Smartphones have advanced significantly, and they offer an advantageous method to tune in to music. In any case, if you’re not content with your smartphone’s sound quality, at that point it very well might be an ideal opportunity to put resources into an external DAC.
At the point when you play a melody on your smartphone, you’re playing an encoded advanced sound record at its most oversimplified a stream of ones and zeros. The thing is, your headphones aren’t fit for transforming that stream into simple sound without the assistance of a, suitably named, Digital to Analog Converter (DAC).
On the off chance that you as of now have a decent set of audiophile headphones and need to ensure you are getting all of the execution out of them then you will need to put resources into a decent headphone intensifier. Ensuring your headphones are adequately fueled is a critical component in having the most ideal sound quality.
Picking the best amplifier is not simple as over the most recent couple of years the versatile audiophile market has been immersed with new models all contributing interesting selling focuses, including set, and costs.
2020 has been an incredible year for purchasing speakers with bunches of new models hitting the market each month. Rivalry from China has caused set up brands to remain alert and a definitive champ is a buyer who presently has a more extensive scope of alternatives at preferable costs over in earlier years. of stuff and our pick was the Schiit Magni 3 however we needed to keep it new and update our rundown of the best 10 earphone amps of 2020 to add a couple of new sections on the lookout.
Without further speculations, let’s get right onto the facts and features of some of the best headphone amplifiers.
Not exclusively is the Award-winning soundKey a fabulous bit of unit, but on the other hand, it’s exceptionally reasonable as well. An amazing mix.
This small headphone amp and DAC is worked to deal with all way of document types, including MP3, AAC, and FLAC. So it’s ideal for everybody, from easygoing audience members to those of us who are more specific about sound quality.
Discussing sound quality, it’s right on target – an extensive introduction is a thing to get done, giving each instrument the space it needs to relax. This is particularly articulated when tuning in to calmer, sparser material, instead of frantic, occupied tracks. Chronicles like this are opened up overall quite wide, permitting the small subtleties space to uncover themselves and giving tunes a widescreen viewpoint some lesser convenient DACs are essentially not prepared to do.
The outcome? A brilliantly point by point soundstage that will do versatile audience members of all stripes pleased. Try not to venture out from home without it.
The Features of the Cyrus SoundKey
Toward one side of the soundKey there’s a 3.5mm attachment for connecting earphones (or interfacing with a framework). At the other, there’s a miniature USB attachment. There’s no need (nor any space) for whatever else.
In this case, Cyrus gives a link ended a miniature USB at the two closures (for use with suitable Android gadgets) and a miniature USB/full-size USB link (for use with PC or work stations).
Those wishing to utilize an Apple telephone or tablet will require the Apple camera pack – so the chain from telephone to earphones turns into a three-links in addition to soundKey issue, which is a long way from exquisite.
Using a dongle to join an external DAC to a smartphone is a long way from remarkable, however, it does rather ruin the ‘significantly better stable with next to no object’s stylish.
The soundKey is prepared to deal with a wide scope of computerized sound document types, most relevantly MP3, AAC, and FLAC – and can deal with records up to 24-bit/96kHz goal. It requires Windows 10, Android 5 (or above), and iOS 9 (or above) of its source machine.
Pros and Cons of the Cyrus SoundKey
|Clean, open sound||Attaching to an iOS device is a faff|
|Loaded with detail||Not as dynamic as some rivals|
|Compact and unobtrusive|
|Cyrus Audio Gaming soundKey DAC & Headphone Amplifier - Each (Graphite)||BUY ON AMAZON|
AudioQuest DragonFly Cobalt
It’s unquestionably not modest, but rather Audioquest’s most up to date Dragonfly is an amazing machine. The Award-winning Cobalt enhances the all-around skilled Red by offering shockingly better lucidity and sonic accuracy. Its fantastic transparency implies that the Cobalt uncovers weaknesses in the source and accounts than others in the family don’t, so you may need to watch those lower-quality chronicles. Yet, give it a decent sign and it’s fit enough to give Chord’s powerful Mojo trouble – and that is something relatively few earphone amps can guarantee.
It shares a large number of similar highlights as the numerous Award-winning DragonFly Red, including the 2.1v earphone yield, bit-amazing computerized volume control, and MQA renderer. Yet, there are additionally various updates, similar to the further developed DAC chip, conveying a more clear, more characteristic sound, and another microchip which speeds up by 33 percent. Furthermore, improved force flexibly separating (expanding resistance to wi-fi, Bluetooth, and cell commotion), a 10 percent more modest fenced in area and included DragonTail USB-A (female) to USB-C (male) connector for use with the developing number of gadgets with the network for the last mentioned.
The Features of the AudioQuest DragonFly Cobalt
There are components imparted to the different What Hi-Fi? Grant winning DragonFly Red, including the 2.1v earphone yield, bit-wonderful computerized volume control, and MQA renderer, yet there have additionally been various huge overhauls.
It starts with another, further developed ESS ES9038Q2M DAC chip, with which AudioQuest guarantees a more clear as well as more regular sound, while the PIC32MX274 microchip draws less current and speeds up by 33 percent. Improved force gracefully sifting, then, is said to build invulnerability to wi-fi, Bluetooth, and cell commotion.
There are several useful upgrades as well, specifically, the 10% more modest fenced in area and included DragonTail USB-A (female) to USB-C (male) connector for use with the developing number of hardware with a network for the last mentioned.
Our lone reservation is with the nature of the DragonTail connector. It battles to stay associated with any of the telephones we attempt it with, a mix of baggy and the heaviness of the Cobalt procrastinating each time we move.
Pros and Cons of the AudioQuest DragonFly Cobalt
|Impressive resolution and clarity||Less forgiving than the Red|
|As convenient as ever|
|AudioQuest - DragonFly Red USB DAC/Headphone Amplifier||BUY ON AMAZON|
The Mojo brags a lot of a similar sound ability as the Chord Hugo, yet without the sticker price of its more costly kin. Its impression is scarcely greater than a Mastercard, yet there’s space for a lot of associations, including miniature USB, optical, and 3.5mm earphone jack.
Fabricate quality is dynamite. It seems like a strong chunk of metal, with its aircraft-grade aluminum packaging delightfully machined and completed to an amazingly exclusive requirement. Also, it’ll last you some time as well – eight hours once completely energized, however, this will fluctuate contingent upon your volume levels and kind of headphones used.
The sound does not baffle all things considered. It’s stuffed with detail and overflowing with understanding. Yet, the Mojo can arrange all that data into a strong and melodic entire that makes it stand apart from the opposition. The introduction is strong, full-bodied yet keeps away from any trace of overabundance wealth at mid-and low-frequencies.
Everything meets up to sound superbly firm. Strongly suggested.
The Features of the Chord Mojo
DAC’s construct quality is tremendous. Regardless of the negligible itemizing, the Mojo feels like a strong piece of metal.
Its aircraft-grade aluminum packaging is flawlessly machined and completed to an incredibly exclusive requirement. Right now just dark is accessible, yet we wouldn’t be amazed if a silver choice showed up eventually.
Once fully operational this a spectacular performer. We tune in to Stevie Wonder’s Innervisions on DSD and are grasped from the indisputable opening bars of Too High directly to the finish of the collection. There’s a lot of detail here, and the sort of knowledge into the chronicle that nothing we’ve heard up until the Hugo can better.
However, it’s not the phenomenal goal that dazzles us most. The Mojo can coordinate all that data into a strong and musical entire that makes it stand apart from the opposition.
It conveys the hard-charging cadence track of Higher Ground splendidly, discussing the tune’s relentless energy with genuine eagerness. The introduction is strong, full-bodied yet evades any trace of abundance extravagance at mid-and low-frequencies.
Pros and Cons of the Chord Mojo
|Informative, subtle, dynamic sound||Tends to heat up|
|Fine rhythmic drive|
|Solid build and good finish|
Chord Hugo 2
Hugo 2 is an odd one. It’s just about small enough to take with you (however this is unmistakably the Intention, as it has its inherent battery), yet excessively huge to sit in a pocket. So it’s not ideal for in a hurry tuning in. It’s likewise not the simplest gadget to use on occasion, generally because it arranged shaded lights, which can get befuddling.
Goodness, and it’s quite expensive, as well.
So what’s it doing on this rundown, you may wonder. Two words for you: sound quality. It’s troublesome for sure to blame the way Hugo 2 believers and conveys your advanced sound records. Furthermore, sparklingly high res ones, yet lower quality records, as well – whatever you feed it, Hugo 2 presents a definite, dynamic, and punchy execution.
There are a lot of contributions to exploit, in addition to aptX Bluetooth also. See past its eccentric looks, and you’ll be remunerated with an abundant point by point, dynamic, and punchy execution. No big surprise it won a What Hi-Fi? Grant for its endeavors.
The Features of the Chord Hugo 2
Hugo 2 highlights all the sources of info and yields you could practically require. Its advanced optical info (a full-size TOSLink) is useful for computerized sound up to 24bit/192kHz, while the advanced coaxial (a 3.5mm attachment) works up to 2bit/384kHz.
The last actual info is a scaled-down USB ready to manage data up to 32bit/768kHz and DSD512. Music can likewise be taken care of to Hugo 2 through aptX Bluetooth.
There are 3.5mm and 6.3mm headphone attachment yields, and a couple of sound system RCAs for association with a speaker.
Notwithstanding being preferred separated and more open over on the first Hugo, we actually can’t accommodate our reference Chord Company (no connection) Signature Tuned Array RCA links to the marginally recessed RCA yield toward the finish of Hugo 2 and need to make do with something a touch duller.
Pros and Cons of the Chord Hugo 2
|Well made and specified||Confusing colors|
|An exotic multi-colored control system||Not very portable|
|Prodigiously detailed sound|
AudioQuest DragonFly Red
Another Award champ, this amp is somewhat more expensive than the aforementioned soundKey, however, you can hear where your additional cash is going: the sound is more unique, with more weight and body. There’s likewise an additional degree of detail that, joined with magnificent low-level elements, implies everything sounds more common, inconspicuous, and expressive. Like the DragonFly Cobalt, the logo even lights up various shadings to mention to you what record design the Red is preparing. It’s a pleasant touch to an all-around great gadget.
Disadvantages? Its help for high-goal music finishes out at 24-cycle/96kHz. What’s more, the reflexive red completion chips a piece without any problem.
In any case, the Red is a remarkably reduced and helpful gadget that can be taken anyplace for a prompt melodic lift. On the off chance that you can live with that somewhat flaky completion (and we positively can), you can consider the DragonFly Red a pretty wonderful PC music redesign.
The Features of the AudioQuest DragonFly Red
AudioQuest has set itself a significant test by giving the Red a £170 sticker price to legitimize, and on paper, the case doesn’t look especially solid. One analysis that can be leveled at the DragonFly range is that its help for high-goal music finishes out at 24-cycle/96kHz.
The Black holds that restriction – however then it is uncommonly reasonable. The issue is that the twice-as-expensive Red is likewise limited.
AudioQuest focuses on various redesigns for the Red over the Black, however: a further developed DAC and earphone amp first of all, in addition to “somewhat amazing computerized volume control contained on the DAC chip itself” that is a major enhancement for the simple volume control operating at a profit Black.
Pros and Cons of the AudioQuest DragonFly Red
|Sophisticated, solid, subtle sound||Red finish seems easily chipped|
|As convenient as ever|
|AudioQuest - DragonFly Red USB DAC/Headphone Amplifier||BUY ON AMAZON|
Chord Hugo TT2
As should be obvious from this list, Chord realizes how to make a respectable headphone amplifier-cum-DAC. Hugo TT2 is a very good quality pleasure. It’s enormously great and not simply in the looks office.
It’s prominently usable gratitude to its numerous computerized contributions of the optical and coaxial assortment, in addition to USB and aptX Bluetooth. There are no less than three earphone yields as well – helpful for tuning in with companions.
Indeed, the TT2 is numerous things to numerous individuals. It’s an excellent DAC, it’s an earphone intensifier, and can even drive a force enhancer or dynamic speakers legitimately. At the press of a catch, you can even get it to have a fixed yield with the goal that it tends to be connected directly to your current enhancer and work as a traditional howdy fi DAC.
Record uphold is broad as you’d expect, yet it’s the sound quality that is terrific. Taking everything in its step, the Hugo TT2 is one of the most finessed and straightforward sounding gadgets you’re probably going to hear.
The Features of the Chord Hugo TT2
Glance through the set-up menus – the TT2’s showcase is little – and you’ll discover an assortment of changes. There are four degrees of the organization’s Crossfeed framework, which means to move the sonic introduction of earphones from being between the ears to something closer to that created by sound system speakers. In contrast to numerous such handling modes, this one truly works and we leave it on the second-most elevated setting.
There are additionally four-channel alternatives, which adjust the introduction marginally and give a ventured decision between unadulterated nonpartisanship and a somewhat hotter introduction with a level of high-recurrence adjusting. We leave this on Filter, the nonpartisan alternative.
Past these settings, you can change the splendor of the presentation just as trade the unit’s benefit among low and high choices (which helps hardware coordinating) when the TT2 is utilized with earphones or a cooperating intensifier.
Items, for example, this Chord have gotten progressively adaptable throughout the long term. TT2 is numerous things. It’s a great DAC, it’s an earphone enhancer, and can even drive a force intensifier or dynamic speakers straightforwardly. At the press of a catch, or for this situation, numerous presses of catches, you can even get it to have a fixed yield with the goal that it very well may be connected directly to your current speaker and work as a regular greetings fi DAC.
Availability is acceptable. To the extent, inputs go there’s a USB, a couple of optical, and two coaxials (utilizing BNC connectors). Utilize Chord’s Blu MkII CD transport with its underlying up-scaling and this pair of BNC sources of info can be utilized together to acknowledge a sign up to 24-bit/768kHz.
AptX Bluetooth is likewise in the menu and the Chord interfaces with our iPhone 6S Plus rapidly and without issue. There are three earphone yields on the front board and the unit has no issue driving different ‘telephones simultaneously by the same token. You can add single-finished RCA and adjusted XLRs to the rundown of yields as well.
The Hugo TT2 has a further pair of outs checked DX. These are planned for use with up ’til now unreleased Chord items, however, the organization has been very quiet about this up until now.
Pros and Cons of the Chord Hugo TT2
|Dynamic, detailed sound||Can be frustrating to use|
|Brilliant build quality|
Zorloo claims that the Ztella is the world’s littlest USB DAC with top of the line sound ability. Try not to be tricked by those minute measurements, however, this DAC has a major character.
The Ztella can be joined forces with a smartphone or PC. If you need to tune in to MQA tracks on an Android gadget you’ll have to download the extra USB Audio Player Pro application, however, in case you’re utilizing an iPhone you’re all set from the off (gave you’ve purchased the rendition from Zorloo.com with a Lightning connector).
The underlying earphone amp can examine whatever you feed into it and enhance its sound to coordinate, without losing admittance to all the in-line controls and the mic on your wired earphones.
With regards to sound, accomplice the Ztella with a couple of impartial sounding or smooth earphones and you’ll be compensated with a spotless, sure stable with huge loads of detail. A splendid sounding earphone amp for the individuals who need extraordinary transportability at a moderate cost.
The Features of the Zoroo Ztella
Zorloo depicts the Ztella as module and-play, in any case, you may need to take a little consideration here, especially in case you’re an Android client and need to get the most ideal sound exhibition from your gadget.
While the iPhone has a digit amazing USB yield, which permits the MQA Core sign to be passed effectively and perceived by the Ztella, an Android gadget’s USB yield is restricted by the abilities of the Android framework thus the sign isn’t bit-great.
It merits bringing up that this issue isn’t selective to MQA – it is a similar situation when hoping to boost the exhibition of any howdy res sound arrangements played employing the Android working framework.
The workaround is downloading the USB Audio Player Pro application, which permits the Ztella to appropriately perceive and deliver an MQA signal at its best. That is more faff than something named fitting and-play ought to preferably include, however it actually performs someplace close to its best without the extra legwork.
The Ztella likewise joins an earphone amp that examinations whatever you plug into it and advances its yield to coordinate – it can convey more than double the intensity of a standard cell phone. If you need to delay the music and settle on a decision, Zorloo has ensured your in-line controls and mic are as yet dynamic when connected to the DAC.
Concerning the opposite finish of the Ztella, the standard association is USB Type-C, which covers the most current smartphone, tablet, and PC makers. A USB Type-A connector is incorporated for use with more established equipment, and a variant with a lightning connector is likewise accessible for those using an iPhone.
Pros and Cons of the Zoroo Ztella
|Clean and detailed sound||Tiresome with bright headphones|
|Lots of energy and excitement||Android users need MQA app|
|Unobtrusive size and form|
This versatile DAC/earphone amp resembles a hip flask and conveys a hit of top-notch sound moving. The most conservative choice in iFi’s reach, it’s the guts of the British brand’s magnificent work area based Zen DAC pressed into a more modest, battery-fueled structure.
The aluminum case feels unshakable and is highlighted by a pleasantly damped metal volume control. Concerning sound quality, the hip-DAC presents the run of the mill nice, refined iFi sound and we especially lauded its “undemanding nature, collaborated with expressive elements and satisfying cadenced exactness.”
To put it plainly, the iFi hip-DAC is a heavenly purchase – yet it’s facing a solid field. Any semblance of Zorloo’s Ztella set exclusive requirements at around this value mark, while the Cyrus adequately stays hard to beat. All things considered, in case you’re searching for a top-notch compact earphone amp, this all-around planned DAC/earphone amp has the right to be a leader.
The Features of iFi hip-DAC
On the front of the DAC, a catch that changes the increase of the inner amp. This makes earphone coordinating simpler, with less touchy models requiring the volume help. We’re not for the most part aficionados of bass accentuation controls, yet the one on this unit is sufficiently inconspicuous to be valuable. It adds a suitable level of low-recurrence haul to the Shure in-ears without sounding exaggerated.
iFi’s items infrequently frustrate on the similarity front, and this one is the same. The hip-DAC will work with up to 32-bit/384kHz PCM and DSD256 documents. MQA is likewise on the menu. So, there’s an extraordinary possibility that the hip-DAC will play anything you desire it to.
There’s a couple of LEDs, one on one or the other side of the volume dial, that show the examining rate and sort of document. They’re not especially instructive, as they don’t separate between the most widely recognized PCM record types. For instance, 44.1kHz and 96kHz documents are both spoken to by a similar green light. Similarly, everything from 176.4 to 384kHz records is demonstrated by yellow. Indeed, even the DSD documents are lumped together absent a lot of thought. iFi needs to improve here.
The hip-DAC is facing some extreme rivalry in this piece of the market. Any semblance of the Cyrus soundKey and Zorloo’s Ztella set elevated expectations for well beneath the £100 mark, while Audioquest’s DragonFly Red conveys excellent sound quality, particularly at its current £135 cost. For absolutely convenient use, Audiolab’s Bluetooth M-DAC nano (£139) stays hard to beat. However, we actually feel that there’s a spot on the lookout for the hip-DAC, even against such fit resistance.
It’s not as little as any of these adversaries and clearly can’t coordinate the remote availability of the Audiolab, which rules taking everything into account. Yet, with battery power, the iFi won’t deplete your telephone or PC in the manner the greater part of these will. That is a major in addition to.
Pros and Cons iFi hip-DAC
|Easy-going by engaging sound||Up against tough competition|
|Battery power||Larger than some rivals|
|Fine build and finish||Sub-par sampling rate indicators|
Schiit Audio Magni 3
It’s a name that has, alongside some generally welcomed items, helped the organization pull in a developing after of eager fans. We’ve needed to get some Schiit items (don’t hesitate to laugh the initial not many occasions) at What Hi-Fi? for quite a while, and we’re happy we did.
The US organization (it is anything but a German family name, as the official site flippantly clarifies) makes a scope of intensifiers and DACs, with an accentuation on items for earphones.
The Magni 3 is the most moderate devoted enhancer in the organization’s portfolio and sits underneath innovatively named items, for example, the Vali 2, Asgard 2, and Valhalla 2, straight up to the Mjolnir 2 at £750. There is a lot of earphone amp and DAC blends, as well, beginning from as meager as £50 (the Fulla).
Loads of items, at that point, and a lot of families. The authors of Schiit Audio cut their teeth at genuine AV organizations in the US, including Theta and Sumo, so have a lot of training with regards to designing intensifiers huge and now little.
The items are planned and made in the US, with the ‘lion’s share’ of parts sourced from near the organization’s California base.
Features of Schiit Audio Magni 3
That spotless front method the vast majority of the activity is around the back. This comes looking like one sound system RCA info and one yield, in addition to two old fashioned flip switches – one for power, one for howdy/lo increase (17 or 6db). That simple yield reveals to you this earphone amp can likewise go about as a preamp, permitting you to associate directly to a couple of fueled speakers.
We haven’t tried an earphone amp this moderate for quite a while. All things being equal, we will in general observe earphone amp and DAC mixes, for example, the Cyrus SoundKey (£99) and Audioquest Dragonfly units (from £90).
In this way, as opposed to arriving at straight for an immediate contender, similar to our regular methodology, we select to simply tune in to the thing. All things considered, in the event that it improves the sound quality from our MacBook Pro to an adequate degree for just £110, it’s a victor, correct?
Running a 3.5mm-to-RCA link from the sound out on the PC to the Magni 3, we plug in a couple of Grado SR325e earphones and caution anybody inside earshot (they’re somewhat cracked).
Flowing’s Masters Essentials playlists are a decent spot to set out toward a choice of MQA hello there res soundtracks and sitting back to listen we end up immediately brought into the music.
Pros and Cons of Schiit Audio Magni 3
|The well-balanced, smooth sound||No-frills styling and features|
|Easy to listen to|
Look at this tank. It’s particularly a work area amp – and you’ll require a sizeable work area, at that. In case you’re searching for something versatile, best look somewhere else. Yet, on the off chance that it’s home earphone listening you’re after, it could well be the one for you.
Sonically, it’s an important expansion to your home sound arrangement. It’s an excessively flawless and clean tune in – indicating submissive tender loving care with regards to the outline of the soundstage. That is an attribute we entirely respect, and few other equivalently estimated DACs portray a phase very as unequivocally as the M-DAC+.
Indeed, even the densest, busiest chronicles are spread out straightforwardly – as far as organizing, center, and sheer three-dimensionality, the Audiolab hands out the subtleties like a saloon tattle.
Include phenomenal forces of association and a cadenced affirmation that a couple of can coordinate, and you have a strong earphone intensifier that legitimizes the cost.
The Features of the Audiolab M-DAC+
It’s been ‘plussed’ regarding detail, as well. The coaxial and optical computerized contributions (there are a couple of each) can deal with 24-bit/192kHz hey res music records, and the USB type-B attachment is useful for documents as powerful as 32-digit/384kHz.
There’s a USB type-An association for Apple items (iPhones from 5 onwards, iPads from theMini 2) and an AES/EBU adjusted advanced contribution for those with support of studio desires.
Yields incorporate sound system RCA, normally, a couple of XLRs, coaxial and optical advanced, and a 6.3mm earphone attachment. Also, the M-DAC+ is prepared to deal with DSD sound as well. So while it could pretty much consider administration to be a work area gadget, it’s prepared to space into full frameworks, enormous or little.
The first M-DAC was a tweaker’s heaven, with no less than seven-channel settings accessible. Each made an unobtrusive however clear acclimation to the sound, and viably delivered the M-DAC a significantly more bespoke suggestion than its ostensible adversaries.
For the M-DAC+ the channel tally is up to an overjoyed eleven, the extra four choices applying to DSD sound.
One region of the detail that remains unfalteringly unfiddled-inside the M-DAC+ is simply the DAC chipset. The ESS Sabre32 9018 remaining parts are very much respected and are thus extended unaltered from the M-DAC.
Pros and Cons of the Audiolab M-DAC+
|Extensive spec||Could use more attack|
|Fine build and finish|
|Organized, tidy, expansive listen|
Final Verdict of the Headphone Amplifier for your Smartphone
The fundamental need when aggregating this rundown of 2020’s best earphone amps was sound quality. There is no reason for having a decent arrangement of earphones on the off chance that you are joining them to a substandard speaker. That said various elements became possibly the most important factor when we were picking our suggestions.
Highlights and availability were significant during our amp tests and a considerable lot of the units recorded beneath have various highlights or plans that may be useful to various purchasers. As enhancer innovation has progressed we have seen numerous models incorporate additional availability choices, for example, adjusted yields and EQ usefulness.
Cost is another thought that assumed a major function as there is where a few units didn’t get included because they didn’t show improvement over another amp yet cost altogether more money. The incentive for cash I believe is imperative to everybody and at one point the theory of unavoidable losses kicks in and it’s difficult to suggest certain models.
At long last, form quality and configuration merit considering. If something will be perched around our work area, I don’t simply need some sort of monster. I don’t should be all extravagant accessories yet somewhat thought going into the tasteful goes far.
Last update on 2021-01-18 / Affiliate links / Images from Amazon Product Advertising API