ARP2600 - Fundamentals of Music Technology - Cyborgstudio.com

SECTION10 S/H MODULEINTRODUCTIONThe sample-and-hold module is actually composed of three discreet modules, each of which can beused on their own. It does make sense that they have been grouped together, however, since both thesample-and-hold module and the electronic switch are dependent upon the internal clock for operation.THE INTERNAL CLOCKThe internal clock is different from just about every other module on the 2600. It is almost never heard,nor was it intended to be heard. The internal clock performs a fairly simple task: It produces a constantstream of trigger pulses, one after the next+15vas shown in Figure 10-1. The drawing on thefront panel of the cabinet also depicts theseconstant trigger pulses, and can be seen in VoltsFigure 10-2.The internal clock has only one parameter,Timeand that is rate. Rate determines how quickly Figure 10-1: The trigger pulses output by the internal clockthe internal clock puts out pulses. The rate atwhich the internal clock puts out trigger pulses can be changed by moving the RATE slider shown inFigure 10-2 up or down. Again, this is the internal clock’s one and only parameter.THE INTERNAL CLOCK’S NORMALSThe internal clock is normalled to three other modules, butunlike the normals that have been examined to this point inthis text, one of these normals cannot be broken. First, theinternal clock is normalled to the sample-and-hold circuit. Thisconnection will be discussed in detail in a moment. Secondly,the internal clock is normalled to the electronic switch. Thisnormal cannot be broken. There are a few ways to work aroundthis problem which will be discussed later in this section. Finally,the internal clock is normalled to the envelope generators.This normal can be broken, but there are two ways to dothis, both of which will be discussed in a moment.Although it is not labeled to this effect, the EXT CLOCK IN Figure 10-2: The S/H Modulejack is where the clock is normalled to the sample-and-holdunit, and it is here that the internal clock’s normal to the sample-and-hold unit can be broken. A pulsewave connected here will trigger the sample-and-hold unit and cause it to sample. However, the incomingpulse wave will not affect the electronic switch, because the internal clock cannot be controlled byan external device. This will be discussed in depth in a moment.075