• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Improving the Aikido line stage...

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#21
I've run a couple simulations of the Aikido, using a CCS or CV power supply.

According to what I've seen, a regulated voltage PSU seems to be superior to a constant-current PSU.

When you use a constant-current PSU, it forces current down the second branch when it really doesn't want extra current - this stresses the bottom right triode. Basically, the second branch is forced to take whatever current the first branch doesn't want ... why make the amp act unnatural?

A regulated voltage PSU seems to make a lot more sense, because then the two branches are allowed to take whatever current is required.

Comments?
 
#22
Does anyone know how these voltage regulators work? If I use two 0D3, it will provide a regulated 300VDC output.


http://frank.pocnet.net/sheets/127/0/0A3.pdf

What about current?

0D3 operates between 5ma to 40ma. There is 35ma of current swing. Will this range be enough of a cushion to satisfy kashmire's concern (instead of forcing current down the second branch, excess current will simply pass though the regulator tube)?
 
#24
sorry to interupt - but I think that mr. broskie did mention something about that network optimization (he was using 6as7 there) - i also belive that he explained it and also how to tune it - not very sure about that but i read it somewhere there when reading about aikido
regards
 
#26
Bas Horneman said:
Yes...rdf has suggested exactly such a thing...earlier in the thread....for "normal" tubes with mu over 15 or so? you should be able to add a potmeter and just tune for best sound/littelst hummmmm. I'm gonna try that with the Aikido PCB's bonny_kjs is sending me.
Click to expand...

great - it would be nice to know is it possible to adjust it only with Your ears and without the oscilocope.....


🙂
best regards
 
#27
http://www.tubecad.com/2005/July/blog0051.htm

found it 🙂
mr. Bas - maybe better to do a little math before - just to check for the expected results - for Your ECC99 mu is around 22 as for my 6n6p - so for the upper res. of 100k the lower res. will be arround 120k
:smash: 😀
best regards

edit - i have thought a little - if we optimize those resistors in follower for the best performance we optimize for the whole circuit - that means that we can't simply put 120k (for mr. bas application) because the tubes are not paired - we have to be arround 120k - how close it will depend how close are the mu's of the tubes - right?😕 🙂 - that means that we would have to optimize circuit every time we substitute the tubes to get the best performance.........:bawling: :smash:
 
#30
Bas Horneman said:

I know .. 🙁 I'm sorry... math is my weak point. But my plan was to use a 25k pot on the bottom resistor...so I would have been ok in the end 😉
Click to expand...

sorry - this was not a critique - i am the same guy - hate math 🙂
but - thought I would help..... 🙂

:smash:

yes - it would be nice to use pot at the bottom res. since the tubes are not paired and everything so You wouldn't end at the calculated value - keep us informed about Your progress - i am very interested to know what happened..... :smash: 🙂 :clown:
 
#35
heater said:
I notice your schematic is a little different from Broskie's original. You have no 1M resistor divider on the top output tube, as Broksie suggests for safety.
Click to expand...

Had a chance to revisit this over the weekend. Spice provides little guidance since the 1 Meg resistors are respectively across cathode-anodes of tubes which are matched perfectly in software. Addition of these resistors therefore has no impact on the sim results but might in reality.
Not much later my notebook motherboard roasted in a BIOS upgrade taking with it access to these sims so I can't offer any help for a while, contingent on the whims of post-Carla Compaq. Might be a long while. 🙁
 
#36
rdf said:


Had a chance to revisit this over the weekend. Spice provides little guidance since the 1 Meg resistors are respectively across cathode-anodes of tubes which are matched perfectly in software. Addition of these resistors therefore has no impact on the sim results but might in reality.
Not much later my notebook motherboard roasted in a BIOS upgrade taking with it access to these sims so I can't offer any help for a while, contingent on the whims of post-Carla Compaq. Might be a long while. 🙁
Click to expand...


that is bad - sorry about that


:hot: :dead: :crackup:
 
#37
not very technical
but
in e-mail to me
JB recommended i
put those safety Rs in

stated they
"actually reduce distorion (and a little gain)"

does sound slightly cleaner - i think

bas

i did mine with ecc99 CF
but even ecc82
ounds better
5687 much more so
6n6p arrived today!!!

dave dove
 
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