[earwaxxer]

Lots of talk about wondering if DAC A++ sounds better than DAC A within a particular brand, and if its worth it, and should I wait etc.
 
IMO, its those reasons why a manufacturer needs to introduce a very reasonably priced piece, like the Schiit's, Wryd's, iFi's, M2Tech, Wadia's etc, have done so we can hear it WITH OUR SYSTEM, and judge for ourselves. I'm not going to audition a $3K DAC that I cant afford. Makes no sense. I will buy/audition a $200 DAC that I may actually may keep, and then think about their higher end stuff as time goes on, and I inevitably start looking for an 'upgrade'.  I have sent some $200 DAC's back BTW, and I feel that was a real 'miss' for that manufacturer, to not take the time and effort needed to make the affordable piece a work of art.
 
I have one piece of Wryd4Sound kit that I really like, and now I 'trust' that I could probably like some of their other stuff, due to how well they did with their $300 uLink USB/SPDIF converter, for example. Same with iFi. I like the iDSD nano. I think they did a superb job, and the sound is 'enjoyable', which was not an easy (cheap) feet for digital only 5-10 yrs ago. Now it is.

 

[iFi audio]

Following on from Super Duper 1.7: SmartPower yesterday, we thought you may find interesting the underlying power supply solution/s we finally solved and the various sub-aspects developed for the micro iDSD.
 
 
Power Supply section special (i)
 
The Meaty Monster is Power Mad!
The power supply is the heart of every audio device. It provides the power which is modulated into audio signals. One just cannot take too much care to the power supply. Within the breast of the beast that is the "Meaty Monster" beats two hearts. And they beat very, very fast. And they draw their power from one of the biggest batteries found in any portable audio device. 
 

 
A. The poor old standard 500mA USB port …
In the micro iDSD, we need a lot of power, to produce one of the most powerful headphone amplifiers fitted to ANY DAC/Headamp, never mind a portable one. Our 18Watt/Hour Lithium-polymer can deliver 18 Watt for one hour, or 1.8 Watt for 10 Hours. That is a lot of power.
 
But standard USB ports are limited to 500mA! This issue not something unique to us, to deliver 1W per channel and power the DAC, clocks and the XMOS USB interface, 500mA are wholly insufficient.
 
"Intelligent Power-Path" (IPP):
A standard USB port offering 500mA is only sufficient to operate the iDSD micro in “xxx” mode (you have to wait for upcoming OTW#2), without leaving any current to charge the battery. 
 
Hence for the micro iDSD, when on USB power, we have developed the special "Intelligent Power-Path" (IPP) battery charger will use battery power to "backup" USB power if more current is needed. So, the micro iDSD will dip into the battery backup to sustain power peaks. This is somewhat like a hybrid car that uses the petrol engine if and when required.
 
 
B. “With such a humongous battery, it will take ages to recharge!”
This is why we integrated a special circuit to detect the attachment of dedicated charges and the special high power USB ports found on many modern computers. The micro iDSD can detect these ports and then can take advantage of the so-called BCP-1.2 standard, able to play audio AND draw 1,500mA from the computer, not just a measly 500mA. This way in normal operation the battery can recharge in only around 5 hours while simultaneously playing music.
 
C. High Power output needs High-Voltage
In order to deliver a powerful headphone output, a powerful and high-voltage power supply is needed. With Lithium-ion batteries limited to around 4.2V maximum, it would mean to either use 8 batteries in series (which requires a lot of space and very complex charging systems) or use some form of power conversion to step-up a single battery voltage to the voltages needed.
 
D. Can I have both Positive and Negative voltages too please?
For uncompromised audio performance, a dual supply with positive and negative voltage is a must. Hence we use power converters to create a symmetrical PSU adjustable from ±4.5V@1,000mA transient to a maximum ±13.5V@500mA.
 
Our first take producing this analogue dual-rail power, using a theoretically very neat design just did not work right, never reaching design efficiency and had to be abandoned. This was the problem we highlighted a month ago.
 
Our next take was to cascade two converters, first one to make an adjustable positive voltage at twice the current required and then a second to invert this power line to provide the negative voltage.
 

This circuit alone is quite challenging (in fact, very challenging), while many power IC's are on offer, very few are fast enough for our needs and even fewer allow the output voltage to be adjusted in real-time! We had to find a chip (we went through more than 100 different ICs) that is sufficiently flexible to allow us to use a rather neat design trick – so we can adjust the output voltage of this converter from our 32Bit ARM Cortex CPU, which has a 12-Bit DAC built-in.
 
This way we can adjust the output voltage between 4.5V and 13.5V in over 4,000 precise steps. This chip operates at around 95% efficiency at 0.64MHz and uses a very small PCB area with a solid ground plane and a shielded choke, so very low radiated noise.
But this leaves us with only a positive supply, no negative line. The next step was to find a way to invert this positive power line.
Again, there is no simple off-the-shelf option; we had to use another "undocumented feature" to create a servo-controlled power converter that precisely inverts the positive rail, so by adjusting the positive rail the negative rail follows precisely to within 1-2mV!
 

Note: Servo-controlled power converter normally only used in $$$$ equipment like the AMR PH-77 (Euro12k/US$12k).

 
 
To be cont'd Part (ii) tomorrow.

 

[roamling]

so if i use the micro iUSB i will be in super dupper mode?

 

[Gkat]

so if i use the micro iUSB i will be in super dupper mode?

same question here...
 
the iusb then is too much to use in combination with the micro?...will the micro benefits more with or without the iusb?...or it doesnt make any difference at all, because of the "power features" already build in micro?

 

[roamling]

same question here...

the iusb then is too much to use in combination with the micro?...will the micro benefits more with or without the iusb?...or it doesnt make any difference at all, because of the "power features" already build in micro?

what i meant was actually that i really need to have an micro iUSB (or an equally self powered usb adapter) to take full advantage of the the turbo mode, because the standard usb port wont do. so i guess the micro iUSB would be rather usefull in that case. i have the iUSB already and cant wait to put it to proper use.maybe the guys from ifi can confirm that

 

[iFi audio]

  same question here...
 
the iusb then is too much to use in combination with the micro?...will the micro benefits more with or without the iusb?...or it doesnt make any difference at all, because of the "power features" already build in micro?

 
Hi,
 
Not in battery-mode!
 
In USB power mode, then the iUSB Power will have virtually nil benefit - try if you like, but unlikely to make much difference.
 
Thanks.

 

[iFi audio]

what i meant was actually that i really need to have an micro iUSB (or an equally self powered usb adapter) to take full advantage of the the turbo mode, because the standard usb port wont do. so i guess the micro iUSB would be rather usefull in that case. i have the iUSB already and cant wait to put it to proper use.maybe the guys from ifi can confirm that

 
Hi,
 
In USB power mode, the Turbo draws on USB power (which can be as low as 0.5A) and due its technology, if it needs top-up, it will draw from the internal battery. This does not affect the actual running of the iDSD as it is seamless.
 
But the Turbo is for the hungriest of headphones like HE-6. We have the Audeze LCD-2 and we dont use that...ooops please wait for OTW#2 coming next week! (you crafty person you).
 
Yes, of course the iUSB Power can be used to supply more juice, but not really for better sonics.

 

[roamling]

   
Hi,
 
Not in battery-mode!
 
In USB power mode, then the iUSB Power will have virtually nil benefit - try if you like, but unlikely to make much difference.
 
Thanks.

 
confused, so the micro iDSD will have the ultra clean and quiet power that the iUSB would provide already built in?! time to sell my iUSB on Ebay?

 

[Gkat]

   
confused, so the micro iDSD will have the ultra clean and quiet power that the iUSB would provide already built in?! time to sell my iUSB on Ebay?

 
roamling, If I understood correct, we must do as you said...sad...cause I recently bought the iusb to go with my nano, and I could instead have waited to give the money to micro...
 
now, if I go on and buy the micro, I will end up with an extra device (iusb), that probably don;t need...not to mention, I will lose money by selling it
 
sad

 

[rickyleelee]

Hi, I have followed most of the technology discussed here. While I do not understand lot of it, it has given me more confidence to look at this and other designs. I have just want to find my retailer to have a listen. Where is my local retailer please?

 

[maricius]

I really hope iFi isn't sacrificing any extra potential sound quality for all these features. While the features make it a much better value, I'm sure we all would like the most sound quality we could squeeze out of our money spent

 

[iFi audio]

Power Supply section special (ii) 
 
The Meaty Monster is Power Mad! cont'd
 
E. Please make the power supply squeaky clean too!
The operating frequency of the switching converters is 0.64MHz & 1.2MHz, 10 to 20 times faster than common power supplies. The high operating frequencies mean that the capacitors and inductors are 5,000 to 10,000 times as small as those used from normal AC power supplies are at least equally, if not more effective.
 
To provide a very clean DC power to analogue stages of the DAC and the audio circuits, our power supply not only employs these power converters  but combines them with LC filtering very similar to those found in "golden-age" professional tube audio equipment (tube blood courses deep through our veins), thus reducing the noise dramatically.
 
Special capacitors from TDK (Japan) are used to offer a performance very close to the perfect capacitor. Taiyo (Japan) chokes are applied which again offers near perfect behaviour, thus minimising any noise.
 
The output noise from the converters before filtering is only a few millivolts, thanks to the very low internal resistance of the TDK capacitors. With our added LC Filtering this noise is further cut by >70dB (3,000 times) so by the time the DC leaves the separate PSU, PCB noise is cut to a few microvolt, as low as the best linear power supplies (so linear power supply not needed for the micro iDSD as it already has a 1^st class power supply in the first place). This voltage is applied to a bank of electrolytic capacitors providing around 70 Watt/millisecond energy storage for signal peaks.
 
The Headphone output buffer is fed directly from this power supply, while the power supply for the analogue stage and for the DAC super regulator is further filtered with another LC filter, attenuating the noise from the power converters even lower, in the theory another 70dB (3,000 times), in practice well below the measurement floor of any current test system, including our in-house Audio Precision 2.
 
The end result is this:

 
F. What about the digital section? No weakest link please.
For the DAC itself, we added an extra layer of Super-Regulators, which is dual-mono (separate for L&R channel) and have self-noise of around 0.5uV, together with the upstream very quiet DC supply, it is really only this very low noise (0.5uV, -126dB below 1V, or 2 million times below 1V!) that is applied to the DAC's analogue stages.
 
We found that using these Ultra-Low noise Super Regulators results in a 2dB improvement of measured noise compared to the DAC chip's manufacturer datasheet. So we can do better than even Burr Brown / TI's own laboratory! Another good excuse to crack open a pony keg. 

 
All of this makes for one seriously meaty Dual-Core heart pumping away 100,000's of times per second to power all the different sections of the "meaty monster".
 
All told, it can wrestle and control even the most demanding headphones out there and make 'em not sing, but soar!
 

 

[iFi audio]

  I really hope iFi isn't sacrificing any extra potential sound quality for all these features. While the features make it a much better value, I'm sure we all would like the most sound quality we could squeeze out of our money spent

 
Hi,
 
A valid enough question.
 
If you do not sonically benefit from our attention to the power supply, then all this extra development work and all the features we have designed in would count for little. Rest assured, you'll like what the micro iDSD does for your music collection.
 
So what does the PSU deliver for sound quality, rather than sheer, raw and unadulterated power?
The sound quality of any audio device, including the "Meaty Monster", is at least 50% PSU.
 
Some listening notes we have made along the way:
1. What you get with the exceptionally low-noise floor (really, really low actually) is resolution and decay. The background is not only darker, it is pitch black. The way a note or chord is struck and the way it decays, it is all there: this comes from instant power supply.
 
2. The high-current, delivered instantly gives dynamics. The iDSD has very fast regulation and ample reserve for short peaks. This brings things to life, so a piano sounds "woody" rather than "glassy."
 
3. The lack of HF noise (despite the use of switching converters) provides something that grabs us above all, it is the tonality/dimensionality, everything just sounds "right." It helps you forget about the micro iDSD and draws you into the music.
 
4. The headphone power amp section delivers on tap and in spades. This is from the large local capacitor banks that support the headphone power amp section. Whatever your headphone, expect serious "meat on the bone." Your headphones will like you. They will be really pushed to the max like never before.
 
After all, it is the Meaty Monster so it can chow down on half of Tokyo for an afternoon snack.
 
Heck, we are more excited than you guys at getting your ears round the micro iDSD.

 

[iFi audio]

Where is my local retailer please?

 
Hi,
 
Take a look here and find someone near to you.
 
http://ifi-audio.com/sales/

 

[mink70]

  The sound quality of any audio device, including the "Meaty Monster", is at least 50% PSU.
 

 
As someone who owns the iDSD Nano, which also uses a battery in its power supply, I'm wondering whether you could kindly compare the power supplies of the Nano and the Micro?