Aphex Channel Instruction Manual download pdf (Page 27)

230

instruction Manual

Aphex Systems Ltd. Model 230Page 26

230

master voice channel

Page 27Aphex Systems Ltd. Model 230

If you already recognize the importance of a good low end and the

potential costs (electronic, sonic and financial) of achieving that

sound with traditional methods, then Big Bottom may be the solu-

tion you’re looking for.

Big Bottom is a relatively simple circuit. The signal is split into two

paths. One path goes to the output unmodified, while the other

path goes through a frequency shaper, a phase shaper, and finally

a dynamics processor. The output of the dynamics processor is

then mixed back into the unmodified signal. The results of the

time and amplitude relationship between the unmodified signal

and the enhancement signal are a dynamically changing frequency

response and longer-duration bass frequencies.

Because the output level of the dynamics processor is constant

over a wide range of input levels, it varies as a percentage of the

mixed output. At lower input levels, when the bass needs the

enhancement, the enhanced percentage is reduced. As the input

reaches the highest levels, the enhancement signal percentage

becomes almost negligible.

At high input levels, the bass is still enhanced because of the longer

duration of the bass information. The peak output level, however,

is hardly affected, if at all. This is in contrast to fixed equalization

or subharmonic generation.

Big Bottom helps maintain the perception of bass when there is

low input level, but it does not diminish the dynamics of the bass

as the input increases. This is in contrast to compression schemes.

The harmonics of the bass frequencies are what subjectively make

the bass instruments real and give them punch. Changing the time

relationship between the bass frequencies and their harmonics

may cause the low end to sound muddy.

Equalization causes a frequency-dependent time shift. So the low

end might be louder, but very often the result will be louder mud.

Because the enhancement signal is added to the input signal and

does not change the original time relationship between the low

frequencies and their harmonics, there is no loss of low-frequency

definition. In combination with a dynamic range without limiting,

low-frequency definition is particularly important for kick drums

and bass guitar.

In the Model 204, Big Bottom has three controls: tune”, “drive”

and “mix”. Tune sets the range of frequencies that will be

enhanced. Drive sets the amount of dynamics processing in the

enhancements signal path. The greater the amount of dynamics

processing, the longer the duration.. or the persistence, of the low

frequencies.

Mix adjusts the amount of enhancement signal mixed into the

output. If the input signal is below threshold, the mix control

works like a simple equalizer. The higher the mix setting, the

greater the equalization effect on the output. Therefore, the drive

setting must be appropriate to ensure sufficient processing. For

that purpose, there is a green LED next to the drive control. When

the LED light flashes on the bass peaks, the signal is at its process-

ing threshold.

Big Bottom can be used on any sound system or storage medium

that can reproduce low frequencies (<100Hz). It will increase the

perception of greater bass energy without substantially increasing

peak output and without sounding muddy.

Fig. 1

Linear System

Audio Waveform

with Dual Tones

TWO-TONE SUPERPOSITION, LINEAR SYSTEM

TIME

AMPLITUDE

Headroom Limit

Fig. 3

Clipped Wave

From Too Much

Bass Boost

(without Big

Bottom)!

TWO-TONE SUPERPOSITION, CLIPPED SYSTEM

TIME

AMPLITUDE

Fig. 2

Linear System

Dual Tone

Spectrum

Purity

FREQUENCY SPECTRUM

AMPLITUDE

Fig. 4

Distortion

Spectrum

From Clipping

(without Big

Bottom)!

TWO-TONE SUPERPOSITION, CLIPPED SYSTEM

FREQUENCY SPECTRUM, Hz

AMPLITUDE

Low Tone

High Tone

Low Tone

High Tone

Clipping

Products

30 100 300 1K 10K3K 30K

The Principles of Superposition

Appendices

1 2 ... 22 23 24 25 26 27 28 29 30 31 32

Comments to this Manuals

No comments

Aphex Channel Instruction Manual Page 27

Comments to this Manuals

Related products and manuals for Audio amplifiers Aphex Channel