Due to a high impedance of 182ohm and low sensitivity of 93dB, RA is not easy to drive. But it wasn’t just the power output of the source, but the actual source and the synergy of its pair up with RA. There were a few surprises, for sure, but after every pair up I returned to SP1000 SS as one of my favorite sources. Obviously, a subjective opinion and a matter of a personal taste.
A&K SP1000 SS (fw 1.08) – holographic soundstage expansion on a level of open back headphones. The sound is fast and the signature is more mid-forward with a very neutral transparent tonality. Bass is extended, deep, very neutral, articulate and multi-layered. Lower mids are lean while upper mids are very transparent, layered, micro-detailed, a little cold, literally on analytical level but not harsh at all. The same with a treble which extends far, very crisp and sparkly, super resolving with a vivid definition thanks to its 12k peak, but it’s not sibilant or harsh or fatigue. A slightly smoother treble control of SP1000 SS (keep in mind fw1.08) allows to push RA to its full potential without being harsh and while remaining super transparent in tonality and very fast in transient response of notes on/off. Just keep in mind, if you want more bass, you have to apply the tape mod.
Following pair ups will be based on a relative comparison to SP1000 SS which I used as a baseline reference.
Sony WM1Z (fw 2.0) – equally holographic open soundstage. The sound sig is still mid-forward, but I hear a more textured rumble in sub-bass extension. Bass is still neutral and fast, but sub-bass has more rumble in this pair up. Lower mids are as neutral, and upper mids have just a little more organic tonality. The big change here is a treble which becomes too crisp and borderline harsh. It gets even worse when you switch to high gain. Of course, this is a matter of a personal taste, where those who prefer more treble energy will enjoy this pair up more than SP1000 SS, but if you are more sensitive to crisp treble, I would suggest trying other sources.
iBasso DX200 w/AMP4 – very wide-open soundstage, though not exactly at holographic level. Sound sig is mid-forward, bass is very neutral, lower mids are lean, while upper mids are transparent, layered, excellent retrieval of details. Treble is crisp and has a nice sparkle, a little smoother than WM1Z, but not on the same level as SP1000, rather somewhere in between of these two. One thing I did notice is a bit less transparency and the speed of the sound being a touch slower.
iBasso DX150 w/AMP6 – very similar to DX200 w/AMP4, except here the upper mids are a little smoother and overall sound is less transparent and not as layered.
A&K AK120ii – soundstage is wide, but not as wide or open as with DAPs above. Overall sound signature is a little more balanced, mids are still forward but sub-bass has more rumble and mid-bass has a little stronger punch. Lower mids are neutral, yet showing a sign of a little more body, and upper mids are a little warmer as well. Treble is crisp but has more control, like with SP1000. While the tonality in this pair up is more ear friendly, the technical performance is not at the top of the game since I’m hearing less transparency, less resolution, and the sound being a little slower.
Lotoo PAW Gold – soundstage is on a holographic level. The sound sig is a little more balanced now thanks to more rumble in sub-bass and stronger mid-bass punch, mids have a great transparency and layering, have a little more body and a touch warmer in tonality. But the treble is back to being crisp and harsh, like in WM1Z pair up. Also, switching to high gain doesn’t help here. Treble has a lot of energy, very crisp, but if you are more sensitive to highs, this pair up not going to please your ears.
Cowon Plenue 2 mk2 – soundstage is wide, but not on a holographic open level. While sub-bass has just a touch more rumble, sound signature still has a more mid-forward presentation. Bass is neutral, fast, articulate. Lower mids are lean, upper mids are a little smoother, very detailed, but not as transparent or layered as SP1000. Treble is crisp, well defined. This is a good pair up, but it didn’t feel like it was pushing RA to its absolute best performance since the sound wasn’t as transparent or layered.
Hiby R6 – while the sound signature in this pair up is the most balanced I heard, the resolution and the transparency of the sound lost its magic here. The sound is smoother and less fatigue, but technically it’s not pushing RA to its best potential. Coincidentally, R6 has the highest OI (10 ohm), but it doesn’t have the best synergy.
theBit Opus#2 – soundstage is wide, but not as holographic or wide open. This pair up has a nice transparent sound with a little more rumble in sub-bass, a touch more body in lower mids, nice transparent detailed upper mids and crisp treble, under more control, like in SP1000. But in this pair up the transparency and the layering of the sound wasn’t as great, and resolution wasn’t as high compared to SP1000.
Using SP1000 SS Line Out, I tested the following amplifiers, or only their AMP section:
Audeze DECKARD (amp section) – keeps the transparency, resolution, and layering of the sound. Adds a little bit of rumble to sub-bass, while overall sound sig is still mid-forward. Also, adds more crunch to the treble which makes it a little harsher. Soundstage is as holographic
XIaudio Broadway S – keeps the transparency, resolution, and layering of the sound, and the soundstage is as holographic. The sound sig is still mid-forward, while I also hear a little more rumble in the sub-bass. Treble is very similar when in low gain, but in high gain it becomes a little harsher. I preferred this pair up over Deckard.
Though both amps (DECKARD and Broadway S) are great and offer a very transparent performance in this pair up, I didn’t find them to offer a significant improvement over SP1000 SS. But when using other DAPs, especially those where I found treble to be a bit hot, the Line Out pair up with Broadway S got the treble under control and brought the transparency and resolution back into play.
iFi iDSD BL (amp section) – soundstage is close to holographic level. Signature is still mid-forward, but I’m hearing more rumble in sub-bass and a little more noticeable punch in mid-bass. Mids are transparent, very detailed, not as cold as the SP1000 source, treble is crisp but not harsh. I like this pair up because it added a little bit of coloring to the sound without affecting too much the resolution and layering, and it gives the sound a more natural transparency.
Cayin C5 – didn’t expect this to be my favorite portable amp pair up! Soundstage is holographic on a level of open back performance, not exaggerated, but very wide and with non-artificial out-of-your head expansion. Sub-bass got a warmer more textured rumble, while mid-bass punches a little harder here. Lower mids are neutral, while upper mids are still transparent and highly resolving, but they got a more natural tonality, and treble is crisp, airy, and under control. When you switch C5 to high gain, the level of transparency goes up which I suspect due to me lowering the volume, perhaps bringing this little amp to a more linear (less saturated) gain region. I also tried the bass boost of C5, which add more warmth to the lower end region of the spectrum, including more body to lower mids, but that affected the transparency of the sound which I didn’t like. So, C5 with high gain and bass off was my ideal setting in this pair up with SP1000 SS.
Oppo HA-2 (amp section) – soundstage is wide, not as holographic or open. The sound sig here is more balanced due to more sub-bass rumble and stronger mid-bass punch, but overall sound became a little less dynamic, a little flatter, and lost some transparency and resolution. Switching to high gain didn’t help. Also, bass boost muddied the sound with thicker lower mids. This was my least favorite pair up.
FiiO A5 – soundstage is wide, not as holographic, but I still hear a more open back sound performance. Sound sig is more balanced with warmer sub-bass rumble, a little stronger mid-bass punch, though bass is a little less articulate in this pair up with overall sound being not as fast. Unlike HA-2, the sound is still dynamic, but a little more colored, less transparent and not as layered. Switching to high gain helped a little bit with transparency and less coloring, but it was not as resolving as the original SP1000 sound. Treble was crisp and under control, but I felt that I wanted a little more sparkle to bring back some airiness. Bass boost made the sound muddy, I wasn’t fan of it. Overall, this pair up wasn’t my favorite either.
oBravo RA-C-Cu review took me longer than expected to finish because I spent a lot of time analyzing this IEM. Plus, I needed additional time researching and testing different sources, considering replacement cable, and going through a massive eartip rolling. This is not an ordinary IEM, thus not a simple review. RA has a unique technology which is exclusive to oBravo and stands out from other IEMs, and it comes with a premium price tag that will probably keep it out of reach of many audio enthusiasts. It’s certainly not for everyone, and just like with any other IEM or full-size headphones, there will be people who going to love its sound and others who don’t.
And just because it has a premium price tag, doesn’t make it automatically the best IEM since at the end of the day the real question is if it’s the best IEM for you, if it hits your sweet spot, and if you are willing (and able) to pay for it. I hope that maybe down the road oBravo would consider using its 2nd gen AMT-II driver in other EAMT models, scaled down with smaller DDs and aluminum shell design. I think many audiophiles who prefer a super transparent crisp fast sound with a soundstage expansion of an open back full-size headphones will enjoy this IEM and will appreciate if there is a scaled down and more affordable version available in the future.