The Mini^3 Headphone Amplifier

A while back, I wrote about the “Alien” USB DAC that I built together with a modest yet quite decent amplifier to drive headphones, the whole contraption being a DIY computer sound card.

This past summer, I built a newly-introduced standalone, portable headphone amplifier called the Mini3. Complete with 9V battery and built-in charging circuit, the whole thing is barely bigger than a credit card, and about an inch thick. Back then, I built the “extended runtime” version, which sacrifices raw output power – not really an issue for most people – for longer play between charges. It sounds good; very, very good, in fact, and for the past six months or so it’s been my everyday headphone amp when I’m working or relaxing.

From a DIY perspective, the Mini3 is not super exciting; there’s a very limited amount of personalization that can be done; thanks to the design and the tiny layout, everybody’s Mini3 is pretty nearly identical. From an audiophile – which I assuredly am not – perspective, the amplifier is midrange, maybe upper-midrange or even entry-level high-end, depending on one’s criteria. It’s a (large) step above a basic Cmoy amp, with a virtual power ground and active signal ground, but the outputs are unbuffered and there’s no ready or easy way to bias the opamps into “class A” operation. (Wherein, in a nutshell, they consume several times more power, for – arguably – a minor increase in performance.) For 99% of people, these aren’t really issues, and the performance is, unquestionably, quite remarkable. It is also, remember, tiny, an advantage whose benefits are not to be overlooked.

I have a lot of spare parts laying around from various projects, and I realized a few weeks ago that I had nearly all the parts to build a second Mini3. So, curious about the difference between the two, I ordered a second circuit board, as well as the chips to build the “high performance” version of the amplifier. I completed it without difficulty, and have been listening to it for a couple days now.

Lack of buffers and power-sucking class-A biasing aside, this is one nice-sounding amp. I loathe audiophile terminology; let’s just say the “high performance” version sounds discernibly different – and in my opinion better – than the “extended runtime” model. It’s not a night-and-day difference, but still quite significant, and both are dead silent, with no hiss whatsoever. If you’re thinking about building one of these amplifiers, and don’t need a really extended (16-20 hours) runtime between charges, by all means get the parts for the high performance version; the extra $5 is well worth it, in my opinion. Besides, you’ll never succumb to curiosity about how much better, if at all, the “higher end” version sounds, because you’ll have it.

They’re not terribly challenging to build, if you’re handy with electronics; everything except the two op-amps are through-hole, and while the op-amps are somewhat fiendishly delicate, they’re not really that difficult to manage. The battery snaps and the casework are probably the most challenging bits.

One thing I’ve found interesting is the way the two versions handle a depleted battery; the extended-runtime Mini3 just up and dies; one moment you’ve got music, the next… nothing. The high-performance version, on the other hand, dies a little more gracefully, if strangely – as the voltage drops below a certain point, you rapidly start to lose the center portion of the stereo mix, so that in a lot of pop and rock music, the lead vocals and sometimes drums, depending on how it’s mixed, fade rapidly away, while the guitar and backing vocals remain, with results exactly as weird as you’d imagine.

So, in a nutshell, if you want a good, small, high-performance headphone amplifier that you can build yourself, seriously consider the Mini^3. Good things really do come in small packages…

Published in: Geekiness, General | on January 21st, 2008| 1 Comment »

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One Comment

  1. On 1/24/2017 at 3:19 am Guitar Headphone Amp Said:

    This is really cool! Its pretty awesome to create a diy project for others to make. Good Job!