I suspect some of you will be very glad to know I have reworked Legato a 3rd time. This time is pretty significant in that there are no coupling caps *at all* - zero - zilch. For those of you craving the purest possible bass and mids. This is it.
The 3rd major version of Legato features trimmers that allow the user to trim out all differential and single ended offset. So, now you can obtain DC coupled bliss.
One important thing to keep in mind is that while the differential and SE offset can be completely zero'd out, there will be common mode DC on the balanced outputs. Most balanced input amplifiers (Sympatico especially) will not be adversely effected by this at all. If your amplifier cannot handle the small amount of common mode DC (6-7 volts) then you will want to add external coupling caps. But this would be a rare case. I do know of some (mostly tube amps) that have center tapped transformer inputs, those would need caps.
Many of you use single ended outputs and those are also completely free of DC once trimmed. No coupling caps needed here ever.
I have been listening critically to this module for about two months. I really am very pleased with the result. Of course like its predecessor the noise floor is way beyond inaudible, and the THD is improved by the fact that there is no cap to add distortion effects at the output.
Now the extra good news. I am so pleased with this module in my initial testing that I have already drawn up one small optional enhancement - an LME49600 in the feedback loop of each SE output. This revision will be Legato 3.1. It is designed for those who want to drive headphones directly from the output stage. One nice feature is that you can easily make the buffered outputputs work SE or Balanced with either one(stereo) or two (dual mono) Buffalo(I or II) DACs. I will describe that setup in more detail in the manual.
We should have both modules available soon. The Legato 3.0(no buffer) version will be available first.
As always a picture is worth a thousand words.
Cheers!
Russ
The 3rd major version of Legato features trimmers that allow the user to trim out all differential and single ended offset. So, now you can obtain DC coupled bliss.
One important thing to keep in mind is that while the differential and SE offset can be completely zero'd out, there will be common mode DC on the balanced outputs. Most balanced input amplifiers (Sympatico especially) will not be adversely effected by this at all. If your amplifier cannot handle the small amount of common mode DC (6-7 volts) then you will want to add external coupling caps. But this would be a rare case. I do know of some (mostly tube amps) that have center tapped transformer inputs, those would need caps.
Many of you use single ended outputs and those are also completely free of DC once trimmed. No coupling caps needed here ever.
I have been listening critically to this module for about two months. I really am very pleased with the result. Of course like its predecessor the noise floor is way beyond inaudible, and the THD is improved by the fact that there is no cap to add distortion effects at the output.
Now the extra good news. I am so pleased with this module in my initial testing that I have already drawn up one small optional enhancement - an LME49600 in the feedback loop of each SE output. This revision will be Legato 3.1. It is designed for those who want to drive headphones directly from the output stage. One nice feature is that you can easily make the buffered outputputs work SE or Balanced with either one(stereo) or two (dual mono) Buffalo(I or II) DACs. I will describe that setup in more detail in the manual.
We should have both modules available soon. The Legato 3.0(no buffer) version will be available first.
As always a picture is worth a thousand words.
Cheers!
Russ
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Thanks!
Correct(for V. 3.1), because the buffer really needs to be in the BAL/SE feedback loop for best result. Otherwise the buffer's performance is not great.
But you can use the board mono (even with one Buffalo, but I would not go that route) and in that case the SE outputs become buffered balanced output.
Cheers!
Russ
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Well thank you. This kind of work is a reward unto itself. Like any good hobby I guess. 🙂
Russ,
You also seem to be using a new type of filter caps on Legato 3. What are they?
Cheers,
Nic
You also seem to be using a new type of filter caps on Legato 3. What are they?
Cheers,
Nic
OMG! This is a great news Russ! Thank you for this!
Thanks,
Fedor
does this means that it can replace Ventus that is used like Bal2SE converter?
Thanks,
Fedor
Actually yes you could, but it would be a little ugly. Not sure I would bother when the cost of these modules is relatively low. But that is up to you. In any case these are not available quite yet anyway.
Cheers!
Russ
Your welcome. 🙂 Actually motivation was my own desire to eliminate coupling caps.
As for using this in place of Ventus, yes you can, but remeber Ventus is really a different type of circuit, and more of a standalone module.
Cheers!
Russ
Those are Epcos metal films. Remember that the module in the picture is a prototype, with parts from my personal stock. Kit parts will be a bit different.
I used 2.2nf at both the comp cap and he filter cap. I am very much liking that combo. We are also using new 2-ohm FETs. I will talk more about those later.
Cheers!
Russ
nice but i have a question.
how much is the output impedance?
i have legato 1 and i like it better with the buffer.
i assume this one will not have?
how much is the output impedance?
i have legato 1 and i like it better with the buffer.
i assume this one will not have?
No, it will not have one, the balanced characteristics are the same as the Legato 2.
If your setup needs a buffered balanced output you could simply use two Legato 3 configured mono.
If your setup needs a buffered balanced output you could simply use two Legato 3 configured mono.
"Uggh"
I share this sentiment as I just finished assembling my V2 only to learn there is a V3! There never seems to be a good time to jump in!
So is a retrofit possible?
I share this sentiment as I just finished assembling my V2 only to learn there is a V3! There never seems to be a good time to jump in!
So is a retrofit possible?
There is nothing wrong with V2. 🙂 Enjoy it.
When you see the schematic (will be available soon - not yet) you will see pretty easily how to modify Legato 2 to null DC.
When you see the schematic (will be available soon - not yet) you will see pretty easily how to modify Legato 2 to null DC.
OK, I've just ordered a Legato (together with a Buffalo II & other stuff). When it arrives, presumably in April when the Buffalo's due, will it be the V3 do you think?
