X-SOZ... just a dream for now

[Giacomo Pagani]

Hi all folks.
First of all a brief intro: this is the first time I write, but I have read a lot on this forum... really the best for diy enthusiasts. I'm a 17-years-old Italian boy, so please forgive me for my English if it's not good.

Well, let's start from the beginning: I have been feeling a sort of admiration for Nelson's jewels since I saw them on the web. Then I found this forum and learned that I could build them... I started studying the Aleph 4 and I wrote several e-mails to Nelson asking him some information. He had been very kind, and I was decided to build that Aleph.
But something made me change my plans: I listened to RD Laura horn loudspeakers, loved and bought them. So the 100 watts of the Aleph became too much for my needfulness.

I just need an amp with NO-feedback, class A single ended operation and an output impedance of about 4 ohms (at best).
In this days I put the eye on the Son Of Zen. I am able to build it, no doubts of any sort (maybe some would come during the work, as it always happens ).
However, I was almost decided when I saw that "X". I could avoid all troubles and go with the classic SOZ... but in this way I would cut a lot of fun.
So I want to and obtain the best I can.

I have tried to read the whole thread about SOZ, but it's quite BIG and I scanned the posts quickly. I hope that my questions won't be stupid or already-answered, in such case I apologize.
My troubles are the following:
- I have found a lot of schemes, but what is the definitive one? For example, I read that some things in some schemes take the project far from the principle of the Zen concept (the two gain stages, if I remember right). What's the best of those works?
The last I have seen is the Henrik's one, but I don't know...
- If I'll do it, I think I'll go for a 50 watt version. What about the components? The original Pass' SOZ page explains clearly all about the devices for the 50 watt version... but what about the new devices in the X?
- the last one: is the X-SOZ still NO-feedback?

I know this is a very long post.... sorry but I'm not able to write without explaining ALL the story.

Thank you all for your attention, and thanks again to Nelson for the great patience he had with me and for allowing people to build his beautiful electronics.

Cheers
Giacomo

P.S.: my DIY works consist in the "Insulto", a SET amplifier from TNT-Audio (transformed in SE penthodes, 4 watts instead of 2) and some cables. Not a big experience at all, but I have been studying electrotechnics for only 1 year and a half until now.

 

[Giacomo Pagani]

Ooooops:

I have tried to read the whole thread about SOZ, but it's quite

I meant the X-SOZ thread. Not the SOZ one.

Sorry
Giacomo

 

[stefanobilliani]

Hallo Giacomo.

I start answer your last question: no the X is a feedback arrangement .

That's all for now .

 

[stefanobilliani]

... and Welcome on board!

 

[Giacomo Pagani]

Thank you Stefano.

So why does Audioguida report "no feedback" for the X amps?
I read that on X-1000, X-600 and X-350.

Giacomo

 

[stefanobilliani]

Really don't know...

 

[stefanobilliani]

...but I know that X employs very small amounts of feedback
compared to some multiple stage feedback amplification arrangements .

SuSy reduces distorsion by a factor of 1/100 without the same amount of feedback!

Also: x feedback do very little to each half of the circuit(single ended) but balanced...

 

[akira]

As far as I know I would say that the last schematic should be the one from Hendrik page 17 of the long thread about XSOZ.

But WOOOW, 50W XSOZ, that will be a big one.

Post some pics when you complete your project. I ll probably also try to build one but 10W will be enough for me.

And yes, X does need some feedback. Check the schematic page 17. The feedback is resistor 212 and 213.

Ciao

 

[Nelson Pass]

So why does Audioguida report "no feedback" for the X amps?
I read that on X-1000, X-600 and X-350.

By that they mean that the output stage is not enclosed
in the "X" loop on those models. People get confused
easily on this issue.

 

[Henrik]

Giacomo

- If I'll do it, I think I'll go for a 50 watt version. What about the components? The original Pass' SOZ page explains clearly all about the devices for the 50 watt version... but what about the new devices in the X?

The XSOZ is scaleable just as the SOZ.
The powerrating is just the same as for the SOZ.
50W SOZ/ZSOZ is quite extreme!
If You want to try my version of the XSOZ, be shure to use some preamp capeable of driving a 120 Ohm single ended load.

 

[Giacomo Pagani]

uhm...

Nice to see that my SOS has been considered, friends
Thank you all.

Well, these are such good news about feedback: in fact, I haven't to care so much for the LOCAL feedback, the matter is the one at the output, which drops the output impedance and introduces a huge temporal distortion. By choosing Laura loudspeakers I have choosen the philosophy of their builder, and I want to respect it at best. I have listened to it... sure it works quite good

So feedback is not a problem... this X is starting to get really interesting

Now, about those 50 watts: I'm not sure at all. I'D LIKE to build the monster(s) in all his greatness, but I'll have to find good bargains. I don't know ANYTHING about the cost, so maybe I'm only dreaming.

Now, let's finish with the usual questions...
I imagined that the "definitive" version were Henrik's one. But I have some doubts about it:
- what about the power dissipation of "X" resistors? Voltage of capacitors?
- on that scheme I see a thing with "probe" written by side... what is it??? And the 15 ohms resistor which is placed in parallel with that "probe", called "Speaker"... what about all this?

A last questions which isn't related with Henrik's job: when I read "low wattage" for resistors, as for some of the resistors in this SOZ, what value should I intend?

Then, you told me that the power supply is the same as the Son Of Zen. OK, I think there shouldn't be other troubles.

I wait for your answer, and just wait... I don't know when I'll start the work. I have to talk with my uncle who is the owner of a company about electronics. I'm sure he can help me saving a lot of money, specially for the huge PSUs and heat sinking.

Thank you all again, it's obvious that if/when I'll do it I'll borrow a digital camera and post some pictures. After all the help I received, half of the work will be yours

With a lot of esteem,
Giacomo

P.S.: it's probable that I'll have other questions/troubles/doubts soon, please don't kill me

 

[till]

A 50W version will be very epensive because you need big heatsinks and transformers. These will be the most expensive parts. The minimum recommendation for you speakers is 1,5 W, not more than 15 for indoor use needed, right? Why don´t you try a small SOZ lets say 2 - 5 W, it will cost about nothing compared to a 50W SOZ because you only need some old junk devices to sloughter. If you will go 10 - 15W without spending so uch money, what about ZEN with lightbulb or ZEN V4 ?
http://www.passdiy.com/amps.htm

I can´t understand why you need 50W with 97.5 dB/W speakers?

 

[Henrik]

Giacomo

- what about the power dissipation of "X" resistors? Voltage of capacitors?

Resistors: 1/4 W or more if You like.
Capasitors: 10V in X-feedback.

- on that scheme I see a thing with "probe" written by side... what is it???

Probe is a measuring tool in the SIMetrix simulator, it´s not a part of the amp.

And the 15 ohms resistor which is placed in parallel with that "probe", called "Speaker"

The 15 Ohm resistor called "Speaker" simulates a 15 Ohm speaker coupled to the amp.

 

[Giacomo Pagani]

thanks

Thank you for the explanation, Henrik.

Till: before all I want to talk with my uncle and see the cost of a 50 watts version. Maybe he can find what I need at a low cost. If not, I'll change my mind.

You shouldn't see the thing in terms of needfulness. The SOZ is a huge beast and I would be VERY satisfacted if I realized it in a big version.
And... once, on the site, you would have found out that Lauras handle 100 watts.
The 50 watts of a XSOZ (no feedback - output impedance similar to the woofer's one) must generate an impressive musical power.
And if I change the loudspeaker, it will be able to drive a lot of other partners.

BTW... what about the current capability of XSOZ? Does anyone know how many amps for peak?

Goodnight all
Giacomo

 

[Henrik]

My 8W XSOZ can deliver 0,8Amp into 15 Ohm, 1Amp into 8 Ohm and 1,4 into 4 Ohm. I haven´t measured it in real life, my simulator tells me that this is the case.
But I can hear some very loud and clear music on this 8W XSOZ.

 

[Roberto Amato]

Re: thanks

A 50W version will be very epensive because you need big heatsinks and transformers. These will be the most expensive parts. The minimum recommendation for you speakers is 1,5 W, not more than 15 for indoor use needed, right? Why don´t you try a small SOZ lets say 2 - 5 W, it will cost about nothing compared to a 50W SOZ because you only need some old junk devices to sloughter. If you will go 10 - 15W without spending so uch money, what about ZEN with lightbulb or ZEN V4 ?
http://www.passdiy.com/amps.htm
I can´t understand why you need 50W with 97.5 dB/W speakers?

I agree with till. I own Laura speakers too and I power them with a 5.5w SoZ. They sound LOUD with 5w. Surely they can sound much LOUDER. I tried them with a 30w amp and a drum test CD... all neighbours at home at the time (about midday) came out (I swear) to see what the matter was... So I would say a 10 to 15w is really enough. Construction problems rise esponentially with a 50w SoZ, it's not just a matter of "scaling up" everything, it's also a matter of mechanical stability (that thing is gonna be heavy) and power consumption. I'm sure you want still to let other people in your home to able to use the refrigerator, air conditioner or washing machine... I'm saying that because I live in Italy too and I know the average AC power at disposal in average homes, much lower than average US ones. Since you have the "insulto" a SE triode amp, if I recall right, you could also consider biamping.

And if I change the loudspeaker, it will be able to drive a lot of other partners.

Laura loudspeakers are very forgiving (they love, actually) low dumping factor amps, but that may not be the case with your next loudspeaker... quite the opposite, instead.

That said... I would sure love to see a properly functioning 50W SoZ...

ciao,
Roberto Amato

 

[Giacomo Pagani]

Thank you Roberto, nice to meet you here

I'll just see. If the 50W version costs me a lot, I will choose a different power rating... maybe 30... or less. I don't know.

I know that your 5.5 amp sounds loud enough, but I want to build the best I can. I won't decide anything until I see the cost.

Thanks again
Giacomo

 

[Giacomo Pagani]

P.S.:

2,4 kW of power consumption is a problem, you're right. I was thinking about it in these days.

I'll decide later. I'll consider it when I see the cost of the beast: if it's a bit high, maybe this matter could definitely change my plans.

Giacomo

 

[till]

I want to build the best I can

Thats a good point. But i´m sure the output Watts are not the most important thing for quality of a SOZ. Quality will much more depend on high quality and good matched Fets and a good powersupply. To build a good power supply for a 5W SOZ will be much easyer (and cheaper) than for 50W.

I would´nd wonder if in case you build both, the smaller one would sound better.

(only my subjektive and personal opinion)

 

[Giacomo Pagani]

Till, I'm conscious of this too.

I meant "powerful", not just "good". It's a sort of desire, not only for the music or HiFi itself.
Satisfaction? Passion? Madness?

Uhm...



I'll see, I'll see.... sure that if I haven't the adeguate PSU components for a huge power supply I won't build a big thing at all.

Let's make big, but let's make good too...

Cheers
Giacomo