Ashly CL-2 Руководство пользователя - Страница 4

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1. Frequency Selection

without saturating the transformer core. (Core saturation is the magnetic

equivalent of clipping, and results in a distorted signal)

To install a transformer in the standard input, cut and remove the two

jumpers (solid color with one black stripe) for each transformer, as indicated in

figure 2. These jumpers are referenced on the circuit board as well. Insert the

transformer assembly into the five pin socket and fasten with the provided screws.

CL-2 DUAL COMPRESSOR/LIMITER ..............................

Figure 3: CL-2 compressor/limiter

The Ashly CL-2 is a peak-sensitive, adjustable threshold AGC (automatic

gain control) device which is optimized primarily for speaker protection. It's

ratio, attack time, and release time are all preset at desirable levels for this

purpose. We use the same VCA (voltage controlled amplifier) found in our other

AGC products, assuring highly accurate, low distortion gain reduction. By

design, our VCA circuit acts as a transparent unity gain amplifier unless it's

detector threshold is exceeded. You can select the input signal level below which

the limiter remains inactive. When signal level rises above this threshold, the

limit LED lights up and the VCA reduces it's gain proportionally. The ratio, or

amount of gain reduction vs. signal level above the threshold, gradually increases

as the signal above threshold increases. This technique has become known as

"over-easy" or "soft knee" among others. The CL-2 ratio settles in at around 10:1

for more of a "brick wall" limiter appropriate for speaker protection. It's fast

attack time (1mSec) and relatively slow release (1.5sec) properly handle tran-

sients and excessively high levels, yet maintain a natural sound.

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Ashly POWERCARD Owners Manual

signal waveform. This kind of sound system distortion occurs when an amplifier

is overdriven and runs out of power during peak signals. In this case, nice round

waveforms turn into harsh sounding squared-off waveforms. Overdriving an

Ashly amplifier will usually be inconsequential to the amp, however the loud-

speaker load will ultimately suffer. Looking at it from the perspective of a speaker

diaphragm, clipped or distorted operation requires an instant acceleration, instant

stop, a change of direction, and instant acceleration again. Since speaker

diaphragms are subject to the laws of physics, they won't take this kind of

punishment for long. The diaphragm may shatter, or it's voice coil may overheat.

In addition to the damage caused by sustained overload, the speaker may also be

damaged by occasional, one-shot high level overload, for example, the sound of

a microphone falling face first onto a hard floor. Even if this type of transient

doesn't destroy a speaker outright, it may damage the speaker surround in such a

way as to cause mechanical abrasion and future failure. Rather than occupy

valuable rack space with outboard limiters, the CL-2 provides driver protection

within the confines of the amplifier itself.

in environments with high ambient noise levels. When intelligibility is important,

a wide dynamic range would render much of the signal inaudible, as the quieter

portions of audio would fall below the ambient noise. If the signal were increased

so that the quietest part could be heard above the ambient noise, most likely the

loudest passage would be too loud. In this application, the CL-2 becomes a

compressor because it literally squeezes the dynamic range into a smaller space.

The difference between the loudest signal and the softest signal is reduced by a

factor of up to ten, depending on where the threshold is set. For example, if the

loudest signal were 50 dB above the softest signal (FM radio has a dynamic range

of 60) and you adjusted your CL-2 threshold control so that the LED threshold

indicator was always on, your resulting dynamic range would be about 5dB. Of

course this is a bit extreme but it illustrates the application. Induction loop systems

are another application which benefit from compression of the dynamic range.

The level control on the CL-2 follows the VCA circuitry, so you can adjust the

amplifier output level without affecting the action of the compressor/limiter.

or bridged mono, only channel one input is used. The grounding jumper on the

barrier strip input connects the input cable ground (pin 1) to the chassis. Under

normal conditions, this should be left in place. See figure 4 for specific connector

locations of the CL-2 input option.

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Ashly POWERCARD Owners Manual

Speakers can be damaged by either excessive power or more often, a clipped

Another application for the CL-2 is to reduce the dynamic range of a signal

Stereo, mono, and bridged mono modes are available. When in either mono

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