[dburna]

I started out to make this a short review, but that was too difficult because this iDAC2 (and the iDSDs for that matter) are such versatile devices.  In conjunction with other iFi gear, there are literally dozens of different ways to deploy them – I have tried only 7 of the possible configurations (below). 

First, a word on the iFi product line: I am impressed with a firm that makes intelligent engineering/design trade-offs and puts out an entire line fits together from a marketing perspective (many complementary building blocks).  That takes a lot of thought and planning.  Example: the iDAC2 volume control (used only for the headphone volume) doesn't have an on/off switch, just volume control.  That's because it is USB-powered – if it's plugged in, it's on, simple as that.  The iDSD has a volume control with on/off switch, useful to conserve battery when on-the-go.   

My rig: I have a dedicated digital rig with Mac Mini (with JRiver Media Center 22) → aRT Legato     (USB → S/PDIF converter) → Audio G-D DAC19DSP (R2R DAC using 1704 DAC chip) → Tortuga Audio LDR → Ncore DIY amp → Horning Perikles Ultimate speakers.  Both the Legato and DAC19 emphasize power supply design – the Legato in particular provides a separate linear power supply to USB and does not use USB power.  In fact, the USB cable I use (provided by aRT) has no power leg in it.  This is a very clean and resolving system.  I have used both tubes before but have settled on SS because of the need to control tightly the woofer section of these speakers.

I performed the following comparisons:
1. Legato vs. iDAC2 (stock) as USB → S/PDIF converters
2. Legato vs. iDAC2 (w/ iUSB iPurifier) as USB → S/PDIF converters
3. iDAC2 (as USB interface + DAC) vs. IDAC2 (interface) + DAC19 (DAC)
4. iDAC2 (as USB interface + DAC) in 16/44.1 vs. upsampling (24/88, 24/176, 2xDSD)
5. iDAC2 (as USB interface + DAC) with/without iUSB power supply (and iPurifier)
6. iDAC2 (as USB interface + DAC) + headphone amp
7. iDAC2 vs. iDSD (first gen.)  as DACs in my main rig

Here's the main takeaways I learned from this comparison.  Note: I am not going into super-detail about each configuration because I would be here all day (and night):

1. I tried the iDAC2 with/without the iPurifier (I don't have an iPurifier2, but I can only assume that is better).  There was a significant improvement with the iPurifier in place – after 10 minutes I wasn't interested in using the iDAC2 without the iPurifier.  If you don't have one with this unit, it sounds fine without.  Once you A/B the pairing, you won't want to go back. Essential.
2. Power supply matters A LOT (duh).  The Legato provided more space/air around notes and a better tonality as a USB → S/PDIF converter.  Legato is a superbly engineered interface.  Then again, it delivers Redbook only......and it is $500-600 for the converter (plus purposed cables).  This is where trade-offs come in.  The iDAC2's USB → S/PDIF interface is very nice, but IMO (given the size constraints on this unit), it is not the absolute strength of this unit.
3. As a headphone amp, the iDAC2 is very good, but it is not top top-tier...nor is it super-powerful like the iDSD/iDSD BL.  Many people (with sensitive ear buds/headphones) will be quite happy with this as-is, however.  Since I am not a heavy headphone user, it fits the bill for me nicely.
4. iDAC2 (w/o iUSB power supply) vs. DAC19 as a DAC: I think the edge (slight) still goes to the DAC19, but it's very close.  Then again, I usually prefer R2R DACs by a wide margin.  iDAC2 has a little more air/detail, but the DAC19 had a little fuller/meatier (but softer, less detailed) presentation.  To me, this is at the heart of the R2R vs. Delta-Sigma differences.  Both DACs acquitted themselves quite well given their approach.  This comparison was much closer than I expected, and I'm sure it was mostly because of the DAC19's power supply.
5. iDAC2 upsampling differences: this is an area where the iDAC2's versatility shines.  I was able to listen to 16/44 tunes played at native bit rate, 24/88, 24/176, and 2xDSD (iDAC2 doesn't do 4xDSD, not that I cared in the slightest).  This was my first attempt at listening to the differences....and I think that the recording quality/bit-rate matters a lot more than the upsampling bit-rate.  Going from 16/44 “up the chain” resulted in a little bit more air and a little bit more separation between notes.  But if you have only Redbook source material, trust me – you aren't missing much by not upsampling.  I think ultimately I liked the Redbook tunes in 24/88, but that could just be the (doctor prescribed) meds that I am on.  ))  I am still open to a different rig (or recordings) providing different results, but (based on this trial) I would be skeptical if someone said that upsampling 16/44 music (to 24/384, DSD, or whatever) caused “the heavens to open up”.
6. iDAC2 (with iUSB iPower) as a DAC: NOW we're talking, baby! All the resolution lost in comparison with my DAC19 is back and more.  It is now more natural/detailed than the DAC19 and is delivering a high, high level of performance.  Quality power rules – DAC chip is secondary. Now I have to go back and see how/whether this improves the iDAC2 as a USB → S/PDIF converter (answer: yes – yes it does).
7. iDAC2 (with USB Power) as a USB → S/PDIF converter: just as iUSB Power improved the iDAC2's DAC capability, it provides a similar boost to the USB conversion.  Now the iDAC2 is really, really close to the Legato – it's a toss-up really, small nod to the Legato....maybe.
8. iDAC2 > iDSD (original) as a DAC.  There is not an enormous difference here, but one does exist....in favor of the iDAC2.  To be honest, I didn't spend as much time with this comparison as with some of the others in order to send this back to Jason in a timely manner.  I was pleased with the performance of both, so I'm not sure I'd dump the iDSD for the iDAC2 unless the cost differential (purchase iDAC2 – sell iDSD on used) was small.

I do have a couple cons....but they are minor:
1. I don't like silver components, I like black.  Told you that my criticisms were minor.
2. I don't like potentiometers.  I have yet to hear one that isn't opaque and/or degrades sound quality.  Before I found LDRs and transformer-based volume controls, however, I didn't really realize this.  Now that I have, it's hard to go back.  But in this small form-factor, what choice is there really if you're going to provide volume control?  iFi's volume control is pretty good -- better than many -- and they do not degrade the sound much, so methinks that's as good as one can do in such a small package.  And frankly, there is some mighty expensive gear using pots as well for volume control.  Using the iDAC2 solely as a DAC bypasses the headphone pot, so all is good in that instance.

Final summary:
1. iDAC2 is versatile as hell...and the synergies with iFi power add-on products are extreme.  It makes for a nice incremental growth path to upgrade the power supply chain over time as finances permit.
2. iDAC2 – and for that matter, all iFi products – performance/price ratio is off-the-charts.  This is one fine DAC.  There are definitely better DACs out there, but none I have heard at the price....and this is competitive with most DACs many multiples of its price.
3. Power supply quality predominates within the (so-called) 'digital chain'.  The iDAC2 is no exception to this.  Nice that there is a growth path for upgrading this over time, but IMO, if you want the iDAC2 to really shine in your main rig, you need to budget for including the power supply upgrades (iUSB iPower and iPurifier, in that order).  If you are using an iFi product as an on-the-go sound source, an iPurifier will serve just fine – again, well thought-out options for a variety of product use cases.
4. iUSB >> iPurifier.  Adding the iUSB Power to the digital chain has a bigger effect than the iPurifier.  When both are added, there is a synergistic effect, but it seems to me like the iUSB is doing the bulk of the heavy lifting.  If you can only afford one, I'd opt for iUSB, but this is of course the more expensive of the two....and needs a two-headed USB cable to work at its best.
5. I'm not inclined to like Delta-Sigma DACs at all.....so why do I like this so much?  Coupled with the ability to try many different sampling rates and power supply configurations, you can find your required performance level and only spend on features that make a difference to you...or fit your budget.  As you upgrade component pieces, the performance/price ratio stays very high.
6. Don't make the mistake I did and upsample anything to a non-integer multiple of the original sampling rate (e.g. 16/44 → 24/96).  It just sounds slightly “off”.
7. My 2009 Mac Mini – even with 8MB memory – can't handle converting to 2xDSD on-the-fly.  I can hear some improvements at 2xDSD, but not enough to overcome the frequent glitches/drop-outs.
8. If AMR can do this much with their iFi line, I am very curious to hear their top-level AMR DACs in my own system.  Jason, are you reading this? 

-dB (unit measure of noise)


Tunes Used:
1. Marconi Union “Distance”
2. Sleep Research Facility “Stealth”
3. Ray Davies “Working Man's Cafe”
4. Primal Scream “More Light”
5. The Raveonettes “Lust, Lust, Lust”
6. Julian Cope “Floored Genius: The Best of Julian Cope & Teardrop Explodes 1979-1991”
7. Tinariwen “Elwan”
8. Emma Pollock “Watch the Fireworks”
9. Various Artists “Wake Up You! The Rise & Fall of Nigerian Rock, Vol. 2 (1972-1977)”

[BRN]

dB,

Very nice and thorough review. I like that you had other DACs to compare to the iDAC2. I found it to be a very good DAC at a very fair price that is very hard to beat.

[Odal3]

Nice review and especially thanks for also posting your great play list. Been enjoying the tunes the whole evening 

[dburna]

dB,

Very nice and thorough review. I like that you had other DACs to compare to the iDAC2. I found it to be a very good DAC at a very fair price that is very hard to beat.

Yes, that was my general view as well.  I haven't really had uber-$$$$ DACs in my house ('cause I can't afford 'em), but I have heard some of the "big boys" at shows like AXPONA.  There's a difference, yes, but it's not enormous.  Good time to be a digital listener as sub $1k DACs just seem to be getting better and better.

One thing to note: I like to assess gear using the music I am listening to at the moment.  Since I have the most "muscle memory" with things that are in rotation, I figure that's a good test to use in A/B.  And the more I test, the more I side with a number of folks who have told me (time and time again) that, other than the room, the major determinant of good sound is how well the source is recorded.  The iFi gear provides a clean window into that for me......without jeopardizing my daughter's college fund.

-dB

[dburna]

Nice review and especially thanks for also posting your great play list. Been enjoying the tunes the whole evening 

That's as gratifying to me as anything.  I like turning folks on to new music.  More rewarding than my day job (lately).   

-dB

[maty]

Hi,

You have a bottleneck in your system: MAC mini has a very dirty SMPS power.

[dburna]

Hi,

You have a bottleneck in your system: MAC mini has a very dirty SMPS power.

As, I would imagine, do the three hard drives full of music I have attached to the Mac Mini.  Was going to look at optimizing that at some point, but instead I am most likely going to replace all of the above with a network streamer.  I am just waiting for iFi to build their "uRendu killer".  Hopefully they are reading this.   

-dB

[maty]

-> https://www.google.com/search?q=mac+mini+linear+psu

[BRN]

I am just waiting for iFi to build their "uRendu killer".  Hopefully they are reading this.

Agree. Would like to see an iFi streamer.

[Pez]

I am very curious to hear their top-level AMR DACs in my own system.  Jason, are you reading this? 

One is on the way to your house! Well... once we receive payment that is. 

dB, what an extraordinary review! Thank you so much for taking the time to do this. Try some software that upsamples everything and converts to DSD. Jriver can do this for most OS. 

[dburna]

Try some software that upsamples everything and converts to DSD. Jriver can do this for most OS.

Actually, I did.  Just didn't mention it much.  Sound definitely seemed to improve, more detail, but I wouldn't call the difference earth-shattering.  Either my ears/ancillary equipment are not good enough or the limitations in the source material (most recordings were not audiophile-level) were the gating item.  I even tried a couple DSD files from Channel Recordings that were an improvement, but they didn't fill me with sorrow going back to my "mere" Redbook source files.

-dB (tin ears)

[BRN]

Actually, I did.  Just didn't mention it much.  Sound definitely seemed to improve, more detail, but I wouldn't call the difference earth-shattering.  Either my ears/ancillary equipment are not good enough or the limitations in the source material (most recordings were not audiophile-level) were the gating item.  I even tried a couple DSD files from Channel Recordings that were an improvement, but they didn't fill me with sorrow going back to my "mere" Redbook source files.

-dB (tin ears)

I felt the same way with the different file types. the iDAC2 does a great job with redbook and other PCM resolutions. The difference between PCM and DSD is not as big as you think and when playing PCM I never felt that I was missing anything.

[Pez]

5. I'm not inclined to like Delta-Sigma DACs at all.....so why do I like this so much?

Our team wanted to answer this for you:

The reason could be that the DAC in the iDAC 2 is NOT a straightforward Delta Sigma DAC. It is a tech unique to Burr Brown (now TI) and only to some of their DAC's.

At AMR we have a long standing preference for Multibit DAC's, especially the Philips Multibit DAC's (which technically speaking are not R2R but based on multi-emitter bipolar transistors), however such DAC's have not been made in a long time and remaining stocks are limited.

This makes them fair game for limited quantity High End devices, but not applicable to more mass market oriented devices. For that we look long and tested many DAC's before we found one option we felt had much merit.

The DAC Chip used in the iDAC 2 (and indeed all the current iFi line - only the original iDAC used an ESS Sabre Delta Sigma DAC) uses an actual multi-bit (not R2R but Thermometer Code) DAC for the to Six bits (the top 36dB of dynamic range) - reaping the benefit of Multibit Technology where DS Systems are weak.

Only the bits below that are covered by Delta Sigma, in effect running at DSD256 Speed and using a comparably low order modulator, compared to more common Delta Sigma DAC's. This helps giving the smooth noise floor and lack of obvious quantitation distortion Delta Sigma DAC's are famous for.

For DSD input however the Chip is internally reconfigured into a pure DSD system, operating radically different. A very clever solution still under patent protection.

We have described this system in a little more detail in an "Industry Feature" Interview at audiostream.com ( http://www.audiostream.com/content/qa-thorsten-loesch-amrifi ) from which this illustration of the DAC operating principle is taken:
Sadly since the TI takeover of Burr Brown many new releases of DAC's abandon this system and use cheaper and simpler pure Delta Sigma system and often even omit the DSD input options.

[dburna]

Our team wanted to answer this for you:

The reason could be that the DAC in the iDAC 2 is NOT a straightforward Delta Sigma DAC. It is a tech unique to Burr Brown (now TI) and only to some of their DAC's.

Thanks for this, Pez (and AMR engineers).  I read the enclosed Audiostream link in its entirety -- one of the best, most understandable explanations of digital audio.  And this explanation of how the BB chip differs from typical delta-sigma DAC chips makes a lot of sense, a practical hybrid solution to a complex issue.  Now I have a better idea of why the iFi products sound as good as they do.  Will be interesting to see if the new iOne Nano uses the same DAC chip.

Gotta say, though -- that picture of Thorsten (with animatronic girl) in the Audiostream article was creepy.  Reminds me of Krieger from the "Archer" series.   

-dB (the d stands for 'Danger Zone')