Except for the RHA Dacamp L1, the CL1 was tested in single ended configuration with this collection of portable amplifiers. Source is the AK380 and my laptop for the DragonFly, Mojo and Hugo 2.
The Fiio A5 is an easy amplifier to recommend to those on a budget as it has two gain settings and Fiio’s typical Bass Boost. The A5 with the low gain setting is powerful enough to drive the CL1 and without the bass boost function you get a neutral and clear presentation where bass has neutral impact and body. From bass to highs the detail level is there with good extension overall. Focus is on the upper mids and treble section with more forward sounding vocals. With the bass boost on you kind of ruin the curve of the CL1 with exaggerated and looser bass. I prefer the A5 and CL1 combo with the boost turned off but for some people the neutral bass presence might be too light for their liking. The left/right separation is impressive in this combo.
The ALO RX’s volume dial goes up a lot further than usual. Bass has good presence and it is there when called upon. Bass is tight and fast. The mids are a little more to the back and the upper mids and treble are more forward sounding. Vocals are more upfront but fairly natural sounding. Layering from bass to highs is very nice. With ALO’s tube powered Continental V5 you get an even richer sound but bass is not there as much as with the Rx. The mids are better though with more body and that’s making the voices sounding more natural as well. The tube smoothness does help to make the treble somewhat smoother and easier to listen to. I quite like this combination.
The Cypher Labs Picollo is one of my favorite portable amps and it controls the CL1 on the lowest gain setting with authority. The piccolo, compared to the ALO amps, makes bass sound bigger with more impact. The overall speed and presentation is clean and clear but a little slower. The mids are very rich and layering from top to bottom is great. Voices sound very natural yet a little warmer and treble is nice extended, yet less soft than on the CV5. With its big brother, the Cypher Labs Duet, the CL1 sounds more neutral but more spacious with even more detail. The Duet also makes the CL1 sounds faster and cleaner. Bass has the right amount of body and impact, the mids are neutral but greatly layered and musical. Treble is extended and energetic and all that on the lowest gain setting. The voices sound a little less warm and more neutral than on the Picollo. This amplifier is the best on technicalities but I’m sure many of you will prefer the warmer and thicker sound of the Picollo.
The AudioQuest DragongFly RED(Roon compliant!) makes the CL1 sound incredibly rich and musical with great layering from top to bottom. Bass is on the bigger and maybe looser side but it’s got great depth. The mids have good body and are very detailed and musical. Treble has a lovely energy and this simply is my favorite source for the RHA CL1.
The extremely popular Chord Electronics Mojo makes the CL1 very clean, fast and clear sounding with great dynamics and detail. You get the typical top quality sound the Mojo always delivers with tight and impactful bass, rich mids and energetic treble but I’m missing a little bit of warmth, body and smoothness here which the CL1 clearly can use (and which the DF delivered). Mojo makes it sound more digital but in the best possible way. If you’re a big fan of the Mojo, you’ll for sure love this combination.
Comparisons (RHA family + same price level)
The RHA T10 has the same injection molded shape and the awesome ear hooks, but the sound is different. Compared to the CL1 the T10 with the reference filter sounds rather dark and slow and the sound isn’t as clean and precise as on the CL1. With the treble filter it clears up somewhat but it nowhere is near the level of the CL1 in clarity, precision, speed and detail retrieval. I actually had a hard time listening to the T10 after all the my time with the CL1. The identical RHA T20 with the reference filter sounds a whole lot more clear but it also has thin mids and forward vocals. The T20 with the reference filter is faster and cleaner sounding than the T10 but it’s not at the same level of as the CL1. With the treble filters the T20 comes closer to the CL1 performance but the precision, clarity and speed of the CL1 is just at a higher level. The CL1 just sounds more natural when properly driven (in this test by the Hugo 2).
Then Etymotic ER4-series is famous for its neutrality, detail and precision and I recently wrote a very positive review of them. And actually the CL1 comes very close to the sound signature of the Etymotic IEMs. The main difference to me is the treble section sounding easier on the ear and the ER4’s have a more spacious presentation. Body wise the CL1 is the biggest. If you like the ER4-series, the CL1 will certainly be close to what you like listening to.
The Radius HP-TWF41 also got a positive review but the sound signature is completely different. Where the CL1 is clear and fast, the Radius is slower and bigger in body. It has much bigger bass, soft voices and very easygoing treble. Compared to the CL1 one could describe the Radius as thick, slow and bassy. They’re that different, and yet the Radius sounds awesome as well, in its own way.
Edit: iSine10 will be added soon!
The RHA CL1 looks gorgeous, is perfectly build and sits very comfortable in the ear. There’s no denying that the RHA CL1 has a focus on the higher mids and treble but that somehow doesn’t surprise me looking at how RHA evolved between with the MA600 and this CL1. It might not please everyone but personally this to me is the best sounding RHA IEM when properly powered.
Power is needed though as the CL1 is a rather hard to drive IEM. The RHA L1 does a great job doing that but my personal favourites are the AudioQuest DragonFly and the Alien+ DAP from Shozy. The CLA sounds even better in balanced configuration but unfortunately RHA chose the mini-XLR connector which limits using it with other gear in balanced mode.
The CL1 has a very specific tuning that won’t please anyone but once you’ve gotten acquainted with its unique sound, it really keeps drawing you back to it. At this price level (€449)/$449) there is some serious competition however (like the Etymotic ER4-series) but if you’re willing to carry around an amp and love a very clear, precise and detailed sound signature with a focus on higher mids and treble, than you should audition the CL1 at a shop near you.