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Survey: Aikido distortion
Survey: Aikido distortion
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Old 28th February 2006, 01:38 PM   #11
Bas Horneman is offline Bas Horneman  Netherlands
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Why do you want the figures by the way Stuart? Would you like to compare them to yours?
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Old 28th February 2006, 01:47 PM   #12
SY is offline SY  United States
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Survey: Aikido distortion
Well, certainly that, but also to probe what the circuit can and can't do, to get an idea of how to really optimize linearity for different applications. I can build about a million variations, but that will take me a million years. So I'm playing around with a couple, but the collective efforts of other guys in their workshops would help map out the design landscape a bit more than it is now.
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Old 28th February 2006, 01:52 PM   #13
anatech is offline anatech  Canada
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Survey: Aikido distortion
Now if I had a digital 'scope with math functions ...

I generally test everything I build. I find it helps explain what I'm hearing sometimes. My non-technical listening audience are unaware of measurements to remain unbiased. Right now I can only do THD and 'scope the residuals.

-Chris
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Old 1st March 2006, 05:31 AM   #14
Geek is offline Geek
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Ooops, regarding my earlier post... I was informed the preamp PCB I listened to was indeed *not* the Aikido. Sorry for the unintentional mislead
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Old 1st March 2006, 06:36 AM   #15
James D. is offline James D.  United Kingdom
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Ummmm... I have done the measurements.... but only on a Pentode Aikido... so not really relevant...

On the pentode Aikido the distortion and spectrum at the output look the same as the distortion and spectrum on the pentode anode i.e. measure the same and has the same spectrum - as far as my measurement setup can tell (say to 5% of measurement).

This using a 6B8-G pentode and driving two PT15s in triode mode PP through and IT phase splitter.

I haven't bothered to measure the all triode Aikido as it sounds so open and transparent that I just listen to it :-) (6N1P and 6N6P)

James
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Old 1st March 2006, 10:57 AM   #16
SY is offline SY  United States
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Survey: Aikido distortion
How much gain did you get from the pentodes?
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Old 1st March 2006, 08:40 PM   #17
James D. is offline James D.  United Kingdom
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Hi SY,

I'm runing the pentodes at a gain of about 65 times.

James.
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Old 1st March 2006, 08:56 PM   #18
2wo is offline 2wo  United States
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I did post a scope photo on another thread

Look under "improving the Aikido line stage"
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Old 1st March 2006, 09:04 PM   #19
SY is offline SY  United States
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Survey: Aikido distortion
Thanks, guys. With triodes, I find the gain to run about 40-45% of mu, so pentode definitely had me curious.

Distortion results I've gotten so far are quite good, but not blow-away. Distortion reduction requires a LOT of supply voltage, and JB's boards are set up so that the same tube envelope carries both top and bottom triode (to more easily allow voltage amp and follower to be different tubes). This means that the tubes' heater-to-cathode voltage ends up being strained. For the case of ECC88-family, one has to take the plate-to-cathode voltage well above the rated maximum to get the distortion to fall below that of a common-cathode stage.

At output voltages more typical of line stages (2-3VRMS) and a 160V supply, 2nd HD is the only one visible at -55dB for the best-selected tube sample and the resistor ratios tweaked for the best distortion null.
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Old 1st March 2006, 10:06 PM   #20
James D. is offline James D.  United Kingdom
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As another example Dave Dove posted his pentode aikido into 300BXLS design a little while ago. I designed the aikido stage and that runs the pentode at a gain of about 110 times.

I have run a pentode aikido at 200 times gain on the bench with no problems and a cascode aikido at a gain of 360 times... yes I'm playing with Aikido RIAA cicuits for a DL103

James
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