldn't just go ahead and construct their own experiments.
I already explained why testing the output is useless for understanding what is going on inside it.

As someone who honestly believes he understands the circuit quite well,
(and it is awfully simple after all),
I just don't feel the need for any experiments.

If I thought there was some remarkable secret,
other than the mistakes in the documented historical analysis,
I suppose I'd think of one, but really there isn't much to discover.

The original Aikido circuit has relatively poor PSRR during signal amplification.
The Mu-Follower circuit has far better, real PSRR at all times,
and it has less stages.

End of story.

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