How To: Gainclone Chip Amp Kit Part 2

How To: Gainclone Chip Amp Kit Part 2

Feb 13, 2009

It's funny... usually we gather materials over the years and store them away where they will never be used. Parts are helpful here and there, but overall, the stuff just sits. When it comes time to do a DIY project, we find new used parts to build with. Yes, "new used". Lately… maybe it's the economy, or maybe there are just too dang many things lying around, we have decided to make use of the old stuff. This is probably how we arrived at the methodology behind this project. Almost everything in it, sans the kit itself, has been collecting dust in the Unplggd parts bin for over 4 years. That is a long time, peeps. Maybe you have some junk that can be put to good use in your garage/closet/mind. Give it some thought. Anyhoo, read on...

Last time we showed you some of the work on the box; a little bit of drilling, lots of cutting, and an obscene amount of grinding with a Dremel tool. This box has been lying around for 5 years, actually, and it is good to finally give it a purpose. Remember: most of the work is in the building of the box.

This time we will go into some of the kit assembly to show how easy it is to build the actual kit. We will also continue work on the box by cutting a wood substructure to add to it. BTW- the wood has also been with us for around 4 years. It's a nice burled maple we had used for who-knows-what:

Back to that in a bit...

Soldering (pronounced "soddering") is something that you need to practice to be good at. The good news is: if you screw up, you can just reheat the part to fix it… up to a point. Basic rule of thumb is: make sure both parts to be soldered together are hot before adding the solder. You can take a look at a previous project we showed you here but you should look up the rest online to get the full story, because we don't have the room to go into it. Try here.
If you want a great video tutorial on soldering go here.
If you have six minutes and forty three seconds and are serious about this soldering stuff- try this one:

Briefly: we hold the iron with one hand and the solder with the other and feed the solder in to the joint after it is heated.

We used rosin core, silver solder, which is generally the solder of choice for audio electronics- no, it's not much more expensive than regular lead solder.

Soldering the parts is very straightforward, the kit comes color coordinated and the boards are marked so you know where to put things. There is also an online gallery which helps when you get stuck.

One thing that you should be aware of is that there is an order to soldering the power supply board. You must solder the resistors on the bottom FIRST before moving on to the large capacitors. Not too big of a deal if you get it wrong, but it's extra work.

Just thought we would point out that this little chip is what does the amplification. Small!

To give you a very confusing point of reference, here is how big all the circuitry is. The big donut on the left is an Avel 330va 25vx25v toroidal transformer and it is what converts the wall electricity to usable voltages for the amp. It's wicked heavy and can be purchased here for $70.

So that is the kit! Small and easy. The rest of the work will be centered around getting it to fit in the box...

One thing this kit does not come with is a volume control. this may seem silly and slightly off-topic having just intro'ed the box, but the reality is that people use the core amp for a lot of different applications, not all of which require a volume potentiometer (which will affect the box). You can use a passive volume pot, a preamp that has a volume control already, or install a stepped attenuator. We are doing the latter, since we want a nice clean signal to get to the amp boards.
Building a stepped attenuator is a whole other story and we had to order special parts from another dealer to get what we needed. Glassware is a company that provides all kinds of circuitboards for the DIYer... they also have some kits. We bought this kit some time ago so the board has been improved since we did. This is difficult to explain in a short sentence, but you essentially have control over balance as well as volume. We will go into the volume control more in the next issue but lets start with how this affects box design.

We wanted to be able to use this volume control with more amps, so we are designing a modular substructure that fits into the bottom of the Chip Amp. We started cutting out the wood this week with a very dull circular saw:

One benefit of cutting with a dull saw blade is that the burned, cut areas of the wood are easy to see in pictures.

Then we mixed up some JB Weld to fill in all the wording that had been cut into the box in its previous life. The writing was ironically very appropriate for what we are doing here, the problem was it was in all the wrong places. It said things like "Input", "output", "+" and "-"; it was sad to see it get covered up:

Once sanding is done, it will be painted over and disappear forevuh, or at least until some future society with an extroardinarily purist method of archeology decides to return it to its original manufactured state.

We forge on, keep your eyes peeled for the next installment.

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