Klark Teknik DN540 specifications Ratio, Compressor Control Functions

Chapter 6: Compressor Control Functions

Release time plays a very important role in compression. During periods of high signal level, gain is reduced. When the signal level falls below the threshold, the gain will increase at a rate determined by the RELEASE control knob. If the release time is short, the gain will rise quickly. A long release time will mean that the gain will stay at its reduced level, only recovering gradually, see Figure 2 “Compression fast and slow release signal envelope graphs”.

The setting of the correct release time is a compromise. If it is too short, background noise can cause effects such as breathing and pumping. A release time that is too long results in a signal that is not compressed, but merely reduced in level. For effective compression the release time must be set as short as possible before modulation of the background noise becomes too noticeable. The ATTEN gain reduction meter will show how much actual compression is occurring. If it is steady, there is little active compression, just a steady-state reduction in level. The faster the meter level moves up and down, the harder the compressor is working.

Ratio

Ratio is the strength of compression above the threshold level and controls the amount of compression applied to signals that are over threshold. Ratio is expressed as a ratio of signal level changes from input to output. For example, when the compressor is set to 2:1, every 2dB input level change will only generate a 1dB output level change, assuming the signal levels are over threshold. The highest ratios are achieved when the ratio control is fully anti-clockwise.

Note: Although the RATIO control knob on the DN540 operates in the opposite way to more conventional units, that is, the ratio is increased by turning it anti-clockwise rather than clockwise, we feel this is better ergonomically. This is because turning the control anti-clockwise results in less output, which matches the threshold and make up gain.

		+20	Output level (dB)
		+10
				Input level (dB)
-20	-10		+10	+20
		-10
		-20
			2:1

		+20	Output level (dB)
		+10
				Input level (dB)
-20	-10		+10	+20
		-10
		-20
		12:1

Figure 3: Compression ratio graphs of 2:1 and 12:1

As can be seen from the graphs in Figure 3 “Compression ratio graphs of 2:1 and 12:1”, the higher the ratio, the greater the effect.

At a compression ratio of up to 2:1, the effect is mild and suitable for the subtle compression of vocals or of a complete mix. At 3:1, compression is becoming stronger and more noticeable. Ratios between 3:1 and 5:1 are suitable for the compressor sound, which is used as an effect in its own right. Higher ratios are used for the control of extremely peaky signals.

	DN540
20	Operator Manual