Roland VS-CDRII User Manual download pdf (Page 6)

When dealing with the various connections discussed in the previous section,

there are two main issues to consider: impedance and balancing. These

concepts are important to understand in order to record each piece of gear at

its best possible quality.

Impedance

Impedance, also known as resistance, refers to the electronic hardware’s

inherent resistance to the flow of an AC circuit. In other words, all electronic

circuits, including cables, have a natural friction-type resistance to the free

flow of electricity, in the same way that a runner encounters resistance from

the wind. A runner is stronger when he or she runs with little resistance from

the wind. In the same way, a low impedance audio signal is stronger than a

high impedance signal because it encounters less resistance.

For practical purposes, impedance between various pieces of gear should

always match. Connecting an output that expects a high impedance input

into a low impedance input can cause problems because too much current is

being sent. For example, a low impedance microphone should be input into a

low impedance mixer input. If you need to connect two devices with different

impedances, you should use a matching transformer to convert the impedance

of one of the devices so that they match.

Impedance Types

Hi Impedance: A circuit whose impedance rating is 1,000 Ohms or greater.

Low Impedance: Any circuit whose impedance rating is 600 Ohms or less.

Balanced vs. Unbalanced

Generally, inputs and outputs of audio gear are either balanced or unbalanced.

Balanced cables use an extra wire as a shield to help prevent noise from being

picked up along the length of the cable run. Generally, quarter-inch cables and

RCA cables are unbalanced, and XLR or stereo quarter-inch cables are

balanced (three connecting pins instead of two).

Every piece of gear has either balanced or unbalanced ins and outs. If you are

connecting a balanced output to a balanced input, you should use a balanced

cable. The connectivity issues can be summarized as follows:

- Unbalanced in/out connected to unbalanced in/out - may as well use an

unbalanced cable; using a balanced cable will not hurt but the extra wire

will not be used and nothing will be gained by using it.

- Unbalanced in/out connected to balanced in/out - same as previous.

- Balanced in/out connected to balanced in/out - should use a balanced

cable; using an unbalanced cable will render the connection susceptible

to noise, particularly on cable runs over 10-15 feet.

5The Basics of Modern Recording

Balanced and Unbalanced Connections

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Roland VS-CDRII User Manual Page 6