The Rx’s sound stage is pretty wide and there’s a good amount of air around the instruments. Not that it’s an overly airy amplifier though, everything sounds very coherent. The Picollo doesn’t have this spacious feeling to it, at least not as much as the Rx. Detail retrieval on both amplifiers is very good and they both have great clarity. The Picollo to me has the edge on clarity though and its background is even blacker than the Rx’s. Both amplifiers are very dynamic but here the Rx is clearly the winner, same goes for speed. In other words, dynamics are really good with the ALO amp and it’s the faster sounding amp of both.
The Rx’s bass is just right for me: it’s not a bass head’s amp but it isn’t bass shy either. It’s right in between and it has a nice punch, good depth and good body. Bass is tighter and faster than Picollo’s bass but that last one has slightly more body and impact to it. I really like both types of bass and it basically comes down to the type of music I’m listening to and the quality of the recording. It’s not that the bass difference between both amplifiers is huge but the differences are clearly there.
The mids section is where the biggest difference between both amplifiers is. The Rx’s mids have more body, are more detailed, smoother and have more air in them while they kind of sound tighter and more basic on the Picollo. They just have less timbre than on the Rx. It’s clear the Rx’s mids are more musical and flowing or smooth as you might call it. At the same time there’s so much happening that I sometimes find the mids to be more fatiguing then on the calmer Picollo. I do prefer the mids on the Rx but I can listen to the Picollo for longer periods it seems. The Picollo from its side, focuses more on the upper mids making them sound more forward then on the Rx.
Treble is fairly extended and is nicely sparkling. It’s never bright or harsh and it’s got good detail. Just like the mids the treble has an airy feel around them. Picollo’s treble is comparable but the mids here have a bit less air and just like the higher mids they’re more forward sounding. Overall that makes the Picollo the more forward sounding one. Picollo certainly isn’t an aggressive amp but it do is more aggressive in the higher mids and treble than the Rx is. I should really call it more “pronounced” rather than aggressive. You’ll mostly notice that with guitars and vocals.
The Rx produces the smoothest and most coherent sound of both amplifiers. Bass, mids and treble just flow smoother into each other than on the Picollo. On the Picollo the bass, mids and treble are more separated from each other. Both amplifiers sound great though and our review of the Picollo was a very positive one too. The amps just sound different and I found myself switching back and forth depending on the song playing on my DAP.
Nathan would call this the “Meh part”. I call it room for improvement
Besides the two earlier points about the placement and size of the volume pot, there are some other things that kind of bother me a bit. First off, I prefer the volume pot of the Picollo: it’s bigger, it’s wider and as a result allows better volume fine-tuning. On top of that Picollo has 3 gain settings.
In general both these IEM specific amplifiers are dead quiet and without floor noise but there always are exceptions. One of them is when you’re using a really sensitive balanced armature earphone like my Earwerkz Legend R. It is so sensitive that you can even hear hiss from the Rx. The question of course is whether this is the amps fault or the monitor’s. In most cases you won’t hear any noise though, and you shouldn’t worry about this at all. ALO tested it with a whole bunch of earphones, but they of course can’t test them all. I just want to point out that you will hear noise with a very limited number of BA monitors, that’s all.
Just a few more words on noise: some people hear it and some don’t. Those who don’t of course can’t see what the problem is and it most of the time leads to useless Yes-No discussions. In general I think consumers have become more sensitive to noise, especially with the increasing popularity of custom balanced armatures monitors. Nathan and I absolutely do not like gear that hisses. I myself always listen at very low volumes and it’s awful when you, during silent passages, can hear background noise. Gear nowadays (and especially at the prices they’re going for) should not hiss. Ever. But back to the Rx.
Matchability & Conclusion
The Rx paired well with all my DAPs but for some reason I liked it most in combination with the iBasso DX90 running the Lurker Firmware. The Rx, unlike the Picollo, doesn’t really manage to drive full sized headphones like the HE400i or other. It’s really built for IEM amplification but I did get good results listening to easy to drive headphones like the B&O H8, Philips L2, X2 and Beyerdynamic COP in example. I however wouldn’t buy it specifically for full sized headphones, focus on your IEMs. My favorite one was the CustomArt Harmony 8 Pro, which I find to compliment the Rx’s characteristics best.
Based on the description of the sound above, you should be able to judge if the Rx will compliment your monitors or not. You should in example opt for the Picollo if you prefer/need more bass body and the Rx would be ideal if you’re looking for a faster sounding very musical amp with great mids.
The Rx is great for use with IEMs: it is pocket friendly, well built, looks great and sounds really good. If you’re not very happy with how your source sounds right now or your DAP just isn’t powerful enough, the Rx might be exactly what you’re looking for. I’ve even been using it in combination with the Chord Electronics Hugo when I was listening to some of my IEMs. Not that the Hugo couldn’t handle it, but the typical Rx sound just is so nice to listen to.
The Rx is available directly from ALO Audio or via one of their dealers. Price is $299 or $349 USD. That’s only $299 for a very good sounding amp and you even get the $149 Green Line cable with it, that’s impressive. If you have a quality set of earphones you almost owe it to yourself to get them good amplification. For this price you should have been ordering it already!
Lofthanza Art
Nice review, thanx!
i wish one day you could write an article about amping in general. What does it do? How much do different amps in different price ranges differ in sound quality? When would someone need an amp? And so on …
For example i have the philips X2 and the ibasso DX90 and i use them together, i clearly dunno if i need an amp or not, coz the DX90 provides me with enough volume. Am i not doing the X2 justice with the DX90 alone? Should i add an amp in the chain? If yes, then please two questions, what amp would you recommend (under $300) , and what sound improvement should i expect coming from the DX90 built in amp?
Thanks!
dalethorn
Here’s a summary I wrote 2 years ago, and looking over it now it’s still pretty much accurate. There’s a LOT to this so go slowly….
http://rockgrotto.proboards.com/thread/9303/introduction-portable-headphone-amplifiers
Lofthanza Art
Thank you! A very helpful summary.
should i understand that the performance of usb dac/amps usually degrades in higher volumes?
dalethorn
There are many ways the sound can degrade, of course. Now the DAC is designed to send its output voltage into an analog amplifier, which may be built into the same enclosure as the DAC. If the DAC has one of those “internal volume controls” that’s controlled by the host computer, then all bets are off, because I can’t say what’s happening where. Today you could have a system volume control, a music player volume control, and a volume control on the amp – all 3 live at the same time. Someone will say “set two of them to maximum and the other you use to control the volume.” It sounds good in theory, but that’s no guarantee it’s the best method. You have to experiment. BTW, you can buy a combo DAC/amp in one enclosure, but the amp might be inferior to the DAC. Or you could buy the best separates, but they might have the wrong synergy. You can experiment yourself, or trust certain reviews. Whatever you do, if you buy a separate DAC and amp, get the best and the shortest interconnect cables you can find. Keep the contacts of the cables and the DAC and amp very clean. If you can, open the DAC and amp and make sure they’re clean inside. If they have removable internal connectors that aren’t permanently soldered in, you may want to clean those occasionally. If you can run your amps from a battery, by building a battery cage to get the right DC voltage, to replace a “wall wart” etc., that can improve the sound.
Traveller2225
Hey Dalethorn I dont know why I didnt think of asking you about this question, I was considering the Alo RX IEM version for my Fidue A83 for my Hybrid in ears, but I also am going to be receiving the Sound magic HP150 which I got on sale for around the house and when I travel from CT to MA. Would this amp power and or drive them well ? or do you have a recommendation maybe a couple portable amps that I could pair wth the dx90 for the Sound magic hp150. thanks a lot for your times and happy new years
dalethorn
I think the E12 would be good for having more reserve power for full-size headphones, since my headphones seem to “breathe” easier when they have extra power for dynamics. But the E12 is pretty much entry level only for sound quality – but then again, for portable use you might not appreciate the finer detail of the better small amps. The thing is, in most of the DAC/amp combos, the amp is the weakest link. The 2 best portable amps I’ve had are the Portaphile Micro and the Decware Zen Head, and you see the reason when you’re paying $400-$500 for a separate amp. But I still like the E12, especially for the form factor. I use mostly the Oppo HA-2 now, which is the same form factor, but it includes a DAC, and probably doesn’t have as much power as the E12. The E12 has been out long enough, that I wish FiiO would come up with a newer better version, with the same form factor, but a higher-fi sound. I also use the FiiO E17k now when my Oppo is down for charging.
Traveller2225
Hey Yeah I can understand for the form factor and price. I do have some decent audio portable amps. One being the Meier 2move, and the other being ibasso pb2. I was leaning towards the pico slim or the Fiio e12A which is based of the off the E12diy edit. taking the most popular setup as far opamp and buffer and making an iem edit with the e12A. I am leaning towards that or the pico slim, because I use mainly IEMs away from my pc( earsonics sm64v2, fidue a83, and will use the 32 ohm sound magic 150).
dalethorn
Last time I saw the Pico Slim it was very pricy.
Traveller2225
Someone is selling on for just over 200 i believe. it is still pricey normally. I dont mind buying and or trading secondhand though.
dalethorn
If it’s used or refurbished, then you’d need a paypal guarantee of satisfaction, and if it has a built-in rechargeable battery, you might need to replace that. When I sell used gear for example, there’s no returns, so you’d have to know what your options are….
Headfonia_L.
thanks. Read Dale’s article first.
Amps tend to get the best out of your headphone, “audiophile” headphones often need more power and current than DAPs can supply so that’s why there are amps basically.
Not all headphones need them, but in case of the X2 you could expect more extension, and a tighter bass in example
dalethorn
Definitely for the X2.
Lofthanza Art
Thank you!
No specific amp recommendation for the X2? Something i can use with the DX90. It can be portable or desktop, coz sound quality is what matters here, but budget is $300.
Headfonia_L.
D Zero / C5 / And a lot more
Brett
Excellent review, as per usual!
It would be interesting to see how this will pair with the new AK JR when it is released.
Out of curiosity, not practicality, would it be able to power Grado P500’s as they are fairly easy to drive?
Headfonia_L.
Thanks Brett. I don’t have the P500 so I wouldn’t dare confirm, sorry
jeff k
i think it would be useful to compare the dx90+alo rx to the dx90 alone. why add an amp when the dx90 has one built in? especially in the case of iem’s, there’s no need for more power. so what’s the external amp adding beyond the dx90’s own amp? i’m not saying that there’s no case to be made, but i’d be interested in seeing that case made.
Headfonia_L.
Sound quality is just better with more power. + With an external amp you could change the sound signature if you’ld want that
jeff k
1. a comparison of the alo’s power with the dx90’s on various gain settings would provide useful context.
2. so would a comparison of sound signatures.
i appreciate being able to read reviews like yours, so i’m not trying to be negative, but to say what would make it even more useful, at least for readers like me. i think the comparison with the cypher is useful, as that’s a comparable piece of equipment, but the other competition to the alo rx is not buying any amp at all.
Headfonia_L.
I see. We don’t really do numbers on HFN very often, besides if the Rx and DX90 numbers are public, you could easily compare them yourself 😉
You won’t easily see comparisons of DAPs to amps anywhere, as they can’t compete in the currrent/voltage section
Just my opinion of course
jeff k
i can see the dx90’s output on e.g. high gain reported as 2.8Vrms and the alo rx’s as 15V [extreme value, presumably, not rms], but what i don’t know is how that affects the sound, especially listening through iems, not cans. unfortunately, most of us don’t have the opportunity to audition equipment, so we rely on the descriptions of others.
ohm image
Jeff, I will be happy to supply RMAA and square wave measurements, but I’ve had some problems with RMAA recently on Yosemite. I had meant to publish all my measurements until this point but have had no end of problems.
BigC
Hi Lieven, is there a desktop equivalent to this amp in the same price range you would recommend to power a Nuforce Primo 8. I’m currently running this iem straight out of a HRT Microstreamer and the headphone output is very noisy.
Headfonia_L.
Maybe Fiio E12A?
Traveller2225
I thought the Fiio E12a was a portable amp as well? I am actually deciding between the two amps. I use sensitive IEMs like the Fidue A83 and my will be using the Full size headphone soundmagic HP150 which is 32 ohms. Do you feel like if one was getting the Fiio E12a for 125$ would it be worth going up to the Alo RX Iem version performance wise?
just_pch
How long is the battery life on the RX? Would you say it would be better to get the Fiio X1 + RX combo compared to an all-in-one solution like the Dx90 on its own?
Vaibhav Pisal
hello headfonia,
i am looking at one of alo amps for iems. how would rx compare to alo international plus only for iems if you tried both? is there a performance gap or both in same level? if performance is similar I might go for international plus.
both are similarly priced but international plus is in warehouse deals so is likely used and no warranty. but it does have useful extras like power for full sized cans, dac and balanced out.
also will international plus be able to power sennheiser hd700? for reference i recently used mojo and felt they needed more power. bass was not present as was with other easier to drive hps.
but my priority is iems. for 700 i have rig sorted and have other things in mind.
thanks in advance