The problem
I have been listening using my Galaxy Tab 7 plus Shure SE215 for more than 6 months now. Recently, I found out that Galaxy Tab 7 has overly high output impedance (25.73 ohm) which will affect the sound of my SE215, which only has impedance of 20 ohm. According to this article, headphone/earphone work best 1/8th of the source output impedance. In this case, SE215 should work best with 20/8 = 2.5 ohm output impedance.
The solution
Cmoy headphone amp has a reputation of working well along with headphone impedance from 16 ohm and above (depending on the amplifier chip and current). SE 215 has impedance above 16 ohm which fits well with this amp. From Ebay, I bought a Cmoy with OP2227 chip and powered by one 9v battery. Similar, to the famous JDSLab Cmoybb but a lot cheaper (plastic case and rechargeable battery setup).
The result (Pros)
I bought the Cmoy amp + shipping cost almost AUD 60 (same setup for JDSLab CmoyBB cost more than AUD100) and the bottom line question, is it worth it? Frankly, I would say NO based on the problem I listed above. For people who is getting a Cmoy Amp because of limited budget, I would recommend saving a little more and get a better quality amp (e.g. Fiio E11, Fiio E07K, CmoyBB).
I have been listening using my Galaxy Tab 7 plus Shure SE215 for more than 6 months now. Recently, I found out that Galaxy Tab 7 has overly high output impedance (25.73 ohm) which will affect the sound of my SE215, which only has impedance of 20 ohm. According to this article, headphone/earphone work best 1/8th of the source output impedance. In this case, SE215 should work best with 20/8 = 2.5 ohm output impedance.
The solution
Cmoy headphone amp has a reputation of working well along with headphone impedance from 16 ohm and above (depending on the amplifier chip and current). SE 215 has impedance above 16 ohm which fits well with this amp. From Ebay, I bought a Cmoy with OP2227 chip and powered by one 9v battery. Similar, to the famous JDSLab Cmoybb but a lot cheaper (plastic case and rechargeable battery setup).
The result (Pros)
- Sound improve with more detail, less noise, quieter background and soundstage widen (music sound like injected with more air).
- Analog volume control rather than digital from my Galaxy Tab, hence more fine control on the volume.
- DIY amp allows swappable electronic component such as the amp IC chip. (However, I won't put my time on swapping the amp chip.)
- Built in rechargeable battery circuit. Save time and money on getting a separate battery charger.
- Battery life - max 6 hours. Recharge is required for every fourth day (2 hours used everyday).
- Separate amp unit - not pocketable. (I put my player and amp into my backpack, not really a con for me.)
- Battery not swappable due to enclosure is screwed tight. (I might want to switch to Lithium Ion battery for longer hour listening in future)
- Plastic case - no radio frequency/EMI blocking. The amp is mean for a portable player, not for cellphone. My bad for not paying attention on this one.
- Low build quality (depends on bad luck) - loose audio socket after 3 weeks of used. Popping sound and lost of volume with a slight movement on the cable. However, it still work well as a desktop amp. Update: I have sent the amp back to the seller for repair and hope the problem will be fixed permanently. The seller repaired and returned my amp back after a week and I'm happy with the result. The volume is much better now and there is no more loose audio socket.
I bought the Cmoy amp + shipping cost almost AUD 60 (same setup for JDSLab CmoyBB cost more than AUD100) and the bottom line question, is it worth it? Frankly, I would say NO based on the problem I listed above. For people who is getting a Cmoy Amp because of limited budget, I would recommend saving a little more and get a better quality amp (e.g. Fiio E11, Fiio E07K, CmoyBB).
