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Old 17th June 2010, 07:38 AM   #1531
Calvin is offline Calvin  Germany
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Hi,

oh, Yes ...Touché ;-)

Even more so a reason to look at the true numbers don´t You think so? *lol*

jauu
Calvin
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Old 22nd June 2010, 06:49 AM   #1532
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Hi Calvin,

Im not 100% sure what type of information you are after, but I can assure you the numbers posted on the ESS sites are true. The third party measurement was done by Steve Peterson of ATECS. I think you will find he would be a reliable source.

ATECS - Audio Test Engineering Consulting Services


Since the numbers were posted in the datasheets, we have actually made better measurements, but have chosen not to bother updateing the datasheets for confusion. The AD797 has consistantly provided the best numbers getting -135dB of DNR (A-weighting) and can do -120dB of THD+N unweighted across from 20 to 20k. We have shown other OPAMPs can do >118 THD+N at 1kHz, which is impressive, but, try measure at 5k and 7k. Thats were almost every other device tested showed "issues" dropping into the -110dB THD+N or lower. The DAC is sensitive to the power supply, but this is acutally on purpose, It would have been very tough to generate a analog reference that can achieve -135dB A-weighted 20-20k on the chip that has 1024 DAC's (64 per pin, 16 pins).

As for the sound of the DAC, it is greatly influenced by the parts connected to it. I believe this is where audio companies can come in and use their knowledge and expertise to have some product differentiation.

For the output stage:

I dont think we ever claimed a current source, but rather a "current mode". The current mode is simply when the current going in and out the pin of the chip is sensed. This mode has the benefit of cancelling 2nd and 3rd harmonics of some of the internal ananlog circuitry. The "voltage mode" is when the pin of the chip has a voltage on it that is being sensed. While this has the 2nd and 3rd hormics (at the -100dB level or so), some people have even claimed this mode is more "tube-like" Its all personal prefference.

I hope this helps out a little.

Thanks

Dustin
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Old 23rd June 2010, 06:14 AM   #1533
Calvin is offline Calvin  Germany
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Hi,

I think I remember that You Dustin were involved in the development of the DAC? Great, I appreciate that You are willing to share some insight to the product and trust Your word.
Could You tell us something about the possibility of single ended usage of the DAC-outputs? How does distortion behave in that case?

jauu
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Old 23rd June 2010, 02:48 PM   #1534
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Hi Calvin,

The question cannot be answered with just a simple statement the way its asked. What type of circuit do you plan to put on the DAC output, what do you mean by "single ended"? If you mean taking the DAC output into a DIFF to SE configuration, the performance of the THD will very from about -90dB or so (votlage mode) to -115dB or so if you use the 2 I/V converter then a DIFF to SE following it.

If you mean just completely ignoreing the DACb outputs, the THD will again be mostly influenced by how much you let the output pins of the DAC move. You could ground the DACb and take the DAC signal into a buffer stage, this would be around the 90dB level at 0dBFS. If you took the SE output into an I/V conveter, you would be back to the -115dB level. If you provide a circuit you have in mind, I can give you some better idea.

Dustin
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Old 23rd June 2010, 03:32 PM   #1535
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Hi Dustin,

What kind of performance should those using transformers (for DIFF to SE conversion) expect, in terms of THD?

Thank you in advance.
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Old 23rd June 2010, 03:38 PM   #1536
qusp is offline qusp  Australia
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I expect it relies on the specification of the transformers used and what/if there is an accompanying circuit or just directly connected. it will be using the voltage mode though unless there is a low impedance circuit preceding it
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Old 23rd June 2010, 05:51 PM   #1537
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Quote:
Originally Posted by chipzahoy View Post
Hi Dustin,

What kind of performance should those using transformers (for DIFF to SE conversion) expect, in terms of THD?

Thank you in advance.

Im not sure, I have never tried this. My guess is that the transformer has more THD than the DAC, so that would be the limiting factor, but im not sure


Dustin
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Old 23rd June 2010, 08:51 PM   #1538
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Hi Dustin,

I'm using transformer output with my Buffalo II. Wired across + and -. I like it alot.

Was wondering if the ESS Sabre chip likes to see the output's + and - current returned to the DAC's AC signal ground @ AVCC/2 (by using the transformer's primary center tap), or is simply wiring the transformer from + to - (and ignoring the center tap as I have done) complete the shortest current path ?

Great job on the Sabre chip, BTW.

-Steve
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Old 23rd June 2010, 09:36 PM   #1539
needsp is offline needsp  United Kingdom
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Hi Dustin, Calvin

I too am extremely interested in using the ESS9018 in a single ended way, with a discrete component I/V stage. I intended to use "half" of the differential output- i.e. to feed the I/V converter from either the + or the - output, and ground. The I/V circuit can be set up to provide 1/2 AVCC on its input.

But you mention grounding "DACb". What did you mean by this please?

Many thanks

Paul
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Old 23rd June 2010, 09:53 PM   #1540
qusp is offline qusp  Australia
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why wouldnt you use the diff out and then sum the output of that into SE? seems the best way to gain all the performance, otherwise you really take a hit to DNR and THD no?? not only by not having all the information there, but also because you throw away ALL of the CMMR and none of the dacs own self-noise is cancelled either
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