Hi-Z vs Lo-Z

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When you are in the music and audio industry, something you will probably hear often is the difference between Hi-Z and Lo- Z when it comes to microphones and things like guitars and basses. If you’re a beginner, the differences between the two and the way they work with your audio equipment can be a bit confusing and a little daunting.

When you are looking for the right cables to add to your equipment, it’s important to know what to look for. Microphones, amplifiers, preamps, and transformers are all something that you will probably want to add to your list of things that you want to add to your setup in order for it to sound the best that it can, and we’re here to help.

The letter Z is the commonly agreed upon abbreviation for impedance. Impedance is measured in ohms and refers to the resistance of a circuit or device to an alternating current (AC). Such an AC circuit can be any two audio devices connected together, like a speaker and amp passing audio signals between one another.

More watts will flow through a speaker with a low impedance than one with a high impedance. This also tends to put a greater strain on the amplifier to try and produce that kind of power. 

Hi-Z

Inside of a Hi-Z cable, there are only the “positive” and ground conductors. Since there are no negative cables- like in a Lo-Z cable- to balance out the charges, both capacitance and reactance suffer with increasingly longer cables. This means your sound will lose quality and get noisier the longer your cables are. 

In general devices with impedances up through 600 ohms are said to be “low impedance”, while devices with impedances of several thousand ohms and up are considered “high impedance”. Usually, we come into contact with these generic terms on microphones (typically low cost microphones), some direct boxes, and certain types of line inputs – on mixing boards, some tape decks, etc.

A typical guitar generally needs to be connected to a Hi-Z input. Otherwise electronics will be “loaded down” and the sound will be significantly altered. A Hi-Z microphone isn’t something one encounters very often in pro audio, and it absolutely needs to be connected to a high impedance input, and even then, like mentioned above,  the cable length can’t be more than 10 or 20 feet before the signal degrades.

Lo-Z

Like mentioned above, most people in the industry associate Lo-Z impedance equipment with microphones, professional audio equipment, and XLR connectors. Lo-z contains a positive conductor, negative conductor, and a ground conductor.

Because of this, it’s perfectly possible to have cables up to several hundred feet long without significant signal degradation or outside RF interference. 

The reason most guitarists aren’t fans of using Lo-Z outputs is because of the tone of Lo-Z pickups; most guitar amps and pedals aren’t designed for operation with low impedance guitar outputs.

Are there Exceptions?

While most standard high and lo-z microphone cables can be identified by the connectors, there are a few exceptions. Before XLR connectors became the industry standard, some manufacturers used different connectors for the microphone end but still used the standard quarter- inch plugs for high-Z and XLR male plugs for low-Z cables on the mixer end.

Line Levels and Preamps

A line leven is the specified strength of an audio signal used to transmit analog sound between audio components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles.

Line levels sit in between other levels of audio signals. In the recording industry, you need a few extra steps to get your signal from Mic Level to Line Level. In order for one to bring a Lo-Z or Hi-Z source up to Line Level, one must use a preamp.

Preamps have one fundamental job: to increase gain- they take a weak signal and boost it up to a line level signal. Every time an amplifier is used in the signal path, it is commonly referred to as a gain stage.

Each gain stage boosts the volume of the signal so that it’s useful to the next device in the signal chain. For example, the weak signal coming from a moving coil in a dynamic microphone’s magnetic fields is much too low to run into processing gear.

To boost its voltage and make it loud enough, one must run it into a mic preamp. To be clear, a preamp is not the solution for every audio problem. A preamp generally won’t solve any problems you may have with your sound- good quality preamp will let you get more out of the good audio you are already getting.

Preamps work well to increase the sound without increasing the gain and that undesired noise. If you were to plug a Hi-Z source into a Line Level input, such as on a Mixer, the audio it would generate would be faint and hard to hear.

When you try cranking the gain to get it up to a better volume, you will have amplified a lot of undesired white noise. With Lo-Z sources like a microphone, the input signal would be even more quiet and would require more gain in order to get it to sound louder.

This is also why most mixers have specific inputs for Line Level sources only; most come with XLR inputs for microphones. For guitars, you can’t plug them directly into the Line Level or the XLR Mic input. Instead, most people tend to use a DI Box to transform the unbalanced Hi-Z signal to a balanced Lo-Z signal, after which the guitar signal can be safely connected to the XLR input on the mixer. 

Once the impedances are matched, the audio will no longer have all kinds of unwanted noise when you crank up the gain knob. Instead, the audio will sound much better. If you would prefer avoiding the DI Box, the option to mic your instrument or your amplifier is sometimes available.

Types of Preamps

If you have a collection of different microphones, you may be looking for a good preamp to go along with it. While there are a plethora of categories you can separate microphones into, they can all fit into one of two categories: clean and colored.

Clean preamps are designed to take an incoming signal and boost it dramatically, while introducing as little coloration as possible. Coloration in this case simply refers to harmonic distortion. 

Colored microphone preamps have a characteristic sound to them. This means they alter the incoming signal by introducing some form of harmonic distortion, like mentioned above, either through the electronics or the use of transformers.

These harmonics often sweeten the sound, making it slightly more complex and allowing it to fit into your audio mix more easily than a cleanly boosted signal. This option will most likely influence future signal processing options.

Transformers and When to use Them

Hi-Z devices were originally designed to operate with vacuum tubes, which are normally high-impedance (or voltage-operated) devices. In designing high impedance transducers, such as a microphone or a guitar pickup, the objective is always to get the most voltage to minimize noise.

Because there are many Hi-Z devices that are in common use, such as legacy guitars and accessories, this connection has remained a music industry standard. 

With Hi-Z connections, high frequencies degrade with common connection distances far more than Low- Z. As mentioned before, they are usually unbalanced and therefore will be more likely to pick up hum and undesired noise.

With vacuum tubes, low impedance devices such as dynamic or ribbon microphones could overcome some of the problems of hi-Z devices by converting from Low-Z close to the tube amplifier using a transformer. When transformers are used, it is much easier to create a better sounding and more balanced circuit.

The same kind of transformer can be used in a reverse fashion, creating the equivalent of a direct box. Because a balanced system uses two wires to carry two identical signals out of phase with each other, noise introduced into those wires can cancel each other out through the action of the transformer or another balancing device that works in a similar fashion.

Transistor amplifiers are, for the most part, current-operated devices and can connect to Low-Z devices easier than vacuum tubes. Almost all audio interconnects- except those involving musical instruments like mentioned above- will likely be Low-Z. These interconnections can be either balanced or unbalanced. The common XLR microphone connector is almost always balanced.

Balanced connections can also sometimes be carried by a quarter inch TRS connectors. Connections carried by RCA and 3.5mm connectors are likely to be Low-Z and unbalanced.

A way to simply put it, Hi-Z is older technology where the instrument or the microphone had to have a high voltage to power vacuum tube devices. Current day Hi-Z equipment is made this way in order to stay backwards compatible with older equipment. Additionally, as electronics advanced further and most audio devices used transistors or transformers, audio equipment began to change over to Low-Z.