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Russ White 21st February 2011 11:51 PM

Legato 3 - Look ma! No caps!
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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.


glt 22nd February 2011 12:59 AM

Very nice!. The LME49600 will only be used for the SE outputs?

Russ White 22nd February 2011 01:04 AM


Originally Posted by glt (Post 2477995)
Very nice!. The LME49600 will only be used for the SE outputs?


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.


jgazal 22nd February 2011 01:49 AM







Great work!

Russ White 22nd February 2011 02:27 AM


Originally Posted by jgazal (Post 2478046)
Great work!

Well thank you. This kind of work is a reward unto itself. Like any good hobby I guess. :)

ichiban 22nd February 2011 04:43 AM

Uggh! Will I be able to mod my newly purchased v2 into this configuration?

Luke 22nd February 2011 07:09 AM

Love your work:)

NicMac 22nd February 2011 09:47 AM

You also seem to be using a new type of filter caps on Legato 3. What are they?

fred_com 22nd February 2011 12:15 PM

OMG! This is a great news Russ! Thank you for this!

an LME49600 in the feedback loop of each SE output
does this means that it can replace Ventus that is used like Bal2SE converter?


Russ White 22nd February 2011 01:23 PM


Originally Posted by ichiban (Post 2478182)
Uggh! Will I be able to mod my newly purchased v2 into this configuration?

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.


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