Now its time to introduce a jack that most associate with the “professional”world….the XLR! In this case, the XLR3

The XLR3 carries three signal wires, usually a positive, negative and a ground. It is extremely important to know how your gear is wired, as the AES standard is pin 2 hot, but many manufacturers go with pin 3 hot. Check with your multimeter to be sure!

The XLR is commonly used in the analog world for microphone cables and balanced, line level cables, and in digital audio as the connector for the AES/EBU digital audio format.

Last time we looked at probably the most common jack you’ll encounter, the 1/4″ mono jack, this time, we’ll meet its close relative, the 1/4″ stereo jack, AKA the balanced 1/4″ jack or the 1/4″ TRS jack

Looking at the picture above, its pretty east to confuse with the 1/4″ mono jack, let’s look at them side by side

Notice that the Stereo 1/4″ jack adds a ring between the tip and the sleeve. These cables are almost always used for carrying balanced, line level signals.

Where the mono 1/4″ jack is meant to carry a signal wire and a ground wire, or the positive and negative wires of a speaker cable, the stereo 1/4″ jack carries TWO signal wires and a ground wire.

When used as a jack for stereo gear, the tip will go to one side of the stereo spectrum and the ring will go to the other. There is no published standard that I am aware of, but for instance, most Sennheiser headphones I’m aware of have the tip go to the left headphone and the ring to the right headphone. Always test to be sure.

When used as a jack for balanced gear, the tip will normally go to the positive wire for the gear in question and the ring will go to the negative side of the gear, with the sleeve wire carrying the ground. Again, double check to be sure, manufacturers will always try and throw you for a loop.

One place you will sometimes find these jacks in use are as insert cables on certain gear, like cheaper mixing consoles. In this case, the tip will go to the send or the return and the ring will go to the opposite end, while the ground is shared by both. In the nearly ubiquitous Mackie brand mixers, the tip in every case I’m aware of goes to the send and the ring is the return. Both the send and return will be unbalanced, and share the same ground. Again, doublecheck to be sure, because many companies will use the opposite configuration.

 Shown here is a female TRS jack. Use your continuity checker to figure out which terminal goes to the tip,  which goes to the ring and which terminal goes to the ground

Whether you’re running a full on recording studio, a PA system, or playing a guitar on stage, everything, and I mean EVERYTHING depends on your electrical signals going from point A to point B as unchanged as possible. On the ends of these signal carriers are connectors usually referred to as “jacks”. You are probably familiar with  a number of these, but how well do you really know your friends and allies, upon whom you entrust everything, and yet probably take for granted?

Let’s look at one you probably interact with more than any other, the 1/4″ jack

Male 1/4″ Mono Jack

Pictured here is a male, 1/4″ mono jack. It might also be called an unbalanced 1/4″ or a TS 1/4″

This is the type of jack you will normally plug into your guitar, and is often found at the end of speaker cables, and various  unbalanced line level cables

At the very end on the left in this picture, is the tip or the T of the TS moniker, and to the right of the little dividing line, is the  sleeve or the S part of the TS. When used on an instrument or line level cable, the tip carries the signal and the sleeve carries  the ground (and shield if present). When used as a speaker cable, the tip usually carries the positive signal, while the sleeve  usually carries the negative signal.

Disassembled Male 1/4″ Mono Jack

Here you can see one of these jacks taken apart.

Above the threaded section on the right side of the jack itself, you can see the eye hole  where you would solder the positive or signal wire that goes to the tip.

Above the threaded section on the left side of the jack, is where you  would connect your ground or negative wire. At the top end of this leg,  you will often see two tabs that can be squeezed together to secure  both wires once they are connected. Doing this adds a lot to the strain  relief of the cable and makes the whole system far more durable.

On the bottom right of the picture is an insulating sleeve meant to keep the signal wires from shorting to the case.

And finally at the top right is the case itself, meant to cover and protect all the delicate insides from damage, when you carelessly toss the  cable on stage, or step on it, or do any other of the various unseemly things musicians do to perfectly good gear.

Panel Mounted 1/4″ Mono Female Jack

Pictured here is a female, panel mounted 1/4″ Mono Jack or female 1/4″ TS mono or unbalanced female 1/4″ jack

In this case, the top eye hole would be where you solder your positive or signal wire to and the bottom eye hole would be  where you solder your ground or negative signal to. But use your continuity checker to be sure….you DO have a continuity checker don’t you?

Last time, I explained what a decibel was, and how it is a dimensionless relationship between two sources

But wait! There’s more. Decibels can have dimensions, as long as they are referenced

Now we’re going to look at the common decibel types you are likely to encounter in the audio world

A referenced decibel unit will usually be written as “dB” with some characters after it to tell you what exactly its referenced to

First off, dBu or dBv (do NOT confuse this with dBV) – 0dBu = 1 miliwatt (mW) coming out of a 600 ohm impedance, or in a more math fun way, 0dBu = √0.6Volts or roughly 0.775Volts. You will usually see this reference in what we used to call “professional” equipment. Often an XLR jack or balanced 1/4″ jack on a piece of gear would be specified as having an operating level of +4dBu

Next, and frightfully confusingly, because of the shared “V” character with the above mentioned dBv, is dBV. For dBV, 0dBV=1 Volt RMS. You will most often see this on what we used to call “prosumer” equiment. Often the RCA jacks or 1/4″ jacks of a device would be specified as having an operating level of -10dBV

Next is a biggie in the modern world: dBFS or Decibels Full Scale. This one will be very important when dealing with digital audio. in dBFS, 0dBFS is as loud as you can get, everything is referenced downward from there, like 0VU = +4dBu = -15dBFS (as a for instance). Get this one straight early on, in dBFS, 0 is the upper limit. Theoretically, anything above there would be just digital hash, though in practice, internally in a DAW (Digital Audio Workstation), you can go above 0dBFS, just dont expect it to make it out of the Digital to Analog Converter (DAC) nicely

Finally you have dBSPL, the one you see the “ghost hunters” and cops running around with in the Sound Pressure meters most don’t know how to use. The “SPL” means Sound pressure level. 150dBSPL is pain, and just about surely hearing damage. 65dBSPL would be about normal conversation level. Measuring SPL is actually pretty tricky, and leads to all sorts of problems regarding noise laws. dBSPL is actually referenced to micropascals. You can look that one up yourself. For our purposes, 80-85dBSPL is about where music “sounds right” most of the time. Just underneath a snare drum can be 125dBSPL – don’t EVER put your ears there if the drummer has a stick in his hands.

When dealing with musical instruments, gear, mixers, software, and other items like amplifiers, you will often see the term “decibel” or often abbreviated as “dB”

The decibel is the unit we use to describe the level relationship between two signals. It is really important to understand that the term decibel, by itself, only refers to a comparison of levels.

A decibel is dimensionless, unless a reference is given, as we will see below.

A characteristic you must never forget about the decibel is that it is logarithmic function and not a linear one.

Guitar players might be familiar with the terms “log taper” vs “linear taper” when it comes to volume and tone knobs on a guitar.

Difference between logarithmic response vs linear response in common guitar potentiometers

Let’s look at some common relationships, to get a better understanding of the decibel

If you double the power (expressed in watts) of an amplifier, you gain 3dB. In a second you’ll see why going from a 50 watt Marshall, to a 100 watt Marshall isn’t nearly the volume jump you’d expect.

If you double the amplitude of a signal (for this case, expressed as peak to peakvoltage), you gain 6dB

Now, if you want to get twice as LOUD as another signal, THAT takes 10dB’s! So if you want an amp that’s twice as loud as your 50 watt Marshall, you are going to need a FIVE HUNDRED watt head!

REMEMBER: Any time you see “dB” without another letter after it, you are seeing a relationship between levels, and not an absolute statement about the level of a single, lone sound

Here is a simple and fun and most importantly, cheap, project for an afternoon. We’re going to turn a plain Jane ukulele into an electric powerhouse!

You’ll need a few things:

1. A piezo transducer, I’m using RadioShack part # 273-0073, which goes for about $2.50
2. A female 1/4″ jack. Either mono or stereo will work
3. A drill and various size bits, up to whatever jacket size your 1/4″ jack uses, usually 3/8″ or 1/2″
4. A hot glue gun and some glue sticks
5. A soldering iron, I reccomend the Weller WLC100 its cheap, and there are replacement tips for it in most major cities
6. Some solder…I still prefer the 60/40 type, but any decent solder will work
7. Various wrenches and pliers
8. An ukulele you don’t mind chancing damage to
9. Whatever else I might have forgotten

So here’s a video that shows the whole process.