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-   -   Some questions on (X)-ONO (http://www.diyaudio.com/forums/pass-labs/126416-some-questions-x-ono.html)

Stefanoo 15th July 2008 04:49 PM

Some questions on (X)-ONO
 
i wanted to know a couple of things if possible:

1- does the circuit have no thump at the powering on/off moment? so is the output relay only used for muting purposes?

About the balance circuit: this ONO doesn't seem to me to be a real balance topology except for a phase inverter at the output that still makes available a balance output but yet doesn't make it a real balance circuitry.

here where my other connected doubt lays on:

2- i have never seen them around and thus i don't know, if such a thing exists or not but, nevertheless, is it possible to have a balance signal at the output of a cartridge?


3- in case point 2 is realizable somehow, wouldn't it be possible and/or has anybody ever tried to use UGS modules in a phono stage?


i hope these questions and especially the last one, won't be as stupid as they look :D

cyclotronguy 15th July 2008 05:52 PM

Balanced cartridge
 
Yes, of course you could have a balanced phono-cartridge..... I've seen them but not for decades. When they were around, as I recall they were moving magnet.

Having said all that, the industry has long accepted the standard that a phono-cartridge is single ended.

Cyclotronguy

Stefanoo 15th July 2008 09:58 PM

interesting, thank you very much for your post, i didn't know that!

After all, pick up are single end, thus, what would make sense: convert a signal originally born as single end or keep it that way?

If Vinyl is far off the best way of reproducing music, would it still make sense to have a balance stereo chain or better keep it all single end?

I was also thinking that question 3 is a little bit tricky.
Since Mr. Pass developed the Xono a little while ago and he basically kept the Ono circuitry/topology then it might be not possible and/or not so convenient, to use the Super Symmetric on a phono stage.
what do you guys think about this?
Has anybody here ever tried/experimented the UGS in a phono stage?

analog_sa 15th July 2008 10:18 PM

Basically all cartridges (ok, i haven't used a MM cart for about 30 years so no opinion about those) produce balanced output. It is the wiring of the arm that may limit the output signal to SE.

There are also fully balanced phono stages - just double all the components and voila.

As for the UGS i don't expect it to be suitable unless it's possible to raise the gain a lot. No idea if the noise performance is ideal but a step-up transformer will likely help. And it will preserve the balanced signal.

There are very polarised opinions about the desirability of balanced phono. I distinctly remember JC per example not being a fan.

luvdunhill 15th July 2008 10:20 PM

Quote:

[i]Originally posted by analog_sa [/i
There are also fully balanced phono stages - just double all the components and voila.

wouldn't that be quadruple? =)

analog_sa 15th July 2008 10:29 PM

2 Attachment(s)
Quote:

Originally posted by luvdunhill



wouldn't that be quadruple? =)


Only if you insist on split riaa. Tubecad have a nice example which is easy but uninteresting to implement in SS. Unless you cascade three UGS stages :)

Stefanoo 15th July 2008 10:59 PM

Quote:

Originally posted by analog_sa
Basically all cartridges (ok, i haven't used a MM cart for about 30 years so no opinion about those) produce balanced output. It is the wiring of the arm that may limit the output signal to SE.

There are also fully balanced phono stages - just double all the components and voila.

As for the UGS i don't expect it to be suitable unless it's possible to raise the gain a lot. No idea if the noise performance is ideal but a step-up transformer will likely help. And it will preserve the balanced signal.

There are very polarised opinions about the desirability of balanced phono. I distinctly remember JC per example not being a fan.

How would you wire out the tonearm in order to obtain a full balance signal?

If i don't \ recall wrong, UGS can gain up to 30dB and therefore 3 of them in cascade would gain over 80dB which is over 10000times which is good match even with a very low voltage output cartridge as for example a 0.22mV.
i don't know if that would work out in practice though.

Would it be possible to extend the design of the ONO and make it completely balance?
When you said double the components, you meant, you would cut the phase inverter out and double the circuit to get the negative side?

Would you see real benefit from doing this?

But then: why would Nelson use a phase inverter instead of doubling all the parts as you suggested?
Just a cost matter concern or what?

analog_sa 15th July 2008 11:30 PM

Hi Stefano

Won't answer all your questions as i'm about to sleep.

Your gain calc is wrong as you don't take into account the losses in a (passive) riaa network - about 20db.

Making the Ono balanced is quite difficult. It is basically an opamp with a frequency dependent feedback. To make it balanced will require a major redesign. And for what? Most designers don't see an advantage of fully balanced phono stages. Probably because of incompatibilities with customer's equipment.

In any case i think a groundbreaking Pass phono stage is long overdue :)

Stefanoo 20th July 2008 10:50 PM

2 Attachment(s)
Thank you very much for your reply.

Just wondering if:


- the 2SK389 are BL types and 2SK170 are BR types?

- on a post i found on this forum Nelson said to replace the 2SC1844 and 2SA991 with high quality 60V NPN and PNP(not all of them but oh well), is there any advice on what to use for these devices?


I am simulating the ONO with PSpice.
Since i don't get really straight how and if the RIAA circuit works i connected at the output the Inverse RIAA circuit taken from the webpage:

http://www.hagtech.com/pdf/riaa.pdf

by doing the frequency analysis i get some weired results going on.

To see if anybody might give me some tips to understand what's wrong with it.


Here is the circuit used

Stefanoo 20th July 2008 10:57 PM

2 Attachment(s)
And this is the plot of the magnitude at the output of the inverse RIAA block.
Why don't i get a flat trace? Is this normal?
I guess there is something wrong ether on the RIAA filter or on the inverse RIAA i am using.

May anybody out there help me out with this a little bit?


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