Trends PA-10 Tube Headphone Amplifier Review

"Whoa, wait a moment. Are you saying that the characteristics of this device permanently alter after a few hours of use? Or are you saying that, after a bit, you get used to it?"

The first and second are probably true.

I've found the more expensive a piece of audio kit, the long the run-in time required for it to sound it's best is. My speakers, amp and CD player took about a month to hit their best. Then again, my Focals are known to have a long run-in period.

Equally as well, it takes a while for your ears to get used to the extra detail when you move up to better kit.

I think the “audiophile” community is slightly oversold on headphone amps; you can’t improve the quality of the signal generated by the output stage of your source, simply by adding an extra amplifier, not in any objective sense. What you’re really doing is re-EQing the sound (often something perceived to be a sound quality change – subjective sound quality if you like). And I’m afraid the scientist in me has an almost allergic reaction to bull**** audiophile terms like “presence” and “richness.” No offence – it’s a good review – but we’re perilously close to espousing the virtues of chocolately, laid-back, liquid-honey music ;)

The truth is, even big over-ear cans are comparatively easy things to drive. Portable devices might struggle to generate sufficient voltage to make high-Z cans go loud enough for you, and that would constitute good reason to get a headphone amp. Notebooks shouldn’t struggle, I wouldn’t have thought. They might have bad bass roll-off, or a crappy frequency response in some other capacity, but sticking another amp on their output isn’t going to improve that noticeably – your headphone amp can’t amplify a frequency which isn’t there. In one sense, low-Z cans represent a more difficult prospect for an amplifier, since they draw more current (present a greater load). Indeed, RMAA tests with one DAP show better freq response with higher Z cans (http://rmaa.elektrokrishna.com/Comparisons/Comparison%20-%20Cowon%20D2%20-%2012%20-%2048%20Ohm.htm). And then it comes down to a question of volume: if your source can drive your cans to an acceptable listening volume for you, then a headphone amp is not going to improve the objective quality of the sound you’re hearing. So a cost effective compromise is to go high-z to improve freq response, but not so high you need a headphone amp. Or, use your low-z cans with a headphone amp, just to try and flatten the f-response a bit. Who knows if that will work though. Surely it would depend on the impedance of the headphone amp, as it appears across the output of the portable?

There is one caveat I can think of however, and that’s if your portable source is producing that “acceptable” volume at a high fraction of its possible output volume. The freq response of the source may not be consistent throughout the volume range. You may get more bass roll-off because there isn’t enough charge left stored in the power-stage (capacitance) to support bass/drum hits, big dynamic swings (I believe these are referred to collectively as transients) at high volumes. Adding another amplification stage effectively splits this load. I just built a CMOY headphone amp for my brother, and you can add nice big power/input caps to support swings/bass at higher volume. Portable devices physically can’t include caps the same size. Then you can turn your portable down to a level at which it produces its optimum f-response, and crank the headphone amp, which has the electrical design to support those dynamic swings at high volume. It’s always a fairly safe assumption that something will behave closer to an “ideal” design at a lower fraction of its operating capability.

Of course, all that said, a tube amp will sound different because it’s a different technology. If you want a tube sound, a tube amp is the only way you’re going to get it out of a portable.