DIY Aleph J: A Build Guide

The Aleph family album includes the following commercially produced siblings and descendants: the Pass Labs Aleph 1.2, Aleph 2, Aleph 3 , Aleph 4 , and Aleph 5 , the Volksamp Aleph 30 and Aleph 60 , and the First Watt Aleph J . (There were also the Aleph 0 and Aleph 1, but they technically had three gain stages and so were a bit different from the others, more like ancestors.)  So what unites all of the Aleph amplifiers? What makes an Aleph an Aleph?  The short answer is that an Aleph amplifier is a pure Class A, single-ended, Aleph current source, solid-state amplifier with only two gain stages.  Unless you're an amplifier designer, that's a lot to digest. Let's break it down.  Class A:  For a basic review of amplifier classes (A, B, AB, etc.), I can do no better than the top Google result at Electronics Tutorials . For our purposes here, it's enough to know that Class A amplifiers intrinsically offer excellent linearity, high gain, and low signal distortion levels.

What tools do you need to build the Aleph J? We're going to break it down into must-have items and "nice to have" items, but keep in mind that you'll find a variety of opinions on DIYAudio about this, so feel free to explore those opinions on the forums.  We are going to focus on tools "good enough for this build," rather than tools "ideal for a lifetime of electronics building." After all, most won't want to spend more on tools than on the amplifier. But some more extravagant options will be mentioned, for those who want high-end tools to work on their high-end amplifier. :-)  We also will assume that you already have the basic household tools (basic screwdrivers, socket set, wire cutter, pliers, drill, etc). Must-Have Tools Soldering Station : Perhaps the most important tool is a good quality, variable-temperature soldering station. While it may be possible  to make do with a simple, fixed-temperature soldering pencil, it's definitely a b

In order to keep this as simple and standardized as possible, we are going to get as many of our parts from the DIYAudioStore as possible. These items are not always in stock at the same time, but the store does offer a helpful "notify me when available" option for anything that may be out of stock. With a bit of patience and a few orders, you should be able to get all of these together. Prices are what they were when this was written and all subject to change, naturally:  Aleph J boards ($25): "This set of circuit boards will make the Aleph J amplifier of Nelson Pass." You'll naturally be needing these.  Aleph J transistor kit ($47): this gets you all of the transistors that you will need, EXCEPT for the input transistors, which are sold separately. The MOSFETs are matched, which matters for the Aleph J.  Aleph J Linear Systems Matched JFETs  ($49): the original First Watt Aleph J amps used Toshiba LSJ74 JFETs that are no longer being made. While you can stil

I recommend that you get your transformer direct from AnTek , as many U.S. builders on DIYAudio have vouched for the quality of the product and suitability for an Aleph J build.  What does a transformer do? Essentially, it converts AC electricity from your wall outlet (120 volts) to a lower voltage (18-20 volts, still AC) that typical audio circuits require. For a more complete explanation of how transformers accomplish this, try this YouTube tutorial from The Engineering Mindset (I recommend their entire electrical engineering basics series ).  So, what transformer to get? The original First Watt Aleph J used a single transformer rated at 300VA with two 18 volt secondary windings. The nearest AnTek equivalent would be this one . But if that's not in stock, you'll do equally well with one offering 20 volt secondaries (like this one , which I got). It should cost ~$40-60 plus shipping, which makes this the most expensive component other than the chassis! 

Now that you've got everything that the DIYAudioStore can provide, and your transformers from Antek, it's time to tackle all the rest of the parts listed on the Bill of Materials (aka BOM) for the Aleph J amp boards , as well as the Universal Power Supply board, plus a variety of connectors, hardware, wire and such, so that you've got everything you need.  Here's the quick rundown of all the other bits and pieces you will need and where to get them: MOUSER : Start with  this Mouser saved cart , which covers all the components from the BOMs. If something is  listed as out of stock:  look for substitute parts on the BOMs ( amp board , power supply ), which list multiple substitution options; if you can't find any of the substitutes listed in the BOMs, ask for substitutions on the " illustrated build guide " or the " noobs guide " threads).  AMAZON : You'll also need 16 gauge multicolored hookup wire for the power supply wiring, which we got

Before we dive into actual building, it might be helpful to review some good build habits that should help things turn out well (and make them easier to fix if they don't).  Practice your soldering skills, pick the right tip size! If you're not confident in your soldering skills, now is the time to watch some YouTube tutorial videos and maybe practice a little (you can use the diode section of the PSU board, which we will not use and should be snapped off). A bad solder joint can be murder to find later. Better not to make bad joints in the first place. Some practice can also help you decide whether you've got the right tip size on your soldering iron. BTW, I set my soldering iron at 650 F, in case you were wondering. :-) Shiny iron : keep your soldering iron tip clean by "tinning" it just before use. Melt a little solder onto it, then wipe on a damp sponge or in wire wool. It should be a shiny chrome when you use it, not a darkened, dull color.  A little blob fo

OK, finally time to start building! This post will provide a high level description of what the power supply does, as well as a step-by-step guide to building the power supply board (additional power supply components like the transformer and rectifiers will be connected when we assemble the chassis).  What is a power supply?   In basic terms, the power supply is responsible for converting the 120 volt alternating current (AC) coming from your wall socket into something that works with the components that make up the amplifier we're building. Those components want to see direct current (DC) at approximately 24 volts (give or take a little). There are several steps to this conversion in the Aleph J that we're building:  Your transformer steps down the 120 volt AC from your wall to 18 volt AC (or 20 volt, depending on which transformer you got) -- here's a great video explaining how that happens; Next, a full wave bridge rectifier converts your 18 volt AC into a pulsating 24

Now, on to the amplifier boards! These do the actual work of taking a line-level input signal from your audio source or preamplifier and amplifying it so that it has enough juice to drive your speakers. I'm always surprised how small the actual amplifier components are -- most of the chassis is taken up with the power supply and the heat sinks!   What does an amplifier do?   The output from your CD player or preamplifier is low voltage (generally, a maximum of 2 volts) and low current. This signal is fine for sending between a source and a preamplifier. But your speakers, in contrast, require a signal with both higher voltage and a great deal more current in order to produce sound.  The job of the amplifier is essentially to remedy this mis-match, by taking a low-voltage, low-current input signal and creating an identical replica of it, but at a higher voltage and current, suitable for driving speakers.  The Aleph J manages this feat with two gain stages. First is the input stage,