Quote:
Originally Posted by
Headzone 
If I just read the specs right, this has better/quite similar measurements compared to O2?
MAGNI specs (Click to show)Frequency Response: 20Hz-20Khz, -0.1db, 2Hz-200KHz, -3dB
Maximum Power, 32 ohms: 1.2W
Maximum Power, 50 ohms: 1.0W
Maximum Power, 300 ohms: 260mW
Maximum Power, 600 ohms: 130mW
THD: Less than 0.005%, 20Hz-20KHz, at 1V RMS
IMD: Less than 0.007%, CCIR
SNR: Greater than 100db, unweighted, referenced to 1V RMS
Crosstalk: -70dB, 20 Hz-20KHz
Output Impedance: Less than 0.1 ohms
O2 specs (Click to show)Frequency Response +/- 0.1 dB Excellent
Max Output 15 Ohms 337 mW Excellent
Max Output 33 Ohms 613 mW Excellent
Max Output 150 Ohms 355 mW Excellent
Noise (ref 400 mV) -105 dB Excellent
Output Impedance 0.54 Ohms Excellent
IMD SMPTE 0.002% Excellent
Crosstalk 15 Ohms 65 dB Excellent
Even among people who philosophically care about the measurements, many will say past a certain point, certain parameters are mostly meaningless. This is just a snapshot of performance, as well all know. Test conditions are often different, so results that look comparable are not necessarily comparable, or they need some adjustment.
Okay, but caveats aside, as an intellectual (and practical, to some degree) exercise, if we trust that their respective testing is all correct...
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- Magni has higher max output power. Note that double output power gets you 3 dB louder volume, which is not a whole lot, so differences may not be as large as they seem to some people. If the actual output level you are using is under the amp's max output power, then there's no difference to you. e.g. if you're using 10mW, which is already a lot for many headphones, it doesn't matter if the amp's capable of 50 mW or 5000 mW. Higher max output power is a good thing, except if you get careless and accidentally fry your IEMs or sensitive headphones with the extra power. (hopefully with them not on your head) That said, many people would be surprised at how little power they actually use for most headphones in normal listening. If 600 mW is not enough for any 32 ohms headphones you own, for example, I don't know what to say. The real test is around ~50 ohms for certain planar magnetics models like HE-6, where the output power levels for both amps should be similar, with the Magna ahead by some 1 dB or so, not a huge deal. NOTE: you would want the higher-spec AC/AC adapter in that case for the O2. But at what distortion levels?
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- Noise for Magni is quoted in SNR, referenced to signal level of 1V. If you do the same for O2, that's -112 dBV unweighted on AC power, even better than that by a tad at lower volume, so the O2 has the advantage. Some people ridicule the O2 for being unnecessarily noiseless at the expense of usability, and I might agree. For the majority of the situations, you're not going to hear the noise floor of the Magni, so it's a moot point. For the most sensitive IEMs, it could be a different matter.
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- Output impedance is less for Magni, which is generally considered better for most headphones and IEMs. But around 0.5 ohms is not going to cause any significant difference for any real-world IEMs, much less most headphones.
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- Crosstalk may vary by load impedance. -65 dB is for 15 ohms on the O2. It's -91 dB for 150 ohms, for example. So it's hard to say without knowing more about the Magni, but all in all, I wouldn't think this level of crosstalk would bother anybody, so it's a moot point.
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- Distortion figures vary by load impedance, frequency, and output level. So THD and IMD figures are not necessarily apples-to-apples comparable unless the testing regimes were the same. A design with presumably more feedback (the O2) should probably have better distortion numbers as load impedance is lowered and output level increased, so I would guess there are probably situations where the O2 does better despite the couple listed numbers looking similar. Check the graphs at that place for more details on O2 performance. There are some different ideas (warranted or not? you decide) among certain audiophiles and designers regarding distortion and feedback, never mind distortion levels that are relevant for headphones listening, so take that as you will. Take a trip to InnerFidelity or wherever else and look how much distortion the headphones themselves are responsible for.
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- Frequency response is comparable, so given the wide range for the Magni, the phase response is probably comparable too. Anyhow, these should be plenty fine for both amps.
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- Note that the O2 has a gain switch, which is useful for switching between headphones or IEMs of significantly different sensitivity, while the Magni is fixed at 5x. That 5x may be inconvenient when using sensitive headphones and IEMs. The O2 also clips inputs no matter what the volume is set to, if the gain and input level are too high, which is a usability liability to the uninitiated. As for other issues of aesthetics and features, I think those are obvious enough.
For that matter, Tyll has a JDSLabs O2 on his bench; maybe a Magni is in the future, so sometime later you may see a comparison using the same test gear, for whatever that's worth.
Anyway, hopefully this is as good as it seems and can be frequently recommended as a good, cheap all-around amp.
Edited by mikeaj - 12/12/12 at 1:21pm
