| stefanobilliani |
| I have applied x susy to my soz : simply wonderful |
|
|
| Stefano |
| Hi Stefano I'm stefano too, what do you mean? Have you got any schematic? I think that SOZ it's alredy supersimmetrical like BZLS. Please let us know. |
|
|
| stefanobilliani |
| Hi Stefano! I have simply look at the aleph x work done by Grey and transpose some parts in a soz front end a little bit modified . Sorry i cannot send any schematic . Also i have not any kind of measure . I 've just feel free to experiment! |
|
|
| ftorres |
| quote: | Originally posted by stefanobilliani
Hi Stefano! I have simply look at the aleph x work done by Grey and transpose some parts in a soz front end a little bit modified . Sorry i cannot send any schematic . Also i have not any kind of measure . I 've just feel free to experiment! |
Very useful post indeed ! Thanks for the informations, and I will try ASAP to cook mine using your recipe
Thanks again |
|
|
| Nelson Pass |
Congratulations on being the first to publicly mention
the X-Zen. I had thought to perhaps hold this one back
until the Aleph X excitement had died down, but the
cat is now out of the bag. |
|
|
| stefanobilliani |
| Thank you mister Nelson Pass.But I have to tell , that day enthusiast took me over! And perhaps i'd need a language translator. I'm talking abouut sonic improvements on Son of zen. I don't know if the topology i use really (- or completly ) takes advantagies from supersimmetry ; but the concepts are there.No operational amps , 2 inputs 2 outputs.Improved stability and output dc offset nearly independent from small variatons of the bias resistors . Maybe only feedback effects ? And sound ... Not find the courage to retourn back to the basic version .Topology is :a soz ( without 1ohm resistor across source pins ) N channel output stage , a differential pair like aleph x ( except drain resistors values ) input stage and feedback from output stage (100Kohm resistor ) + resistor versus ground . I listen to this amp and music are very good and i find that lack of compressions that make the listener play records ... and play ...So at the moment i'm happy .Other <technical> thing are here to say Hope true.Thank you again. |
|
|
| Stefano |
| Hallo, I'm Stefano from Italy, I want to ask you if the BZLS & SOZ are or not quite "supersimmetrical". I'm dreaming to build a BZLS + volume + newest Zen in balanced mode without output caps to use it like an integrated. Tank you for your experience. |
|
|
| Nelson Pass |
Either you guys are very polite, or the idea of an Xzen
is boring, as I expected more response to this.
Polite maybe? :)
Please note my posting in "Experimental......" |
|
|
| Ian Macmillan |
| The idea of an X-Zen is far from boring, though I don't see how it would significantly differ from the Aleph-X concept. I suspect that others simply haven't noticed this post buried in this thread. |
|
|
| Variac |
As Stefanobilliani points out: For a Son of Zen now that's exciting
for Zen : Ho hum
Maybe cause I'm still working on the SOZ! |
|
|
| mrothacher |
Maybe my post is the boring one. I'm the "experimetal design" guy. The circuit I'm working on isn't really an X ZEN - its more of a "two stage class a mosfet circlotron that has potential to be an X circuit" Right now I'm working on the "no overall feedback" version. My thought was to get it working well without gobal feedback, then try to apply super-symmetry. I'm having trouble with it at the moment, so maybe I should abandon it in favor of working up an X ZEN. I was really attached to the idea of an "X-CIRCLOTRON" the name alone sounds cool.
Thanks
Mike |
|
|
| Petter |
OK, so since nobody else is jumping into this:
Take an X1000 input stage
Beef up all FET's with the usual Zen types
Lower voltages significantly
Increase current to required level (speaker impedance/power required, voltage ...
Omit output stage ....
You may go to the X100 reverse engineering thread to see schematics you can lift.
Petter |
|
|
| Nelson Pass |
Mike,
A cool name is half the attraction.
The Roger Corman approach:
First you think of a killer name
Then you draw up a really amazing poster
Then you shop is around for distribution
If you get enough distribution, then you make the movie
Please note that Roger Corman made a couple hundred
movies and only lost money on the one featuring
William Shatner. |
|
|
| Ian Macmillan |
| quote: | | Originally posted by Petter |
Take an X1000 input stage
Beef up all FET's with the usual Zen types
Lower voltages significantly
Increase current to required level (speaker impedance/power required, voltage ...
Omit output stage ....
Assuming you are referring to the folded cascode diff pair (as in the Pass patent) - I am having difficulty squaring this with Nelson's hint:
| quote: | | Originally posted by Nelson Pass |
You could explore creation of an X circuit with
a pair of inverting "current feedback" type chips,
if such a thing exists. These would have say a
gate for the negative input and a source for the
positive input. More to the point, you would have
a power inverter on the output stage of each.
Note particularly the mention of power inverter on the output stage. I don't think the folded cascode counts as an inverter, and last time I played around with this idea I couldn't see how to make use of the phase inversion. I ended up using a follower output stage but with the 'Aleph' active current source.
I also tried the circuit without an output stage but found that the gain was excessively effected by the load impedance. Maybe another "trick" is involved. I'll have to get my thinking cap on...
Ian. |
|
|
| Ian Macmillan |
| Apologies - I made something of a hash with the quoting in my previous post. :( Please read carefully to avoid any misunderstanding. I'll try to do better next time. |
|
|
| Nelson Pass |
What I was describing would be a tortured effort at
using IC's to create an X amp. It could be done as a
concept, but who would want to?
All this comes from my original comment that you can't
build X front ends out of op amps as a practical item. |
|
|
| Ian Macmillan |
| Ah, so maybe Petter is on the right track. I can see I will have to dig out my notes at trying the folded cascode X front end without output devices. I seem to recall that gain variation with load impedance was the main problem. That and getting sufficient gain with low Z loads. |
|
|
| mrothacher |
The B Movie King!
Nelson:
Would this make you the Stanley Kubrick of audio?
Dr. Pass:
Or, How I Learned To Stop Worrying And Love Source Degeneration
:D |
|
|
| GRollins |
Stefano,
Like so many others, you were caught when I ran out of time to answer e-mail. My apologies. Just to verify that I understood what you posted above...you ended up using a front end?
Grey |
|
|
| Nelson Pass |
My admiration for Kubrick and Corman stems from
creating art on their own terms.
The proper word I believe is *Auteur*
Picasso is another fine example, but not a film maker |
|
|
| stefanobilliani |
Grey,
yes , I do . |
|
|
| mrothacher |
I think it can be accomplished with one gain stage.
Figure 1 from the patent - delete the output stage - Hmmm - Fascinating. |
|
|
| stefanobilliani |
Here is how I worked te get te X version of Son of Zen.
( this time seriously )
Patent by N. Pass number 5.376.899 and SoZ circuit at my hand:
first scaled R1 and R2 values from 8 to 4.7 ohm each.
Than take 2 P channel gain devices IRF 9240 and following patent, joint each Source to the Drain(s) of new Soz .Put 12V across Gates to cascodin' this devices each with zener diods .
Following step : current sourcing to output this folded cascode .
I put 10 ohm power resistor to each halve .
Now ; susy connection (or feedback) .I choose a 100K ohm resistor.
The circuit went up with 12V rails . For my preference i set gain resistor (R7 soz circuit) at 8.2 ohm.
It works fine .
Thanks all for suggestions .
Ps. I let you imagine how much current it draws. |
|
|
| Ian Macmillan |
Stefanobilliani, it is hard to visualise what you mean without a schematic. I suspect I will have many questions, but first it seems to me that we need a common reference from which to start. To this end I have attempted to interpret your description and translate it to a schematic. Let me know in what respects it is wrong (as I am sure it will be) and I will try and update it. I look forward to some interesting discussion!
Ian. |
|
|
| stefanobilliani |
Ian , thank you very much for help. With this schematic everything
will be clearer!
It is exatly what i intended exept for gain devices that are IRFP240 and IRFP9240. |
|
|
| Variac |
If you make a preamp to match we can call it:
X Wife of Zen
;) |
|
|
| rothko |
Hi!
Concerning X-SOZ, I have questions.
1. SOZ already has balanced topology.
This means that common noise or distortion can be canceled.
Is there any special reason to design X-SOZ topology?
2. How about the efficiency of X-SOZ compared with SOZ?
3. I already have 8ohm power resistors for SOZ.
If I replace 4ohm resistors with 8ohm resistors, what will
happen? |
|
|
| jam |
Ian,
How about replaceing R13 and R12 with current sources?
Jam |
|
|
| stefanobilliani |
Rothko,
I drive soz like source follower for a period , this means remove R1 and R2 and circuit still have not problems. This with 12volt rails and power supply rated at about 150va par channel. Any way it will need a large heat dissipation.
Efficiency , i think should be the same. Especially the current throug complete circuit will be about double.
At Passlabs web site there are interesting articles about Supersimmetry, that will give you some careful informations .
One of these aims even low distorsion and noise in audio circuitry.
Please take this as an exploration. I remember you that Nelson Pass , on another thread , posts that later, x series will compare as variatons of the original zen amps at Passdiy web site.
Stefano |
|
|
| Ian Macmillan |
Jam, regarding your question about current sources. Please note that this is not my design – I was just acting as scribe for Stefano. I do have some thoughts though regarding current sources and these appear below.
Stefano, glad to be of help and I’m pleased that my interpretation was not too far off the mark. Sorry about the MOSFETs – I don’t current have symbols/models for those you used (but will rectify this shortly). Now that we have a point of reference I can raise all those questions that I have had since first hearing about this concept! Some of these are not directly about your implementation and are intended as open questions to the forum.
First off, I find myself questioning why you would want to use folded cascades (or cascades at all for that matter). I appreciate that Nelson’s patent 5,376,899 shows this topology, but it is perhaps worth pointing out to the uninitiated that SuSy is not dependent on it. You can in fact convert the SOZ design to use SuSy with just a couple of resistors. I attach a schematic of one such variant but I should also say that I have not actually built it.
Current sources or resistors, how to decide? The previously mentioned patent shows current sources for diff pair tail, loads and cascode output loads (R12 and 13 in my previous post). But this was intended as a line level or power amp front end. When this topology is called upon to deliver substantial current (e.g. driving a speaker) without an output stage, one is effectively driving the speaker with a pair of current sources. In general this is not too clever as the circuit will show substantial output impedance, even with feedback applied. Current sources come into their own in situations where it is possible to take advantage of lower power dissipation, or when the additional impedance is welcome, e.g. to increase gain. I don’t see that either of these apply in this situation.
I admit to being intrigued by the idea of an X Zen that uses both SuSy and Nelson’s ‘Aleph’ current source. But maybe I am simply going off at a tangent in what will turn out to be a fruitless pursuit. I cannot see how to apply this to the folded cascode topology and suspect this to be the wrong direction. The attached schematic could quite easily be converted to use ‘Aleph’ current sources but I think the diff pair tail would have to remain resistive. A pity as the circuit will have poor CMRR and poor performance if driven by a single ended input like this. Power dissipation in the tail resistor will also be quite high L
Anyway, I am now just thinking out loud. How about some of you clever folks making some suggestions?
Ian. |
|
|
| grataku |
Ian,
I looked at your schematic (thank you very much for posting it)....
Maybe I am being tricked by the way it is drawn but I don't see the "X" topology in your schematic. What I see is an soz with an additional inverted gain stage. |
|
|
| Ian Macmillan |
Grataku,
Presumably you are referring to my earlier post since you mention an additional gain stage...
The "inverted gain stage" is not really an additional gain stage at all, it is a folded cascode (non-inverting, voltage gain only) and hence the circuit is more of a glorified diff pair. It is however, SuSy in that distortion from one side of the diff pair is fed, in phase, to the other (whilst signal is in inverse phase). The 'trick' if one can call it that, is the addition of feedback from output to input gate of each side. This causes distortion from one half to be fed to the other (via their sources) by a process that Nelson referrs to as input gain conduction. Does this help any?
Ian. |
|
|
| Nelson Pass |
Excellent job, Ian, that's twice you have won the
(single) prize offered.
I don't recognize the phrase "input gain conduction", tho. |
|
|
| Ian Macmillan |
I was quoting from memory. The actual words from the Patent:
| quote: | | Each stage feeds its amplifier output negatively to the positive input of the other stage, while at the same time feeding its distortion and noise contribution positively, via input gain transistor conduction, to the other stage |
Thanks for your kind words.
Ian. |
|
|
| Nelson Pass |
Lawyers wrote that.
I often refer to cross-coupled error correction, or
cross-coupled feedback in reference to the circuit.
I notice that a lot of people still don't "get" the circuit,
and that is understandable.
The essence is still using a symmetric feedback arrangement
around a differential pair which isolates error from signal
and uses it to make distortion on two halves identically
in phase and thus cancelled. |
|
|
| Ian Macmillan |
Took me a logn time to 'get' the concept too... Sometimes when I get caught up in the details it still eludes me :(
Ian. |
|
|
| Nelson Pass |
By the way, your prize is in the capable hands of the
Postal Service. |
|
|
| grataku |
"I notice that a lot of people still don't "get" the circuit,
and that is understandable."
Don't mind me Nelson, I am just a chemist. The principle is trivial to understand (now that you worked it out) but I can't follow the schematic. I 'll come around, eventually.
What's most important to me it's how it sounds. If the whole idea sounds anything like the BOSOZ I must build something with susy. If I was a little richer I wouldn't have to understand anything and I could just buy an XA. |
|
|
| Ian Macmillan |
For many of us I think it is more a case of a lot richer :( Actually I would love to hear a real XA but unfortunately there are not that many over here in the UK.
Ian. |
|
|
| Nelson Pass |
Since they start shipping next month, that would be
understandable. |
|
|
| griff |
| Nelson, have you found yourself an Australian distributor yet? |
|
|
| Nelson Pass |
Our procedure has usually been to allow the distributors
to find us. This saves all manner of time, as anyone we
talk to is already interested. |
|
|
| Ian Macmillan |
I am suprised at the apparent lack of interest in the concept of an X-Zen. Can this really be or are others too busy with other projects? Or perhaps you are waiting for Nelson to publish his next installment in the Zen series?
I've already offered one schematic but nobody has yet torn it apart (or said anything else for that matter). Perhaps it was just too far off the mark?
Ian. |
|
|
| till |
| shure interested, of course waiting for the ZEN X variation, and awaiting Zen var. 4 urgently! looking at passdiy every day! |
|
|
| Variac |
I'm very interested. especially in the
X rated son of Zen or X Wife of Zen
I'm afraid that this Son of Zen version will be overshadowed by the plain Zen version which Nelson is cooking up, so I hope this SOZ version gets developed here. Sadly, I am too ignorant to contribute, what are those circles with voltages and wave shapes in them anyway? Hey you guys, pitch in and get this done, with parts spec'ed and everything pedantically spelled out, so I can make one....This is new territory - come on!!!! |
|
|
| Erik Johansson |
| quote: | Originally posted by Variac
I'm very interested. especially in the
X rated son of Zen or X Wife of Zen
I'm afraid that this Son of Zen version will be overshadowed by the plain Zen version which Nelson is cooking up, so I hope this SOZ version gets developed here. Sadly, I am too ignorant to contribute, what are those circles with voltages and wave shapes in them anyway? Hey you guys, pitch in and get this done, with parts spec'ed and everything pedantically spelled out, so I can make one....This is new territory - come on!!!! |
If the X Son of Zen can be built with my matched IRFP240 transistors I think it´ll be the project for me. I´d love to build the Penultimate Zen but I can´t get the IRFP044 transistors for it over here. :(
/Erik |
|
|
| Freddie |
| Erik, You can use IRFP240 instead of IRFP044. |
|
|
| Erik Johansson |
| quote: | Originally posted by Freddie
Erik, You can use IRFP240 instead of IRFP044. |
Nice, so now I have 2 options :)
I found a guy here in Gothenburg (du kanske vet vem det är, Micke, han som säljer Scan-Speak, Vifa och Peerless element) who is selling matched IRFP240 transistors. 4 of them would cost ~$15.
/Erik |
|
|
| Freddie |
| quote: | | Nice, so now I have 2 options. I found a guy here in Gothenburg (du kanske vet vem det är, Micke, han som säljer Scan-Speak, Vifa och Peerless element) who is selling matched IRFP240 transistors. 4 of them would cost ~$15. |
Yes, I have bought parts from him a couple of times. Actually I'm waiting for some parts for my new preamp.
/Freddie |
|
|
| stefanobilliani |
Please, is there anybody able to indicate me how to find a tool
for circuits editing?
Thanks in advance .
Stefano |
|
|
| Ian Macmillan |
Variac et al, I'm a bit busy at the moment but when I can find a few spare minutes I'll have a crack at dreaming up a few schematics. I've recently been distracted by a related thread about output stage topology and the importance (or not) of low output impedance. It is a fascinating subject and if correct, may mean that a number of circuit ideas that I had discounted may actually be viable. I take your point about being overshadowed by Nelson's next Zen installment but so be it.
Stephano, try downloading one of the Spice simulation packages with schematic capture that are referenced in many other threads. Circuitmaker has a pretty good schematic editor even if its simulation capability is a little suspect.
Ian. |
|
|
| stefanobilliani |
Thanks Ian.
After the exploration with Nelson's patent I rebuild the circuit as it was when I started the thread.
I believe it is the right circuit.
First becouse it sounds wonderful! After that , as i "try" to explain up above , it is really a " feedback arrangiament around a differential pair".
If this amplifier counts 2 stage of amplification then , the diff pair is the input stage . Son of ZEN ( as we all know it ) is the OUTPUT stage.
Feedback presents a signal that is out of fase with the corrisponding input .
When ready I'll try to post the circuit.
This amp deserve ALL OUR attention! SOUNDS GOOD !
"Really no kiddin "
Stefano |
|
|
| grataku |
Ian
it's not that people are not interested in your post I think is more due to the information overload, the fact it's summer, and the fact that probably few really know what you and Nelson are talking about.
More on the same topic we discussed last time since I didn't see the XSOZAlt you posted. It is now even more apparent that I don't get the circuit but we knew that already.
What I see is a perfectly fine SOZ with added local feedback via R25 and R26. Here is a question that will clarify my degree of confusion: what happens if you disconnect and swap the right side of R25 with the left side of R26? Would the distortion be added instead of getting subtracted? |
|
|
| Ian Macmillan |
Grataku, I take your point about information overload, it being summer etc. I guess we are all too busy right now.
Regarding your question about transposing the ends of R25 and 26. Were you to try this, I think you would end up with more serious problems than whether distortion would be added or not. Connecting the resistors in this way would cause the output signal to be fed back positively with respect to the input signal, with the usual (undesirable) result. Ignoring this for the moment, distortion from one side of the diff pair would be fed back to the input of the other producing an inverted replica at the drain of the latter. Given the differential nature of the output, this would be seen as increased distortion at the load. But as I said before, this is somewhat academic.
Does this help any? I'm really not trying to confuse even if maybe it seems that way.
Ian. |
|
|
| bob12345678 |
Thanks Stefano for the circute. Has anyone else built this,how
much current does it draw with the 12v rails and are circute
boards available yet. One last thing how would the preformance be if used with a single ended source?
Thanks, Bob12345678 |
|
|
| ergo |
| Check this one out... |
|
|
| Nelson Pass |
While this circuit looks like it would work fine, It doesn't
qualify as an X circuit as there is incomplete symmetrical
communication of the error signal from one side to the other.
To do this, M3,4,7,8 would have to have their Sources
attached to a current source of some sort, not a voltage
source. |
|
|
| Ian Macmillan |
Looks interesting and is somewhat similar to something I had in mind. However, I was going to include the 'tail' current source and I would omit the input buffers. I believe I understand the purpose behind the buffers: presumably to achieve decent high frequency response without a murderously low imput impedance. I'm a little reluctant to include them though for two reasons: 1. I with them I am not the circuit qualifies as a Zen (it is now two stage) and 2) if you are going to add an extra stage, why not build an Aleph-X?
A small word of caution, if you do add the 'tail' current source then something will need to be done to achieve DC stability...
Nice to see some interest at last :)
Ian. |
|
|
| stefanobilliani |
| Do you like it? |
|
|
| stefanobilliani |
| Do you like it? |
|
|
| Nelson Pass |
Wouldn't you like to work some light bulbs in?
;) |
|
|
| bob12345678 |
As I eagerly await the Penultimat ZEN article I will
go ahead and build a small SOZ. If I chose to use light
bulbs would Grow Lux lamps make the listening experience
more mellow or tend to add more veiling of a non audio nature?
Regards, bob12345678 AKA Woody |
|
|
| Variac |
Remember, you can use lights with a reflector, pointing back and up at the wall. i.e. wallwashers. Then you might get usable light AND tunes. I think they still have 120v track lights, which have lots of interesting fixtures to choose from. Just bolt the fixture to the base and hardwire them.
Mark |
|
|
| stefanobilliani |
Yes , I like light bulbs. For example, I used 2 x 60W / 24volt replacing R1 and R2 (ref. SOZ circuit) .
I put one of these to each half of the circuit replacing all others current sourcing resistors(R3 -4 and R5 , R6)too. R7 was 0.47ohm. |
|
|
| Ian Macmillan |
:confused: Do I like your XSOZEN? Hard to say, I don't understand it and I doubt that it will work. As far as I can ascertain, the circuit will not attain a useful steady state condition, let alone pass a signal. Was this post intended to be serious? Have you tried it and do you believe it works?
Ian. |
|
|
| stefanobilliani |
| Every day I listen to music with this amplifier. |
|
|
| Ian Macmillan |
Sorry to sound like a disbeliever, but are you sure you transcribed the circuit that you are listening to correctly? I was being serious when I said that I couldn't see how it can work. DC conditions aside, I don't understand the function of the two ZTX550s connected bewteen the diff input pair and the output stage. To me, it looks like the output of the IRF9610 are fed into the collector of the ZTX550's - what is the purpose of this arrangement? I also do not understand the purpose of the two parallel 8R resistors connected between the negative power supply and the output stage Sources. What is the intended value of Vds for the output IRFP044 in this configuration?
Sorry if this sounds negative - it is not supposed to be. Perhaps I am a bit slow but I would like to understand the operation of your circuit, particularly if it sounds as good as you say.
Ian. |
|
|
| stefanobilliani |
I apologize . In effect there is a big graphic error .Ztx 550 are there to cascode the diff pair and output from IRF9610 must go to the each emitter of Ztx 550 and NOT into collectors .
APOLOGIES to everyone .
8 ohm and 1 ohm are POWER resistor : all 8 ohm 50W , 1 ohm 20W.
8 ohm resistors in parallel connected between negative supply and output stages are current sources for the output stages exactly like it is for SOZ circuit.
Vds , would be about 7.5 volt .
I like your interest and I thank you for let US know there are errors on the schematic…
Stefano |
|
|
| Ian Macmillan |
:) Ah, now I begin to understand... I'll have a closer look at this tonight and maybe run a few simulations. Thanks for taking the time to respond.
Ian. |
|
|
| stefanobilliani |
| Here , a corrected version: |
|
|
| Peter Daniel |
| Does that circuit sound better then original SOZ? |
|
|
| stefanobilliani |
It sounds in a different way, certainly. I don’t know how much the difference can be pronounced if your Original Soz was rated ,for example 30W. Mine was rated 5W. It seems to me more dynamic, even more <faster> to solve intricate orchestral masses , with good tonal equilibrium.
Also , speakers I use are nearly 3 ohm of impedance at higher frequencies , in this compartment something is changed with this amp. Bass is deep and well placed . Stereophonic scenery is <magic> with my eyes that sees over the wall without apparent concentration to the present. It is absolutely free from noises. Total silence . Without regulated supplies.
Stefano. |
|
|
| stefanobilliani |
It sounds in a different way, certainly. I don’t know how much the difference can be pronounced if your Original Soz was rated ,for example 30W. Mine was rated 5W. It seems to me more dynamic, even more <faster> to solve intricate orchestral masses , with good tonal equilibrium.
Also , speakers I use are nearly 3 ohm of impedance at higher frequencies , in this compartment something is changed with this amp. Bass is deep and well placed . Stereophonic scenery is <magic> with my eyes that sees over the wall without apparent concentration to the present. It is absolutely free from noises. Total silence . Without regulated supplies.
Stefano.
PS . something wrong goes with previous posting . |
|
|
| Peter Daniel |
| I was thinking about building 10W SOZ, but now X SOZ sounds even more interesting. I would probably do it without cascode. How it works with single ended sources? |
|
|
| stefanobilliani |
It sounds in a different way, certainly. I don’t know how much the difference can be pronounced if your Original Soz was rated ,for example 30W. Mine was rated 5W. It seems to me more dynamic, even more faster to solve intricate orchestral masses , with good tonal equilibrium.
Also , speakers I use are nearly 3 ohm of impedance at higher frequencies , in this compartment something is changed with this amp. Bass is deep and well placed . Stereophonic scenery is magic with my eyes that sees over the wall without apparent concentration to the present. It is absolutely free from noises. Total silence . Without regulated supplies.
Stefano.
Sorry if I post it three times but some word fails |
|
|
| stefanobilliani |
| It works without cascode. But for single ended sources I doubt. Because Gates of Original Soz are virtual grounds while in this case a voltage is present at the input pins .Probably it works not as well as it can… But you could convert into balanced operation your source in other ways … |
|
|
| Ian Macmillan |
I think it works without the cascode too thoughI doubt that it will affect single ended input operation significantly (but I haven't tried it). More importantly though, I think there is still an error in your schematic. As shown the cascodes are incorrectly biased. Swapping the 10k resistors to connect to lower to -ve and the upper to ground would help.
To me this does not represent an X-SOZ, it is much closer to the Aleph-X concept, i.e. two gain stages. I suspect the latter to have better performance than this variation, although maybe this is based on my lack of understanding of the role of some of the parts in your design.
I still think that it is a fairly simple matter to convert a SOZ to X operation by the addition of two resistors as I posted earlier. I've yet to hear why this simple modification will not work.
Comments anybody? This is a rather small discussion group at present.
Ian. |
|
|
| Nelson Pass |
You're right, I would call that 2 gain stages. A cascode
I don't call a gain stage, usually, and a darlington is
questionable, but we can bend the rules and still stay
within the "zen" concept.
Earlier, someone commented on simply using the front
end in the patent with the folded cascode and all, which
if scaled up for current would make an interesting Xzen |
|
|
| nania |
Ian Macmillan
Did you post a circuit of the values and location of the resistors in your X-SOZ circuit? I think I must have missed it, I'll look again. |
|
|
| Ian Macmillan |
Nelson, doesn't Sephano's earlier circuit qualify as a scaled up X front end, albeit without all the current sources? Schematic attached again (Stephano-X-SOZ) below in case you missed it before.
Nania, I did post an idea before with some plausible resistor values though I wouldn't call it a fully developed implementation. I've attached this again too (Ian-X-SOZ).
Ian. |
|
|
| Ian Macmillan |
I see my attachments were lost in my previous post. Let me try again... Stephano's first as I can't see how to attach two files.
Ian. |
|
|
| Ian Macmillan |
Here is my variation. Perhaps someone could explain to me how I can attach two files in future? I suppose I could include then both in one zip file.
Ian. |
|
|
| nania |
Ian Macmillan
Actually, I was able to find it in an earlier response of this thread but I downloaded the one just posted to compare. The idea of X-SOZ monoblocks that can operate at 8 watts with 21dB peak headroom in a 10" cube is the ultimate dream amp for me. I have never built an amp so forgive my naivete but would I be able to fit the electronics for 21dB (128W) of headroom in a 10" cube without inviting noise and other undesirable effects? I'm picturing a massive toroid with 0.25 Farad of capacitance driving that single stage, is it even possible? Is this a question for (zen Master Builder) HPotter? |
|
|
| AudioFreak |
| only way to attach multiple files is to put them all in the same zip or just link to them. |
|
|
| Henrik |
Great thread this one, thanks to Stefan and Ian, an not to forget "The One and Only".
I am going to rebuild my last SOZ, an because of that I am interested i this XSOZ. I would like to keep the original soz without currentsources, and only experiment withe adding some feesback resistors (like in the attached scematic) and some inputcaps.
Therefore i have some questions:
1)
Will i obtain all ore some of the benefits from this x-Construction in the attached scematic, or do i need the currentsources like Ian suggests in Ian-X-SOZ.
2)
Since SOZ only consist of one diffrential stage there is no X to see as i the AlephX. So my questin is: Does the feedback in the XSOZ goes from out- to in+ and from out+ to in- through the cources of the mosfets, by conditions stated by the tail? And if not how?
May be i am totally wrong in my conception of the X-thing, so if anyone could explain, i would be a happy littel boy on 53. |
|
|
| Peter Daniel |
[QUOTE]Originally posted by nania
would I be able to fit the electronics for 21dB (128W) of headroom in a 10" cube without inviting noise and other undesirable effects? I'm picturing a massive toroid with 0.25 Farad of capacitance driving that single stage, is it even possible? [/QUOTE
10" cube, with proper heatsinks, is good for about 200W of class A dissipation. 10W SOZ dissipates 250W per channel. Am I correct in my calculations?;) Because if I am, you can only put 10W SOZ mono in one cube.
This is what I have prepared for my 10W SOZ monoblocks. Footprint is 6x6" and height is 18". Forced air cooling. |
|
|
| Ian Macmillan |
Henrik, no problem with using resistors rather than current sources for the Drain loads. The only disadvantage is lower efficiency (more power disipated in the resistors due to the need for increased voltage to compensate for the voltage drop across said resistors). One can also use either current source or resistor for the diff pair 'tail'. Here the current source will give better performance with a SE input.
I wouldn't try looking too hard for the magical X, it is more a concept than a particular topology. The essence is arrange the feedback such that signal is fed back negatively and distortion positively (to the other half). The latter cross feedback is indeed via the MOSTFET Sources.
Ian. |
|
|
| Nelson Pass |
Both Stephano-X-SOZ and Ian-X-SOZ are properly
X circuits. They both provide cross-coupled error
correction through the Sources of the input differential
pair, and reduce differential error through symmetric
feedback. The output of each side taken alone looks
like the open loop performance (except for gain), but
the differential waveform is greatly improved due to
error cancellation.
Henrik, it is not essential to have a constant current source
bias for the diff pair to get X benefit, but it does help. If you
are driving the circuit balanced, it is less necessary, but if
you drive it single-ended, you really want the current source. |
|
|
| Variac |
Hmmmm thats a tough one. It seems that the resistor approach would be more in keeping with the SOZ concept: less efficient and less active devices, so that seems right. AND most people use a Balanced line source as a pre amp so Nelson says not such a big deal. SO this would differenciate it from the X Aleph.
BUT, with current source, it is beginning to sound like
" The Greatest Amp ever Made" and I'd hate to miss out on that!
I guess we need to compare both someday...like when they exist! |
|
|
| Nelson Pass |
Still more gratuitous Haiku:
Comparisons made
already but unrevealed.
Do it yourself here. |
|
|
| nania |
HPotter
Is the email listed for you on this forum active? I've written you several times without a reply so I'm prompted to ask. Very innovative of you making narrow towers. I bought a pair of Vandersteen 3's just for nostalgia of the Trade Center Twin Towers. Several visitors have also remarked on the association without any promting so I guess there is real pathos here.
Do you have a parts list and layout schematic for your SOZ monoblocks. I am curious why you think you needed to force air. The eighteen inch height would seem to be able to generate enough thermo differential to accelerate at least 5 ft3/min. Could you reconfigure the layout so an air channel can be guided directly over the mosfet? |
|
|
| Henrik |
Ian and Nelson, thanks a lot for your concerning answers to my questions.
Ian:
I have alredy build the SOZ, in the original design, and it playes butiful thou.
I just want to reorganise some of it, i underestimated the heatdissipation from the dioderectifiers. Besides from that, i am in the mood for som heat, it's ok.
So your good news to me is, that the use of resistors instead of currentsources wil leave me at least some benefits from the "crosscoupled error-corrections" (wow! I would love to have som of that) delivered by the "X"-circiut.
I am driving my SOZ with the Balanced Zen Linestage, so i get pretty good performance without a currentsource at the tail.
I am happy that you can confirm, that the X-thing works throu the mosfet Sources.
Once again Ian, thanks for your answer, but i can´t promise you not to dig a little more into the "magical X".
Nelson "The One and Only":
I just reread all the posts in this thread, and found, that you already had given some of the answers, but sometimes your writing is very compressed, so as a reader you have to stay close to every word of yours, and if you get it, it is very clearley spelled out. Besides from that i just read your wellwritten article on Su-Sy, wich gave me the kick to look deeper ito your patent, most intresting.
In your reply, you indicated, that in nonbal. mode i woudn´t achive much from the X-coupled circiut, but since i am drving the SOZ in bal. mode i schould get some or the most of the error-correction.
Never the less, i will try it out.
Accordingly to my simulation of the circiut with and without x-feedback, it seems as i will loose some gain. My Org. SOZ will go to full swing (13v) at 0,9v input and with the x-feedback it needs 1.8v, so i need to adjust my linestage to deliver this increesed gain. Then the question is, will the increesed gain in my linestage generate more noise and distortion than cancelled in the X-feedback?
Many people have told you, how kind you are revealing your knowlege in this forum, so that i will do once more. A big thank you.
When i have made the first test with this magical-X, i will come back, it will not be tomorrow, it takes time when you have to do things like staying alive without starving.
On mondy i will more tha stay alive, i am going on vacation to Nordkap in Norway for at least 4 weeks, putting ny head and lounges into this cleen air and intensley look at teese huge mystical mountins in front of the wild North Sea.
so long. |
|
|
| Henrik |
Ian, i just unrestood your warning against looking too hard for the magical-X, of cource you are wright, the X just by accident became an ikon for the cross-feedback, the essence is to get the cross-feedback no matter how it looks.
So my reply to yo will be: I can´t promise you not to look deeper into te essence of cross-feedback. But since you didn´t warn me against this, there is no meaning in this answer. Sorry for my misunderstandig.
Any way thanks again. |
|
|
| Nelson Pass |
You can get quite good performance from the X circuit
and a single-ended input, but the diff pair is constant
current sourced when you do.
With the feedback on SOZ, the gain will go down, but you
can short the Sources together to get the gain back up. |
|
|
| Ian Macmillan |
Henrik, glad to be of help. You may have noticed that in my earlier posting, I also shorted the Sources together for greater gain. This does of course result in an increase in common mode output noise but this is of little consequence in this application.
Nelson, I see you have hinted several times about the folded cascode X front end from the patent being a potentially interesting X-SOZ. I also see that nobdy has yet taken the bait, although presumably Stephano's circuit comes close. Does the master fancy dispensing a little more of his free advice to give us an inkling of why this approach might be better than the obvious one I already posted? Or is this perhaps the subject of a forthcoming article? I cannot fathom the advantage of the folded cascode in this application - it just seems to have additional overhead in terms of more current sources. Maybe it has something to do with the flexibility of DC biasing of the output?
Ian. |
|
|
| Nelson Pass |
Well it does offer DC coupled rail-to-rail swing, and
the diff pair sees constant voltage, so you can get
less distortion, more bandwidth.
With the folded cascode there are some additional
efficiency losses, but Xing a diff pair is not particularly
efficient either.
I wouldn't want to spoil your fun with too much
advice ;) |
|
|
| stefanobilliani |
WOW ! I will start following the SOZ concept that is for me the absence of active current sources.
I would like to build a front end like on patent . But ,
Not taking POWER output directly from the cascode device ( stephano-x-soz) will leave me the choice of :
Design the front end for lower power levels , that is to say 100 mA or so , and go on with a Power
Source follower/ common drain arrangement.
The Pass class A amp article give me inspiration.
Will this be two stage too?
Suggestions are welcome:) |
|
|
| Variac |
Way to go!
Ste fa no!
So you agree that a true Zen doesn't have active current sources.
Despite Nelson steering us toward the active design, I am also really curious about the passive (?) approach. If you are changing your existing design, just change one channel so you can compare!! Or are you going to whip up a schematic first?
Are you and Henrik both doing this approach (with different designs?) or is there a difference? |
|
|
| Henrik |
I shouldn´t sit here doing this, but i am too exited to wait.
Nelson
Thanks for the tip on shorten the sources together. I can see in my simulatator, that it will give me allmost all gain back to normal, and with less noise than if i increesed the gain in my Balanced Zen Linestage by decreesing the resistor tying the sources together. And i promise you, never never in my hole life, to drive this thing from an unbalanced linelevel source!
Ian
I noticed that you had shortend the sources together in one of your previus posts, but i wasn´t shure if it had something to do with your draincurrentsources or not. Now when Nelson mentioned it, i gave it some thoughts and sims, an now i se things more clearly, i hope. Isn´t that great!
Variac
As i see Stefanos project, he will add 2 more mosfets than in the org. SOZ, i am only trying out a modification of a SOZ, that i allready have build, into a X-SOZ.
In the attached file you will se what i intend to doo, an if sombody should have any comments or suggestions, they are more than welcome.
I didn´t expect to get so close to the idear of an X-SOZ that quick, what i need now is to know if it performs better than te original SOZ. |
|
|
| Henrik |
| I have mooved the inputcaps to the feedbackloop to avoid DC at the input and to keep the original biaspoint at the mosfets. |
|
|
|
