NuForce Icon iDo USB DAC Headphone Amplifier

Icon iDo is a dedicated USB digital-to-analog converter/headphone amplifier for iPods, iPhones, and iPads. The little desktop component extracts digital audio data from those devices in "USB Host" mode, which means it cannot be used as a USB/DAC with computers.

What it is
The iDo is a cute little thing -- just 6" x 4.5" x 1" -- and it shares its all-metal chassis with NuForce's other Icon desktop amplifiers and DACs. Setup is super-easy, connect any Apple mobile device to the Icon iDo with the included 30-pin sync/charging cable, plug the wall-wart power supply into the iDo, and you're good to go. If space on your desktop is tight orient the iDo vertically (it comes with a secure stand for that purpose), or lay it down. The iDo is available in black, white, blue, or red. It's $249.

Start making sense
I have to admit I didn't quite understand the logic of making an AC powered device for iPods, iPhones or iPads, so I asked NuForce's Jason Lim about the iDo's raison d'être. He explained it was designed for people who bring their Apple devices to work and want the best possible sound, but don't have access to music on their computers. If you want a USB DAC for your computer NuForce's Icon HD ($349) is the way to go. Want a portable USB powered headphone DAC/amp? Check out the Icon Mobile ($79).

The iDo's DAC is much the same as the one used in NuForce's uDAC2, but the maximum sample rate is 48-kHz, with up to 24-bit resolution. The amp has a 5 ohm output impedance and drives headphones up to 300-ohms. And yes, iDo recharges your Apple device when it's not playing music.

The connectivity quotient is decent, there's a USB input, and coax digital and RCA analog outputs. Upfront you'll find a volume control, a green digital lock LED, and a blue LED that moves along a long slot to indicate volume level. That's fine, but then I noted that when I changed the volume on my iPod Classic the iDo's volume changed. That didn't make sense, the iDo was hooked up via the iPod's 30-pin digital output, which I always think of as fixed in level. Jason Lim explained that's the way the USB Host system works, he said "The volume is always set to max on Apple mobile devices when it is connected to the iDo. The iDo will accept Apple's remote control to change the volume on Apple devices." Whatever, I used the iDo's volume control for all of my listening tests.

There's a 1/8" mini headphone jack on the front panel, but I wish NuForce had also included a 1/4" jack. The iDo will mostly be used at a desk, and sometimes with full-size headphones terminated with 1/4" plugs. Sure, you can snap on a 1/8" to 1/4" adaptor, but they can be pretty bulky. Why not put 1/8" and 1/4" jacks on the iDo?

I used a bunch of headphones, including my two Audio Technicas, the ATH-WS55 and ATH-M50, B & W P5, BlueAnt Embrace, Sennheiser HD-580, Grado RS-1, Audeze LCD-2 full-size headphones, and Jerry Harvey JH-13, Monster Turbine Gold, and Klipsch S4 in-ear monitors for my testing. My iPod Classic was the only source for the listening tests, and most of the music was encoded in Apple Lossless. Even with the super efficient JH-13 in-ears the iDo was dead quiet, and added absolutely no noise or hiss. The iDo worked its magic with most of the headphones, but it was less terrific with the Audeze LCD-2. There the sound was thin and I felt the iDo was out of its comfort zone. The AT-M50 was the primary headphone for the bulk of my listening time.

On to the listening ...

NuForce Inc.
382 South Abbott Ave
Milpitas, CA 95035
(408) 890-6840

mward's picture

This product feels a bit like a solution in search of a problem. I guess the suggestion of it being a product for people who listen to iPods at a desk at work because they can't put their music on their work computers is a reasonable scenario for use, but I can't imagine it's a huge market.

I think it's mainly a shame that they didn't add a USB input for use with a computer. I can't see buying a DAC/amp just for use with iPods, but I could see buying one that would work with an iPod and a computer.

Or maybe this device would be better served if it just provided a digital audio output from the iPod without headphone amp functionality, like a less expensive Wadia iTransport. Then it could be used in conjunction with NuForce's (or anyone else's) headphone amps.

Anyway, seems like the execution is good but the concept is lacking.

funkmeister's picture

I'd be interested to hear this compared to a DACport LX through a really nice headphone amp. I understand the HP amp on the standard DACport is less than stellar.

Anyway, so the iDo's circuit is based on a uDac2? I've heard the uDac2-HP and I own an Icon HD. There is a world of difference between those two. I did some direct listening comparisons for a while. I didn't care for the uDac2 any more than straight out from my computer's headphone port, but the Icon HD opened up a whole new world of audio enjoyment. Lot's of detail and richness. It sounds like the iDo has one but not the other.

Also, I know you can get the iPad's camera kit and use any Class 1 USB Audio DAC on it (an iPad). I don't know about the other "iDevices" though.

Limp's picture

"The iDo's DAC is much the same as the one used in NuForce's uDAC2".

I'd be really surprised if this is an actual step up from the headphone out of an iPhone.
Sorry mr. Gutenburg, but I find little credence in your ramblings.

DaBomb77766's picture

The DACs in Apple's products are pretty good this really any better than a LOD to a similarly-priced amp? I think that's the real question here - this could be a product that "solves" a problem that was never an issue to begin with.

I'd certainly be interested in how it sounds in comparison to an amp fed with an LOD...

John Grandberg's picture
with the prior comments. With the Pure Audio i-20 letting you tap the digital data from your iDevice for just $99, it's hard to justify paying any more. I guess if you intended to use the built in headphone amp... but then you could just use the i-20 and find a stand alone amp for $150 or less and be in the same price range as the iDo.
HeadphoneAddict's picture

I liked this review, and agree with the findings. I do really like the iDo and use it almost every day. I especially appreciate being able to use the Apple remote to control the volume and skip tracks, and being able to use it with my iPad as well (no funny shaped cradle that wont fit an iPad).

The iDo's primary job may be to replace the DAC and amp in the iPod with a nicer set for desktop listening, but in my case I use the iDo feeding the coax into my nicer CEntrance DACmini. Basically, when I don't have my Macbook plugged in or turned on to use my DACmini via USB with lossless audio, I get the same sound quality with my iPod > iDo S/PDIF coax digital output > DACmini. It's like using a CD player's S/PDIF output for lossless music into your DAC, but with no moving parts!

The iDo headphone jack is more than adequate for casual music listening and sounds like my uDAC-2. It doesn't have a lot of juice for demanding headphones, but with most of them it gets the job done better than my iPod. However, it does sound even better when feeding it's RCA outputs into a better amp, or feeding the coax output into a better DAC + amp.

I routinely feed the RCA outputs into my Pico Slim or RSA SR-71b balanced amp to listen to my custom IEM. Just like with my uDAC-2, I find the iDo's RCA line-out sound quality is better than the headphone jack, and it rivals the RCA outputs of my more costly Pico DAC-only, but without having to boot up the computer to get that sound quality from a USB DAC.

Sure, it's more expensive than the Pure Audio i-20 dock, but when you consider vs the Wadia digital dock that costs a lot more and doesn't include an amp or upgraded DAC, then the $249 price becomes much more attractive.

I'll concede that a budget desktop amp like the HiFiMan EF2A or Travagans Red sounds a little better than the iDo's headphone output, but to me the iDo is all about being a great source, extracting lossless digital music from the iPod and doing a better job converting to analog, or sending pure digital output to an even better DAC than the one included. Having a decent headphone output is just icing on the cake.

The only thing I'd like to see added is the ability to act as a USB DAC for a computer as well, or maybe having pass-through video via the line out dock to an output on the back of the iDo. I did ask about the lack of 1/4" jack, and Jason Lim told me that they simply could not squeeze a 1/4" jack onto the PCB without a major re-design.

Mochan's picture

"Sure, it's more expensive than the Pure Audio i-20 dock, but when you consider vs the Wadia digital dock that costs a lot more and doesn't include an amp or upgraded DAC, then the $249 price becomes much more attractive."

Larry, I think you're looking at this the wrong way. The i20 is still the single best iPod dock out there. It does everything the Wadia does, only better, and has a dock that actually fits an iPad to boot, AND can be controlled with the iRemote, AND is only like $80.

In my opinion, it isn't so much, "The iDo is actually a great deal even if it's more expensive than the i20, because it's a much better product than the Wadia," but rather, "The Wadia is an over-priced, non-versatile product that is put to shame by the excellent and unbelievably affordable i20. The iDo isn't as great a deal compared to the i20, but at least for the extra dollar you are paying over the i20 you get a built-in amp and a sleeker form factor."

I personally don't think the iDo needs to be a USB DAC, though that would be nice, but it's more crucial for it to be battery-powered. I am hoping Jason can create a battery-powered version of this soon. I can live with it being slightly larger than it is now if it will sport an internal battery.

dalethorn's picture

Has anyone actually listened to this with a decent and efficient headphone, and compared the quality at some length with the sound of the iPod/iPhone alone? Driving the same iPod-compatible headphones? I even found some reviews that say the sound in this amp is EQ'd somehow and not flat. ???

Mochan's picture

Dale, the DAc portion of this sounds relatively flat, but the amp section is not. The amp, which I find to be mediocre at best, is a bit hot in the mids nad bass, but otherwise is not bad at all. However I doubt it can power 300ohm cans like NuForce claims, IMO. I don't have any 300ohm cans anymore, my hardest to drive cans are the K701 and LCD2 -- I think both are around the 60-80ohm range but as we all know the K701 is significantly trickier to drive than many 300ohm cans, and the LCD2, while relatively easy tod rive, still scales better with a better amp.

Needless to say, I don't like how the K701 or LCD2 sounds with the amp of the iDo, but it drives everything else I have really well -- including the MS400 you gave me.

I've been using it with the MS400 -- as you know very efficient -- and my Merlins, which are also very efficient. This is dead silent, and the SQ is significantly better than any iPod or iMod with LOD.

I also tend to agree with Project85. I have both the iDo and the i20. As digital transports, the two sound pretty much exactly the same. I would imagine they sound exactly the same as the CLAS, the HP-P1 and other Onkyo Wadia/whatever transports are available for the iPod stuff.

The i20 is like less than half the price of the iDo, and that's a big thing... if you are just using it as part of your setup at home with all the amps and DACs plugged in. The i20 is actually better as it has a physical dock for the iDevice, and has more output options (optical).

The iDO is a more specialized device in that it has a (rather mediocre) amp attached, and is a much sleeker form factor. The DAC in it is top-notch, and I have all but canned my iMod->LOD setup in favor of the iDo. The remaining issue is that it has no battery powre, so it must be hooked up to a wall outlet. Its built in amp is not as good as some of my other portables like the C&C X02 or the RSA Mustang. But it is pretty good for lesser devices and is an excellent amp for any IEM you have, and less power-hungry headphones -- again it drives all my cans fine except for the K701 and LCD2.

Because of its awesome form factor and built in amp, it is ideal to turn into a semi-portable device. Right now, with some velcro and a battery pack, I have turned the iDo into a "portable" device untethered by wall sockets, with the Energizer XP8000. Battery life in this mode is quite good, lasts about half a day always on, and this is really a much better system than the iMod + Mustang to drive things like my Merlins or the MS400 or EWS9.

It's also considerably bulkier, but the iMOd + XO2 or Mustang isn't really a pocketable setup so they are still almost in the same class of portability.

Later on I will explore transferring the innards of the XP8000 directly into the iDo's case and see if I can turn it into a fully portable CLAS-type device. I am curious to open the chassis of this up and see if it has enough space for a battery inside. Making it fully-battery powered in its current form factor would make a really killer setup, and far more economical than the over-priced CLAS.