THanks Nelson and ZM. I got such a good laugh at the end of the work day
Devious smile. I can see you guys snickering like a couple of young troublemakers.
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why do you need to match the JFETs ?
I'm thinking here about Triodes. They behave like multiple triodes in parallel with slightly different characteristics - and so the curves 'lean to the right'. A mixed bag of JFETs might be just the thing to produce a similar behaviour. Of course, you might not want to do that
Nice photo!
why do you need to match the JFETs ?
I'm thinking here about Triodes. They behave like multiple triodes in parallel with slightly different characteristics - and so the curves 'lean to the right'. A mixed bag of JFETs might be just the thing to produce a similar behaviour. Of course, you might not want to do that
Nice photo!
Interesting, I must admit that for me, ultimate distortion cancellation is not the goal. I like the idea of playing with harmonics and from what i understand, triodes tend to favor the second. This amp allows quite a bit of play and i am going to take advantage of it. I am now thinking that perhaps the best thing to do is minimize distortion, then add some SE bias back in for the warmth I enjoy so much. Makes me think of getting hugged by a runway model vs Kim Kardashian. I just like a little something soft and rounded to grab on to.
Of course this design has stoked the fires for an M2 clone. HAve all the goods, why not.It is a geat picture isn't it.
So i just spent an hour listenig to the F6 again. I wanted to try other options base don Ilquams findings. I tried Rs of .15Ohms and both caps tied to below the Rs. Listened to two Patricia Barber songs. Then I tried smae configuration with top fet having Rs of .23ohms and bottom staying same. Caps connected in the same way. Listened to same two songs. Then went back to original conf of Rs at .15ohms, top cap connected below Rs and bottom cap connected above Rs. Listened to same two songs. I have to get measurements, but it simply is not the same amp. With either of the first two settings, the amp sounded good, but just doesnt stand out. Honestly, nothing special. But with thrid and original configuration, it was if a veil had been lifted. Completely different sense of space, both vertically and depth wise. As i said, I have to get some numbers to see what is going on, but for me the two comparisons are a joke. Same amp, but not in same league. IMO it really is that drastic a change. Can someone give possible explanation. I will try to get numbers this weekend and see what the minds can come up with.
@ZM,
She was first voluptuous figure that popped into head. Guess the old media hammer works after all, even if subconsciously.
@ZM,
She was first voluptuous figure that popped into head. Guess the old media hammer works after all, even if subconsciously.
THats kinda what i thought, but everything Ilquam has shown invloves complete cancellation of 2nd. If that is what the other configurations are giving me, no thanks. I have to stop being lazy and get some numbers and start connecting some dots. Thanks for the idea, BTW. As if i didn't already have a problem
The plot in post #1454 http://www.diyaudio.com/forums/pass-labs/216616-f6-amplifier-146.html#post3155280 (and others) did not have 2nd order cancellation. http://www.diyaudio.com/forums/pass-labs/216616-f6-amplifier-146.html#post3155280 Unfortunately, at the time of my earlier plots, I did not have the capability for separate plots for 2nd, 3rd, and higher harmonics to see what is going on.
THats kinda what i thought, but everything Ilquam has shown invloves complete cancellation of 2nd. If that is what the other configurations are giving me, no thanks. I have to stop being lazy and get some numbers and start connecting some dots. Thanks for the idea, BTW. As if i didn't already have a problem
Buzz: Do your self a favor and change your source resistors to 0R47 and put 10R pots around them with the caps tied to the wipers. Because the impedance of the gate is high (> 10K), the AC source resistance for degeneration becomes Rsw/10R*0R47, where Rsw is the pot's resistance between source and wiper. This gives you complete freedom to experiment with arbitrary combinations of degeneration resistances without changing components and needing to rebias. You can make live adjustments. To the best of my knowledge, nothing is sacrificed by this circuit modification.
If you remember, this was my suggestion. I agree, this gives greatest freedom and I will do it. I have some pots on order and on the way. Odd thing is, I had more luck moving the cap, vs changing Rs. As for the harmonics, I was referring to post #1969. They seem to indicate distortion characteristics. In my playing with Ba3, I liked a little more second, as it added a little bloom to the sound. I have always found this to sound closer to what i hear in person. Nelson has suggested that it mimics the "asymmetrical nature of air". Where the perfect line is, I don't know, but I like the idea forwarded in the "Leaving Class A" article, where there is a suggestion of adding a little SE bias for low level musical reproduction, and then transitioning to a cleaner, less distorted level, for higher output. It jsut sounds more musical to me. 100% opinion of course. I really souhld take the time to learn something so that i can give some numbers info with my opinion. It seems to be more accepted in a forum like this. Makes sense to me considering the high level of talent found here and their unwillingness to accept normal audio spew.
Seldom do I see anyone that is good with "numbers" being able to correlate the numbers to more depth - space, vertical and horizontal, and air around instruments, etc. The harmonics are one thing, the really fun stuff is less about numbers, I think.
Rush
ZM: You might be right about 4K posts. 
I think the schematic has converged, but there is still a lot to learn about how parameter choices affect the sound. I think you are right about the Zen Pot on the front panel, but why only one? Having two pots lets you play with damping factor also. 
I think the schematic has converged, but there is still a lot to learn about how parameter choices affect the sound. I think you are right about the Zen Pot on the front panel, but why only one? Having two pots lets you play with damping factor also. I kinda admire this thread
2K posts , still without official schm
I bet we can make 4K
I do believe the numbers are important. They help define/explain what it is we are hearing. For me, hearing comes first. This assumes of course, that you have Master ZEN of audio feeding you info and schematics. DiyAudio ROCKS!
+2
well , one can leave upper one with fixed (non)degeneration , while having Zen Amount pot on lower one
then put pot on front plate , and write SIT 1 wannabe
At .05 ohms, Ilquuam is basically at no degeneration. Just toss it
+3
Toss it? I haven't converged to any final conclusion about what sounds best.
What I have been doing is explore the range of measurable performance. Having found that this amplifier is capable of being adjusted to have low 2nd harmonic distortion, with the pots, I can do experiments with listening preferences.
I intend to do exactly what I recommended to you: Rs=0R47 and easily accessible pots. Currently I am using multi-turn Bourns trimmers, but 4 turn shaft pots would be more convenient.
What I have been doing is explore the range of measurable performance. Having found that this amplifier is capable of being adjusted to have low 2nd harmonic distortion, with the pots, I can do experiments with listening preferences.
I intend to do exactly what I recommended to you: Rs=0R47 and easily accessible pots. Currently I am using multi-turn Bourns trimmers, but 4 turn shaft pots would be more convenient.
At .05 ohms, Ilquuam is basically at no degeneration. Just toss it
+3
Just having a little fun. I actually think a little degeneration may be better than none, as the sound-stage can grow too much vertically. It is really recording dependent. But that is what is cool. This amp kinda shows you what was done in the audio booth at mastering. I tend to swing more towards ZM's idea of pot across the lower Jfet, leaving the upper alone. Sound wise, I haven't noticed much when switching Rs up top. Ill investigate different values there tomorrow.