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Old 20th January 2010, 03:38 PM   #21
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Some more recommendations:
Lundahl psu chokes are quite good.
Use EI type power transformers.
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Old 20th January 2010, 03:39 PM   #22
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Originally Posted by leadbelly View Post
Glad to help. I notice that you have tightened the scope of your request somewhat nonetheless

I submit to you for thought that there is an inherent weakness in ALL the PCB's that are available for the Aikido; the dual triodes are split as 1st/2nd stage instead of top/bottom. This is because Vhk becomes a design limitation and the top triodes can't have an elevated heater. My quest for the ultimate Aikido would involve trying P2P construction and using a tube that is both suited for the 1st and 2nd stages, such as a 6DJ8 or a 6SN7 or equivalents.

To go even 1 step further: why use dual triodes? Use 4 tubes/channel. Then you can REALLY optimize.
leadbelly,
I willing to listen to all of the suggestions anybody wishes to make with regard to this aspiration of mine.I'm also happy for all posters to consider the ideas put forth by the other posters to this thread.There would be ideas which a new poster could put forth,which would be instructive to all the other posters.The whole idea of this thread is to consider what may be possible.

I proposing a blank sheet design faithful to the concept of the Aikido.The thing I'm tryin to tease-out of the vast knowledge-base here at diyaudio.com is;

How would we go about getting the absolute best out of this design?

We are getting some fine ideas brought to the board already.Thank you,gentlemen.

Last edited by theophile; 20th January 2010 at 03:50 PM.
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Old 20th January 2010, 03:43 PM   #23
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How would we go about getting the absolute best out of this design?
By building/listen/voice. Repeat for months.
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Old 20th January 2010, 03:44 PM   #24
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the dual triodes are split as 1st/2nd stage instead of top/bottom
Hmmmm .... not sure if I understand the advantages of this. Would you use two filaments supplies, one referenced to the bottom cathodes and one reference to the top cathodes?

If you did this, it would destroy some symmetry and reduce rejection of noise radiated by the filaments? For example, stage 1 would be exposed to the radiated noise created by two separate filaments supplies, and stage 2 would not create the proper antiphase relationship for cancellation. Instead, the noise could constructively and destructively interact, creating intermodulation and beat harmonics.

Quote:
using a tube that is both suited for the 1st and 2nd stages
Why create a new requirement of a single tube that is optimized for both positions? The top/bottom configuration disallows dissimilar valve configurations (i.e. 12AT7 for stage 1 and 12BH7 for stage 2). Naturally, you can circumvent this by using 4 valves per channel. You can still use dual triode envelopes, but not connect the second side. Part of the Akikdo circuit is the flexibility of using different valves for the 1st and 2nd stages, so the configuration can be more optimal than the limitations of a single tube for both stages.

p.s. although, I have found the 6CG7 works wonderfully well in both positions.
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Old 20th January 2010, 03:48 PM   #25
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Yeah now you've convinced me...

Does ultimate only extend to what is audible or also looks
I have stated repeatedly(elsewhere)that given the choice between a Haut Couture visual designed,poorly sounding component and one which looks like a dog turd with RCAs and a Volume control but which sounded like the hand-picked Angelic Choir:

There is no choice.The dog-turd is the frog-prince whose looks do not reflect what lies beneath.

Gorgeous looking,crap sounding components may as well be left unconnected.They serve their purpose better that way.

If I could have both,why not?The music has to take precedence.Never the other way around.
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Old 20th January 2010, 03:53 PM   #26
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Single most important thing for performance of the Aikido- the highest B+ you can get away with (careful of heater to cathode ratings!). A well-designed solid state supply with active regulation will pin down the B+ solidly and let the circuit reach its maximum capability. Tube regs are fun and pretty, but vastly inferior in performance.
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Old 20th January 2010, 05:24 PM   #27
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tube regs are fun and pretty, but vastly inferior in performance.
Tube regs are also inconvenient. They need filament power, burn off a couple watts, and are bigger than diodes.

However, I've found tube regs are highly desirable over solid state when considering sonics. I've tried all sorts of diodes with and without RC snubber networks: Schottky, soft-recovery, FRED, fast, etc.

Tube regs also work much better with constant current than with demand-peak currents. Same thing for choke-filtered power supplies. The impedances of tube regs (DCR impedance) and chokes (AC impedance and DCR) are more favorable for steady-state currents.

This thread broke down into a SS vs. tube reg debate.

Quote:
Single most important thing for performance of the Aikido- the highest B+ you can get away with.
I run my 6CG7s at about 315V at 10mA, a very nice place on the curves. I could raise the voltage another 25-30V, but it would actually increase output impedance a little. Would require me to swap the power transformer, which isn't that hard, but I'd need to buy new ones.
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Old 20th January 2010, 05:28 PM   #28
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Well, I can't make a value judgment on the sonic merits of having the supply rail move around with signal and by itself, but if one's view is that the preamp ought not to change the input signal except for a scalar, then an SS reg is unquestionably superior. If one wants the preamp to act as an effects box, then ignore anything I have to say.

My comments on B+ were directed toward linearity. Take a look at the distortion spectrum as you raise and lower the rail voltage. The higher the rail, the lower the distortion AND the greater the reduction in higher order distortion. I posted some results on this a few years ago.
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Old 20th January 2010, 05:47 PM   #29
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The higher the rail, the lower the distortion AND the greater the reduction in higher order distortion. I posted some results on this a few years ago.
That was also my experience some time back when tuning a SRPP stage. It's made of a single 6BL7 and runs from a PS at nearly +600V. I use that configuration as the predriver in my 211 SETs. Is there an easy way to find the info you posted?
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Old 20th January 2010, 05:54 PM   #30
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Search for a thread called "Survey: Aikido distortion." I had some of my results from ECC88 and 6SN7 types.
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