are you sure that you'll have needed DC voltage on lower mosfet's gate?
anyway-seems that 5460 is also too wimpy for task - driving even one gate of mosfet; besides-I'm not so sure that you can believe in software predictions ,it's possible that plain resistor is better sounding variant than CCS (or CS,if you wish)........I tried both variants sometime (even if not in exact Babelfish prototype) and plain vannila resistor is better for my ears;
hehe,it's not likely that Papa is pinching two resistors and one lousy BJT to save and prolong his Lab for another decade;I'm sure that he listened (more than ) both variants.......
find Jfets capable of 10mA at least (look at Papa's post few numbers above ) and try with them ; it's pretty re-searched area before "us" ...JC,NP and other old ##### measured and listened all that......
anyway-if you wish,nobody can't stop ya to make your own variant of any amp,but law's of physics are still stronger than we are
anyway-seems that 5460 is also too wimpy for task - driving even one gate of mosfet; besides-I'm not so sure that you can believe in software predictions ,it's possible that plain resistor is better sounding variant than CCS (or CS,if you wish)........I tried both variants sometime (even if not in exact Babelfish prototype) and plain vannila resistor is better for my ears;
hehe,it's not likely that Papa is pinching two resistors and one lousy BJT to save and prolong his Lab for another decade;I'm sure that he listened (more than ) both variants.......
find Jfets capable of 10mA at least (look at Papa's post few numbers above ) and try with them ; it's pretty re-searched area before "us" ...JC,NP and other old ##### measured and listened all that......
anyway-if you wish,nobody can't stop ya to make your own variant of any amp,but law's of physics are still stronger than we are
I'ld like to ask this question, regarding driving the output transistors. At lower voltages The IRFP044 has been said to be better. Well where are we 15V? But, I can see where you might have trouble driving all that gate charge with JFETs. But, recently the 5th generation IRFP044N has come to my attention. Have I missed something? This part has a little trouble with the Pd and the RthJ, but check out the capacitance/Gate charge numbers. Isn't it very close to the 240 parts? With greater gain? Wouldn't that be a worthwhile device for this situation??? I haven't tried any sims yet or anything. I don't remember seeing any discussions regarding it? What would be wrong with the IRFP044N device
Yeah, I understand what you're saying. The MOSFETs need some drive because of the gate charge. I might just go ahead and build a mini-A type of amp instead. I have the mosfets for that anyway. I just thought JFETs might be different. Then again, maybe I will build it, if only to see if the spice predictions are in the ballpark compared to the real deal.
About the IRFP044N... If that is the only difference, it might be a real winner. If I didn't have 50 or the 240's, I would definitely consider those. Are they readily available?
About the IRFP044N... If that is the only difference, it might be a real winner. If I didn't have 50 or the 240's, I would definitely consider those. Are they readily available?
Well, my first thought about the 60db of gain, was something more like: That's what they do over in the Solid State Forum... Not that you are wrong or anything. And I certainly don't want to make you feel bad. I'm sure it works. But, Zen Mod's comments regarding resistors sounding better are likely due to the Pass philosophy of simplicity, restraint with the gain bis, minimal Feed Back, etc.
I would suggest trying "degenerating" some of the gain of using the active load and linearizing it also at the same time. Enough current is difenately a requirement but, most or all the Alephs only had 10mA per leg right? Driving 2, 3, 5 or whatever, pair of gain transistors??? Getting closer to that number may be a good start. But getting the JFET stage gain closer to the 9610's stage gain would also be a good start.
Just a thought.
Another thought, Have you seen the Self "Blameless Amp"? He uses a follower, I beleive he may call it a beta enhancer, driving his voltage gain stage. Back when Ckoky did the jfet amp I played around with siming a follower like that between the JFETs w/active load and the output stage. Yes it's another stage, but a simple one...
I would suggest trying "degenerating" some of the gain of using the active load and linearizing it also at the same time. Enough current is difenately a requirement but, most or all the Alephs only had 10mA per leg right? Driving 2, 3, 5 or whatever, pair of gain transistors??? Getting closer to that number may be a good start. But getting the JFET stage gain closer to the 9610's stage gain would also be a good start.
Just a thought.
Another thought, Have you seen the Self "Blameless Amp"? He uses a follower, I beleive he may call it a beta enhancer, driving his voltage gain stage. Back when Ckoky did the jfet amp I played around with siming a follower like that between the JFETs w/active load and the output stage. Yes it's another stage, but a simple one...
Thank you for the comments.
I knew I would probably hang myself out to dry with the active load, as far as popular opinion is concerned. I'm not so sure that it's a bad idea, though. In my opinion (and I could be totally and completely wrong) the point is not to add more gain stages. More gain stages seem to push the harmonic balance toward the higher orders. But, why not try to increase the gain on a single stage, or two? Is an active load that much different than a cascode? Maybe it is, maybe not. I would like to hear comments on this either way. If it was all bad, would Nelson have used something similar on the Aleph P1.7? Correct me if I'm wrong, but aren't the upper current sources acting as an active load?
The simulations indicate the same type of harmonic balance with the active load as without- a falling series of harmonics, only much lower in level. I know we don't design with our meters, but I can't see how this would sound worse.
I really do like the degeneration idea... maybe there is a sweet spot to be found this way; the active load giving some room to play with the open loop gain, controlled by the degeneration. Interesting idea.
I knew I would probably hang myself out to dry with the active load, as far as popular opinion is concerned. I'm not so sure that it's a bad idea, though. In my opinion (and I could be totally and completely wrong) the point is not to add more gain stages. More gain stages seem to push the harmonic balance toward the higher orders. But, why not try to increase the gain on a single stage, or two? Is an active load that much different than a cascode? Maybe it is, maybe not. I would like to hear comments on this either way. If it was all bad, would Nelson have used something similar on the Aleph P1.7? Correct me if I'm wrong, but aren't the upper current sources acting as an active load?
The simulations indicate the same type of harmonic balance with the active load as without- a falling series of harmonics, only much lower in level. I know we don't design with our meters, but I can't see how this would sound worse.
I really do like the degeneration idea... maybe there is a sweet spot to be found this way; the active load giving some room to play with the open loop gain, controlled by the degeneration. Interesting idea.
jfet clarification
Before anyone buys parts, I just wanted to make sure everyone knows the 2sj174 is not a jfet, but a mosfet. The correct jfet does not have the prefix 2s in front of it.
The correct part is j176 from www.allelectronics.com.
5 for a $1.00
If you have the zvp3310a p channel mosfet that one sounds wonderful too. I have a hard time deciding which one I like better between the zvp3310a and j176 jfet. They both have their own unique sound.
I would need to build two amps with these front ends, to try and see which one I really liked, but off of my memory from listening sessions both had qualities I liked over each other.
Regarding Nelson's diyop amp article that has been a great inspiration to all of my variations on the Aleph front end. That has been one of my favorite articles of his offerings!
His jfet matching in this article applied to N channel jfets. Would that also apply to P channel jfets except for reversing the S and G? I get the pins mixed up so if anyone is familiar I would like the exact pins to swap and to verify if this would be the best for matching the j176 jfets?
I know they are not the same as mosfet matching already according to this diyop amp article.
Bill
Before anyone buys parts, I just wanted to make sure everyone knows the 2sj174 is not a jfet, but a mosfet. The correct jfet does not have the prefix 2s in front of it.
The correct part is j176 from www.allelectronics.com.
5 for a $1.00
If you have the zvp3310a p channel mosfet that one sounds wonderful too. I have a hard time deciding which one I like better between the zvp3310a and j176 jfet. They both have their own unique sound.
I would need to build two amps with these front ends, to try and see which one I really liked, but off of my memory from listening sessions both had qualities I liked over each other.
Regarding Nelson's diyop amp article that has been a great inspiration to all of my variations on the Aleph front end. That has been one of my favorite articles of his offerings!
His jfet matching in this article applied to N channel jfets. Would that also apply to P channel jfets except for reversing the S and G? I get the pins mixed up so if anyone is familiar I would like the exact pins to swap and to verify if this would be the best for matching the j176 jfets?
I know they are not the same as mosfet matching already according to this diyop amp article.
Bill
Just a remark, without stating what is better or worst :
J176 is a JFET from Siliconex (Vishay), transconductance 4.5mS, Ciss 20pF, noise 20nV-sqrt(Hz).
2SJ74 is a JFET from Toshiba, transconductance 22mS, Ciss 105pF, noise 0.95nV-sqrt(Hz).
I use both, but Vishay mostly as cascode or current source.
Patrick
J176 is a JFET from Siliconex (Vishay), transconductance 4.5mS, Ciss 20pF, noise 20nV-sqrt(Hz).
2SJ74 is a JFET from Toshiba, transconductance 22mS, Ciss 105pF, noise 0.95nV-sqrt(Hz).
I use both, but Vishay mostly as cascode or current source.
Patrick
nobody special, Yes, I agree with everything you said, I think. Even regarding the beta enhancer... Your not hanging youself out
your trying things. I like to try all these ideas on the sim too What sim do you use
I don't have to much to say about the active loading vs. the cascode. I believe the cascode idea relies more on the gain device and it's characteristics at a stable drain voltage. With the active load you are introducing an apposing load that tries to maintain a stable current By using a complementary device it would seem, it's the way to go. There is more to understand there but I'm not sure I do
Yes, the 1.7 uses this techniqe, along with many others. I think there is some publeshed Doug Self info(for free) regarding the Blamesess design that may be informative. I'm not sure where though... I may have it saved somewhere here. He goes through optimizing each stage.
Thanks EUVL, I know the ones I have are JFETS
BTW, Many JFETs drain and Source pins are interchangable That's weird I know, but try it on the simulator
your trying things. I like to try all these ideas on the sim too What sim do you use I don't have to much to say about the active loading vs. the cascode. I believe the cascode idea relies more on the gain device and it's characteristics at a stable drain voltage. With the active load you are introducing an apposing load that tries to maintain a stable current
By using a complementary device it would seem, it's the way to go. There is more to understand there but I'm not sure I do Yes, the 1.7 uses this techniqe, along with many others. I think there is some publeshed Doug Self info(for free) regarding the Blamesess design that may be informative. I'm not sure where though... I may have it saved somewhere here. He goes through optimizing each stage.
Thanks EUVL, I know the ones I have are JFETS
BTW, Many JFETs drain and Source pins are interchangable
That's weird I know, but try it on the simulator
flg,
I'm using circuitmaker student version most of the time. It seems to do an adequate job for most of what I need.
Thanks for the clarification on the difference between the cascode and the active loading. I know there is a difference, but the way you stated it made it somewhat clearer to me.
I wonder what it would sound like with a pair of JFETs running heavy bias, cascoded, and with active loading similar to the Aleph P1.7?
It's easy to play with this stuff for hours, but I don't think I can come to any conclusions until I build it and try a few different things.
BillWW
Thank you for the clarification on the jfet/mosfet part numbers.
I'm using circuitmaker student version most of the time. It seems to do an adequate job for most of what I need.
Thanks for the clarification on the difference between the cascode and the active loading. I know there is a difference, but the way you stated it made it somewhat clearer to me.
I wonder what it would sound like with a pair of JFETs running heavy bias, cascoded, and with active loading similar to the Aleph P1.7?
It's easy to play with this stuff for hours, but I don't think I can come to any conclusions until I build it and try a few different things.
BillWW
Thank you for the clarification on the jfet/mosfet part numbers.
nobody special, Here is the Self page that I thought you might find interesting
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
> You have tried both jfets.
Why would one want to use a high-noise, low-gain part if there is (hardly) any disadvantage for the opposite ?
There are good reasons why the like of Nelson Pass, John Curl, Erno Borbely all use Toshiba JFETs, even when they are becoming obsolete.
I said hardly, because the Toshiba's has higher capacitance. But one can get round that, by using lower resistor values, or by cascoding.
Find out for yourself. Order a 2SJ109 (matched dual) or a bunch of 2SJ74s (to match), and try it in place of the J176's.
If you are worried about too much open-loop gain, you can always reduce that by source degeneration (by adding source resistors to the diff pair). You get better linearity as a bonus.
Patrick
Why would one want to use a high-noise, low-gain part if there is (hardly) any disadvantage for the opposite ?
There are good reasons why the like of Nelson Pass, John Curl, Erno Borbely all use Toshiba JFETs, even when they are becoming obsolete.
I said hardly, because the Toshiba's has higher capacitance. But one can get round that, by using lower resistor values, or by cascoding.
Find out for yourself. Order a 2SJ109 (matched dual) or a bunch of 2SJ74s (to match), and try it in place of the J176's.
If you are worried about too much open-loop gain, you can always reduce that by source degeneration (by adding source resistors to the diff pair). You get better linearity as a bonus.
Patrick
2sj109 and 2sj74
Where are these available now? MCM is out of the 2sj109. Apparently they were popular and sold out.
I can not find very many places to buys these now. I am left with my j176 jfets, which sound fine, but I have no way of comparing these to mine to see which I prefer now.
Bill
Where are these available now? MCM is out of the 2sj109. Apparently they were popular and sold out.
I can not find very many places to buys these now. I am left with my j176 jfets, which sound fine, but I have no way of comparing these to mine to see which I prefer now.
Bill
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.