[iFi audio]

  Hi ifi,
 
Thank you for sharing info of the micro iDSD! I own a nano iDSD and I am very satisfied with it. My question is, according to the PCB photo, the micro iDSD utilizes two BB DSD1793 DACs (in dual mono mode), the same as the nano iDSD, why don't you use a higher end model, such as PCM1792/1794/1795? At least those models have better specs, and are more widely used. 

 
Hi,
 
Fair enough question!
 
Why not "more modern and or better spec chip's?"
 
Simple. On paper they may look great. But in practice, because they do not sound particularly good to our ears.
 
Designing a DAC or ADC Chip is a bit of a black art. Compare it to cooking. Everyone can boil water, few can make even a passable, never mind outstanding Crème brûlée.
 
Many ADC/DAC Chip's that deliver outstanding performance seem to result from lucky accidents, where someone in the big corporate hierarchy got it right.
 
They got it right either because they knew exactly what they are doing and design for sound quality (something that is not easily, if at all "measurable"), or by sheer accident (the million monkeys, million typewriters and Shakespeare gig). In the history of digital audio there have been a number of ADC and DAC Chip's (or discrete solutions) that were outstanding. 
 
The "exceptional sound quality DAC's cover all possible technologies.They range from antique "stacked" 4-Bit bipolar DAC's in the early Accuphase CD-Players and discrete resistor ladders in the Korean-made Fisher brand vertical loading CDP (in case you were wondering, similar to this one below) Thorsten still gets misty-eyed over the sound quality (it was uneconomic to repair in the late 90's).
 

 
They include the Cirrus Logic CS4328 and NPC SM5872 pure Bitstream (Delta Sigma) DAC's that were pioneering in the 90's.Their ranks feature stalwart multibit champions like the Philips TDA1541A (our all-time personal favourite), Burr Brown PCM63 (and it's grandson PCM1704) and the discrete Ultra Analog DAC modules. They range all the way to the original ESS ES9008 DAC (the "magic" seems to have dissipated somewhat in the ES9018 and a lot in the ES9018K2) and the gob-smackingly good (for the money) ES9023 which we use in the iDAC.
 
The PCM1793 and the PCM/DSD version DSD1793 are also in our view, part of this Pantheon. Despite somewhat less than outstanding technical specs, we found that a fairly simple implementation of this chip, with tube output stages and fed HD (PCM) audio was a serious challenger for a TDA1541 with tube output stage playing CD-Audio. Alas, the newer and supposedly superior TI Designed DAC's sold under the Burr Brown Brand are not their sonic equal. So we do not use them.
 
As for Spec's, our Thorsten has personally done the full Audio Precision 2 work-up on the final production level iDSD micro prototype (as it will be manufactured). He found that the A-Weighted SNR of the final version, with all tweaking and tuning came in at around 119dB, for a 2V analogue output level that is within a very small distance of what is physically possible.
 
Give the DSD1793 a really, really good PSU and operate it Dual-Mono, and you are not far off the spec's for the later stuff. Yet it sounds (to our ears) a whole lot "meatier" (read: good). And of course, it helps greatly that it does not manipulate the signal and keeps DSD and PCM as they are.

 

[audioholik]

  What is the giveaway?  If they do digital volume control on the DSD stream, this is very likely to convert the DSD data into NON-DSD data (does not necessary mean that they are converting into PCM, but converting into something non-DSD at the very least).
 

 
Some do convert 1-bit PDM to say 6-bit PDM, but it's still PDM (DSD).
 
HQPlayer can serve as a good example, as it uses two different volume control methods for PCM and DSD, one is done in PCM domain, the other in DSD domain.
 
http://www.signalyst.com/consumer.html

 

[iFi audio]

  Mr. iFi audio,
 
Can you please help me understand how the timing is handled in block two of the first image and in the DAC conversion section within the second image?  Is a single clock used?  Multiple clocks for DSD and PCM?  What about multiples of 44.1 kHz and 48 kHz?
 
My apologies if this has all been answered already in this thread.  Thank you.

 
Hi,
 
1. Block Diagrams
The first block is a diagram representing what happens the signal as it passes through BB chipset ie: not internal conversion from DSD to PCM to DSD or such.
 
The second block diagram is a "global picture" showing our view that to ensure the highest sound quality, in our view, one should focus on the "first half" of how the recording was done (DSD in this case) and ensure that the "second half" of playback is also retained DSD throughout.
 
Good audio, like a "soccer" match, it is a game of "two halves."
 
We leave the listener to enjoy as in its native state (if they so wish).
 
2. Clocks and Global Master Timing
Neither. A whole "GMT" clock platform is used. So there is no one clock or even two or otherwise.
 
We use Zero Jitter memory buffer and GMT Femto precision clock for all audio signals and clocks, respectively. These were first used in the DP-777 DAC by AMR. They represent a "different angle" on the whole specific implantation.
 
The GMT (Global Master Timing) module is a clock that is designed to give very low jitter and to be programmable to any number of frequencies with extreme precision. as it "Globally" controls all.
 
We use this to deliver fixed clocks for USB derived PCM and DSD, all clocks that control conversion are either directly this clock or are re-clocked to this master clock module. 
 
As what one might call "jitter" in the USB audio system amounts to several milliseconds, large memory buffers are used to "de-jitter" this extremely high jitter source, output jitter from the memory buffer is down to the GMT Clock's jitter..
 
For SPDIF the iDSD micro uses the same self clock and AMR's custom control software to track the long term average of the source clock, rejecting jitter from the source. During recent testing we used the "jitter generation" function of the AP2 to test how well Zero-Jitter and GMT really work.
 
We were able to apply over 50nS (50 nano seconds, 50,000 picosecond, 50 Million femto seconds) of 400Hz square wave jitter to the SPDIF signal from the AP2 with no jitter visible in the audio output. 
 
We had to turn off Zero-Jitter and GMT by hacking our own software

, so we could show what 50nS jitter really look like (graph in the near future, hint, it is awful), as neither the AP2's own SPDIF input nor any other DAC in house (except the DP-777 that shares the same architecture)  could even LOCK onto this signal, never mind filtering out the jitter.
 
We'll upload these graphs in the next few days as we know you like this kinda stuff.

 

[technobear]

Mr. iFi audio,

Can you please help me understand how the timing is handled in block two of the first image and in the DAC conversion section within the second image?  Is a single clock used?  Multiple clocks for DSD and PCM?  What about multiples of 44.1 kHz and 48 kHz?

My apologies if this has all been answered already in this thread.  Thank you.

Notes on clocking:

http://www.head-fi.org/t/711217/idsd-micro-crowd-design-software-design-notes-4-no-ordinary-dsd-page-56/645#post_10606215

 

[tf1216]

Notes on clocking:

http://www.head-fi.org/t/711217/idsd-micro-crowd-design-software-design-notes-4-no-ordinary-dsd-page-56/645#post_10606215

Thank you technobear.

 

[iFi audio]

   
Some do convert 1-bit PDM to say 6-bit PDM, but it's still PDM (DSD).
 
HQPlayer can serve as a good example, as it uses two different volume control methods for PCM and DSD, one is done in PCM domain, the other in DSD domain.
 
http://www.signalyst.com/consumer.html

 
Hi,
 
As for "Some do convert 1-bit PDM to say 6-bit PDM, but it's still PDM (DSD)."
 
From our perspective, we absolutely avoid conversion wherever possible. Our simple comment is: If it is still DSD if 1 = 6, otherwise it is something else. If it walks like one, quacks like one...
 
We have no comment on HQ player. It comes from the school of maximum digital manipulation. We respect Misa's views but we're at the other end of the spectrum sorry!

 

[audioholik]

  From our perspective, we absolutely avoid conversion wherever possible. Our simple comment is: If it is still DSD if 1 = 6, otherwise it is something else. If it walks like one, quacks like one...

 
FYI - DSD can have more bits than 1.
 
Some DSD DACs simply utilize multiple 1-bit elements (this shouldn't be confused with multibit PCM of course).
 
See example below:
 
http://www.signalyst.com/hardware.html

 

[iFi audio]

   
FYI - DSD can have more bits than 1.
 
Some DSD DACs simply utilize multiple 1-bit elements (this shouldn't be confused with multibit PCM of course).
 
See example below:
 
http://www.signalyst.com/hardware.html

 
Hi,
 
DSD =Direct Stream Digital = Sony/Philips trademark for a specific format defined as:
 
Audio Signal Encoding - 1-bit Direct Stream Digital
Sampling Frequency (kHz) - 2822.4 (64 times to CD）
Modulator - 7th order(6th or 8th optional)
 
Based upon the above, standards and definition by Sony/Philips, if it has more than 1-Bit, it is not DSD.
 
Again, we don't wish to bring Miska and HQ Player into it as we are going by Sony/Philips as they developed the stuff!
 
Sorry. 

 

[audioholik]

   
Hi,
 
DSD =Direct Stream Digital = Sony/Philips trademark for a specific format defined as:
 
Audio Signal Encoding - 1-bit Direct Stream Digital
Sampling Frequency (kHz) - 2822.4 (64 times to CD）
Modulator - 7th order(6th or 8th optional)
 
Based upon the above, standards and definition by Sony/Philips, if it has more than 1-Bit, it is not DSD.
 

 
If we were to follow this old marketing definition to the letter we couldn't even say that 5.6MHz or 11.2MHz DSD formats are DSD, as they are not 64 times the CD sampling rate as stated above.
 
DSD is basically sigma delta modulation (without the usual PCM steps employed in conventional DAC chips) and it can be 1-bit or 5-bit, 5.6MHz or 11.2MHz, or 22.4MHz.

 

[pompon]

Friend of mine tries the nano on his power amp and found it good after one hour.
While it's with battery, I can't let it play all time. Any manner to use the USB power just to keep unit warm and ready and when we want listening with the best quality switch battery on?

I never switch off my main gear to prevent to have a long warm up before have a good depth of soundstage and see my speakers disappear.

 

[zzzmonster]

Friend of mine tries the nano on his power amp and found it good after one hour.

While it's with battery, I can't let it play all time. Any manner to use the USB power just to keep unit warm and ready and when we want listening with the best quality switch battery on?



I never switch off my main gear to prevent to have a long warm up before have a good depth of soundstage and see my speakers disappear.

 


Hi,

Not sure if it is the rest of my gear, but I feel that on my IDSD Nano, the headphones out sound quality is much better than the rca out. Both test i used running on battery power. RCA seems to lose some of the details and a bit of the magic. But the headphones out is really good.

 

[BillsonChang007]

iFi Audio should open a live chat section to answer all these questions as well as for some of us asking xD enjoy reading all these as well thought

 

[wmy5]

By 'natively' I mean bit perfect without upsampling or conversion.

You got your distortion figures back to front there. The DSD1793 is lowest at .0004%.

Thorsten explains it better than I ever could:
http://www.head-fi.org/t/711217/idsd-micro-crowd-design-super-duper-1-8-the-3-5mm-input-page-54/60#post_10404689

 
It's TI website that got distortion figures back to front. PCM1792 has .0004% and DSD1793 has .001%, according to the datasheet. 

 

[audiofrk]

The PCM1793 and the PCM/DSD version DSD1793 are also in our view, part of this Pantheon. Despite somewhat less than outstanding technical specs, we found that a fairly simple implementation of this chip, with tube output stages and fed HD (PCM) audio was a serious challenger for a TDA1541 with tube output stage playing CD-Audio. Alas, the newer and supposedly superior TI Designed DAC's sold under the Burr Brown Brand are not their sonic equal. So we do not use them.  

if the dsd1793 can reach the TDA1541 when pared with a tube output stage, how come there's no tube stage in the either the idsd micro or idsd mini? I think i would have noticed some tubes sticking out of the boxes.
 
so I guess what I'm saying is ....I WANT TUBE!!!

 

[BillsonChang007]

  if the dsd1793 can reach the TDA1541 when pared with a tube output stage, how come there's no tube stage in the either the idsd micro or idsd mini? I think i would have noticed some tubes sticking out of the boxes.
 
so I guess what I'm saying is ....I WANT TUBE!!!

iFi should seriously consider a tube amp some day xD iFi-Audio Micro iTubeAmp xD