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Micro iDac 2 Product page


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On 7/4/2018 at 5:06 PM, DuckToller said:

Hi,

did you lately had a look on your product page for the Micro iDac 2 ?
https://ifi-audio.com/portfolio-view/micro-idac2/

image.thumb.png.2d417a89777f6076a1531eea4dc3b1bb.png

Looks kinda (un)healthy ...
regards & get well soon
Tom

 

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  • 4 months later...

Question for @mansr about the iDAC2 and DSD1793

 

There the Burr Brown DSD 1793 d/a-conversion chip. It a remarkable device that does DSD natively. For PCM the top 6 bits are done using a ladder converter while the lower ones are done using a multibit converter. This means that it gets precision for the upper 6 bits from the precision of the resistors in the ladder converter as where for the lower bits the precision is determined by the precision of the clock. In DSD mode only the clock precision is determining the precision.”

 

What does “the upper 6 bits” mean/refer/relate to? Is it related to the upper frequencies of the music? Or the “loudest” parts?

 

And then the same for the lower bits - what is that? I guess the answer to the top 6 bits will help to understand the lower bits.

 

Asking here in the iDAC2 thread but I guess this relates to all iDSD models since all use the DSD1793.

 

Cheers in advance

 

 

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1 minute ago, Em2016 said:

Question for @mansr about the iDAC2 and DSD1793

 

“There the Burr Brown DSD 1793 d/a-conversion chip. It a remarkable device that does DSD natively. For PCM the top 6 bits are done using a ladder converter while the lower ones are done using a multibit converter. This means that it gets precision for the upper 6 bits from the precision of the resistors in the ladder converter as where for the lower bits the precision is determined by the precision of the clock. In DSD mode only the clock precision is determining the precision.”

That doesn't make a lot of sense.

 

1 minute ago, Em2016 said:

What does “the upper 6 bits” mean/refer/relate to? Is it related to the upper frequencies of the music? Or the “loudest” parts?

 

And then the same for the lower bits - what is that? I guess the answer to the top 6 bits will help to understand the lower bits.

The datasheet offers this explanation:

 

image.thumb.png.1c644847fe2b018ca03fcc705ef107b9.png

 

"Digital input data via the digital filter is separated into 6 upper bits and 18 lower bits. The 6 upper bits are converted to inverted complementary offset binary (ICOB) code. The lower 18 bits, in association with the MSB, are processed by a five-level third-order delta-sigma modulator operated at 64 fS by default. The 1 level of the modulator is equivalent to the 1 LSB of the ICOB code converter. The data groups processed in the ICOB converter and third-order delta-sigma modulator are summed together to an up to 66-level digital code, and then processed by data-weighted averaging (DWA) to reduce the noise produced by element mismatch. The data of up to 66 levels from the DWA is converted to an analog output in the differential-current segment section."

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15 minutes ago, mansr said:

That doesn't make a lot of sense.

 

The datasheet offers this explanation:

 

image.thumb.png.1c644847fe2b018ca03fcc705ef107b9.png

 

"Digital input data via the digital filter is separated into 6 upper bits and 18 lower bits. The 6 upper bits are converted to inverted complementary offset binary (ICOB) code. The lower 18 bits, in association with the MSB, are processed by a five-level third-order delta-sigma modulator operated at 64 fS by default. The 1 level of the modulator is equivalent to the 1 LSB of the ICOB code converter. The data groups processed in the ICOB converter and third-order delta-sigma modulator are summed together to an up to 66-level digital code, and then processed by data-weighted averaging (DWA) to reduce the noise produced by element mismatch. The data of up to 66 levels from the DWA is converted to an analog output in the differential-current segment section."

 

Thanks but that still doesnt help me to understand what Thorsten @AMR/iFi audiomeans by “the upper 6 bits of PCM delivers slam”:

 

“It uses a 6 Bit Multi-bit DAC for the upper 6 Bits of PCM Audio and delivers the warmth and slam Burr Brown Multi-bit DAC’s are so famous for. Any bits below this are converted with a low order 256 Speed Delta Sigma modulator (in effect DSD256), giving PCM playback the smoothness Delta Sigma DAC’s and DSD are famed for.

 

https://www.audiostream.com/content/qa-thorsten-loesch-amrifi-audiostream-addendum-pcm-vs-dsd#HT2PWoCcI5zLIRXP.99

 

 

How does the upper 6 bits = slam?

 

What is the upper 6 bits that Thorsten and the datasheet refer to? Does it relate to upper frequencies? The loudest parts?

 

What parts of the music are the upper 6 bits? I’m trying to understand how upper 6 bits relates to slam.

 

Thanks again

 

 

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10 hours ago, mansr said:

The top 6 bits of each PCM word.

 

It's marketing nonsense. Ignore it.

 

Hehe thanks. So there's no relationship between "the top 6 bits of each PCM word" and how that affects dynamics/time domain performance etc?

 

That's what I assumed/guessed Thorsten means by "slam"? @AMR/iFi audio can you kindly ask the boss to help explain?

 

While I'm asking in the iDAC2 thread, since all iDSD models use the DSD1793, it would help immensely.

 

 

 

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7 hours ago, Em2016 said:

 

Hehe thanks. So there's no relationship between "the top 6 bits of each PCM word" and how that affects dynamics/time domain performance etc?

 

That's what I assumed/guessed Thorsten means by "slam"? @AMR/iFi audio can you kindly ask the boss to help explain?

 

While I'm asking in the iDAC2 thread, since all iDSD models use the DSD1793, it would help immensely.

 

 

 

 

It's already been said, please take a look here: 

 

https://www.audiostream.com/content/qa-thorsten-loesch-amrifi

 

... and here:

 

https://www.audiostream.com/content/qa-thorsten-loesch-amrifi-audiostream-addendum-pcm-vs-dsd

 

 

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3 minutes ago, AMR/iFi audio said:

 

I've actually quoted those articles above... they don't explain how "the upper 6 bits" relates to more slam though... 

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He's saying the warmth and slam are inherent in the TI/Burr-Brown multi-bit chip, not that it is inherent in the top 6 bits themselves.  And then he claims that using Delta Sigma for the lower bits gives them the "smoothness" that is supposedly inherent in DS.  So marketing can thus claim that they get the best of both worlds by using a hybrid approach! lol

 

So, this begs the question, do TI/Burr-Brown chips have warmth and slam?  Also, does Delta Sigma inherently have smoothness?  And  can combining approaches actually give the desired qualities of the two approaches?  And what ratio works best?

 

Now, if the different chips in themselves produce a different sound, I suppose it would make sense that whichever approach handles the highest bits would have the predominant effect on the overall sound, so their approach would then have more "slam and warmth" as a result of having the TI chip "on top" (that is, if these chips actually have such characteristics in the resulting sound).  Having the "smoothness" effect added by DS handling the lower bits, on the other hand...perhaps they have done extensive blind testing which has shown that smoothing can be increased by 4.8% while only reducing the "slam" by 17.1%, which was the optimal compromise, resulting from their chosen ratio of bits for each approach.  Originally, they had tried having the TI/BB on the bottom, with DS on the top bit only, but that resulted in reducing slam by 94.3%, which obviously didn't please any of their test subjects.  Additionally, DS on the top for any number of bits greater than one had the dreaded effect of adding at least 3 veils for the first additional bit, and increasing exponentially from there.

 

Bear in mind that the above are simply my "theories*" on what occurred in their blind testing (which they may not have even conducted haha), as I was not a participant.

 

 

*aka, "wild ass guesses," which have as much in common with actual theories as anything in audio marketing speak.

请教别人一次是5分钟的傻子,从不请教别人是一辈子的傻子

 

 

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