Building the Driver PCB

Welcome back, friends and followers! Let’s get going with another installment of this Audio Note Kit 1 build, shall we?

Today we’ll be building the Driver Board PCB, which will be our first foray into soldering lots of components onto a printed circuit board. Buckle up and come along for the ride.

First, the board itself is a beautiful, bright red. it is made of a glass-like material, feels very solid and as you can see in the photo below, it’s also quite thick and comprised of several layers. The layout is very tidy. Audio Note Kits says their PCB’s are laid out with the smallest possible signal paths and I see no reason to doubt this.

IMG_0186

This feels like a good point to share that – given the truism that “hard wiring sounds better than using printed circuit boards” – I saw references on the web to folks who have tried to “hot rod” this kit by eliminating the PCB’s altogether and completely hard-wiring their build, such as this guy, who heavily modded the original, British Kit 1 – whoa.). This seems spectacularly risky and complicated to me, which is why I won’t be doing it in this blog, or ever.  😉

It’s also a fitting time to mention that a fellow named Paul Brookes in the UK documented his Kit 1 build back in 2005 and did a very thorough job of it. This was the very first version of the Kit 1, so there are some significant differences, but also a lot of similarities. It’s interesting to see how the design evolved over the past 10 years!

Moving on:

The striped, shiny bits in the picture below are resistors. They are color coded with stripes to show their resistive values. I am not a huge fan of this color coding system, but no one is listening to me, so what’s the use? (Why not just print the value on the side of the resistor? Other than the inarguably fun, candy-like appearance of all those stripes, I find the whole thing obtuse.) Anyway, Audio Note Kits does thoughtfully provide a resistor color code calculator on the web site which I found a little hard to use. I did some googling and came up with this one, which I like better. To each his or her own.

The resistors attach to the PCB’s in two ways. In the much easier scenario, the leads go through holes in the board. Bend the two leads at right angles, poke them through the holes, apply solder to the PCB, then flip the board over and snip off the extra length of leads, and you’re all set, like this:

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In the more common and more challenging scenario (at least for a rank beginner in soldering), the resistor must be soldered  to two silver “pads” on the surface of the PCB. This involves, first, crimping the leads on the resistor with your needle-nosed pliers like so:

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Then you trim off all but about 1/4 inch of the leads, like this:

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Next, you “tin” the pads with a glob of solder, like so (see the pads next to the rectangle marked R20 in this picture):

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And then, by holding the resistor in place with a pair of pliers, you can just heat the tinned pads with your soldering iron, and voila, the resistor is soldered in place!

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Doing this over and over again, taking care to put the correct resistor values in the correct places, yields this lovely and very aesthetically satisfying result:

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Next, we mount and solder the three valve bases:

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Then, flip the PCB over and solder four pieces of ground wire as directed:

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The board is almost completed by affixing a number of capacitors, including two fancy Black Gates (the two, smaller ones at the top of the picture).

CORRECTION: I want to point out a very easy to commit error in the building of my Driver PCB so that those of you who reference this blog as you build a Kit 1 in the future don’t make the same error. It’s not a catastrophic mistake, in fact, the amp will work fine even if you make the same error that I did, but hey, if you’re going to all this trouble, you might as well get it right, eh?

Here’s the deal. Look at the solder points marked C1 through C4 in the photo above. Then look at the photo below and you’ll see the four brown, ceramic capacitors installed in those positions on the PCB. These caps perform some sort of electrical filtering function and are NOT in the musical signal path of the amp. However as pictured below, they are in the WRONG position on the PCB.

Now, go back up to the photo above. Notice that right above the pads marked C1 through C4 there is an unmarked pad, connected to C1 to C4 by a white line. What I did INCORRECTLY was to solder my ceramic caps to these two points. This is very easy to do, especially since the two pads are perfectly spaced to accommodate the brown ceramic caps currently supplied with the Kit 1. However, this isn’t where those caps go! In fact, in this position, the caps are simply shorted out!

Instead, the lower lead of each cap should connect to the unmarked pad above the pads marked C1 through C4, and the upper lead should connect to the unmarked pad next to W20 through W23, near the upper edge of the PCB. Look down just at the very bottom of this post, and you’ll see two of the caps in their proper position…

IMG_0201

You’ll note that there are four empty rectangles in the picture above. These will eventually be occupied by four large Mundorf Supreme Gold/Silver/Oil coupling caps, but the manual recommends waiting until the end of the build to install them so as to ease the task of wiring between the PCB’s.

The last step here is easy: as shown below, we attach 8 hex standoffs on the resistor side of the PCB; these will be used to mount the Driver Board to the underside of the metallic valve plate later on.

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Addendum: A Word About Tools…

As promised in the last post, let me say a word about tools for the building of this kit.

Of course you will need a soldering iron. These can range in price from quite inexpensive for a simple iron to much more expensive for an all inclusive soldering station. As you can see below, my iron is nothing special: a 35 watt iron from Weller that I bought at Fry’s Electronics a few years ago and has held up well (as opposed to the Radio Shack iron that I bought that stopped working after a short time…) I also purchased a little stand that has a place for a wet sponge, which you use to clean the tip of the iron as you work.

IMG_0203

As for hand tools, here, from top to bottom, are the essentials:

  • A wire stripper/cutter, for removing insulation from wire. Yes, you can do this with a standard pair of scissors but you’ll be much more likely to sever the wire when you don’t want to. Trust me, get yourself a proper wire stripper.
  • A set of needle-nosed pliers. This will prove absolutely essential in manipulating the leads of electronic components as you prepare them for soldering, etc.
  • A wire cutter. This picture shows two kinds. First, a standard snipper that works from the side, and a second type that can be used from the top. You’ll need this to snip wires and component leads, e.g., to trim excess capacitor leads after soldering them to a PCB.
  • And, not shown, a Phillips-head screwdriver.

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You shouldn’t have to pay very much at all for these. Places like Harbor Freight in the USA have entire sets of appropriate tools for very little outlay.

Until next time, take care!

CORRECTION as referenced above: Here’s where those brown caps belong:

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