Objective2 headphone amplifier review

Objective2 + ODAC Review – Not without a flaw

A legendary headphone amplifier and DAC under heavy scrutiny

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

AURALiC TAURUS headphone amplifier and ARK MX+ DAC
Pinnacle of headfi pr0n: AURALiC TAURUS MKI and ARK MX+ DAC with Audeze LCD-3 headphones

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.

Objective2 models available from Mayflower Electronics

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.

Objective2 headphone amplifier with Sennheiser HD600

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

Objective2 headphone amplifier

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.

Objective2 output power as a function of load

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.

Discussion on Objective2 + ODAC Review – Not without a flaw

  1. HeadphoneAddict HeadphoneAddict says:

    ThatMichaelM on Twitter didn’t seem to agree with my choice to list the high gain of Objective2 as a con.

    @Headph0neAddict If you have very sensitive headphones (with low impedence), using an amp is moot. Not a fair con IMO.

    I appreciate that, but at the same time I want to explain why I still listed it as a con. Firstly, people get an amplifier for several reasons. Maybe their onboard soundcard is of poor quality and has a hiss, hum or similar. An amp with a low noise floor such as Objective2 will benefit you a lot in this scenario, even if you have low impedance high sensitivity headphones. In fact, especially if you have very sensitive headphones, because they will present the low level noise much louder due to their higher efficiency.

    The more efficient the headphones the more prone to noise they are. So amping is not just about having enough power to present dynamics, it’s also about having a low noise floor, little crosstalk and things of that nature. The most detrimental factor to sound quality is having a constant hiss in the background. It will mask out micro details and be an annoyance during the silent parts of the music.

    Another thing is that a lot of people have multiple headphones, some which require a lot of power and some that doesn’t. I’m sure a person like this would consider high gain in combination with low level channel imbalances to be a flaw, as he would then possibly have to use one amplifier for his power hungry and less sensitive headphones while he would need another amplifier/headphones output for his more sensitive pair of headphones or IEMs, depending on his preferred listening levels. This should not be necessary and is probably exactly why Mayflower Electronics offer other gain resistors to alleviate this problem.

    The third reason is that you might want a headphone amplifier with low output impedance to improve the damping factor between your low impedance headphones and the output. In that case the Objective2 headphone amplifier is perfect, but again, this con might limit the flexibility depending on the sensitivity, channel imbalances and SPL preferences of the user. A lot of headphone outputs have a high output impedance as we know, so again, it’s not just about having an abundance of power that makes people consider getting a headphone amplifier.

    So, this is the reason why I listed it as a con. These two factors combined (low level channel imbalances and high gain) limit the versatility of the device and if addressed would make the Objective2 a better amp imo.

  2. Michael says:

    My point of contention on Twitter with your review is merely to point out that it is entirely unnecessary to use an amplifier with very sensitive, low impedance headphones. These particular kinds of devices are typically designed to be used on phones and music players. Because your IEMs require very little power to drive, it is in my view unfair to mark this down as a flaw in the equipment.

    Anyone looking to purchase an amplifier should have a general idea of the power requirements of the device that they are currently using. You mentioned that an amplifier/DAC combo would be useful in a situation where the user has bad or otherwise faulty onboard audio. I agree with you. There are a plethora of external amplification devices — both cheap and expensive. If the headphones in question do not require an amplifier to be properly driven, a cheaper solution might be the best route.

    That is not to say that the O2/ODAC is not capable. It is. I have one. Depending on the use case, however, an amplifier of the O2’s caliber may be overkill for some people.

    If price is not the point of concern, I will say that Mayflower offers one of the best warranties for amplifiers that I’ve seen. A 10-year warranty is fantastic, especially for the price point.  Tyler, again thank you for that!  That says a lot!

    • HeadphoneAddict HeadphoneAddict says:

      Hi again, Michael. Appreciate that you came here so I could explain my reasons further. I asked you to come here, but since your point was very valid I wanted to reply to it even if you never showed up. Hence why I made this comment about the limitation that arose from the combined flaws of Objective2.

      As you can see from that comment I don’t agree with you that low impedance, high sensitivity headphones does not need an amplifier. An amplifier can offer more benefits than just enough power to drive the headphones.

      I have owned the Objective2 for about 8 months now and used a wide variety of headphones with it. As you can see from the review I’m very positive towards it, but felt it necessary to inform about its limitations as well. 

      Also, I have a lot of respect for Mayflower Electronics and what Tyler is doing (I’m a small entrepreneur myself). I don’t know the guy besides nagging him for a discount on the O2, but I believe in the cause for and reason behind his company. I could have gone to JDS Labs instead, but I chose Mayflower Electronics because it’s a small operation where essentially one man tries to innovate and improve upon the design as much as the design license allows him to. I think he was first out with the rear mounted power for instance, and that alone is a big selling point imo.

      My goal as a (subjective) reviewer is to disclose all my findings no matter what interests they might hurt. Hell, me saying bad shit about equipment even hurt my personal financial interests.

      • If I say something negative about equipment, say the lack of need for high end audio cables, do you think cable manufacturers will advertise here? Nope.
      • Do you think people will be more likely to click my affiliate links and purchase what’s being reviewed if I am a hard critic? Nope.
      • Do you think companies are eager to send me review samples or give me discounts when I’m a hard ass critic? Nope.
      • Do you think people who have already spent money on gear I review and criticize will like my opinions and start following me? Nope.

      I try to be open no matter what conflicts of interests there are. That’s my main goal.

      • Michael says:

        An amplifier can offer more benefits than just enough power to drive the headphones.

        If the onboard audio, for instance, is causing interference such as hissing or is cheaply made, an amplifier can help. An amplifier’s main job is to increase volume while remaining transparent. Even you agree with this. I’m not sure there’s much more one can expect.

        An amplifier is not going to make a cheap pair of headphones sound magical. If anyone you know believes this, I think we can both agree that they have been duped by marketing.

        • HeadphoneAddict HeadphoneAddict says:

          Let me give you an example for why people might want to get a headphone amplifier other than having enough power to drive a pair of headphones.

          Having a low output impedance is one of those reasons. Having a low output impedance is especially important for low impedance headphones. Furthermore low impedance headphones are generally high sensitivity. So in this case you might consider getting a headphone amplifier not for the power it has but because you want an amplifier which will give you a better damping factor which in turn gives you more transparency and objectively speaking better sonic performance.

          When a low output impedance headphone amplifier has high gain in combination with channel imbalances on low level settings the versatility drops, as people who want to buy the amplifier to get the better damping factor for their low impedance high sensitivity headphones or IEMs will experience problems dialing the volume level without suffering from the channel imbalances.

          One of the selling points of Objective2 is the low output impedance, so people will automatically assume that it is good for low impedance headphones (which are generally high sensitivity). This is not the case when the gain is high and there are channel imbalances, hence why it is a flaw in my opinion.

          • jefe32 says:

            I agree with your review and your post. I think some people just see things a certain way and that’s it. While great that you were respectful and courteous in your responses as well as in-depth, I don’t think Michael really wanted to see any point but his own.

            • HeadphoneAddict HeadphoneAddict says:

              Thanks jefe32. Nope, didn’t seem like he wanted to take it on-board. Generally speaking and from my experience doing reviews is that very few people can handle criticism of products they own. Not listing that limitation as a con would not be a very truthful and not even mentioning the problems even worse. One day I’ll write an article on the dilemmas you get into when trying to drive traffic to your content and being up front about what you find.

  3. Jérémy Levesque says:

    Nice review! JDSLab offers different gain options when purchasing but Mayflower Electronics doesn’t… Do you know if their O2/ODAC combo can handle my DT880 600ohms headphones??? Thanks for helping. 


    • HeadphoneAddict HeadphoneAddict says:

      Yeah, I noticed that a few days ago. As written in the review Mayflower Electronics also offer other gain resistors but they don’t have it built into the cart system right now, so it looks as if it has to be done by shipping them an email. They should definitely make it an integral part of the cart system to make the order process more stream lined like JDSLabs has done.

      The Beyerdynamic DT880 is 96dB efficient (they don’t state if that’s 1Vrms or 1mW), but they do state that their power handling is 100mW and that they’re 600 Ohms (nominal, which means they can vary). If we assume that they are 600 Ohm the O2 can throw them 94mW which is damn near close to the limit of the driver, which again is 100mW. So yes, the O2 is absolutely able to drive your Beyerdynamic DT800 headphones to very, very loud levels. If the 96dB efficiency rating is for 1mW then you will be able to play them at 110dBSPL (LOUD) even when you reserve 6dB for amplifier headroom (which gives you less distortion and better sound quality).

      So to sum up, O2 is able to drive your DT880 600 ohms headphones very, very loud even when you operate the amplifier well within its limits to avoid distortion.

  4. IE800 says:

    Thanks for the great review!
    Could you clarify one thing though; what gain (1x or 2.5x) were used in “low gain” mode on your 02+ODAC?
    I’m very curious to see if this (at 1x) would work fine with IE800 as I’m still worried about precisely these drawbacks you brought up.
    Best wishes!

    • HeadphoneAddict HeadphoneAddict says:

      Hello, and you’re welcome. Since the ODAC which is integrated in my device has a 2Vrms output I assume it’s 1x gain in low gain mode.

  5. thekrautdog says:

    Great review! Many thanks. I can't see a date on this page so I have no idea how old this is but I have a question…

    If I ask Mayflower to install the different gain resistors to help alleviate the one issue, does that mean that the maximum power output will necessarily drop? Making it a "choose one or the other" and a "you can't have it all" situation? If the answer to this is obvious to most I apologize…I know little about the technicalities of such devices, I just want to enjoy the benefits :). Many thanks for any wisdom/advice!

    • HeadphoneAddict HeadphoneAddict says:

      Yes, unfortunately you will lose some gain (power) with different resistors. :( At the same time I have never used this amp at anywhere close to full capacity as I like my hearing :D Not making excuses for them though. I think it's a shame it has channel imbalances and I heard nothing about this problem before I purchased the amp. If I did know beforehand I would probably look elsewhere… It is an annoyance and it shouldn't be that way. Even smartphones doesn't have channel imbalances so a standalone amp you pay good money for def shouldn't have an imbalance…

      This review is about 8 months old or so, and if you don't already know there's a new revision of the O2. I'd contact JDS and Mayflower and ask them about the issue directly and if it has been fixed. If you do, I hope you come back here and let us know.

  6. Giovanni says:

    Hello, thank you for this awesome review.
    If I buy the portable edition, can I use it plugged to the power plug almost every time? If yes, the batteries will deteriorate?

  7. Mike Lloyd says:

    Good review, thanks! How do you know that the channel imbalance is with the amp and not the DAC? I may have missed it in the review if you separated the two, so my apologies in advance if so!

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