steve jones said:
you meant like in primary called WE topology (monkey also ,if I remember correctly)....
why not- with some source resistor trimming......
invoking AC current feedback.......
I must go to sleep now.......monitor looks too funny.....
I'm on a short tether as far as time goes.
choky,
As far as bias goes, keep in mind that you're not trying to drive a dozen MOSFETs, just one or two. You won't need as much current to drive a reduced Gate capacitance.
steve,
Looks to me as if it'll work, if that's the way you want to go. You won't be able to parallel devices unless they're really well matched.
Grey
choky,
As far as bias goes, keep in mind that you're not trying to drive a dozen MOSFETs, just one or two. You won't need as much current to drive a reduced Gate capacitance.
steve,
Looks to me as if it'll work, if that's the way you want to go. You won't be able to parallel devices unless they're really well matched.
Grey
Sure looks pretty, Choky🙂 Thanks for sharing.
Maybe I should start looking for some of those sj109's. Are you sure they need to be the "V" type? I have a slight suspicion that they could be a bit hard to get. Well, ofcourse they are hard to find no matter the suffix.
NP said the Aleph-J is the best sounding Aleph ever, so I am inclined to follow your work on this, pretty closely, Choky😉
Steen🙂
steenoe said:
sharing?
where's da blooodyyy coursing smiley when I need it???!!!
I didn't share anything-Nelson does.
Gray-I can easily made tube Aleph (with tube front end) but this is little puzzle or exercize,maybe even more entertaining than making own version...
have you on hand some simple rule of thumb-how much driving current I need for xxx amount of capacitance?
I see (in last few days I looked at this particular problem) several praised amps with weeny current in driver stages (LTP,dedicated VAS,buffers,whatever is in case).......
can't be that they are all wrong and that I'm on right side with my tooboolar approach
steen-again- 😉
I presume,or-in other words-I'll sleep in peace if 109 are V iteration;]
you know- I don't care if I choose to run some tube at max specs,or even close to-just because tubes are waaaay more forgiving for that;
I have slight suspicion that tiny Jfet isn't in same mood
Oh, you share a nice piece of footwork allright😉 Ofcourse I know the amp is NP's😀
I am working on obtaining some of those 2SJ109V's right now🙂
Hopefully I get a few positive feedbacks, from some obscure sources🙂
Steen😎
steenoe said:
In that case-maybe your familiar speed in making stuff .....
hehe-you can have A J before me,just because I'm not sure that I have everything needed ....few doughnuts have few volts AC too much (I can test with variac,but for final version I must unwound few turns) etc
my main problem,beside schematic validity , is to choose between passive and forced cooling....
and I must find source for cheap'n'good 😉 few additionall hundrrrreds of kilomicroFarads
btw-how your house refurbishing is going?
Too slowly, no surpise😱
I dont intend to jump into this project right away. First of all the schematic needs validation ofcourse, furthermore at least a pdf for a board would be nice also🙂 I dont think I am up to P2P wire that beast🙂 Other than that, I am ready to go😀
Steen🙂
Edit. What do you suggest for the trafo secondary voltage? Something like 22 volts?
what else than 25/1,2steenoe said:
psud will tell what exactly with CLC
or CRcccccccccccccccccccc
Holly Molly!
Aleph 1.2
11mA through half of LTP feed gates of 12 (TWELVE!!!!) IRF244......
bingo!
Aleph 1.2
11mA through half of LTP feed gates of 12 (TWELVE!!!!) IRF244......
bingo!
humble question to Master
Nelson,I hope that I didn't misuse your good will for info sharing with my posts regarding Aleph J.
I know that is maybe too late for this sort of question,but if you think that is too early for back-engineering of Aleph J,I'll ask mods to delete related posts.
😕
like always-thank you for your spirit ,in first place.
Nelson,I hope that I didn't misuse your good will for info sharing with my posts regarding Aleph J.
I know that is maybe too late for this sort of question,but if you think that is too early for back-engineering of Aleph J,I'll ask mods to delete related posts.
😕
like always-thank you for your spirit ,in first place.
choky said:
I didn't use the 1 nF lag compensation or compensation on
the npn in the current source, but I do recommend about 7 pF
across the 221K feedback resistor.
Nelson Pass said:
tnkya Master;
I see that you ignore my previous post with question regarding abusing .....
in fact-seems that you already decide when you sez which Jfet is in LTP........
anyway-can you say few words about most criticall parameters in driver stages,regarding capacitive load (gate of output mosfet)?
obviously-I was wrong when I think that input capacity is sooo demanding.......
or I already missed something you sayed before.........
in any case-I was just shocked when I realize that Aleph 1.2 (long time not opened pdf in my "Passssssss" folder ) have exactly same input stage as any other Aleph,and that you drove (hehe-I'm bloody good with changing times in English😉 ) 12 gates with just 11mA through half of LTP................
I hope that you have fun this dayzzzzzzzz........
I have-with your J puzzle
The question is not how many devices Nelson is driving, but how much Gate capacitance. From there the conversation biurcates and you have:
a) Gates of devices that are cascoded
--and--
b) Gates of devices that are not cascoded
Cascoding devices doesn't so much make the capacitance go away as make it irrelevant. Crazy people like me are suspicious of cascodes for various reasons, but even I admit that they have their uses. (Particularly when the Lovoltech devices can't take much voltage.)
Non-cascoded devices present more of a challenge, but it's not un-doable. The Gate capacitance needs to be charged and discharged in order to get the job done. The more current you have available, the better. More specifically, what you're looking at is the slew rate. If you don't have enough current, you'll start seeing distortion in the high frequencies first. The current is still struggling to charge the Gate up to a given voltage when the signal passes it heading the other way, having already reached the top of the mountain and gotten tired of waiting, it's heading back to the valley. Since the Gate never got up to the necessary voltage, the waveform is malformed and this constitutes distortion.
There's one other thing to look at with slew rates, and that's the voltage you're trying to swing. If you're only going for 1/10th of a volt, it doesn't take as long to charge the capacitance as it would if you were trying to reach, for instance, 30V. In other words, you'll need more current in order to charge a capacitor to 30V in the same period of time that you could successfully charge it to .1V.
Having said all that, we've backed at least part-way into the answer. The front end in an Aleph doesn't need to swing nearly as much voltage as a normal front end because the Aleph output stage has gain. As a result, you're only looking for enough current to charge the output Gates over a few volt span, not 30 or 50V.
Grey
a) Gates of devices that are cascoded
--and--
b) Gates of devices that are not cascoded
Cascoding devices doesn't so much make the capacitance go away as make it irrelevant. Crazy people like me are suspicious of cascodes for various reasons, but even I admit that they have their uses. (Particularly when the Lovoltech devices can't take much voltage.)
Non-cascoded devices present more of a challenge, but it's not un-doable. The Gate capacitance needs to be charged and discharged in order to get the job done. The more current you have available, the better. More specifically, what you're looking at is the slew rate. If you don't have enough current, you'll start seeing distortion in the high frequencies first. The current is still struggling to charge the Gate up to a given voltage when the signal passes it heading the other way, having already reached the top of the mountain and gotten tired of waiting, it's heading back to the valley. Since the Gate never got up to the necessary voltage, the waveform is malformed and this constitutes distortion.
There's one other thing to look at with slew rates, and that's the voltage you're trying to swing. If you're only going for 1/10th of a volt, it doesn't take as long to charge the capacitance as it would if you were trying to reach, for instance, 30V. In other words, you'll need more current in order to charge a capacitor to 30V in the same period of time that you could successfully charge it to .1V.
Having said all that, we've backed at least part-way into the answer. The front end in an Aleph doesn't need to swing nearly as much voltage as a normal front end because the Aleph output stage has gain. As a result, you're only looking for enough current to charge the output Gates over a few volt span, not 30 or 50V.
Grey
tnx Gray;
almost entire content of your post is more than familiar to me,but few last sentences are ,hm, just revelation;......reinvented wheel right on top of my head 😉
I'm still (like you once before?....!) used to toobz,where voltage is prominent factor,even if I'm personally on "pretty heavy current" side of tube bunch,so -that means that I rarely think in range of just few volts......and I must confess that I don't think just every day about MM and MC stages ,where signal range is almost there.....
so I just slipped (right term?) that those bloody gatesssss need just few volts of swing for full blast,even if I'm well aware that I'll never need full blast from any iteration of Aleph or any SS amp in my life.
my spks are mostly pretty efficient,and most demanding ones are sort of LS3/5,but they are always in almost near-field use,without need for too much muscles...(hehe-even if I know that they on moderate level eat more current than KHs on chest hurting levels 😉 ) .
somewhere up the thread I wrote few thoughts regarding cascodes and cascades.
in toobz,I don't like cascodes (SRPP,Mu, White,whatever) just because I adore xformers as finall element in chain;cleverly implemented,nothing can compare with that.
cascodes are almost same -good for avoiding,if you can.... 😉
I don't want to say that I have prejudices (as many DIYers have),but I always try to follow KIS principle,meaning that -fewer stages,sound must be better.
but-and there is always some "....but," , sometimes is not easy to make something from nothing....
Nelson's J is for me one hell of good reason to try to learn something about SS constructions, mostly just because I conclude that it must be fine example of investing engineering,passion and sense of humor in one (for someone-just ) mechanical gadget;
hehe-just like one nice book writer wrote - "when you work on m cycle,you in fact work on your self...)
almost entire content of your post is more than familiar to me,but few last sentences are ,hm, just revelation;
......reinvented wheel right on top of my head 😉I'm still (like you once before?....!) used to toobz,where voltage is prominent factor,even if I'm personally on "pretty heavy current" side of tube bunch,so -that means that I rarely think in range of just few volts......and I must confess that I don't think just every day about MM and MC stages ,where signal range is almost there.....
so I just slipped (right term?) that those bloody gatesssss need just few volts of swing for full blast,even if I'm well aware that I'll never need full blast from any iteration of Aleph or any SS amp in my life.
my spks are mostly pretty efficient,and most demanding ones are sort of LS3/5,but they are always in almost near-field use,without need for too much muscles...(hehe-even if I know that they on moderate level eat more current than KHs on chest hurting levels 😉 ) .
somewhere up the thread I wrote few thoughts regarding cascodes and cascades.
in toobz,I don't like cascodes (SRPP,Mu, White,whatever) just because I adore xformers as finall element in chain;cleverly implemented,nothing can compare with that.
cascodes are almost same -good for avoiding,if you can.... 😉
I don't want to say that I have prejudices (as many DIYers have),but I always try to follow KIS principle,meaning that -fewer stages,sound must be better.
but-and there is always some "....but," , sometimes is not easy to make something from nothing....
Nelson's J is for me one hell of good reason to try to learn something about SS constructions, mostly just because I conclude that it must be fine example of investing engineering,passion and sense of humor in one (for someone-just ) mechanical gadget;
hehe-just like one nice book writer wrote - "when you work on m cycle,you in fact work on your self...)
Kinda like writing a story...even if the bulk of the story sounds familiar, a surprising ending can make the tale shine like a newly minted penny. Had to make sure all my characters were in place before revealing that it wasn't the butler who did it; it was the gardener.
Grey
Grey
Errr . . . 🙄
Cascoding is explained not only as providing low input capacitance, but also as providing a frozen operating voltage (e.g. Vds). And the frozen operating voltage reduces distorsion without sacrificing of the beloved 2nd or 3rd harmonic distortion.
What element makes it suspicious . . . ? 🙄
Regards
jh
Cascoding is explained not only as providing low input capacitance, but also as providing a frozen operating voltage (e.g. Vds). And the frozen operating voltage reduces distorsion without sacrificing of the beloved 2nd or 3rd harmonic distortion.
What element makes it suspicious . . . ? 🙄
Regards
jh
Everything you say is true. The trick is to take it one step further. Let me see if I can build a case this way:
1) Does the topology of a circuit have an effect on the sound quality?
Obviously. You can choose circuits that tend more towards even order harmonics or odd order harmonics. You can choose circuits that produce lower order harmonics or higher order harmonics.
2) Do the active devices in a circuit have an effect on the sound?
Of course. Active devices introduce distortion. They do not have ruler-straight transfer curves...which is why they call them curves instead of lines.
3) Do the passive devices in a circuit have an effect on the sound?
Though there's still some foolish rearguard action, this was demonstrated thirty years ago for caps and can be heard with any other component you care to name if you have a decent system.
So, where does this leave us?
Most people would put cascoding under category 1 and forget about it. Well, unarguably, it is a topology choice. But...it also falls under 2 and possibly under 3 as well, depending on how picky you want to get.
Inevitably, people focus on the device sitting under the cascode. Look, it's snug as a bug in a rug! We've taken all this load off the device...etc. etc. etc. Pretty much the same points you just made. Again, I say that it's all true. But note that there's a tendency to overlook the cascode device itself.
The cascode still has to swing voltage and current, even if it has relieved the device beneath it of the voltage burden. Who's going to relieve its burden? Another cascode device? (Yes, you can find examples of several cascodes stacked on top of one another, but let's just assume the usual arrangement.) Once you look at the cascode itself, you can make all sorts of arguments based on the capacitances of the cascode device or the thermal drift as the device heats and cools due to the large swings of current, etc. All I'm saying is not to get so blinded by the benefits to the gain device that you forget the cascode itself.
So what to do? For starters, don't use a cascode unless you actually need one. In the case of these Lovoltech JFETs, it's pretty much inevitable that you're going to have to in order to get anything more than the smallest signal out of them. They need help in order to stand even modest voltage. That's fine, and I'm quite happy to use a cascode in this case because it's actually needed.
It's like current sources. Some people use them the way they use salt on food--without thinking. It's a reflex action. There's a blind, habitual aspect to this that is bothersome. Sometimes the best current source is a current source. Sometimes the best current source is actually a resistor.
Likewise, sometimes the best cascode is no cascode.
Assume nothing. Make each component and each topology choice earn its right to be there. Never throw anything in "because that's the way it's always done" or "everybody knows this is best" or "because I saw it once in a Rowland Research schematic and they must know what they're doing." Actively point to each and every component of your schematic and ask yourself why it's there. If you can't answer, take it out. Even if you can answer, ask yourself if it's really necessary or is there perhaps another way to accomplish the same thing.
All this is just an elaborate way of reminding yourself to create simple circuits.
Grey
1) Does the topology of a circuit have an effect on the sound quality?
Obviously. You can choose circuits that tend more towards even order harmonics or odd order harmonics. You can choose circuits that produce lower order harmonics or higher order harmonics.
2) Do the active devices in a circuit have an effect on the sound?
Of course. Active devices introduce distortion. They do not have ruler-straight transfer curves...which is why they call them curves instead of lines.
3) Do the passive devices in a circuit have an effect on the sound?
Though there's still some foolish rearguard action, this was demonstrated thirty years ago for caps and can be heard with any other component you care to name if you have a decent system.
So, where does this leave us?
Most people would put cascoding under category 1 and forget about it. Well, unarguably, it is a topology choice. But...it also falls under 2 and possibly under 3 as well, depending on how picky you want to get.
Inevitably, people focus on the device sitting under the cascode. Look, it's snug as a bug in a rug! We've taken all this load off the device...etc. etc. etc. Pretty much the same points you just made. Again, I say that it's all true. But note that there's a tendency to overlook the cascode device itself.
The cascode still has to swing voltage and current, even if it has relieved the device beneath it of the voltage burden. Who's going to relieve its burden? Another cascode device? (Yes, you can find examples of several cascodes stacked on top of one another, but let's just assume the usual arrangement.) Once you look at the cascode itself, you can make all sorts of arguments based on the capacitances of the cascode device or the thermal drift as the device heats and cools due to the large swings of current, etc. All I'm saying is not to get so blinded by the benefits to the gain device that you forget the cascode itself.
So what to do? For starters, don't use a cascode unless you actually need one. In the case of these Lovoltech JFETs, it's pretty much inevitable that you're going to have to in order to get anything more than the smallest signal out of them. They need help in order to stand even modest voltage. That's fine, and I'm quite happy to use a cascode in this case because it's actually needed.
It's like current sources. Some people use them the way they use salt on food--without thinking. It's a reflex action. There's a blind, habitual aspect to this that is bothersome. Sometimes the best current source is a current source. Sometimes the best current source is actually a resistor.
Likewise, sometimes the best cascode is no cascode.
Assume nothing. Make each component and each topology choice earn its right to be there. Never throw anything in "because that's the way it's always done" or "everybody knows this is best" or "because I saw it once in a Rowland Research schematic and they must know what they're doing." Actively point to each and every component of your schematic and ask yourself why it's there. If you can't answer, take it out. Even if you can answer, ask yourself if it's really necessary or is there perhaps another way to accomplish the same thing.
All this is just an elaborate way of reminding yourself to create simple circuits.
Grey
GRollins said:
No ball, one strike . . . ! 😀
Wife: "Aya . . . nice to have . . ."
Me: "Err . . . necessary . . . ?"
Wife:
Me:
I will go to the Krazy corner and ask myself . . .
Regards
jh
Regardless of all the other things going on in my life, I must say that my wife has been unfailingly supportive of my "Mad Scientist" fiddlings. That is a boon beyond reckoning and I am well aware of it. Her predecessor got rather bent if I even thought about doing electronics, much less followed through.
Grey
Grey
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