ACF-1 stupid question,
The quote is under the table of tubes..
I thought R3 and R6 were ie top and bottom balanced in the above its not? OK we have the cap..but..
With a 6dj8 looking at the table its 10mA across 200 ohm..LED?
ACF -1 pdf is here on the right:
http://www.tubecad.com/2011/01/blog0198.htm
Regards
M. Gregg
The quote is under the table of tubes..
R6 bypassed = LED ?
I thought R3 and R6 were ie top and bottom balanced in the above its not? OK we have the cap..but..
With a 6dj8 looking at the table its 10mA across 200 ohm..LED?
ACF -1 pdf is here on the right:
http://www.tubecad.com/2011/01/blog0198.htm
Regards
M. Gregg
Last edited:
ACF-1 stupid question,
The quote is under the table of tubes..
R6 bypassed = LED ?
I thought R3 and R6 were ie top and bottom balanced in the above its not? OK we have the cap..but..
With a 6dj8 looking at the table its 10mA across 200 ohm..LED?
ACF -1 pdf is here on the right:
Aikido Cathode Follower 2 & Impedance Multiplier Circuits and the PS-6
Regards
M. Gregg
No LED used here. It refers to bypassing the cathode resistor with a capacitor, though I don't see why you would in this circuit, as it increases distortion.
I'm thinking about this..
http://www.diyaudio.com/forums/tubes-valves/76025-ping-sy-led-cathode-bias-3.html
Regards
M. Gregg
I'm thinking about this..
http://www.diyaudio.com/forums/tubes-valves/76025-ping-sy-led-cathode-bias-3.html
Regards
M. Gregg
Hmm, well, in any case, I'm not sure it's possible to LED bias an aikido circuit, since the circuit relies on symmetry between the top and bottom triodes and you would have to LED bias both of the cathodes. I just don't think it would work, and the Aikido circuit should probably just use unbypassed resistors. I think you will be quite happy with the performance.
Hello Merlinb,
I was thinking about this and switching the bias for different tubes using LEDs. Which would seem to "Remove" the upper cathode resistor. However it still leaves the R9/R8 situation..
The other idea was to remove the cathode capacitor..(LED on the bottom)
Its only a guess I think a yellow LED gives about 2V for the 6DJ8
Regards
M. Gregg
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How low do you really need it to go? a 6DJ8 in the Aikido circuit is already a very low output impedance, probably much lower than you need.
Well the switch and select is a possible maybe..
I'm just wondering about the distortion..
Regards
M. Gregg
Well the switch and select is a possible maybe..
I'm just wondering about the distortion..
Regards
M. Gregg
The distortion is also quite low using just resistors.
I think possibly you are agonizing over it too much(don't we all do that though)
The circuit sounds very good, and I tinkered with mine quite a bit, but kept going back to the stock build. Maybe build stock first and go from there?
The distortion is also quite low using just resistors.
I think possibly you are agonizing over it too much(don't we all do that though)
The circuit sounds very good, and I tinkered with mine quite a bit, but kept going back to the stock build. Maybe build stock first and go from there?
I might have a play..
(just to see what it sounds like)Regards
M. Gregg
OK,
I have done a quick and dirty mod..
My Aikido is now running 6DJ8 with one green LED in the cathode of the bottom tube R3 is shorted out and its running....just powered up!
B+ is at 200V as per Aikido spec.
I intend to make this a better install and have a serious listen..
I can hear the removal of the resistors<<and the colouration..
Regards
M. Gregg
I have done a quick and dirty mod..
My Aikido is now running 6DJ8 with one green LED in the cathode of the bottom tube R3 is shorted out and its running....just powered up!
B+ is at 200V as per Aikido spec.
I intend to make this a better install and have a serious listen..
I can hear the removal of the resistors<<and the colouration..
Regards
M. Gregg
Last edited:
OK,
This is hard to put into words. I'm not going to get into a debate.
1..don't use LEDs to bias the Aikido. A simple resistor or resistor and cap is better.
The effects I found YMMV..
The Aikido seems to show the "sound of components quite well"..
In fact so well its ridiculous.
However not after an LED is used to bias it.
Great you may say, however with that comes an effect.
If you are listening to music it will rock the house..listen to films and its a different ball game its not real any more!
It sounds like the bandwidth is limited in the extremes of the sound. I found this in an OTL in the past preferring a resistor and cap bypass.
This is a simple solder and see test this is what I did.
Fit Jantzen Z cap and you get detail. Fit the LED you lose it and the Z cap sounds like a standard LCR £50p part. OK so the LED is some how removing mush heard as extra detail. Complete B****** its almost acting like a filter or attenuator..
And here it is again..the same old stuff audiophile nonsense..
Its interesting to note the standard resistors sounded better in the Aikido than the Audio parts..
If you fit different resistors in the aikido. Especially in the R3 and R6 position..
The ones I tried standard Maplin MF OK real sounding. With metal edge to the sound.
Takman Rey MF bloated it made the aikido sound old school sort of warm with a 2nd harmonic feel. Not very nice!
Change the volume pot same effects, fit Tantalum resistors similar effects!
Now we have heard it all before..however the Aikido line stage is a great way to play with parts.
I have learned a lot more than I'm saying here, however in some ways
I wish I hadn't tried it..
So if I had an LED biased Aikido and fitted different parts I would have a whole different take on it compared to the standard Aikido.
The soldering Iron is back on with some standard Maplin MF going back in..
If I had tried to measure it I don't think I would have an answer..however this isn't a slight change..YMMV
In a different circuit..who knows..the LED might sound great..I would imagine with just music..If I hadn't tried all the above I would not have believed it!
NB this isn't an attack on LED bias I was hoping for great things..and I was surprised at the outcome..Its probably the application that's wrong..however... I am still surprised as I type this if this is the true "Sound" of components..Yes I know components don't have a sound lets call it the effect of components on sound or bad application of components take your pick..
I guess one thing that annoys me is I have to admit..the standard resistors sound better...YMMV..I have re educated myself in a few hours..
Now I know whats happening...I have learnt quite a lot..there is more to the underlined statement..
Regards
M. Gregg
This is hard to put into words. I'm not going to get into a debate.
1..don't use LEDs to bias the Aikido. A simple resistor or resistor and cap is better.
The effects I found YMMV..
The Aikido seems to show the "sound of components quite well"..
In fact so well its ridiculous.
However not after an LED is used to bias it.
Great you may say, however with that comes an effect.
If you are listening to music it will rock the house..listen to films and its a different ball game its not real any more!
It sounds like the bandwidth is limited in the extremes of the sound. I found this in an OTL in the past preferring a resistor and cap bypass.
This is a simple solder and see test this is what I did.
Fit Jantzen Z cap and you get detail. Fit the LED you lose it and the Z cap sounds like a standard LCR £50p part. OK so the LED is some how removing mush heard as extra detail. Complete B****** its almost acting like a filter or attenuator..
And here it is again..the same old stuff audiophile nonsense..
Its interesting to note the standard resistors sounded better in the Aikido than the Audio parts..
If you fit different resistors in the aikido. Especially in the R3 and R6 position..
The ones I tried standard Maplin MF OK real sounding. With metal edge to the sound.
Takman Rey MF bloated it made the aikido sound old school sort of warm with a 2nd harmonic feel. Not very nice!
Change the volume pot same effects, fit Tantalum resistors similar effects!
Now we have heard it all before..however the Aikido line stage is a great way to play with parts.
I have learned a lot more than I'm saying here, however in some ways
I wish I hadn't tried it..
So if I had an LED biased Aikido and fitted different parts I would have a whole different take on it compared to the standard Aikido.
The soldering Iron is back on with some standard Maplin MF going back in..
If I had tried to measure it I don't think I would have an answer..however this isn't a slight change..YMMV
In a different circuit..who knows..the LED might sound great..I would imagine with just music..If I hadn't tried all the above I would not have believed it!
NB this isn't an attack on LED bias I was hoping for great things..and I was surprised at the outcome..Its probably the application that's wrong..however... I am still surprised as I type this if this is the true "Sound" of components..Yes I know components don't have a sound lets call it the effect of components on sound or bad application of components take your pick..
I guess one thing that annoys me is I have to admit..the standard resistors sound better...YMMV..I have re educated myself in a few hours..
Now I know whats happening...I have learnt quite a lot..there is more to the underlined statement..
Regards
M. Gregg
Last edited:
Final update,
I ended up with a mix of components,
The 6DJ8 are running 250V B+ (Maida reg) with 300 ohm for r3 and r6 (maplin MF).<<NB standard resistors..
Running 10mA as per Aikido spec.
The grid stoppers are Takman REY 300 ohm,<<<takes the edge of the MF..
Input capacitor is Jantzen Red Z at the moment..
The input pot is a law faked pot with Tantalum resistor.
Regards
M. Gregg
I ended up with a mix of components,
The 6DJ8 are running 250V B+ (Maida reg) with 300 ohm for r3 and r6 (maplin MF).<<NB standard resistors..
Running 10mA as per Aikido spec.
The grid stoppers are Takman REY 300 ohm,<<<takes the edge of the MF..
Input capacitor is Jantzen Red Z at the moment..
The input pot is a law faked pot with Tantalum resistor.
Regards
M. Gregg
Last edited:
An interesting test,
Plug the source straight into the power amp and compare with the Aikido and direct in..or a Passive pot..
However then you have to ask what is the difference with a cable with drive and without...if it sounds the same what then? Is the Aikido transparent..well it is with Maplin MF resistors, because it sounds the same except for a little bass increase.<<the sound of drive or the sound of the resistors/circuit? So the Aikido sounds like a wire without gain... Er is it plugged in... Oh OK so it doesn't work if its not plugged in so I have a circuit that is working..
The above is fun however...a wire without gain..(which wire)
Regards
M. Gregg
Plug the source straight into the power amp and compare with the Aikido and direct in..or a Passive pot..
However then you have to ask what is the difference with a cable with drive and without...if it sounds the same what then? Is the Aikido transparent..well it is with Maplin MF resistors, because it sounds the same except for a little bass increase.<<the sound of drive or the sound of the resistors/circuit? So the Aikido sounds like a wire without gain...
Er is it plugged in... Oh OK so it doesn't work if its not plugged in so I have a circuit that is working..The above is fun however...a wire without gain..(which wire)
Regards
M. Gregg
Last edited:
You did ensure, of course, that the LED bias and resistor bias put the valves on exactly the same bias point? If not, you are merely comparing one bias point against another bias point. (And, just to check, you didn't try to use LED bias for the active load - that would significantly reduce its impedance and increase distortion).
Bias point was the same..
However you have a way of stating the obvious..
(Particularly when I hadn't thought about it) Yes you are correct..again!
Regards
M. Gregg
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