Alesis K2661 specifications Input, SampleModeSamples131072KChannel=2, RecordAutoTimerPreview, 14-3

Sampling and Live Mode

Sampling Analog Signals

Input

On the SampleMode page, you’ll set the conditions for your sample recording. Depending on the input type you select, a different set of parameters will appear on this page. When you’ve selected analog input, the page appears as in the diagram below. The differences between analog and digital sampling are discussed in the section called Sampling Digital Signals on page 14-8.

SampleModeSamples:131072KChannel=2

Sample:NoneSrc:Ext

Input:AnalogTime:1sMon:Off

Gain:0dB

Rate:48.0KHzL

Mode:StereoR

Thresh:Off-dB6040*16*840

RecordAutoTimerPreview

The digital meters at the lower right of the display give a good indication of your sample level. When you send a signal from your sample source, you should see the meters respond.

Src

The possible values for the Src parameter are Internal (Int) or External (Ext). Choose a value of Ext when you want to sample the signal from an external source that’s connected to one of the K2661’s sampling inputs. Use a value of Int if you want to sample the K2661’s own output.

Gain

The meters are calibrated in -dB units. A level of 0 dB indicates the maximum signal without clipping. The sample will be free of clipping as long as the meter levels don’t exceed 0 dB. For optimum results, you should adjust the K2661’s Gain parameter (or the gain from your sample source) so that the signal stays below 0 dB. Otherwise, the signal will be clipped, causing the loss of sample data, and usually resulting in audible distortion of the resulting sample. A few clips (fewer than 100) may not cause any appreciable distortion. You’ll get the best signal-to- noise ratio with meter levels as close to 0 dB as possible, although you’ll find that samples with maximum meter readings as low as -12 dB can sound remarkably noise-free.

The relatively slow LCD output of the meter levels cannot show every peak in the incoming signal. Therefore, you won’t necessarily see every transient in every sample you take. You will be able to see any transient that is clipped, however, since whenever a clip occurs, the K2661 will display the word “CLIP” above the meters, and will flash the Master-mode LED. It will also give you the number of clips in each sample before you save it.

Rate

After you’ve set your levels, you need to select the sample rate. You have four rates to choose from. The tradeoffs that determine your best sampling rate are frequency response and storage requirements. Higher sample rates capture more frequency content from your samples, but take up more memory. Lower rates give you more sample time, but don’t give the same frequency response as higher rates. Rates of 29.4 or 32 KHz yield a flat response up to about 14 and 15 KHz, respectively. 44.1 and 48 KHz yield a flat response up to 20 KHz, which is the upper limit of audibility for most humans. The lower rates may be adequate for most sounds, since many sounds have little content above 15 KHz. Sounds with a great deal of high-frequency content, such as cymbals, should probably be sampled at the higher rates. You can save memory by using lower sample rates for sounds without much high-frequency content—acoustic or electric bass, for example.

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