Progressive steps to DIY for musicians and recordists

If you use electronic gear in the making or recording of music, you will have to eventually deal with the realities of maintenance and repair. Depending on the amount (and type) of gear you own, this can quickly turn into an expensive proposition.

Vintage gear, while typically exceedingly well-made and durable, is old, and will need maintenance and the occasional repair. Exactly how much and how often depends, of course, on condition, age, and how well it has been treated over its life.

Modern gear, while typically new, often uses cheap components, boasts shoddy craftsmanship, and employs any number of modern production methods designed to make manufacturing expedient. Unfortunately, these modern construction techniques often compromise durability and repairability.

Some new gear, often referred to as "boutique" gear, will combine the old-style construction techniques (and, ideally, most of the component quality of the best vintage gear) with the newness of the modern gear. For these items, you will likely be set for awhile, provided you care for them. But for the rest of it, periodic maintenance and repair is inevitable.

You needn't be afraid of nor intimidated by the prospect of learning to work on this stuff yourself. Most solid-state gear can be worked on safely by following the most minimal and obvious of precautions (i.e. don't work on the item with it plugged in). Most tube gear requires a bit more care and caution, but a healthy respect for the levels of voltage and current present is what you need to keep you safe-- there is no need for fear.

I will outline here a few simple projects that will put you on your way to doing most simple-to-moderate repairs on your musical gear yourself, saving yourself time and lots of money while perhaps having a bit of fun in the process.

As with most things, having the proper tools will make your job infinitely easier and more enjoyable. The tools needed to have an easy time of music electronics projects are relatively inexpensive-- you can get going for around $100, maybe a little more, maybe a little less (depending on the soldering iron you choose and what you already have laying around). Here are some essentials:

• Good soldering iron with temperature control (Weller WES51 and Hakko 936 recommended for quality and cost-effectiveness). This will set you back about $75-90 if you shop around. The Circuit Specialists CSA-1A is supposedly a re-badged Hakko 936 available for less than $40 and represents a good, cost-effective option. Avoid inexpensive Radio Shack irons and the like. Trust me. This is the most important tool you will buy, and a cheap iron will make soldering effectively several times more difficult.
• Vacuum desoldering pump. About $5-15. I use one called a "Soldapullt."
• A few alligator-clip test leads. I've never needed more than 3-4 at a time. They usually come in a package of 5-10 for a few bucks
• Decent digital multimeter. Needs not be expensive-- $20-30 is fine. If you're going to get really serious, an expensive Fluke multimeter really is better. For just the occasional maintenance job, an inexpensive 15-range or better meter that reads at least 500VDC is more than adequate.
• a wooden or plastic chopstick or similar for probing around in a piece of gear for mechanical disturbances/cold solder joints. DO NOT use a pencil or anything with carbon or metal in/on it. Free, usually.
• Phillips and flat-headed screwdrivers of a few sizes (one each large/small is good). You probably already have these. Cordless electric screwdriver or electric drill is a godsend.
• Needle-nose pliers and wire cutters. You probably have these, too.

Optional but handy for various applications:

• Cordless electric drill. Handy for chucking screwdriver bits into to get chassis out in a hurry. Also essential for drilling holes in aluminum chassis for pedals or scratch-builds.
• Wire stripper. Just costs a few bucks at a hardware store, but will likely be one of your best purchases. Makes stripping wire easy and worry-free, and keeps you from the frustration of accidentally nicking wire in the process.
• A small 'parts drawer' with various values of caps and resistors. I bought a "parts assortment" of resistors for a few bucks that has saved me many trips to the store and many days waiting on mail order. It's also handy to have a few capacitors around.
• Component lead bender. Hoffman sells these. Basically it's a little piece of plastic that costs a couple bucks that helps you bend component leads neatly at right angles.
• Variac. This is a variable transformer that allows you to reduce the voltage coming out of the wall (and all voltages in the gear you are working on in proportion). Useful for firing up an amp with old caps and re-forming them. Can be expensive. I don't have one, but if you have a retired engineer dad with one in the basement, it certainly would be handy to snag it. Maybe grab that oscilloscope next to it, too, and also the signal generator-- both will come in handy as you get more experienced.

Now that we have the tools, what will we do with them?

First, start making some cables. Quality bulk cable and connectors can be ordered from Redco. Starting with single-conductor instrument cables is a good idea. Making cables will give you practice stripping delicate wire without damaging it or causing shorts, and will also give you good practice soldering. Before beginning, I suggest watching or reading one of many soldering tutorials available on the web.

Building cables is a fairly low-stakes game. There is nothing to shock you, and if you mess up stripping a wire or soldering, you can just cut an inch off the cable and start again. If it's a total loss, parts are inexpensive. If it's a success, you have built something immediately of use to you (the bulk cable and connectors sold by Redco are first-rate quality-- the cables you make will be superior to all but the most high-end boutique cables). If the single-conductor-shielded instrument cable is a success, try an XLR microphone cable next, which can be a bit more challenging. You may also wish to replace the speaker in a guitar amplifier.

With the skills learned from cable-making, try and tackle a simple fuzz, overdrive or boost pedal kit. I recommend the kits from build your own clone. They come with all parts and instructions, and they even offer a simple kit called the "Confidence Booster" for first-time builders. The Confidence Booster is free with the purchase of another kit! If you totally butcher the Confidence Booster, you can return your purchased kit and keep the mangled parts free of charge. Building effects pedals-- especially simple fuzz, boost, or overdrive pedals-- is fun and safe. You are dealing with low voltages and low currents, so there is zero chance of electrocution. None of the parts are that expensive individually, so if you fry a few things it usually won't set you back much. You will learn to be careful with soldering temperature, you will learn some peculiarities of circuit-board soldering, and you will deal with some planning and mechanical assembly. There will likely be some 'growing pains,' but the end result is usually very satisfying.

At this point, you may wish to work on a tube amplifier of some sort. Tube gear requires a brief and obligatory note about safety: Nearly all tube gear will have electrolytic capacitors capable of storing deadly amounts of power even with the gear off and unplugged. For this stuff, you need to learn to identify and discharge the caps (a very easy process that has been outlined countless times on the web-- It doesn't need repeating here). For starters, never work on a live (i.e. on and running) amp. If you do, you should keep one hand in your pocket at all times to keep from forming a path to ground across your heart. If you are inside a live amp, do not work barefoot on a concrete floor, do not wear any jewelry, have someone around to look on just in case, etc. This is mostly common-sense type stuff, and most of it doesn't come into play until the more sophisticated projects, but it bears repeating.

Start with the simple jobs. Since you have already located the electrolytic caps and discharged them, and since they often need replacing in older gear anyway for maintenance, you may want to start with a cap job. I recommend starting on an amplifier with discrete, as opposed to can-style multi-section capacitors. Amps with tag-board or point-to-point construction are infinitely easier to work on than amps with printed circuit board construction.

If your cap job or other simple maintenance is a success, try building a small kit-form guitar amplifier like a clone of a tweed Fender Champ. This will teach you a lot about what does what in tube audio gear, and will equip you with a lot of the knowledge necessary to diagnose and repair gear in the future. This project tends to be rather expensive, but the end result is often worth the expense.

The best advice for learning to maintain your own gear is to read a lot and get your hands dirty. I recommend downloading (for free) the NEETS manuals, or the Naval training series paid for by the U.S. Navy. Most of what you need to learn about electronics is spelled out in these modules.

There is also a lot of good advice on several internet fora dedicated to music electronics. Often, there are friendly and knowledgeable people on these sites that seem to enjoy walking a first-timer through a project and answering questions.

Working on stuff is fun, tweaking gear for maximum performance is musically satisfying, and you can save a pile of money working on your stuff. The information is out there and the tools are cheap, so go for it!

The misleading story of the guitar amp RMS "watt"

One of the greatest misconceptions among users of guitar amps is the notion that the output power of the amp-- usually (mistakenly!) referred to as "wattage"-- is somehow directly correlated to the perceived loudness of the amplifier.

In reality, the amount of voltage and current across the speaker terminals is only one of several factors that help determine how loud the amp will sound to the listener.

Amplifier manufacturers usually market amplifiers with ratings in "RMS watts." RMS stands for "root mean square" and is a statistical measure to calculate the mean, or average, amount of voltage or current delivered into a given load. First of all, it should be pointed out that there is technically no such thing as an "RMS watt." RMS is a way to measure voltage or current, not power. But the notion of an "RMS watt" prevails somehow as the standard by which amplifiers' loudness capacities are judged.

However, eschewing semantics for a moment, one might wonder: Why isn't an amp's power rating the best means of mentally estimating its capability to be loud? And what other factors should I consider?

First, it helps to understand a bit about how the human ear works. The human ear can detect a staggeringly wide range of sound pressure levels. The level of sound pressure that causes permanent hearing damage is more than a million times greater than the sound pressure produced by the faintest sound a human can hear. For this reason, the decibel is a logarithmic unit of measure. An increase of 3dB is equivalent to a doubling of sound pressure in Pascals (Pa), the SI unit of measure for pressure.

What does this mean? Well, for our purposes, it means that all else being equal, a 100 watt Marshall head is not "twice as loud" as a 50w Marshall head, as many seem to think-- it is only a scant three decibels louder.

Further complicating matters is that power ratings are taken with respect to a given "%THD," or percentage total harmonic distortion. If an amplifier is rated 100w with 1% THD, that means it develops 100w across the speaker terminals, with one percent of that power coming in the form of distortion products (i.e. stuff not present in the source input). If it is 100w with 5% THD, then 5% of the output comes in the form of harmonic distortion.

Complicating matters significantly (and impeaching the usefulness of that measurement for our purposes) is that guitarists almost never use their amplifiers with distortion content that low. Even 10% THD or more can sound "clean" in a guitar amp-- with the soft clipping of a tube amp, the onset of distortion into significant percentages manifests itself as a gentle compression or 'fattening' before true clipping occurs.

Beyond this, guitarists often like a little (or a lot) of audible distortion in their sound, so they deliberately induce audible clipping-- likely 50% THD or more. So while a typical 1% THD power rating might be relevant in a hi fi amplifier, it is almost never terribly relevant to actual use in a guitar amplifier.

Besides output power, here is a list of a few factors that can affect a listener's perception of how loud a guitar amplifier is, in no particular order:

• Number of speakers
• Efficiency/sensitivity of speakers
• %THD tolerable to the user/listener
• Onset of core-saturation in the output transformer
• Ability of power supply to keep voltage up when amp is pushed
• voicing/frequency content of amplifier

Let's take them in order, in brief.

First, the number of speakers is critical. Addition of a second, equal speaker, provided the amp will drive the additional load, will usually net an extra 3dB in loudness, roughly equivalent to doubling amplifier power. This is the largest source of the "more watts means louder" myth. A 50w Marshall is often paired with a single 4x12 cabinet while a 100w Marshall is often paired with two 4x12s. No wonder it seems "twice as loud!" A 22w Deluxe Reverb has a single 12" speaker whereas an 85w Twin Reverb has two 12" speakers (and usually very efficient ones, at that). For this reason, 'physical size of the cabinet' is often a more accurate predictor of loudness than the RMS power rating.

Secondly, the efficiency/sensitivity of the speakers matters a lot. Not all speakers are created equally. In a loudspeaker, only a fraction of the current input is turned into sound energy; the vast majority is dissipated as wasted heat energy. Some speakers are more efficient than others. For example, a JBL D120F has approximately 102dB efficiency at 1W white noise @ 1m distance. A less efficient speaker might only have, say, 96dB efficiency at the same power and distance. Consequently, a 25w amp through the JBL could easily sound louder than a 50 or even 60w amp through the less efficient speaker, especially when set up for clean operation.

Thirdly, the farther you are pushing an amplifier past the %THD used for its power rating, the more unpredictably it will behave. Amps do not stop getting louder once they hit 1% THD. They will continue to get louder as well as more distorted, and the nature of those distortion products will influence how loud an amp seems.

How much louder it will get past that point usually has to do with one of the following factors:

Output transformers are varying sizes. Sometimes they are small and will exhibit a behavior called "core saturation." When this happens, the transformer reaches its limits and cannot allow any more current to pass through. It will distort audio passed through it. In other words, it can serve as a "bottleneck" for the power trying to get from the tubes to the speakers. Consequently, a bigger output transformer will often allow an amp to keep getting louder as it is driven into clipping.

As another factor, the power supply feeds the amp the power it needs to amplify sound. If a power transformer, rectifier, or other components within the power supply are limiting the amount of power that can actually be used for amplifying, that can put a ceiling on how loud an amp will get. So a small power transformer might also limit an amp's ability to keep getting louder past the point of rated % THD.

Finally, the voicing of an amplifier can affect how loud it sounds. The Fletcher-Munson curve indicates that certain frequencies in the speech-range appear louder to humans, as our ears are more sensitive to them. An amplifier with a lot of those mid-band frequencies will conceivably seem louder to a human than an amp containing a lot of spectral content outside of that range.

So, in other words, largely ignore the numbers. When gauging whether or not an amplifier will be loud enough (or too loud) for your needs, focus more on the number and size of the speakers-- with speaker efficiency as a secondary factor-- and then the size of the transformers. Bigger output transformers almost always equal the ability to have more headroom and give up more volume even as the tubes saturate. Big power transformers, large filter cap values, and solid-state rectifiers signal a power supply that will keep up and won't mush out before the output tubes flat-line. All of these things are better clues than the rated output as far as determining how loud the amp will be when you crank it up and bounce it off a chair. Of course, you could always just judge by the physical size of the cabinet.