This is a review of the Objective2 + ODAC combo with rear power. Objective2 is a headphone amplifier, whereas ODAC is a USB DAC. Both were designed by NwAvGuy and while you can build both yourself by getting an Objective2 DIY kit, this unit was assembled by Mayflower Electronics.
Furthermore, this unit was bought at a discount of $35 because I asked for it, arguing that I’m a a BIG boy, elite reviewer who expect massive discounts on products I want to review, haha.
Since the story of how the Objective2 headphone amplifier and the ODAC came to be has been told so many times we’ll skip that part and sum up why the Objective2 amp was created. The O2 and ODAC was created to be a small, portable, transparent and low cost headphone amplifier and DAC, primarily for headphones.
The reasoning behind these two devices is that when an amplifier and a DAC measures well they will sound transparent meaning there will not be any coloration by boosting the bass to accommodate bass heads, lowering the upper midrange to avoid sibilance and listening fatigue or anything like that. They also aim to have a low noise floor, low distortion, good channel separation as in little crosstalk, enough power for most headphones and with relation to the ODAC – low jitter.
Reviewing the sound quality of Objective2
It’s hard to review neutral gear in terms of sound quality, because they have no house sound to speak of. With some headphone amplifiers you can say that the mids opened up, the highs were a bit rolled off, that the highs have a lot of air, that the amp hits hard in the midbass, that tube so and so gave you sweet female vocals but with neutral gear it’s much more difficult. They don’t have any particular sound signature and you’re listening to your headphones more than the headphone amplifier.
I bought Objective2 not because I was particularly interested in it myself, but because I needed a well known neutral amplifier and DAC to review headphones on for the amazing HeadphoneAddict Youtube channel. My expectation from this little DIY looking device was that it would sound thin, imploded and have fatiguing highs.
The first impressions of the Objective2 with ODAC was «Wow, it sounds so clean, wide, spacious and have non fatiguing highs». This impression has stayed with me for the whole time and I quickly jumped on the Objective bandwagon, raving about the qualities of cheap and neutral amplifiers in the comment section below my Youtube reviews.
I suspect that the clarity and good grip the amp has is because of the low output impedance. When using low impedance headphones such as Denon AH-D7000 with an amplifier such as the output transformer less Woo Audio WA2 which has a high output impedance you get this kind of swollen, gushy and goopy sound (which is quite enjoyable for some genres actually). Not so with the O2. Clarity is the name of the game here.
Objective2 and ODAC – VS – high end head-fi
My most memorable neutral headphone amplifier and DAC combo was AURALiC TAURUS MKI with AURALiC ARK MX+ DAC. That system, and particularly the headamp is one of the best headphone amplifiers I’ve ever heard, but the price is prohibitively high and what you get in comparison with the Objective2 will probably not be worth it to you unless you have a big chunk of money to burn.
My God, I must admit that just by looking at that archive photo of my old rig makes me drool buckets. That is the pinnacle of headfi pr0n imo. But let’s get back to the sound quality comparison.
What you get with the TAURUS in comparison to the Objective2 is more power, a tighter grip on the bass, better holographic layering, smoother sounding highs and better resolution which in turn gives you more detail, but again, it’s much more expensive and since the improvements over the O2 are subtle you just got to bow down to NwAvGuy for the performance of the Objective2 with ODAC. This combo is worth it’s price if you are after a neutral all-in-one headamp and USB DAC that drives most headphones as loud as you need them to be and don’t care for fancy pants looks (like me).
Overview of different models of Objective2
Objective2 from Mayflower Electronics comes in a variety of configurations. Here is a collage of the different options it can be set up with.
As you can see the least pimped version has all inputs and outputs on the front while the most pimped version has a 6.35mm (1/4″) TRS output on the front as well as an integrated USB ODAC, at the rear you can get rear mounted power and a pair of RCA connectors in addition to the USB input of the Objective DAC.
Strike a pose Objective2 – you’re being reviewed!
The reason why I chose Mayflower Electronics over other suppliers is because I like audio gear to be black. «Once you go black you never go back», haha. Furthermore I particularly enjoy the amber led as blue leds are so overused it’s not even funny.
Mmmmmmm, looks sharp, doesn’t it? :) The Sennheiser HD600 headphones together with Objective2 is a super neutral combo at an affordable price. Wonder how much one would need to spend in order to achieve the same level of sound quality with stereo, probably a lot.
My unit has a 3.5mm (1/8″) TRS jack for the headphones but I use a pigtail adapter from Sennheiser because that doesn’t put a lot of strain on the output when used with conventional 3.5 to 6.35mm adapters.
Features of the Objective2 with ODAC
The RCA inputs/outputs on the rear has the same function as the small 3.5mm (1/8″) TRS input/output on the front. When the DAC is in use the analog inputs turn into outputs with a constant gain. This enables you to use it with a set of powered studio monitors, another headphone amplifier, regular computer speakers, a preamp or similar. It’s important that the device you connect has the ability to control the volume as this output has a constant gain. If the speakers you connect to this output does not have a volume control it will play loud, but you can of course use the volume control on your computer if no such option exist.
If you disconnect or disable the USB based ODAC these outputs revert back to being inputs for analog signals.
Flaws of the Objective2
Flaw number one is that of the potentiometer. I have channel imbalances at the lowest volume settings. This sucks for more reasons than one. Firstly, it could have been avoided by using pots that have tighter tolerances. Yes, they do cost more, but at the same time it will function properly and not limit the versatility of the amplifier.
This brings us on to the second flaw, and this is a design and not a implementation flaw: The O2 has a gain button on the front, when this is pushed in the gain goes up. The idea behind this button is that it will give you better control of the volume dial. This is important because some headphones are very sensitive and will play very loud even at low level settings.
And that’s the problem, even when the gain is not enabled the volume is still loud. Because of this you might not want to use very sensitive In Ear Monitors (IEM’s) or headphones with the Objective2, especially not if you like your hearing and often listen at non dangerous SPL levels.
If we factor in the channel imbalances and the high gain, we see that these two flaws combined reduce the versatility and flexibility of the headphone amp. You might say that what’s the point in using a headphone amplifier with very sensitive headphones anyways, it’s not like they need a lot of power. Well, if you have an Objective2, I’m sure you want to use it regardless of which headphones or IEM’s you want to use?
If the potentiometer had not had any channel imbalance the higher gain would be easier to live with, but combined the flaws result in limited versatility for high sensitive devices and audio geeks who listen to sensitive IEM’s at low levels.
Fix for the high gain with IEMs and sensitive headphones
After publishing this review Mayflower Electronics tweeted that they have a solution for the high gain.
@Headph0neAddict great review. Your problems with IEMs would be solved with different gain resistors we can install for free :)
So if you plan on using the headamp with sensitive headphones or IEMs make sure you inform them about this so the correct resistors will be installed. This will give you more flexibility and travel with the volume pot, which in turn can be dialed out of any possible channel imbalances.
Review of ODAC’s specifications
The DAC supports up to 24/96 and does not need any drivers, it’s plug and play.
Chances are you do not need more than 24/96 and will find that you’re using 16/44.1 for the most part anyways. I use 24/96 to keep the noise floor low when I record audio for youtube videos because that enables me to boost certain areas of the audio (correcting for Zoom H4N’s slight low frequency roll off and getting a weightier voice) without getting the noise floor up into the audible range. Even for this purpose I’d say it’s more than good enough.
The only issue with this DAC is if you have some well mastered higher res tracks in your music archive that you’d like to listen to you have to down sample them. I don’t think that matters to sound quality personally, but it’s cumbersome to have to down sample.
Is Objective2 powerful enough?
Based on manufacturer specifications I plotted and did regression on output power as a function of load and this is what it looks like.
I also did some calculations and can verify that the O2 headamp will drive most headphones out there with substantial headroom. This is important as you want to amplifier to operate well within its limits as distortion will increase as you approach the power limit.
If you’re in doubt if the Objective2 will be able to drive your headphones chances are it will, because you would otherwise have known that your cans were hard to drive and need special care in the amp department.
Objective2 with ODAC pros & cons
Pros are (1) excellent sound quality for the price, (2) flexible switching of inputs and outputs, (3) low output impedance and (4) enough clean power for 99 % of headphones out there.
Cons are (1) channel imbalances, (2) high gain even in low gain mode unless other gain resistors are installed, (3) less portable than many other offerings nowadays and (4) only USB interface for the DAC.
Objective2 with ODAC review conclusion
We must realize that the Objective2 and ODAC was engineered to be a stripped down low cost device with excellent sound quality. It achieves that goal even with the powered version, but I wonder if the battery powered version can bring even more sound quality as you have a better source of power when using batteries over so-so wall warts like my unit has.
I do recommend the Objective2 headphone amplifier and ODAC but remember to have the correct gain resistors installed if you’re going to use it with very sensitive headphones or in ear monitors.
Also, I think that Objective2 is only semi portable even if you get the battery powered version because even though it’s small there are other amplifiers that are smaller and more suitable for use on the go. The O2 is excellent if you just want to throw it in your laptop bag and bring it with you on a business trip etc though.
So, that pretty much sums up this review of the Objective2 + ODAC. It’s a powerful and neutral combo with very good clarity at an affordable price. If you plan on getting the O2 and would like to support my work, consider buying this amplifier through this Amazon US affiliate link, it will not cost you anything and you’ll help me a lot.