DIY: Gainclone Chip Amp Kit

DIY: Gainclone Chip Amp Kit

Jan 30, 2009

You know we love tubes and all things analog, but there is another trend in DIY sound amplification that has been hard to ignore: "Gainclone" amps. This term is going to be new to a lot of you, but to a diehard group of internetters, this is the holy grail of amplifiers. We have been secretly watching the movement from the shadows for the past few years and finally decided we had had enough of hiding on the sidelines. Brian Bell (or Briangt) of sent us one of his increasingly famous kits to build a little powerhouse out of.

It would prolly be a good idea to give a little (paraphrased and abbreviated) background on Gainclone amps to get us started. The original solid state Gaincard amplifiers were designed by a man named Junji Kimura- you could say that Koji Teramura had a hand in the design as well, having some very nicely tuned ears to lend to the project. This was basically the birth of 47 Labs. Read more here. All credits aside, what emerged was an amplifier that had only nine parts per channel. NINE. If you have ever opened a typical big box store type amp, you will see an ocean of parts and complexity. The signal path, which refers to the electrical route that the music signal passes through, is under two inches long on this one. Wow. And it sounds amazingly good... use your own audiophilic adjectives, they apparently all apply.

Now this is all well and good but the real greatness comes from the price: about $2k. Considering that most amplifiers that sound half as good cost 5 times that, we are talking about quite an achievement.

Ok, fast forward a couple years to a curious bunch of engineers who decide to build this themselves. After much trial and error, they create their own versions of this amp. Now being DIYers themselves, they understand that $2k is a lot for most people to spend on an amp, even if it IS a relative bargain. A lot of things are starting to catch up in technology now, including chip availability and ease of circuitboard manufacture. Attack of the clones, or Gainclones begins.

Fast forward again to right now and there are a few small manufacturers of Gainclone kits. These kits come with either just circuit boards that you need to add parts to or circuitboards that come with all the parts. You can get nicer parts or nicer boards, stereo, or dual mono (which is like stereo, only with completely separate circuitboards and power supplies for each channel). Basically, a DIYer's paradise. It is still a DIY market, so very specialized, but a lot of people are catching the bug.

So why build your own? A lot of reasons. Maybe you have something you want to do with the sound, mixing up parts and so forth. Maybe you want to save some cash and you feel your time will be well spent on this. Maybe you want to learn something about audio and maybe... you just want to build a cool box to house it in.

So Brian sent us a basic kit: a LM3886 (refers to the amplification chip) based stereo (about 65watt per channel) kit. This is a very straightforward product that is really easy to put together. Be forewarned- none of these kits comes with a power transformer, but he will recommend one to you if you axe. The kit costs around $70 and the transformer will cost almost the same. After that, you will need things like a volume potentiometer (errr... knob), a power switch, connection terminals for your speakers and your cd player/ipood/rekit playah/... source. Don't forget stuff like wires and soldering equipment.

Most of the work is in the box building, which can be a lot if you're not careful. We weren't... on to the project:

We haven't soldered yet, cuz we were working on the box first, but take a look at the parts- yep, that's all of them- most of the parts are for the power supply (which is not in the pic), which is not in the signal path:

We found an old computerish box that may once have been used for science. It is super cool and quite holy... hehe, filled with holes. We also picked up a heatsink from an old thing or something. It's nice and dramatic- maybe more than we need, but rly kewl.

In order to get the heatsink to fit in the box, we needed to mark things off with a white pencil:

Then we drilled some holes to get our jigsaw started and began cuttin'. The trick here is to drill holes that round out corners for you:

You can see how we used the tape to avoid scratching the box. We are going to repaint it, but we want to do as little work as possible to refinish everything:

This is what it looked like right after cutting:

And this is what a little dremeling will do to those edges:

Further dremeling to round off the edges and follow the naturally occuring curves:

And what it looks like with the heatsink all fit in... there is a severe amount of dremeling that went into making this all fit together, we will spare you the gory details:

(We actually vacuumed all the aluminum dust from the yard. Vacuuming outside is cool. You don't want that crap in your dirt.)
Stay tuned for more chip amp action...

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