If you were to convert the output stage to a follower, I think you could increase the values of R10 and R11 to 100K or so with acceptable high frequency performance. This would let you reduce C1 & C2 to 2.2uF for about the same low frequency cutoff.
You could try this in the simulator to see how it works. Just move the speaker between the two output stage sources, reference R10 and R11 to ground instead of to V-, short out R4, R5, R6, and R7, and omit R13 and R36.
Follower operation of the output stage will require more voltage swing from the BOSOZ input section, but it can handle this easily if you increase R29 & R30 as needed.
I realize that this takes the idea in a different direction from the X-SOZ concept, but it might still be an interesting thing to try.
You could try this in the simulator to see how it works. Just move the speaker between the two output stage sources, reference R10 and R11 to ground instead of to V-, short out R4, R5, R6, and R7, and omit R13 and R36.
Follower operation of the output stage will require more voltage swing from the BOSOZ input section, but it can handle this easily if you increase R29 & R30 as needed.
I realize that this takes the idea in a different direction from the X-SOZ concept, but it might still be an interesting thing to try.
Joe Berry
Thanks for your suggestions.
You can´t X the topology you mention, as you yourself said.
It certainly coud be an interesting construction, but my head is X´ed these days. Thanks anyway!
It seems as I can reduce the C1 and C2 to 10-100uF by a special trick without more limited lowfrequensy roll off. I have to try it.
Erik
You can get them from IRF´s homepage: http://www.irf.com/product-info/models/
By the way, i am using SIMetrix intro v. 4.1, wich is very nice and free.
Thanks for your suggestions.
You can´t X the topology you mention, as you yourself said.
It certainly coud be an interesting construction, but my head is X´ed these days. Thanks anyway!
It seems as I can reduce the C1 and C2 to 10-100uF by a special trick without more limited lowfrequensy roll off. I have to try it.
Erik
You can get them from IRF´s homepage: http://www.irf.com/product-info/models/
By the way, i am using SIMetrix intro v. 4.1, wich is very nice and free.
Hallo!
Just today I try to modify substantially the original circuit.
The results are on the attached schematic.
The idea comes from the Bride Of Zen.
(Be ready to build an x Boz...)
For real life test (sigh ... I haven't got a simulator) I use instead of R1 R2 two ligh bulbs that has a value of resistance around 5 ohm or so. That seems to me right since the gain decrease with the resistors.
I trimmed R5 and R6 to obtain across R3 and R4 1.5 volts that let flow current for 1.5 Ampere par halve.But I would like to run each halve at a current of 2 amps ( when I'll buy the right transformers)
And rise a bit the imput impedance.
How it sounds? Incredible !
Just today I try to modify substantially the original circuit.
The results are on the attached schematic.
The idea comes from the Bride Of Zen.
(Be ready to build an x Boz...)
For real life test (sigh ... I haven't got a simulator) I use instead of R1 R2 two ligh bulbs that has a value of resistance around 5 ohm or so. That seems to me right since the gain decrease with the resistors.
I trimmed R5 and R6 to obtain across R3 and R4 1.5 volts that let flow current for 1.5 Ampere par halve.But I would like to run each halve at a current of 2 amps ( when I'll buy the right transformers)
And rise a bit the imput impedance.
How it sounds? Incredible !
Attachments
More test at the horizon!
I have worked a little with the basic idea and included some X to the BSOZ too.
I have reduced C1 and C2 from 560uF to 100uF, and the reason this coud be done is, that I have included C3 and C4 in the feedback loop at the XSOZ.
C3/4 makes the feedback roll off at around 4Hz and is almost gone at 200mHz. This roll off makes the signal at the input pass through in total open loop under 200mHz. Since C1/2 starts rolling off at 4Hz, this roll off takes the amount of open loop down to equal the flat toplevel until you gets under 200mHz. By ajusting C1/2 and C3/4 you can modulate the frequency response, but the X will start roll of at 4Hz and be gone at 200mHz. This partnership between C1/2 and C3/4 makes it difficult for the X-SOZ to be coupled to other preams, it really needs thos caps in (X)BSOZ. Some test is needed to hear if this is a good idea. May be you coud reduce C1 and C2 even more.
The implementation of the buffer was easy, an helpd the X-BSOZ to do better than 82kHz high roll off at -3db. If the X-BSOZ benefits from the buffer, I don´t know, but it is worth a try.
Some resistorvalues shoud be adjusted, this is a fairly raw sketch.
These are the main reasons why the scamatics loks like the attached file, wich alo contanis some graphs.
I would very much apreaciate some comments.
I have worked a little with the basic idea and included some X to the BSOZ too.
I have reduced C1 and C2 from 560uF to 100uF, and the reason this coud be done is, that I have included C3 and C4 in the feedback loop at the XSOZ.
C3/4 makes the feedback roll off at around 4Hz and is almost gone at 200mHz. This roll off makes the signal at the input pass through in total open loop under 200mHz. Since C1/2 starts rolling off at 4Hz, this roll off takes the amount of open loop down to equal the flat toplevel until you gets under 200mHz. By ajusting C1/2 and C3/4 you can modulate the frequency response, but the X will start roll of at 4Hz and be gone at 200mHz. This partnership between C1/2 and C3/4 makes it difficult for the X-SOZ to be coupled to other preams, it really needs thos caps in (X)BSOZ. Some test is needed to hear if this is a good idea. May be you coud reduce C1 and C2 even more.
The implementation of the buffer was easy, an helpd the X-BSOZ to do better than 82kHz high roll off at -3db. If the X-BSOZ benefits from the buffer, I don´t know, but it is worth a try.
Some resistorvalues shoud be adjusted, this is a fairly raw sketch.
These are the main reasons why the scamatics loks like the attached file, wich alo contanis some graphs.
I would very much apreaciate some comments.
Stefano
I have just tried your scematic in the simulator, it could do much better.
You have biased (in your scematic) the fets with only 3.6V, wich produces only 300mA draw in both mosfets, you wanted a reasonable draw at 1.5 A.
You are having a bias voltage at the drains at about 22.5V, wich leaves only a 1.5 voltage swing with 8 Ohm speaker, and no headroom at all.
By the way, I think your scematic looks more like Nelsons Zenlite.
You shoud get your self a simulator
, it is a great tool in the designing process 
. SIMetrix free simulator is so easy to use 
.
You can downlod it here: http://www.newburytech.co.uk/Pages/download.html
I have attached a pdf and a simetrix-file of your scematic.
Hope you can use my feedback.
I have just tried your scematic in the simulator, it could do much better.
You have biased (in your scematic) the fets with only 3.6V, wich produces only 300mA draw in both mosfets, you wanted a reasonable draw at 1.5 A.
You are having a bias voltage at the drains at about 22.5V, wich leaves only a 1.5 voltage swing with 8 Ohm speaker, and no headroom at all.
By the way, I think your scematic looks more like Nelsons Zenlite.
You shoud get your self a simulator
, it is a great tool in the designing process . SIMetrix free simulator is so easy to use .You can downlod it here: http://www.newburytech.co.uk/Pages/download.html
I have attached a pdf and a simetrix-file of your scematic.
Hope you can use my feedback.
Sims
I've downloaded the Newbury Tech simulator, and I can see why it seems to be so popular around these parts.
Has anyone tried out any Linux schematic capture/Spice simulators? There seems to be quite an array, each in a varying state of doneness according to the project pages. Rather than download each one, I figured I'd check here to see if that trail has already been blazed.
Erik
I've downloaded the Newbury Tech simulator, and I can see why it seems to be so popular around these parts.
Has anyone tried out any Linux schematic capture/Spice simulators? There seems to be quite an array, each in a varying state of doneness according to the project pages. Rather than download each one, I figured I'd check here to see if that trail has already been blazed.
Erik
Hallo!
Henrik,
please take a look at the schematic of Bride Of Zen: I use the same sistem to fine biasing the circuit except for R105 10k instead of 100k.My error , the results are not 10k to ground but at least 20k(or more).
But my circuit effectively runs 1.5A par halve.The drains are at about half the PS or to say 10-12volts.
Probably with light bulbs(24v 60W each) things are different (?).
I'm not Joking , the performance has nothing to do with the previous Xsons.
No doubt , this is X.
Thank you for the simulator: I will download it sooner.
Henrik,
please take a look at the schematic of Bride Of Zen: I use the same sistem to fine biasing the circuit except for R105 10k instead of 100k.My error , the results are not 10k to ground but at least 20k(or more).
But my circuit effectively runs 1.5A par halve.The drains are at about half the PS or to say 10-12volts.
Probably with light bulbs(24v 60W each) things are different (?).
I'm not Joking , the performance has nothing to do with the previous Xsons.
No doubt , this is X.
Thank you for the simulator: I will download it sooner.
Erik
I have only tried simulators to windows, so I don´t know those for Linux.
Stefano
I am shure, that your bridged or balanced Zenversion souns good.
But in my opinion it contains no X.
You have build a diffrential stage without a tail, both mosfet-sources are tied to ground through its own resistor, and is hereby separated from each other.
In my understanding they need to share one and the same currentsource, thus the feedback can be comunicated from one mosfet to the other through their sources.
I am pretty shure You need a diff. pair with a tail.
I have bin dooing some sims since my last post.
I am still not satisfied with them, so no tests has ben done.
My goal is to make a seperate preamp and outputstage, but in order to understand the scirciuts interplay i have made the sims as integrated amps. I found one solution for an integrated amp wich looks very promising, but it can´t be separated besause af the global feedbackloop.
I have only tried simulators to windows, so I don´t know those for Linux.
Stefano
I am shure, that your bridged or balanced Zenversion souns good.
But in my opinion it contains no X.
You have build a diffrential stage without a tail, both mosfet-sources are tied to ground through its own resistor, and is hereby separated from each other.
In my understanding they need to share one and the same currentsource, thus the feedback can be comunicated from one mosfet to the other through their sources.
I am pretty shure You need a diff. pair with a tail.
I have bin dooing some sims since my last post.
I am still not satisfied with them, so no tests has ben done.
My goal is to make a seperate preamp and outputstage, but in order to understand the scirciuts interplay i have made the sims as integrated amps. I found one solution for an integrated amp wich looks very promising, but it can´t be separated besause af the global feedbackloop.
Hi Stefano
Shure, but even more important, they are tied together with item 40 (low value resistor), otherwise there would not be any diffrential behaviour, wich is the path for the X-feedback.
By item 40, 42, 43 (resistors) and the two currentsources 26 an 27 you can controle the degree of diffrential behaviour to introduce some coupelig loss in the recoursive feedbackprocess, and thus reduce "the hall of mirrors" effect in ceartin circuits.
Doesn´t seems to be a problem for the Aleph-X or Grey have fixed this in an other way, since it only have one currentsource at the diff. pair.
This is how I understand the patent and the X, and I am shure there is much more to this, and also, I could be wrong.
Shure, but even more important, they are tied together with item 40 (low value resistor), otherwise there would not be any diffrential behaviour, wich is the path for the X-feedback.
By item 40, 42, 43 (resistors) and the two currentsources 26 an 27 you can controle the degree of diffrential behaviour to introduce some coupelig loss in the recoursive feedbackprocess, and thus reduce "the hall of mirrors" effect in ceartin circuits.
Doesn´t seems to be a problem for the Aleph-X or Grey have fixed this in an other way, since it only have one currentsource at the diff. pair.
This is how I understand the patent and the X, and I am shure there is much more to this, and also, I could be wrong.
X or not
Henrik, You are absolutely right regarding your comments about what it takes to have the "X Factor". Whether it is two current sources separated by a resistor (PI network) or one current source and two resistors (T network) is pretty much irrelevant (except perhaps for power dissipation).
The coupling loss to reduce the hall of mirrors effect is really only an issue for preamps where a significant amount of common mode noise might be a problem for whatever it is connected to - particularly if used single-ended.
For a power amp, a relatively large amount of common mode noise is less of an issue as it is effectively rejected by the speaker, i.e. it does not see common mode voltage as a signal at all.
Ian.
Henrik, You are absolutely right regarding your comments about what it takes to have the "X Factor". Whether it is two current sources separated by a resistor (PI network) or one current source and two resistors (T network) is pretty much irrelevant (except perhaps for power dissipation).
The coupling loss to reduce the hall of mirrors effect is really only an issue for preamps where a significant amount of common mode noise might be a problem for whatever it is connected to - particularly if used single-ended.
For a power amp, a relatively large amount of common mode noise is less of an issue as it is effectively rejected by the speaker, i.e. it does not see common mode voltage as a signal at all.
Ian.
Ian
Thanks for pointing out the terms "PI-network" and "T-network" and for confirming my thoughts abot how the "X" works.
I got your point on the preamp consideration when driving a singleended poweramp.
Nelson
I remeber an earlier post of Yours, where You explaind the reason why it took you so long to get the X to work, You then mentiond the need for a simple circiut (2 gainstages or less).
And that is why Grays Aleph-X don´t have this problem with "hall of mirrors" effect when using one currentsource at the input diff. pair.
So thanks, I wont bother to do this with a T-network with one resistorbased currentsource, but witout additional resistors to reduce the differntial gain, since this gain is needed in the feedbackloop.
I try to make X-BSOZ and X-SOZ witout buffers, I think I can do it, but the problem is to keep the high roll off at a reasonable high level.
Thanks for pointing out the terms "PI-network" and "T-network" and for confirming my thoughts abot how the "X" works.
I got your point on the preamp consideration when driving a singleended poweramp.
Nelson
I remeber an earlier post of Yours, where You explaind the reason why it took you so long to get the X to work, You then mentiond the need for a simple circiut (2 gainstages or less).
And that is why Grays Aleph-X don´t have this problem with "hall of mirrors" effect when using one currentsource at the input diff. pair.
So thanks, I wont bother to do this with a T-network with one resistorbased currentsource, but witout additional resistors to reduce the differntial gain, since this gain is needed in the feedbackloop.
I try to make X-BSOZ and X-SOZ witout buffers, I think I can do it, but the problem is to keep the high roll off at a reasonable high level.
I don't find I need buffers unless the source starts
sounding crappy into 500 ohms or so. Unfortunately,
this seems to be very common.
In addition, I talk to lots of people who get nervous with
loads less than 47K. Myself, I say it's a pitiful preamp
that can't source the 200 microamps that it takes to clip
a 10K input.
On the other hand, many of the complaints about the
sound of the Zen amps are traced back to input impedance.
sounding crappy into 500 ohms or so. Unfortunately,
this seems to be very common.
In addition, I talk to lots of people who get nervous with
loads less than 47K. Myself, I say it's a pitiful preamp
that can't source the 200 microamps that it takes to clip
a 10K input.
On the other hand, many of the complaints about the
sound of the Zen amps are traced back to input impedance.
It is funny because i was thinking about why you raised the input impedance of ZEN V4 to 47K... Even when you run the design inverted to minimize capacitance modulation it will not go completly away....
But i can see know when you drive it from a passive preamp.
The most opamps and discrete should have no problem driving into 500Ohm or less. i guess this is a bigger problem as mentioned?
Sonny
But i can see know when you drive it from a passive preamp.
The most opamps and discrete should have no problem driving into 500Ohm or less. i guess this is a bigger problem as mentioned?
Sonny
Nelson and Sonny
I wondered too why you Nelson raised the inputimpedance to 47k at Zen V4, working with tis XSOZ stuf it became very clear to me. And I understand this compromise, it is my impression, that the buffer only degrees the soundquality very little, specially compared to the sins comitted by an preamp not able to drive the presented load, that is some degradation worth talking about.
It is easy to make the BSOZ drive even 100 Ohms load.
I have made some simulations of a X-BSOZ and a X-SOZ connected to each other, where I got a frequensey respons like this:
-0 db @ 1Hz.
- 0,15db @ 20 kHz
-3db @ 100kHz
This is the best I can do for now, with a little less gain It can go -0.1db at 20kHz, wich was my goal, tests will show how much gain I need.
I tend to do some comparatative tests between the different types, with and without buffers.
I will come back when this is done, though I think it will take quite some time to do this, as I also have to work for living.
I wondered too why you Nelson raised the inputimpedance to 47k at Zen V4, working with tis XSOZ stuf it became very clear to me. And I understand this compromise, it is my impression, that the buffer only degrees the soundquality very little, specially compared to the sins comitted by an preamp not able to drive the presented load, that is some degradation worth talking about.
It is easy to make the BSOZ drive even 100 Ohms load.
I have made some simulations of a X-BSOZ and a X-SOZ connected to each other, where I got a frequensey respons like this:
-0 db @ 1Hz.
- 0,15db @ 20 kHz
-3db @ 100kHz
This is the best I can do for now, with a little less gain It can go -0.1db at 20kHz, wich was my goal, tests will show how much gain I need.
I tend to do some comparatative tests between the different types, with and without buffers.
I will come back when this is done, though I think it will take quite some time to do this, as I also have to work for living.
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