The following is the review I did in the past for earmass.com, so I'll just copy and paste it into here, simply because it's mine, haha XD
Side by Side
(From left)BTG,Bos 4 and BOS3LE
O2 Amp comparisons:
Summary: Both sounds just about the same, no difference in sound signature is detectable, difference mainly in builds and size
JDS Labs : Smaller housing, better volume pot and jack qualities, power and gain button spacing is tighter, volume easier to control because of its tightness.
Leolabs: larger housing, cheaper rate for purchase, jacks not as tightly secured as JDS used, no branding on the unit at all, it’s a DIY after all. Springs can be seen at the power button and gain button, revealing a slight loose house fit and volume control.
Both has the same gain amount, as they build based on the reference design.
Output cleanliness: Since both has about the same SQ, we shall compare how clean the signal passes through the amp to output. On low gain, the differences are not very noticeable, but on high gain are different. All my units are low impedance, so on a high gain, I will be able to detect which distorts sooner.
JDS: The output is far cleaner than of Leo, there are less clippings and distortions detectable. On several occasions, the whole SQ seems to be sleek and cleaner. We can’t blame the differences cause sources for components in Malaysia is not very wide, quality components are quite costly. A DIY is very hard to beat one made by companies, but a very good effort by Leo, hence for this, unless you are up for a premium price, might as well take Leo’s unit for a run. The output cleanliness is only detectable when you have sensitive rigs, which I suppose mainstream listeners tend not to have.
BTG Audio Interconnect
Build: BOS3LE has sleeving, which is a good thing, prevents damages to the cables, but tends to be harder to bend. Sleeving caused it to “remember” the position it was bent. Repairs to this cable may be troublesome, the repair will need to first take off the sleeves, and then only make repairs, then sleeve back again, in this situation, and workmanship may cost more. Silver Rean plug is used on BOS3LE which I expected on first look will be more vocalist sounding, and I was right.
SQ: The sound of this cable tends to bring the whole song more forward. It places the singer quite near the ears. What I think it outshines is the guitars, the guitar tends to sing better in this cable compared to the other cables. Since it brings in a very forward sound, naturally, vocals will sound best in this too. Pronunciations of the singer can be heard really clearly, every word can be heard well with no misses.
Build: Build wise is similar to BOS3LE, although uses silver sleeve so that can be easily differentiated from BOS3LE. Memory effect tends to be lesser on the BOS4. If BOS4 was put together with the BOS3, we can see that the BOS3 bent more than BOS4. Gold Rean plug, which normally I expect a relatively wide soundstage and dynamics, and I might have a good feeling on this one.
SQ: BOS4 has a much better pronounced bass, but lacks separation in the bass hits when fast bass drums roll in. Soundstage on BOS4 is an A+ on this, feels something like a small hall, echoes are slight longer and lasts a bit. Vocal on the BOS4 is slightly laid back and mix into the songs together, overall what can I say is this is slight balanced, so you hear everything, and nothing pops out from the crowd. Recommended as a cable for flat EQ listeners.
BTG Audio cable is the cable I bought myself, and it has no sleeving, and yet more expensive than the other cables I have seen, excluding exotics like ALO Audio.
Build: BTG Audio build has in comparison lost to BOS due to lack of sleeve and shielding, but since mine is a right angle jack, it is more convenient to use than of BOS, and cable doesn’t need to be bent, saves the trouble of memory cable, and cable will have lesser bent pressure, so damage chances will be lower. Oxidation will be a problem with the cable, and BOS is the winner in build comparison.
Availability, Convenience and options: well, unless BOS has the option of a full series of jacks, doesn’t seem that BOS wins over BTG. BOS is easier to get than BTG, so win goes to BOS. BTG has to be ordered from the US, and payment by Paypal. With an expensive postage included, it can be a hassle to get one. The price is more expensive than BOS line up at a shorter distance, which will cause more considerations.
SQ: BTG Audio by far has the best bass among the 3, every single beat of the bass drums can be heard clearly, bit by bit, how many steps did the drum make. This will explain the clarity level of BTG. I believe that the BOS uses copper cable, and BTG is a silver one, so the cable is about details, all details will not be missed out. Vocal wise is just below BOS3LE, slightly laid back than BOS3, but not as far as BOS 4.
So Far Away, God Hates Us – A7X –Guitar, Bass, Vocal
紅塵客棧 – jay Chow – Instrumentation, Soundstage
Life of the party, Be your everything – Boys Like Girls – Vocal, Bass
Gotham’s Reckoning – Hans Zimmer – 24 bit instrumentation, soundstage, dynamics
Chicken fried – zack brown band – guitar, dynamics
JDS Labs: much cleaner output, bass is lesser, but I can feel the whole song has cleaner cymbals and distortion rate is lower.
Leolabs: well, “dirty” output doesn’t mean it will sound bad. It sounds good in dynamics and vocality, but there are distortions and clippings here and there for not pickers / really sensitive IEMs, and the “dirty” sound results in a flatter sound output too.
Side note: on normal headphones, pop sound is not apparent, but once I use the CIEM, there tends to be a slight pop on both devices, sensitivity can pick up things some cant.
Equipments: JDS O2 / Leolabs O2 + UM Miracle+ BTG Audio Cables for CIEM and also at the interconnect
In this second review, I will be using the JDSLabs amp as the focus output, so decisions can take on consistencies.
SQ: Bass is still not very well separated. Continuous bass drums couldn’t be sorted out piece by piece, vocal is more forward than I expected. Seems my first review didn’t go off course too much. Not much pronounced highs, cymbals are placed at the rear together with the drums, only make the suitable appearance as recordings should be. Instrumentations are also still brought to the forward positions, not covering the vocal, which is what people need in their music, instrumentations stay at the back, where they should be.
Soundstage: since I mentioned that almost all sounds are brought to the front, that counts into “not much soundstage to be said”.
Dynamics: Seems that there will occasionally be mix ups, where certain instruments couldn’t be taken into the suitable position, and becomes quite unsettling to the very familiar songs.
SQ: instrumentations and drum sets make a pronounced appearance, vocals take their positions really well at the middle, but not overwhelmed by the instrumentations. Continuous drums can be well separated, and I can manage to count how many hits on the bass drums did the drummer hit it. Very well balanced mixture overall. Not forgetting, the BOS4 seems to have a better gain and volume than of the BOS3, might have to do with the plugs used, gold = best conductivity = faster throughput = less resistance which finally equals more throughput
Soundstage: Can be sensed that it can project soundstage echoes to quite a distance. Echoes from the instrumentations seems to be able to be pulled longer before it ends, overall a really good soundstage offering given here. Doesn’t give a “studio” feel to music, instead is “entertaining”.
Dynamics: Compared to BOS3, there are more details revealed, and they mix in the overall music “just right amount”.
SQ: BTG has better pacing and speed compared to BOS, there is also a “unexplainable glare” it adds to the music, makes the music feel they have “emotions”, it might be due to the fact that it uses silver cable and REAN plug, the whole transparency level just won over BOS totally. Vocal is still defeated by BOS3LE, soundstage is defeated by BOS4, but others, well everything else BTG owns them hands down.
Soundstage: Although not as wide as the BOS series, it does give a sense of “hollowness” in it. My ears can roughly estimate the distance of the instrument, and how far off the echo roughly is.
Dynamics: The overall music feel is very well mixed, with placements slightly more accurate, and takes into consideration “the glare” I mentioned, it is a very nice little cable, but do consider the price, it is quite steep, ouch! For a shorter than both BOS cable, it is way more expensive than them.