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Old 20th September 2011, 04:10 PM   #601
glt is offline glt  United States
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Hi Russ,

What is the CMRR of Legato? (If I remember, for IVY it was limited by resistor matching being 60 db with .1% matching)
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Old 20th September 2011, 06:49 PM   #602
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Quote:
Originally Posted by glt View Post
Hi Russ,

What is the CMRR of Legato? (If I remember, for IVY it was limited by resistor matching being 60 db with .1% matching)
Hmmm lets clarify the two things.

First 60db would be the worst case for IVY-III with .1%. It would be more accurate to cite a range.

Next legato is not a differential amp, no global feedback so it is not appropriate to compare it to IVY-III in that regard.

Legato is simply an I/V stage (actually 2 pair of independent non-inverting I/V stages) output is essentially the same as the input just converted from current to voltage. Pretty much exactly what you would get with a plain resistor at the output pins to GND - only the output of the DAC does not modulate to the same degree because of the low impedance. As with the simple resistor it will come down to the output levels/value matching. If there is a slight mismatch there will be some differential error given a common mode signal. So essentially any common mode signal is still there at the balanced outputs. But that's what's wonderful about balanced signals, it does not matter in the least. On IVY-III the output common mode is dictated in large part by the device. That is why it is not a straight up comparison.

Where CMRR would come into play to a larger degree is at the BAL/SE stage. I will leave it to you for homework to figure out what the CMRR of that would be. I have never bothered to figure the exact value out for myself. It would depend to some degree on the parts chosen.

One nice thing is because most of the common mode noise on the ES9018 is extremely high frequency (far above audible) the passive filters actually get rid of almost all of it before it can really come into play. So practically the "CMRR" (if you want to call it that) is superb. That's why its important to have those low pass filters. Even if there is a small error between the balanced halves those very high frequencies in play would have been filtered out.

Cheers!
Russ
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Last edited by Russ White; 20th September 2011 at 07:17 PM.
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Old 20th September 2011, 07:36 PM   #603
glt is offline glt  United States
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Russ,

Thanks for the clarification. My question was motivated from the previous question. A practical observation (at least for me) is that for IVY, you could afford to be flexible in location and wiring. For Legato, it is important to care about location and wiring, so the best is to put it right under the Buffalo.

Yeah, I know there is cmr on the bal-se conversion, but with IVY there is additional cmr at the inputs of the balanced amp. But if you are feeding a balanced amp (itself having cmr) then you "loose" the additional cmr of IVY if you use Legato (which I plan to use). I am sure all of this is probably inaudible, but it looks good on paper :-)
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Last edited by glt; 20th September 2011 at 07:41 PM.
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Old 20th September 2011, 07:44 PM   #604
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Good point.

Yes I would agree with that, but the slightly mitigating factor is the balanced signal and low impedance involved. The nice thing about a low impedance is it is somewhat more immune to picking up outside noise, but not much in this particular case. So I would *ALWAYS* use the shortest length you can can practically do.
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Last edited by Russ White; 20th September 2011 at 07:48 PM.
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Old 20th September 2011, 07:55 PM   #605
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Quote:
Originally Posted by glt View Post
But if you are feeding a balanced amp (itself having cmr) then you "loose" the additional cmr of IVY if you use Legato (which I plan to use). I am sure all of this is probably inaudible, but it looks good on paper :-)
That is why the best approach is to eliminate (filter out) any common mode signal you can (other than DC sometimes).
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Old 21st September 2011, 03:21 AM   #606
angcl is offline angcl  Singapore
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Quote:
Originally Posted by Russ White View Post
Yes is you use only a single end of the DAC output you will be throwing away quite a lot of what gives it incredible dynamic range. But you can do it if you like, just remember the DC offset so you will need an AC coupling cap.
In that case ,i am consider to get IVY-III stage.
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Old 21st September 2011, 08:45 PM   #607
ejaouen is offline ejaouen  France
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Hi,
I am thinking getting a buffalo3 but I do not have ess9018 datasheet and wonder if this DAC PCM inputs are 5v tolerant ? because I intend to feed that board from a wavefront optorec chip (al1402g = 8channel 24bit receiver chip= Alesis ADAT) which has 5v TTL level outputs. Also can I easily configure this buffalo3 in a 24bit standart right justified PCM mode (bitclock being 64fs = same mode as PCM1794A has) ?
Thanks a lot in advance
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Old 21st September 2011, 10:13 PM   #608
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Standard firmware is for I2S input. So you would need custom firmware or external control.

The interface pins are 5V tolerant according to ESS but I have never had occasion to test that.
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Old 23rd September 2011, 05:22 PM   #609
Bunpei is offline Bunpei  Japan
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Quote:
Originally Posted by Russ White View Post
It should work just fine (though i have not tried it exactly like you say). This would not be dual mono, but would be stereo with 8 DACs in parallel.

I would say give it try if you feel like it.

Just keep in mind power requirements and the fact that your I/V stage will have double the output swing unless you adjust it.
Being encouraged by Russ' comment, I tried the stacking of two BIII boards.
Its joint mechanism is similar to that adopted in IVY III board.
Naturally, I could get the doubled output and I felt more sonic energy. I can't say anything, however, about the improvement of SNR.
The draw of + 5.5 V in total is 0.74 A!
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Old 24th September 2011, 09:27 AM   #610
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Looks very nice, indeed!

What IV converter did you use when you tested with doubled output?

BTW,
what is that black "thing" in the middle?


/S

Quote:
Originally Posted by Bunpei View Post
Being encouraged by Russ' comment, I tried the stacking of two BIII boards.
Its joint mechanism is similar to that adopted in IVY III board.
Naturally, I could get the doubled output and I felt more sonic energy. I can't say anything, however, about the improvement of SNR.
The draw of + 5.5 V in total is 0.74 A!
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