ON THE BENCH - #1 — AudioTechnology
DIY… or what to do on the weekend.
Text: Rob Squire
With the footy season finally drawing to a close, for some of us there’s now time available to turn our attention to other activities. For me, that means building some DIY audio kits over lazy summer weekends. It may come as a surprise to many that a person such as myself, who spends all week fixing pro audio equipment, would be picking up the soldering iron on a Saturday afternoon and putting together an electronics kit project. (It certainly comes as a surprise to the missus who has visions of projects involving spades, forks and dirt!). I’ve been building kit projects since I was a kid and the process of doing this has not only added to my understanding of electronics but has furnished me with numerous pieces of equipment that enjoy regular use.
For many of us who spend – or would like to spend – the bulk of their time just using audio equipment, there’s still an attraction to building DIY gear, which goes something like this: ‘surely I could build this stuff cheaper myself!’ Unfortunately, it’s no longer quite that simple. More recently, the manufacturing and retail costs of semi-pro and pro audio equipment have plummeted, and in 2009 this price rationale is hard to maintain. Given this situation, what good reasons remain for pursuing DIY electronics?
JOINING THINGS TOGETHER
Well, for starters, it’s pretty reasonable to suggest that basic soldering should be a part of any audio engineer’s skill set. Being able to repair a mic lead mid session might just be the difference between capturing a performance while it’s hot and everyone downing instruments while the bass player drives across town to get a lead repaired or replaced. (In my experience it’s always the bass player who picks up these jobs). Whether you’re repairing or making up mic leads or other cables from scratch, this can be a good way of dipping your toes into DIY and at the same time improving your soldering chops.
LEARNING HOW IT WORKS
Putting together a DIY electronics kit can also be an excellent way of deepening your understanding of how things work. This is particularly so in the case of projects issued by electronics magazines where, not only are the assembly details presented, there’s also a detailed description of how the circuit works. For many people who end up making careers out of electronic design or repair, such circuit descriptions have often formed the starting point of their education.
There is no doubt that an extra degree of satisfaction is enjoyed when you’ve pulled a killer guitar sound using a mic pre you’ve built yourself. At this point it is also probably worth dispelling one significant and potent myth: that a piece of DIY gear can’t be as good as something you buy off the shelf. Today there are all sorts of kits available for DIY construction that will rival the quality of anything coming from a manufacturer, and this point shouldn’t be understated. If you have the time, reasonable soldering ability and can follow instructions, you can build a world-class piece of audio gear. Alongside of this, there are also some items of equipment you can build from a kit that simply aren’t readily available or affordable off the shelf.
EXAMPLES & POSSIBILITIES
Rattling around in the bottom of my tool bag is a small audio frequency oscillator. About the size of a guitar stomp box and battery powered, it’s one of the handiest additions to my tool kit. Producing sine waves from 40Hz to 18kHz with an adjustable output level, it saves loading my 20kg test set into the boot of my car every time I head out on jobs where I don’t need the precision and extra features my ‘professional’ audio oscillator provides. The kit for this unit costs less than $30, and depending on your level of expertise, could be put together in an afternoon. One fortuitous aspect of the design of this particular unit is that, with the level control up full, the unit generates a signal level of 4.5dBu, which in many practical situations is accurate enough to be considered your +4dBu reference level. Being battery operated the unit is ‘earth free’ and so while its output is unbalanced it will happily drive both balanced and unbalanced inputs without creating hum or earth loop issues. Naturally, I can’t help myself when it comes to building kits, and always find a way to modify the circuit to better suit my specific requirements. In the case of the oscillator being so tantalisingly close to +4dBu output level, I’ve made a couple of small changes to the unit.
By simply adding two resistors to the output level control, one on each end of the volume control, I now have a level control that ranges between –40dBu and +4dBu, rather than the original range. This means if I want a typical mic level to check out a preamp, I rotate the level control fully counter clockwise and I know I’ve got –40dBu. If I want to check out a line level signal path I rotate the level control hard clockwise for +4dBu. I also installed a male XLR socket onto the case rather than the supplied RCA – generally speaking, a much friendlier connector in the pro audio world. This is a perfect example of one of the great things about DIY. As your confidence and abilities increase you can start to customise your project to produce a unique unit that exactly meets your requirements.
WHERE DO I GET IT?
Historically, electronics magazines were the fundamental resource for development of DIY projects with the actual kits being released through either electronics retailers or a few small enterprises that were set up specifically to supply the kit builder. In today’s PEA (post internet era), however, the options have broadened considerably with a number of companies producing high quality kits aimed fair and square at the recording studio operator and musician. In the world of kits there are essentially two types supplied: one called ‘short form’ and the other, ‘complete’ or ‘full’. A short form kit contains just the printed circuit board (PCB) and components to solder to it. With these kits you will need to supply a case, machine any holes required and sometimes add additional extra parts (or kits), such as power supplies, to produce a finished unit. Complete or full kits, on the other hand, supply everything you need to produce a finished unit, and these often include high-quality pre-machined cases with whatever labels are required printed or engraved on them. Many of these full kits yield a finished product that not only performs as well as any product you can purchase but look as good to boot.
Without trying to pull together an exhaustive list, some of the suppliers of these kit projects are:
JLM Audio: an Australian business owned by Joe Malone, that supplies high quality kits mostly in short form but also some complete kits. JLM specialises in mic preamps, DIs and power supplies.
Elliott Sound Products: another Australian providing designs and raw PCBs only for a broad range of audio and non-audio projects.
Silicon Chip: an Australian electronics magazine that designs and describes all sorts of electronics projects, including many audio projects. While it doesn’t supply kits directly, many of its projects are available through Altronics and Jaycar. To give you an idea of the sorts of projects developed by Silicon Chip and available from Altronics, there’s the aforementioned audio oscillator, a very high quality headphone amp, stereo power amps and, just released, a stereo D/A converter that will beat the pants off many you can buy off the shelf.
Hamptone: tube and Fet mic preamp kits.
PAiA: have been around for a long time producing kits especially for the experimental musician… need a Theremin, for example?
Fivefish: produces a number of kits specifically for 500-series lunchboxes. The 500-series lunchbox is rapidly becoming the go-to format for DIY audio kit designers mainly because once the case is purchased, you’ve got a fully prepped standard format into which projects can be slotted. All power and I/O connectors are ready to go and the lunchbox power supply can cater to more than one module.
Seventh Circle: these guys pose the rhetorical question: “Who makes the best preamps for the money?” and then supply the answer: “You do!”. The company specialises in high-performance preamps based around some of the vintage American and British classics.
BYOC: ‘Build Your Own Clone’ produces kits that replicate some classic guitar pedals. This is a good stop-off point for guitar players exploring DIY.
WHAT DO I NEED?
Fundamentally, the two main things you need to test the DIY waters is time and enthusiasm and it won’t work trading one off for the other! Beyond that you’ll need some tools with a basic kit consisting of a soldering iron, sidecutters, long-nose pliers, multimeter and a set of screwdrivers. Probably one of the hardest aspects of DIY is finishing the unit off by installing the circuit into a case along with all its required connectors and controls. As you’ll soon discover, machining a case yourself to house the DIY circuit involves more specialised tools such as a drill, drill bits, nibblers and the like. If you opt for a project that doesn’t come supplied with a pre-machined case you’ll quickly learn where all the time, effort and end costs go into manufacturing a product!
It always make sense to start out on a project that’s within your abilities and since a good soldering technique will be essential to the success of any project the obvious staring point is to make up some cables before moving onto a small and simple PCB-based kit. A clear guide to soldering can be found at www.solderinguide.com. A magnifying glass and good light can be a bonus to enable close inspection of the solder joints to confirm that there’s a good flow of solder between the component and the PCB pad. Dry solder joints, where the solder is sitting on the component as a ball rather than flowing onto the PCB pad, will result in either incorrect operation of the circuit, or arguably worse, intermittent operation.
When assessing a kit project you must assess if the presentation of the kit supplies the amount of construction information that meets your abilities. Different kit suppliers will assume a certain level of electronics understanding and it’s important to ensure that your current abilities match the level of detail supplied with the kit. By all means push the envelope; after all, one of the good reasons for embarking on DIY is to gain knowledge and an understanding of what’s going on behind the knobs. However, it’s equally important to make sure the job’s achievable.
Any project that involves installing mains transformers, wiring and ultimately connection to mains power should only be undertaken if you clearly understand how to do this safely. Most kit projects that use mains power very clearly explain how to wire up this part of the circuit and deviating from the explicit instructions, including any mechanical assembly, is a risky business. For these projects it’s always a good idea to get your work checked over by a qualified technician and tested and tagged – it’s the law after all.
From making your own mic cables to building a compressor, the options for DIY audio are wide open. And whether you’re ultimately looking for a new career path or the simple satisfaction of building something yourself, it can pay to look beyond what is available off-the-shelf to what you can create to put back on it!
Which reminds me… I’ve got to go and put another coat of stain on the bookcases I’m building.