Constant Vgs at buffer
Ian
You wrote in an earlier post:
"Connecting the buffer in this way effectively operates it at almost constant Vds (due to the Vgs of the diff pair MOSFET)."
I have simulated both connectings (tail/zener) and there is not any difference in the Vgs behaviour, at least not in the simulator.
But there is a difference in the Vds swing, not in the amplitude, but in the shape, wich is normal sinus when connectig is to the zeners, but som way irregular when connested to the tail.
But ther is no difference to se at the output to the spaeker.
Ian
You wrote in an earlier post:
"Connecting the buffer in this way effectively operates it at almost constant Vds (due to the Vgs of the diff pair MOSFET)."
I have simulated both connectings (tail/zener) and there is not any difference in the Vgs behaviour, at least not in the simulator.
But there is a difference in the Vds swing, not in the amplitude, but in the shape, wich is normal sinus when connectig is to the zeners, but som way irregular when connested to the tail.
But ther is no difference to se at the output to the spaeker.
The unregular shape of the Vds behavior at the buffer is caused by the Vgs of the diffpair, but it seems as if this irregularity dont show up at the gates of de diffpair. The buffer Vds is affecet by the tail, but this forced change in Vds is not to be seen at bufferoutput. It seems as if there is no feedback here at all.
So, for now I see the connecting of the buffer to the tail rather than to -Ve as somethig usable, but if there is some benefits to this I don´t know.
But again, can You trust simulation in this delicate matter, I don´t know, but I have an Idear of what to look for when making some experimens.
Ian, thanks for your answers.
So, for now I see the connecting of the buffer to the tail rather than to -Ve as somethig usable, but if there is some benefits to this I don´t know.
But again, can You trust simulation in this delicate matter, I don´t know, but I have an Idear of what to look for when making some experimens.
Ian, thanks for your answers.
Stefano
I am confused over Your last post.
I am truley sorry if I have offended You in any way, that was not my intention, what so ever.
I am confused over Your last post.
I am truley sorry if I have offended You in any way, that was not my intention, what so ever.
Stephano,
I have no problem with bmp files and I can view your circuit just fine. I pointed out the lack of the X factor since I thought that this thread was supposed to be about x-rated soz - it is after all called x-soz 🙂
Ian.
I have no problem with bmp files and I can view your circuit just fine. I pointed out the lack of the X factor since I thought that this thread was supposed to be about x-rated soz - it is after all called x-soz 🙂
Ian.
Henrik , I'm truly not offended .
An Aleph circuit is a very good source for study ( even unbalanced)
say Aleph 4 .
The output on that circuits is not taken at the differential pair.
Neither feedback.
An Aleph circuit is a very good source for study ( even unbalanced)
say Aleph 4 .
The output on that circuits is not taken at the differential pair.
Neither feedback.
Stefano
I am rearley happy about that.
Aleph 4 is indeed a subjet to learn from.
So you was aming more to a bridged Zen-thing rather than an X?
I am rearley happy about that.
Aleph 4 is indeed a subjet to learn from.
So you was aming more to a bridged Zen-thing rather than an X?
Henrik,
Having read your comments and pondered the circuit some more, I find I am in broad agreement with you. The 4.7uF input capacitor will probably do just fine – I only raised the value as the roll off is gentle and begins at around 10Hz with the 4.7uF value. In retrospect I agree that it is better to use a high quality part rather than a larger value.
I’ve also taken a long hard look at my reasons for connecting the buffer drains to the diff pair tail and have concluded that it really doesn’t offer any significant advantage over a fixed voltage reference, other than perhaps a reduction in parts. Distortion for a 10V peak to peak sine is about 0.39% either way.
There is of course another way of doing things entirely, i.e. use the buffer AC coupled in the same way as the Zen v4. The drain of the buffers can then be connected directly to ground. Of course some way must then be found to restore the correct bias for the output devices. I should say however, that when I tried this I could only see worse distortion no matter how I did the biasing (approx 0.6%). I don’t much care for the additional capacitor either, so perhaps this is a dead end.
Finally, can (should?) we trust simulation in these delicate matters? Personally I don’t think so, the final arbiter must always be ones own ears. Simulation is just a useful tool that can help in avoiding the pursuit of ill conceived ideas and sometimes save the odd blown device!
Ian.
Having read your comments and pondered the circuit some more, I find I am in broad agreement with you. The 4.7uF input capacitor will probably do just fine – I only raised the value as the roll off is gentle and begins at around 10Hz with the 4.7uF value. In retrospect I agree that it is better to use a high quality part rather than a larger value.
I’ve also taken a long hard look at my reasons for connecting the buffer drains to the diff pair tail and have concluded that it really doesn’t offer any significant advantage over a fixed voltage reference, other than perhaps a reduction in parts. Distortion for a 10V peak to peak sine is about 0.39% either way.
There is of course another way of doing things entirely, i.e. use the buffer AC coupled in the same way as the Zen v4. The drain of the buffers can then be connected directly to ground. Of course some way must then be found to restore the correct bias for the output devices. I should say however, that when I tried this I could only see worse distortion no matter how I did the biasing (approx 0.6%). I don’t much care for the additional capacitor either, so perhaps this is a dead end.
Finally, can (should?) we trust simulation in these delicate matters? Personally I don’t think so, the final arbiter must always be ones own ears. Simulation is just a useful tool that can help in avoiding the pursuit of ill conceived ideas and sometimes save the odd blown device!
Ian.
Sorry , on my Italian-English ditionary I don't find the verb aming.
But seems to me that the correction of error can be done adding feedback even were it seems not to be required.
But seems to me that the correction of error can be done adding feedback even were it seems not to be required.
Stefano
You know, it´s not always things comes out right, specially not when you pushes arond with a computer-keyboard. If You change aming to aiming, I am shure You will find it in Your dictionary.
Ian
I am too tired to give you some answers to nigt, but to morrow.
You know, it´s not always things comes out right, specially not when you pushes arond with a computer-keyboard. If You change aming to aiming, I am shure You will find it in Your dictionary.
Ian
I am too tired to give you some answers to nigt, but to morrow.
Ian
It seems as if we share the same basic poit of view on this X-SOZ, based on simulation.
4.5 uF at the input.
Buffer-drains to fixed voltge ref.
Since there is no advantaged in using the the diff. pair tail as voltage refrence, I suggests the use of Zener, all though it means a few parts more.
You tried to use ground as Vref., but it didn´t pay off, on the contrary, an also implied more parts in the signalpath.
I also like the ground to be used exclusively for the signal path, and nothing else, this also for aesthetic reasons.
I woud say we have tried to make it right and simple.
We also shares the same judgement on the simulator.
I have "trimmed" the peeks of a square wave signal with C3 and C4, like a nice haircut
So there is only one thing to do now, an that is to bring this X-SOZ out of the simulatoor and in to real life, music, air, ears and and all that.
I have named the attached file HenrikIan- X-SOZ with buffer Ver.01.pdf, so if You want to add something in a new ver. nr, You ar welcome.
It seems as if we share the same basic poit of view on this X-SOZ, based on simulation.
4.5 uF at the input.
Buffer-drains to fixed voltge ref.
Since there is no advantaged in using the the diff. pair tail as voltage refrence, I suggests the use of Zener, all though it means a few parts more.
You tried to use ground as Vref., but it didn´t pay off, on the contrary, an also implied more parts in the signalpath.
I also like the ground to be used exclusively for the signal path, and nothing else, this also for aesthetic reasons.
I woud say we have tried to make it right and simple.
We also shares the same judgement on the simulator.
I have "trimmed" the peeks of a square wave signal with C3 and C4, like a nice haircut
So there is only one thing to do now, an that is to bring this X-SOZ out of the simulatoor and in to real life, music, air, ears and and all that.
I have named the attached file HenrikIan- X-SOZ with buffer Ver.01.pdf, so if You want to add something in a new ver. nr, You ar welcome.
Henrik,
Looks like you have done a nice job so I don't have much to add. The only change I would make is to set R16 and R10 at 470k to give around 5v at Q1/Q2 drains. This maximises headroom (symmetrical clipping) at +/- 12v peak. This also drops the voltage at the gates of Q3/Q4 and hence you may need to change the value of the zeners to compensate (I used 16v to set the drain at -3v).
Ian.
Looks like you have done a nice job so I don't have much to add. The only change I would make is to set R16 and R10 at 470k to give around 5v at Q1/Q2 drains. This maximises headroom (symmetrical clipping) at +/- 12v peak. This also drops the voltage at the gates of Q3/Q4 and hence you may need to change the value of the zeners to compensate (I used 16v to set the drain at -3v).
Ian.
Ian
Glad that You like it.
I have redrawn the scematic, so most of the partnumbers have changed. I have done this to keep the good old SOZ numbers intact as this one is the mainissue.
My first values for R16 and R17 was 360k, a value that kept the original biaspoint at Q1 and Q2.
You suggested 680k, and I agreed with You.
Reconcidering these values, I found, that Yours 470k is the best solution for the headroom. I don´t know why I didn´t saw the reduced "headroom" at 680k, though it is verry obvious in the graph I have attached along with the new scematic.
So R16 and R17 = 470k and 16V zeners at the bufferdrains it will be for now.
C5 and C6 is there to remove the noise from the zeners, I don´t know if they really are needed or not, but if they shall remoove any noise, they have to be conciderable larger than the first 10nF, if they are 100uF, noise will have a -3db rolloff at 500Hz. Test in real life will tell if they are needed or not.
As You can see, I have added some back to back zeners and gateresistors at the input.
Is there any particular reason why NP didn´t put these in Zen Var. 4 ? I like the protection.
I was surfing for some information on the Millereffect, and I found som nice article by Kieth Herron at his homepage. http://www.herronaudio.com/tastubes.html
In this article he points out verry clearley the need for wider band amplification, the X-SOZ can´t deliver that bandwith he claims, but X-SOZ with a buffer can, when simulated.
But wee don´t know before wee have heard it.
Glad that You like it.
I have redrawn the scematic, so most of the partnumbers have changed. I have done this to keep the good old SOZ numbers intact as this one is the mainissue.
My first values for R16 and R17 was 360k, a value that kept the original biaspoint at Q1 and Q2.
You suggested 680k, and I agreed with You.
Reconcidering these values, I found, that Yours 470k is the best solution for the headroom. I don´t know why I didn´t saw the reduced "headroom" at 680k, though it is verry obvious in the graph I have attached along with the new scematic.
So R16 and R17 = 470k and 16V zeners at the bufferdrains it will be for now.
C5 and C6 is there to remove the noise from the zeners, I don´t know if they really are needed or not, but if they shall remoove any noise, they have to be conciderable larger than the first 10nF, if they are 100uF, noise will have a -3db rolloff at 500Hz. Test in real life will tell if they are needed or not.
As You can see, I have added some back to back zeners and gateresistors at the input.
Is there any particular reason why NP didn´t put these in Zen Var. 4 ? I like the protection.
I was surfing for some information on the Millereffect, and I found som nice article by Kieth Herron at his homepage. http://www.herronaudio.com/tastubes.html
In this article he points out verry clearley the need for wider band amplification, the X-SOZ can´t deliver that bandwith he claims, but X-SOZ with a buffer can, when simulated.
But wee don´t know before wee have heard it.
Reading Herron's article, I observe that he regards limited
bandwidth as stuff that doesn't make it to 20 KHz, and
I'm certain most here would agree.
Why do you think any of the Zen amps don't make it
to 20 KHz, much less the 100 KHz numbers they measure?
bandwidth as stuff that doesn't make it to 20 KHz, and
I'm certain most here would agree.
Why do you think any of the Zen amps don't make it
to 20 KHz, much less the 100 KHz numbers they measure?
Hi Nelson!
I am very sorry, that I have expressed my self in a way that could be interpreted the way You did.
So I will try to do better now.
I know that all the Zen amps makes it beyond 100KHz, and that is great.
When I wrote "the need for wider band amplification" it was not ment as to say that wee need more bandwidth than the Zen amps can deliver, I know that they do better than 100KHz.
Measurements by NP:
........................20KHz..........100KHz
BOSOZ................-0db...........-0.3db
Zen V4.............-0.1db...........-1.4db
SOZ..................-0db...............-0db (Flat from DC to several MHz)
Measurements in my simulator:
.......................20KHz...........100KHz
SOZ...................-0db.............-0.3db (I still beleeve in DC to XMHz)
X-SOZ................-1db...............-8db
X-SOZ+Buf......-0.05db............-1.4db
What is new to me, is this statement in Herrons article:
"We found that a 3-millibel variation in the frequency response curve can change a listener's perception of the unit. This could explain the audible improvements often associated with wide bandwidth in audio equipment. A loss of frequency response in terms of decibels at 100kHz will mean, in most cases, a drop in frequency response of several millibels at 10kHz - a perceptible change. Many of the colorations (sonic variations) heard in audio equipment will correlate with frequency response variations. It is somewhat surprising that one can consistently hear such small differences between electronic components when the listening is done with speakers that vary in response by several decibels."
Since amplifiredesign also is the art of compromises, all Herrons products keeps within 20 Hz to 20 kHz ±0.1 dB.
May be all this i crap, but there coud be somthing in this.
Said in an other way, all Your Zens do the same, and most of them even much better.
When I modifyed Your SOZ, wich by its nature have really nice frequencyrespoce, into an Henrik-X-SOZ, the cost of this was decreesed bandwidth. After reading Herrons article I got this overwhelming feeling of "Audiofile anxiety" (one of Your own expressions as far as I remember) and claustrophobia caused of the Henrik-X-SOZ limited bandwidth, and that, at least of all, we don´t want, don´t we?
Nelson, still friends!
I am very sorry, that I have expressed my self in a way that could be interpreted the way You did.
So I will try to do better now.
I know that all the Zen amps makes it beyond 100KHz, and that is great.
When I wrote "the need for wider band amplification" it was not ment as to say that wee need more bandwidth than the Zen amps can deliver, I know that they do better than 100KHz.
Measurements by NP:
........................20KHz..........100KHz
BOSOZ................-0db...........-0.3db
Zen V4.............-0.1db...........-1.4db
SOZ..................-0db...............-0db (Flat from DC to several MHz)
Measurements in my simulator:
.......................20KHz...........100KHz
SOZ...................-0db.............-0.3db (I still beleeve in DC to XMHz)
X-SOZ................-1db...............-8db
X-SOZ+Buf......-0.05db............-1.4db
What is new to me, is this statement in Herrons article:
"We found that a 3-millibel variation in the frequency response curve can change a listener's perception of the unit. This could explain the audible improvements often associated with wide bandwidth in audio equipment. A loss of frequency response in terms of decibels at 100kHz will mean, in most cases, a drop in frequency response of several millibels at 10kHz - a perceptible change. Many of the colorations (sonic variations) heard in audio equipment will correlate with frequency response variations. It is somewhat surprising that one can consistently hear such small differences between electronic components when the listening is done with speakers that vary in response by several decibels."
Since amplifiredesign also is the art of compromises, all Herrons products keeps within 20 Hz to 20 kHz ±0.1 dB.
May be all this i crap, but there coud be somthing in this.
Said in an other way, all Your Zens do the same, and most of them even much better.
When I modifyed Your SOZ, wich by its nature have really nice frequencyrespoce, into an Henrik-X-SOZ, the cost of this was decreesed bandwidth. After reading Herrons article I got this overwhelming feeling of "Audiofile anxiety" (one of Your own expressions as far as I remember) and claustrophobia caused of the Henrik-X-SOZ limited bandwidth, and that, at least of all, we don´t want, don´t we?
Nelson, still friends!
Henrik
some people with good ears will hear 100mB (.01dB) differences in a fixed frequency controlled test. I have never heard of anyone being able to reliably discern more than 1dB differences of a complex waveform in phase.
some people with good ears will hear 100mB (.01dB) differences in a fixed frequency controlled test. I have never heard of anyone being able to reliably discern more than 1dB differences of a complex waveform in phase.
yldouright
I allready feel much better, thanks!🙂
Actually, I have never tested my hearing this way, it should be worth a try.
If these buffers produceses som sonical benefit, bandwidth or not, then they shall stay, else out.
I am looking forward to try them anyway.
I allready feel much better, thanks!🙂 Actually, I have never tested my hearing this way, it should be worth a try.
If these buffers produceses som sonical benefit, bandwidth or not, then they shall stay, else out.
I am looking forward to try them anyway.
I would certainly agree that -1 dB at 20 KHz is going to
be audible to your more discerning listener.
There must be something going on with your simulation
to get so much drop off. Can you post a schematic?
be audible to your more discerning listener.
There must be something going on with your simulation
to get so much drop off. Can you post a schematic?
Nelson!
Shure I can post a scematic, here it is, my X-SOZ without buffer.
I really woud like to get some feedback on the freequensy responce. Thanks!
C1 and C2 at the scematic is the outputcaps in BOSOZ (10uF at the moment), without these the low frequensy will become a "rollup" because of the cap in the feedbackloop have a roll off at around 0,7 Hz, and thus no NFB here.
But all this is simulations. I haven´t got a scpoe yet to do the measurement, but I will get one within a month or so.
Mesurements or not, I am still happy with the sound of my X-SOZ, but I have this feeling it coud do even better.
Shure I can post a scematic, here it is, my X-SOZ without buffer.
I really woud like to get some feedback on the freequensy responce. Thanks!
C1 and C2 at the scematic is the outputcaps in BOSOZ (10uF at the moment), without these the low frequensy will become a "rollup" because of the cap in the feedbackloop have a roll off at around 0,7 Hz, and thus no NFB here.
But all this is simulations. I haven´t got a scpoe yet to do the measurement, but I will get one within a month or so.
Mesurements or not, I am still happy with the sound of my X-SOZ, but I have this feeling it coud do even better.