Aphex Channel Instruction Manual download pdf (Page 18)

230

instruction Manual

Aphex Systems Ltd. Model 230Page 16

230

master voice channel

Page 17Aphex Systems Ltd. Model 230

wire is the source and which is the return alternates

accordingly. In this regard, balanced and unbalanced

lines are the same. They both need two conductors.

What makes a system unbalanced is when one of

the wires is formed into a tube that wraps around

the other conductor, without touching it, such that

the outer conductor can be said to “shield” the inner

conductor. This describes all of the coaxial cable used

for video, cable-TV and radio as well as most of the

high fidelity audio cables.

Balancing

If both conductors are identical insulated wires that

are twisted together, then they form a balanced line.

This describes telephone lines, microphone cables,

and most professional audio cables. Typical balanced

cables include an additional shield wrap around the

twisted pair, but this is not strictly required for bal-

anced lines to work properly.

Many people, because they have more experience

with unbalanced wiring, think that balanced is con-

fusing. Believe it or not, balanced lines are really

easier to understand than unbalanced. There is no

grounding issue with balanced, and the way it works

is perfectly natural and simple. Balancing naturally

rejects hum and noise and eliminates all sorts of com-

plications in interfacing.

Balanced transmission works something like this.

7.0 Appendices

Appendix A: Balanced and Unbalanced

Lines and Operating Levels

Interfacing all types of equipment with balanced

and unbalanced lines and can sometimes be trouble-

some. First you have to somehow connect balanced

to unbalanced and then you have to deal with dif-

ferent levels. This tutorial will teach you about the

principles of balanced and unbalanced lines, wiring

standards, and how to effectively interface them.

Standards

Professional audio equipment usually comes equipped

with inputs and outputs that are balanced using

3-pin XLR connectors and sometimes 1/4 inch phone

jacks as well. This equipment most often is designed

to operate at +4dBu, a professional industry stan-

dard. That translates to a magnitude of 1.23 volts

RMS (Root-Mean-Squared).

Consumer gear has unbalanced I/O as standard, usu-

ally on RCA jacks. The normal operating signal level

follows the IHF (Institute of High Fidelity) standard of

-10dBV, or 0.316 volts (316mV) RMS. Converting to

dBu dimensions, this works out to be the same as

-7.79dBu. There is therefore a difference of 11.79dB

between pro and consumer operating levels.

Grounding

There is the notion that some king of earthly “ground”

exists out there that sinks all the noise and acts as

some kind of a shield. You see wires connected to

ground rods and water pipes that are supposed to

get a good ground. This is not a correct interpreta-

tion of grounding from an audio standpoint. Proper

grounding of equipment and wiring is important and

you will gain a better understanding of that as you

read along.

Balanced -vs- Unbalanced

Every audio signal is connected through a circuit. The

circuit must contain two conductors to create a com-

plete return path. In other words, a signal voltage is

conducted to a piece of equipment by injecting a cur-

rent into a wire. That current has flow though to the

destination through the wire and return back to the

source through another wire. Since audio is an alter-

nating voltage, swinging through negative and posi-

tive polarity, the current through the two conductors

changes direction each alternate half cycle. Which

Figure 1 Balanced Line Model

Figure 2 Unbalanced Line Model

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 31 32

Comments to this Manuals

No comments

Aphex Channel Instruction Manual Page 18

Comments to this Manuals

Related products and manuals for Audio amplifiers Aphex Channel