Banned
Joined 2002
> Nevertheless, Papa's circuit says nothing about them.
He mentioned somewhere in the thread 4mA bias, so BL.
If you guys believe in JFET magics, then don't use MOSFETs for the output stage. Find yourselves some Sony power JFETs, or design a pure N-JFET follower for the output stage using cascoded LU1014s.
Patrick
He mentioned somewhere in the thread 4mA bias, so BL.
If you guys believe in JFET magics, then don't use MOSFETs for the output stage. Find yourselves some Sony power JFETs, or design a pure N-JFET follower for the output stage using cascoded LU1014s.
Patrick
Banned
Joined 2002
I agree. But that is purely my personal opinion.
I also prefer SE amps to complementary.
So that is why I am not building the F4.
I think I have given enough hints.
A possible solution for a follower using LU1014s is the circuit I published in the MOSFET follower headamp thread. You only need to change the source resistor to values similar to ZV9, and raise the supply rails by 3V or so.
And of course you need minimum 6, probably 12x LU1014s if you are not using push-pull.
Patrick
I also prefer SE amps to complementary.
So that is why I am not building the F4.
I think I have given enough hints.
A possible solution for a follower using LU1014s is the circuit I published in the MOSFET follower headamp thread. You only need to change the source resistor to values similar to ZV9, and raise the supply rails by 3V or so.
And of course you need minimum 6, probably 12x LU1014s if you are not using push-pull.
Patrick
Link to the above mentioned follower circuit :
http://www.diyaudio.com/forums/showthread.php?postid=1130743#post1130743
My SUGGESTIONS :
1) Replace :
2SK1529 with IRFP240
3R3W with 0R68 10W (read article on ZV9 at passdiy.com)
2) Parallel as many as you consider adequate for power and output impedance.
3) You would probably need a low impedance follower between signal source and input to the paralleled LU1014s.
Patrick
http://www.diyaudio.com/forums/showthread.php?postid=1130743#post1130743
My SUGGESTIONS :
1) Replace :
2SK1529 with IRFP240
3R3W with 0R68 10W (read article on ZV9 at passdiy.com)
2) Parallel as many as you consider adequate for power and output impedance.
3) You would probably need a low impedance follower between signal source and input to the paralleled LU1014s.
Patrick
Nelson Pass said:
Thanks Mr. Pass !
Point taken.
It's only that this quotation from Aleph 5 owner's manual was such a seductive reading:
"Problems with push-pull amplifier designs associated with crossover distortion have been
discussed elsewhere at length, and one of the primary results is non-monotonicity. Class B
and many AB designs have distortion products that dramatically increase with decreasing
signal. This is reduced greatly by Class A mode, but crossover distortion remains as a lower
order discontinuity in the transfer curve.
For reproducing music as naturally as possible, push-pull symmetric operation is not the best
approach. Air is not symmetric and does not have a push-pull characteristic. Sound in air is a
perturbation around a positive pressure point. There is only positive pressure, more positive
pressure, and less positive pressure.
Push-pull circuits give rise to odd ordered harmonics, where the phase alignment reflects
compression at both positive and negative peaks and crossover nonlinearity near the zero
point.
Push-pull operation in amplifiers is commonly portrayed by the analogy of a two-man saw
cutting down a tree. Certainly if we are cutting down trees by hand, we would opt for this
method, as it would be much more efficient.
As we are not cutting down trees, I much prefer the image of a violinist holding the bow at one
end with one hand. Only in this manner does the musician gain the degree of control and
precision required to produce the range and subtlety required by music. And so it is with
single-ended amplifiers."
I suppose that I just got carried away with couple of sentences at the end.
Thanks again for all you gave us.
Single-Ended Push-Pull Followers
And a push-pull version :
http://www.tubecad.com/2004/blog0023.htm
Patrick
And a push-pull version :
http://www.tubecad.com/2004/blog0023.htm
Patrick
Babowana said:
My interpretation is that f4 input jfets need no current.
I believe that Papa must be knowing what GR, BL and V mean.
Nevertheless, Papa's circuit says nothing about them.
Papa was half sleeping when he was writing down the manual?
Or, was half lost himself in a reverie?
Don't confuse the current required to drive the device itself and the current it supplies to drive the next stage. While it's true that the input requires very little current to drive, it does require some. Not in the resistive sense, since the resistive aspect is effectively infinite, but in the capacitive aspect because the Gate needs to be charged and discharged.
The Idss of a FET is more related to the current available to drive the next stage than to how hard the device is to drive.
Grey
juma said:
Thanks Mr. Pass !
Point taken.
It's only that this quotation from Aleph 5 owner's manual was such a seductive reading:
"Problems with push-pull amplifier designs associated with crossover distortion have been
discussed elsewhere at length, and one of the primary results is non-monotonicity. Class B
and many AB designs have distortion products that dramatically increase with decreasing
signal. This is reduced greatly by Class A mode, but crossover distortion remains as a lower
order discontinuity in the transfer curve.
For reproducing music as naturally as possible, push-pull symmetric operation is not the best
approach. Air is not symmetric and does not have a push-pull characteristic. Sound in air is a
perturbation around a positive pressure point. There is only positive pressure, more positive
pressure, and less positive pressure.
Push-pull circuits give rise to odd ordered harmonics, where the phase alignment reflects
compression at both positive and negative peaks and crossover nonlinearity near the zero
point.
Push-pull operation in amplifiers is commonly portrayed by the analogy of a two-man saw
cutting down a tree. Certainly if we are cutting down trees by hand, we would opt for this
method, as it would be much more efficient.
As we are not cutting down trees, I much prefer the image of a violinist holding the bow at one
end with one hand. Only in this manner does the musician gain the degree of control and
precision required to produce the range and subtlety required by music. And so it is with
single-ended amplifiers."
I suppose that I just got carried away with couple of sentences at the end.
Thanks again for all you gave us.
Don't overlook the necessity to counteract consumer resistance to something different from what they happen to be accustomed to. Given the prevalence of push-pull amps, a single-ended topology is going to have to overcome a certain amount of suspicion to make it in the marketplace.
It's a business, not a religion. Don't get too hung on any one viewpoint.
Grey
Banned
Joined 2002
