080 SECTION TEN: S/H MODULE

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1. Connect the INT CLOCK OUT jack to an input on the mixer. Try to increase the clock’s rate high enough that its square wave output can be heard.

2. Flip the S/H gate switch below the EG’s to the lowest position so the internal clock will trigger the EG’s. Create a patch in which the VCO-1 and 2 are tuned in unison and fed to the VCF. Use the ADSR generator to modulate the VCF’s Fc. Try changing the clock’s rate, and try changing each of the stages of the EG.

3. While conducting experiment #2, use a pulse wave from VCO-3 in LF mode to trigger the EG’s by connecting it to the S/H GATE jack. What happens? Why does this happen?

4. Create a patch using all three oscillators tuned in unison and routed to the filter. Add 50% resonance, and close the filter. Connect the VCF’s output to jack A on the electronic switch. Connect jack C on the electronic switch to the mixer and raise that mixer input’s level. Now sweep the filter’s Fc up and down to create a pulsing sound with a filter sweep. CD track 53

5. Create a patch using all three oscillators tuned in unison and routed to the filter. Add 50% resonance, and close the filter. Connect the VCF’s output to jack C on the electronic switch. (Decrease the volume of the speakers before moving on to the next step.) Connect jacks A and B to the LEFT INPUT and RIGHT INPUT jacks. What is happening and why? CD track 51

6. Tune two oscillators to different pitches and connect an output from each to jacks A and B on the electronic switch. Connect jack C either to an input on the filter or directly to the mixer.

CD track 54

7. Connect two different control signals to jacks A and B of the electronic switch. Now connect jack C to the FM input on a VCO. CD track 55

8. Connect the pulse output of VCO-3 to the EXT CLOCK IN jack while conducting experiment #5, and notice that it has no effect on this patch. Why is this?

9. Use the S/H to sample the noise generator (be sure to raise the level on the noise generator). Use the S/H output to FM VCO-1 and VCO-2. Raise the clock rate slider about halfway, route the VCO’s to the filter, then the mixer and add a little reverberation. CD track 56

10. Now use the S/H output to control the Fc of the VCF. CD track 57

11. Create a few different ‘feedback’ patches. Because there are so many variables in this patch, your results may sound nothing like those on the CD. CD track 59

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1. What is the internal clock’s only parameter?

2. When and where does the internal clock put out trigger pulses and/or square waves?

3. What three things does the internal clock control?

4. Which of the internal clock’s normals can and can’t be broken?

5. Describe how the internal clock can control the EG’s.

6. Describe how to synchronize the internal clock with an external source.

7. Name the two main kinds of patches the electronic switch can be used for, and give examples of how each could be useful.

8. Step by step, describe the process by which the S/H unit samples incoming voltage.

9. Name three ways the S/H unit can be used.

10. How is the level of voltage being input to the S/H unit attenuated?

11. Why are the electronic switch, the internal clock, and the S/H unit grouped together on the ARP’s cabinet? (Clock) Rate Distribution Patch Electronic Switch Feedback Patch Internal Clock Sample Sample-and-Hold S/H

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To this point, all of the experiments and examples have used the modules contained in the ARP exclusively. While this is a won- derful way to learn about the ARP, one must understand that the 2600 is most powerful and useful when used with other devices in a studio. Unfortunately, connecting devices directly to the ARP’s modules usually doesn’t work particularly well, since the signal coming from these devices is much weaker than the sig- nals the ARP uses. Before signals from devices such as CD play- ers, tape decks, or other synthesizers can be used, they must be

amplified. Amplified means ‘made louder,’ which means increas-

ing the height of the waveforms. This job is left to an amplifier.

The amplifier, found in the upper left hand corner of the ARP’s cabinet (see Figure 11-1) is referred to as a preamplifier because it amplifies signals before they go to other modules. The job of a preamplifier is to raise the level of a signal to match a specific level.

The preamplifier’s input is not labeled, but it is the left most jack on the module. Unfortunately, the ARP 2600’s designers chose to use an 1/8” jack here. While this conforms to the jacks on the rest of the instrument, this would have been a very good place to put a 1/4” jack, since most external equipment that one might want to connect to the ARP has 1/4” jacks.

Following the white line which indicates the patch of the signal through the module, one can see that the gain parameter is the next item encountered. Gain is another word for volume. Although all of the other controls on the 2600 have sliders, the preamp

features a rotary knob. The farther clockwise this knob is turned, the greater the amplification of an incoming signal. In Figure 11-2, one can see a square wave both before and after amplification.

In its default mode, the preamp can increase the height of a waveform up to ten times its original

height (when the gain knob is set to MAX). While this might seem like a lot of amplification, it really isn’t. There are times when more is needed. Thus, the preamp allows the user to set the range of values over which the gain knob will function. This is set using the switch labeled RANGE. This switch has three possible settings: 10x, 100x, and 1000x. When set to 10x, the preamp will increase the waveform’s height tenfold when the gain knob is in the MAX position. When the switch is set to 100x, the preamp will increase the waveform’s height one hundredfold when the gain knob is in the MAX position and so on with 1000x. Of course, 1000x is a great deal of amplification, and there are limits to what the preamp circuit can handle.

Figure 11-2: A square wave before and after amplification Before Amplification After Amplification Figure 11-1: The ARP 2600’s preamp

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The preamp has a range of amplitudes of signals that it can handle. As long as signals stay within this range, the preamp will faithfully amplify signals, and put out what comes in, only louder. (See Figure 11-3)

The distance from the top of the black rectangle in Figure 11-3 to the bottom represents the preamplifier’s dynamic

range or the range of amplitudes which the preamp can ac-

curately reproduce. However, it is entirely possible to amplify a signal to the point where the peaks and troughs of the waveform reach outside the dynamic range. (See Figure 11-4)

The preamp cannot handle the highest points of these waveforms, and they become clipped off when they reach the end of the dynamic range. This phenomenon is known as clipping or distortion. The word distortion has many uses, but one must think of it as the actual shape of the waveform being changed or distorted, similarly to the way a funhouse mirror distorts the image of one’s face. When the waveform in Figure 11-4 emerges from the preamp, it will look like Figure 11-5.

Because the actual shape of the wave has changed, so has the harmonic content, and thus the waveform’s timbre.

This waveform which was formerly a saw wave will sound more like a square wave. In fact, as the amplitude is increased, the waveform will become more like a square wave. In this sense, the preampli- fier can actually be used to reshape the incoming waveform and turn it into a different wave.

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To this point, nothing has been said about whether dis- tortion is a good thing or a bad thing. For many years, distortion was considered to be a very bad thing. Distor- tion in a recording was to be avoided at all costs. The faintest crackle was considered to be the sign of a poor recording. During the late 1950’s and early 1960’s, gui- tar players discovered that if they increased the volume of their amplifiers enough, distortion would occur and change the timbre of their guitars. Distortion thus became a popular effect for guitars. In the 1990’s, artists such as Skinny Puppy and Trent Reznor of Nine Inch Nails have taken distortion to a new level, distorting everything from their voices to all of the musical instruments in a song.

Figure 11-3: A saw wave within the preamp’s dynamic range

Figure 11-4: A saw wave which has exceeded the preamp circuit’s dynamic range