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OK, all you budding Billy Hydes and Ringo Starrs out there . . . here’s your chance to own a low-cost “drum kit” which can produce just about any musical sound you can think of – and there’s not a drumskin in sight! You don’t even need to buy a pair of drumsticks! by John Clarke SILICON CHIP MIDI DRUM KIT PART 1 36  Silicon Chip siliconchip.com.au F a similar way to a real drum set, so its operation is more or centuries, drums have been an integral part of natural. music, used in everything from tribal music through There is no doubt that a real drum kit with its highly jazz, rock and blues, right through to symphony polished crash plates, finely crafted drums and the physiorchestras. In many cultures, drums play an integral part cal presence of the instruments all arranged in a group is during ceremonies and religious events. an impressive sight. An electronic drum kit just doesn’t Modern drums tend to be based on instruments that quite have the same appeal because electronic drum kits are used in established cultures. For example, from the are basically uninteresting to look at. Afro-Cuban cultures we have been introduced to the bongo After all, with a real drum kit, you can see the instruand the congas while from the American native Indians ments and even watch them working, particularly with the comes the tom tom. Cymbals of various descriptions have Hi-Hat, the cymbals and the foot-driven drum. originated from Europe, Turkey and China. For these reasons, MIDI drum kits are not often used for Traditionally, drums have tended to be made from live performances but mainly for recording and producing natural products such as carved timber and animal skins synthesised music. while cymbals are usually manufactured from brass. These An electronic drum kit’s claim to fame is therefore not instruments have a charm of their own and produce a its looks but instead its versatility and the significantly unique sound that is dependent on the products used in lower cost than is available with any “physical” their manufacture. drum kit. Modern instruments are made using It is also much easier to transport high-technology materials such as and it produces sound in a form stainless steel, aluminium and its rs ake spe d that can readily be recorded. alloys, plus many types of plastics. an ter pu com • Sound output via a Tables 1 and 2 show the The sound produced by these or synthesiser drum sounds that can be instruments can be tightly ard nd sta the for selectable used with the SILICON CHIP controlled so that each in• Up to 21 instruments kit set drum MIDI Drum Kit when strument has a distinctive a sets Brush, Jazz and Orchestr ing connected to a synthelud and consistent sound. inc 2) DI MI ith 7 extra kits (w e siser located within a Often, these sounds • tim e on the at yed pla • 7 instruments can be musical instrument are recorded in a digiment .7 to select another instru No nt me tru (such as keyboards), tal form so that they ins of l tro • Footswitch con Hat) or via a computer can be played back us(eg, closed and open Top hand plate and foot that has a sound card. ing a synthesiser. The te, pla on ssi rcu pe e lud gers inc its Synthesisers suptechnique for record- • Instrument trig un n tio activa porting the MIDI level te ing is called sampling. pla r ge trig pressure on the 2 standard can also Other synthesiser • Volume level can vary with striking pressed e: wide variation, two com reproduce the exsounds are not recordum vol d pa sor sen for settings tra sounds ranging ings at all but synthe- • Four and a fixed full level gs tin set d an el from 27 to 35 and sised sounds made uslev e um vol ections, patch and from 81 to 87 for the ing oscillators, noise and • LCD shows sensor sel els nn right cha sitioning within left and po standard kit plus the envelope control to recrege sta nd sou le tab jus • Ad d) car nd sou ith (w other drum sets. These ate the required effect. ter pu thesiser or com • Can be used with a syn include the Room, PowOnce the drum sounds s nection (DB15) or serial (DB9) con er, Electronic, TR-808, are recorded or created, we • MIDI out, sound card available Jazz, Brush, Orchestra and can replay them repeatedly ter ver con B US to Sound Effects sets. just by signalling the syntheial ser a • USB operation via Most synthesisers and computsiser to play a particular sample. red     • Plugpack powe ers with sound cards manufactured The data sent to the synthesiser is in after 1995 are likely to support these extra a format called MIDI (Musical Instrument drum sets. Digital Interface) and includes information such as the Of course, if you know enough about music software, you required instrument to be played, its volume and its posican generate your own set of sounds using VST (Virtual tion in the left and right sound stage. Studio Technology) or similar hardware emulators, or add By adding sensors to detect when the recorded “drum” in already created drum patches yourself. sound is to be played, we can drive the synthesiser with the MIDI signal to faithfully reproduce the required drum Presentation sound whenever the sensor is struck. (For a more detailed The MIDI Drum Kit electronics is housed in a plastic box description of MIDI and the way it works, refer to the “MIDI that can be mounted on a stand along with the pad sensors, Theremin” articles in SILICON CHIP, April/May 2005). or used as a freestanding unit with the sensors remotely This is the basis of an electronic drum kit – and the proattached. It includes a Liquid Crystal Display, which can ject presented here, the SILICON CHIP MIDI Drum Kit. It can show the selected drum (or other sound) for each sensor reproduce a vast array of drum sounds without having to pad input, the various settings and the overall volume and use conventional instruments to make the sounds. left to right positioning. Six pushbutton switches are used Drum sounds can be initiated using an electronic keyto change the settings. board to play the instruments or you can use a drum kit. Eight RCA inputs at the side of the box are for the seven The advantage of the drum kit is that it can be played in Features siliconchip.com.au November 2005  37 SENSOR PAD1 SENSITIVITY PEAK HOLD VR1 STORAGE AN2 IC1d, D1 SENSOR PAD2 VR2 EN RB3 RS LCD DATA AN4 IC1c, D2 SENSOR PAD3 RB4 VR3 RB1 RB0 AN1 R IC4 COUNTER CLK IC1b, D3 SENSOR PAD4 VR4 SENSOR PAD5 SWITCHES S1 – S6 AN3 IC1a, D4 VR5 IC3 LED1 AN0 λ IC2b, D5 SENSOR PAD6 VR6 AN5 IC2c, D6 SENSOR PAD7 VR7 RB5 IC5 OPTOCOUPLER AN6 RB2 OUT TO GAMES PORT MIDI OUT IC2d, D7 FOOT SWITCH MIDI INVALID LED IC6 RS232 CONVERTER TO SERIAL PORT Fig.1: the block diagram of our new MIDI Drum Kit. Its operation is explained in the text. sensor pad connections and the foot switch. Other connections are at the rear of the box and are for the MIDI-out, the serial connector, the games port connector and the DC power sockets. One of the DC sockets is for the 9V DC plugpack input and the other for DC output to connect to optically- operated sensor pads. A power switch is included and the LED adjacent to the MIDI socket shows the “MIDI invalid” indication. More about this later. Synthesiser As mentioned before, there is neither a synthesiser nor amplifier within the MIDI Drum Kit – it must be connected to an external synthesiser and the audio output of this synthesiser connects to headphones or to an amplifier and loudspeakers, mixing desk, etc. By far the most common source of a synthesiser is the one inside a standard personal computer or laptop – every sound card has a synthesiser. Another source is an electronic instrument such as a MIDI keyboard. The MIDI Drum Kit can be used with either of these synthesisers. Signals from the MIDI Drum Kit are sent as a series of codes that command the synthesiser to produce sounds. The codes are sent in MIDI format – this is a standardised signal used by the music industry to control synthesisers. We mentioned before the MIDI Theremin article from April 2005. What is different about the drum sounds in MIDI is that they can only be used on one channel (or two channels for MIDI 2) out of a total of 32 channels available for use with MIDI. These are channel 10 plus channel 11 when using the MIDI level 2 standard. In addition, while other channels produce notes of a particular instrument setting, channel 10 produces a sampled sound of an instrument for the note selection instead. 38  Silicon Chip The instrument setting for the other channels becomes the patch number for the drum set. To connect to a MIDI musical instrument, you connect a MIDI lead from the MIDI Drum Kit’s MIDI socket to the instrument’s MIDI input. When connecting to a computer, you have three possible options: (a) use the games port (if the computer has one), which connects directly to the computer’s sound card; or (b) use the serial outlet and connect this directly to a serial port on the computer (again, if the computer has one); or (c) use the computer’s USB port. A games port, which has a DB15 connector, will accept MIDI signals directly. However, many modern computers do not have a games port and some very modern ones don’t have an RS232C serial port either. Those computers will, however, have at least one (and usually several) USB ports. If you do not have a games port or serial port, then the only way to use the MIDI Drum Kit is via a USB port. For this, you will need either a MIDI-to-USB converter or a serial port to USB converter. MIDI-to-USB converters currently cost around $140, while serial-to-USB converters are only about $40, so if you need to use the USB port we recommend the serial-to-USB option. In either case, software will need to be installed in order for the USB ports to respond to the signals sent by the MIDI Drum Kit. There is a difference! When using the serial output from the MIDI Drum Kit to make the computer connection, the signal sent by the MIDI Drum Kit is not genuine MIDI standard. This means that the MIDI signal provided on the MIDI output cannot be used to drive a MIDI instrument when the unit is configured for siliconchip.com.au serial output. In this case a LED lights to indicate that the MIDI output is invalid. The oscilloscope waveforms in Fig.2 show the difference between the genuine 31.25k bits/second MIDI signal (yellow trace) and the serial port’s 38.4k bits/second rate (blue trace). In the latter case, the transmission is completed in a shorter time than for genuine MIDI. Software Software is required when using the computer as the synthesiser source. The main software is the sequencer program. This accepts the MIDI signal sent by the MIDI Drum Kit and directs it to the sound card’s synthesiser. The sequencer also provides many other functions such as the ability to record the music, store it and play it back. Panning from left to right, instrument change, looping and quantisation effects are also available. We used Rave, a freely-available sequencer program that can be downloaded from the internet. The software works with Windows 95, 98, Me, 2000, NT and XP. We will explain how to download, install and use the software in a later issue. Professional sequencers can also be used and these have the advantage that you can edit and create your own sounds. Software for the serial port driver works with Windows 95, 98, Me, 2000, NT and XP. The Serial to USB port driver works with Windows 98 through to XP. justed to match the sensitivity of other sensor pads. Following the sensitivity adjustment, the signal from each sensor plate is rectified and the peak value from the sensor is stored. A microcontroller is used to monitor the stored signals from the sensor plates at the analog inputs AN0-AN6 and the “foot switch” input RB2. If a signal at any of the PAD inputs reaches a predetermined value, then the microcontroller decides that the associated sensor pad has been Block Diagram Fig.1 shows the block diagram for the MIDI Drum Kit. Sensor pads from PAD1-PAD7 are connected to identical circuitry, including a sensitivity trimpot, a peak-hold buffer and storage. The sensitivity adjustment allows any sensor to be adsiliconchip.com.au Fig. 2: these oscilloscope waveforms show the difference between genuine MIDI and the “serial MIDI” for the computer’s sound card. As you can see, the lower trace is completed over a shorter time. November 2005  39 struck and a MIDI signal is produced at output RB5. This is then applied to an optocoupler, the MIDI output socket and the RS-232 converter. The optocoupler provides isolation between the MIDI Drum Kit and the computer connection via the games port. This prevents hum loops forming if the MIDI output is also connected to a synthesiser. The RS-232 converter converts the 0-5V signal from the microcontroller to a nominal ±10V signal for the serial port. When using the serial port connection, the “MIDI invalid” LED lights to indicate that the signal on the MIDI outlet is not able to drive a synthesiser. The microcontroller also drives the LCD and monitors switches S1-S6. Input RB2 of the microcontroller checks if the footswitch is open or closed. +9V +5V PAD1 VR1 20k 100k 100nF 100k Digital circuitry The digital circuitry comprises IC3, IC4, IC5 and the LCD module. IC3 is a PIC16F88 microcontroller from Microchip. It includes features such as a 10-bit multi-channel analogto-digital converter and a serial output that can produce MIDI format signals at 31.25kHz bit rate, with the required stop and start bit. The serial output can also be set to provide the 38.4kHz signal suitable for the serial port on a computer. Either of these two bit rates is accurate when the microcontroller operates at 16MHz and we do this using crystal X1 between 40  Silicon Chip 12 13 D1 4 IC1d 14 A K 100k +5V PAD2 VR2 20k 100k 100nF 100k The circuit The MIDI Drum Kit circuit can be divided into two parts: the analog section (sensor plate input circuitry) and the digital section (the microcontroller, LCD and switches and the MIDI output sections). The circuitry for pad inputs PAD1-PAD7 is identical. The signal source can be either a piezo transducer or an optical sensor circuit (as we shall see later). The signal from each pad is tied to the +5V supply via the full 20kW resistance of the associated trimpot. In each case, the trimpot wiper can be adjusted between the full signal level, when set fully toward the Pad signal input, or to no-signal when the wiper is set at 5V. The signal is AC-coupled with a 100nF capacitor to remove the DC voltage, so that only the AC signal from the sensor passes. The DC level is then set at a nominal +2.5V using a voltage divider comprising two 100kW resistors across the 5V supply. IC1 and IC2 contain operational amplifiers (op amps) wired as peak detectors. Normally, the output sits at the same voltage as the non-inverting input (eg, pin 12). When a signal is applied to pin 12, the op amp’s output varies in response to this and the diode at the output charges the 1mF capacitor to the peak of the signal. When there is no signal at the input, the voltage across the 1mF capacitor will be discharged via the 100kW resistor across it, but not before microcontroller IC3 measures the peak voltage that was present on the 1mF capacitor (ie, at input AN2 of IC3). Immediately IC3 detects this voltage, input AN2 is set to be an output and it is able to discharge the 1mF capacitor via the 2.2kW resistor as soon as the voltage at the cathode of D1 falls. The footswitch input is tied to the 5V supply via a 1kW resistor. This sets IC3’s RB2 input high when the switch is open. When the switch is closed, RB2 is pulled to ground. These levels are also detected by IC3. 10 µF 9 VR3 20k 100k 100nF 100k 8 IC1c A K 100k +5V PAD3 D2 10 IC1: LM324 D3 3 2 1 IC1a A K 100k +5V PAD4 VR4 20k 100k 100nF 100k D4 5 6 7 IC1b A K 11 100k +5V PAD5 VR5 20k 100k 100nF 100k +9V 5 6 PAD6 100k 100nF 100k 7 IC2b A K 100k +5V VR6 20k D5 4 IC2: LM324 D6 10 9 IC2c 8 A K 100k +5V PAD7 VR7 20k 100k 100nF 100k D7 12 13 IC2d 14 A K 11 100k +5V FOOT SWITCH 1k 2.2k SC 2005 MIDI DRUM KIT Fig.2: the circuit looks complex – but compare it to the block diagram and it’s easy to understand the operation. 7805 IN GND OUT siliconchip.com.au +5V 100nF +5V 100 µF 14 2.2k 1 Vdd AN2 RB4 10 10 µF 1 µF RB3 9 4 16 2.2k 3 AN4 RB0 6 10 5 14 6 13 7 12 IC4 4040B Q1 9 11 Q4 CLK Q3 1 µF RB1 7 11 3 2.2k 18 R Q2 6 RS DB7 DB6 2 (JAYCAR 1) EN LCD MODULE DB5 5 7 8 9 1 (JAYCAR 2) 10 +5V 8 S5 S6 S1 S2 S3 10k S4 MIDI INVALID LED1 4 RA5 220Ω 2 A λ K +5V AN3 1 µF 2 IC3 PIC16F88 RB5 220Ω 11 IC5 6N139 λ 3 1 8 8 470Ω 10 µF 100nF 6 17 4 AN0 220Ω MIDI OUT TO SYNTHESISER 5 2.2k 4 16-PIN HEADER 100k 220Ω +5V 16 2 12 5 7 1 µF TO GAMES PORT 9 15 5 2.2k VR8 10k 3 DB4 Q5 AN1 1 µF 2.2k CONT 1 µF AN5 1 µF 2 1 µF 11 2 14 1 OSC2 2.2k 13 OSC1 15 16 1 X1 16MHz 1 µF 33pF 8 33pF 5 4 22k 7 TO SERIAL SOCKET 8 6 1 µF 6 1 µF 5 15 DB9F +9V REG1 7805 +5V 5 D8: 1N4004 LED K K A 4 RB2 Vss D1–D7: 1N4148 3 AN6 1 µF IC6 MAX232 A OUT IN POWER S7 D8 K A 9V DC IN GND 10 µF 10 µF 470 µF 9V DC OUT K A siliconchip.com.au November 2005  41 End-on and side-on views showing the eight inputs (left); above is the DC in/out, games port socket, serial socket, invalid MIDI LED and MIDI output pins 15 and 16. IC3 is supplied with 5V between pins 14 and 5, with 100mF and 100nF capacitors decoupling this rail. The 100nF capacitor reduces high-frequency noise and the 100mF reduces the supply impedance at lower frequencies. The LCD module is driven from IC3, using outputs RB4 and RB3 to control the Enable and Register Select inputs on the module. The data lines are obtained from IC4’s counter outputs, Q1-Q4. IC4 is driven at its clock and reset inputs via IC3 outputs RB0 and RB1 respectively. IC4 is included to expand the two RB0 and RB1 lines into four outputs to drive the data lines for the LCD module. This expansion also allows the circuit to monitor the opening and closing of six switches. Note that the LCD module has eight data lines but we are only driving the upper four bits (DB4-DB7). Data therefore must be sent as two 4-bit blocks in order to drive the display. The enable input and the register select input are control lines to place characters on the display and to set the character position. IC3’s RB0 line provides clock pulses for counter IC4 and simultaneously turns the “MIDI Invalid” LED on or off, as required. It can do this because when the LED is supposed to be off, the clock pulses are so quick that they don’t have time to light the LED. Switches S1-S6 are monitored using IC3’s RA5 input, which is normally held high via the 10kW resistor to the 5V supply. The input will be pulled low if any switch is closed and its corresponding switch connection to IC4 is also pulled low. Since IC3 has full control over the state of IC4’s inputs and outputs, it is able to determine if a switch is closed and which one it is. The output comes from RB5 of IC3. This provides the signal for the MIDI output socket and the games port via optocoupler IC5, along with the serial output via RS232 driver IC6. The signal to the MIDI output socket is fed via 220W resistors, one from output RB5 to MIDI socket pin 5 and the other from 5V to MIDI socket pin 4. In the case of the LED optocoupler, when RB5 turns its LED on, the internal transistors are also switched on and the output (pin 6) is pulled to ground. When the LED is off, the transistor is off and the output is pulled to pin 8 via the 470W resistor. The 100kW resistor from the base of the internal transistor within IC3 to ground speeds up the transistor turn-off. When the circuit is connected to a computer games port, pin 8 of IC5 is connected to the computer’s 5V supply. Note that the grounds are shown with a different symbol to the rest of the MIDI circuit. This indicates that the grounds are different – the transistor side of IC5 is connected to the computer’s ground rather than the MIDI circuit’s ground. The 5V supply on the transistor for IC5 is decoupled using 10mF and 100nF capacitors. IC6 converts the logic levels (0-5V) on the micro’s RB5 output to RS232 voltage levels (±10V) to drive pin 2 on the serial port. With only a +5V supply rail, the MAX232 generates the higher positive and negative voltages required for RS232 communications using two internal charge-pump Specifications Sensor pad volume range: .......................................................................................................... From full to off in typically >120 steps Left to right pan: ............................................................................................................ 128 steps from 0 at full left to 127 for full right Main volume: .....................................................................................................................................from full volume at 127 to off at 0 Sensor pad volume range: ...................................................................................................36dB max range on Wide variation setting, ......................................................................................................................................................18dB range on compressed 1 setting, ................................................................................................................................................12dB range on compressed 2 setting and ...................................................................................................................................0dB range on the Fixed maximum volume setting. Delay from sensor strike to MIDI signal out: ................................................................................................................ typically ~1.2ms Latency (delay between MIDI out signal to sound produced): ......................................................................... depends on synthesiser Repetition rate for sensor pad:......................................................................adjustable from 0 to 255 in steps of 4 corresponding to a ............................................................................................................................. maximum of 224ms or a slowest repeat rate of 4.4/s. ................................................................................................................................. (Typically set at 100 for a repeat rate of about 9/s.) Sensor Threshold: ........................................................... adjustable from 0 through to 127 in steps of 1. Values of less than 5 typical. Current consumption:............................................................................................................................................. 150mA with 9V DC in MIDI out: .......................................................................................... 5mA loop, electrical isolation for games port (31.25k bits/second) Serial out: ............................................................................................................................................RS232 levels (38.4k bits/second) 42  Silicon Chip siliconchip.com.au The case is used upside down with the two stacked PC boards “folded into” the case; the display board held in from above. The case bottom then becomes the front panel. Full constructional details will commence next month. voltage converters. One converter doubles the supply voltage to +10V (nominal) and the other inverts the result to obtain –10V. Four external 1mF capacitors provide the necessary storage and filtering. Power for the circuit is via a 9V DC plugpack. It plugs into one of the DC input sockets and is switched by S7. After passing through polarity protection diode D8, a 9V (nominal) supply is available, as well as a +5V supply, provided by REG1. Another DC socket, wired in parallel with the power input socket, provides a 9V outlet for the optical sensor pad circuitry. It doesn’t matter which socket is used for which. Sensor pads The sensor pad circuitry comprises either a piezo transducer or an optical pickup – see Fig.3. The optical sensing circuitry uses an infrared LED and phototransistor in the one package. Light from the LED strikes the phototransistor which causes it to conduct. When the light is partially or fully interrupted between the LED and phototransistor, the conduction of the transistor reduces depending on the amount of light that is blocked. The LED is supplied with current from the 9V supply. Since this is unregulated, the supply is heavily filtered using a series 470W resistor and 470mF capacitor. This smooths the voltage before driving the LED via another 470W resistor. Diode D9 is included to provide reverse polarity protection. siliconchip.com.au Latency One sometimes troublesome aspect when playing sounds with MIDI is latency. This is the delay from when a sound is played via a keyboard or drum kit sensor plate to when the sound is actually produced and heard. The delay can sometimes be quite noticeable when the synthesiser in a computer is used for playing the sounds rather than the synthesiser in a musical instrument. The latency is largely dependent upon the sound card’s capabilities and the software that’s used with it. We’ll look at this in more detail when we describe using the software in a later issue. However, the latency of the SILICON CHIP MIDI Drum Kit between detection of a sensor plate being struck to sending the MIDI signal is minimal; typically 1.2ms. Generally, it is accepted that an overall 10ms delay is unnoticeable. The SILICON CHIP MIDI Drum Kit can be used with up to eight sensor pads to allow playing seven instruments simultaneously (no, you don’t need seven hands!). The eighth input can be used with a foot-switch that changes the instrument selection. It is ideal for operating the open and closed Hi-Hat cymbals – eg, the closed HiHat sound is generated when the seventh sensor pad is struck and the foot-switch is pressed (closed), while the open Hi-Hat sound is generated if its struck and the footswitch is open. Sounds produced when the sensor pads are struck can be any that are available within the particular selected Drum November 2005  43 TABLE 1: DRUM SET DESCRIPTIONS Patch Number 1 9 17 25 26 33 41 49 57 Drum Set Name Standard Kit Room Kit Power Kit Electronic Kit TR-808 Kit Jazz Kit Brush Kit Orchestra Kit Sound FX Kit Description The General MIDI Standard drum kit. The only kit specified by General MIDI Level 1(35 to 81 inclusive). Similar to the Standard kit but with more ambient percussive sounds. Similar to the Standard kit but with more powerful kick and snare sounds. Made up of sounds emulating those of various electronic drum machines. Analog drum kit that is reminiscent of the Roland TR-808 Rhythm Machine. Jazz-styled set that is nearly identical to the Standard kit. Similar to the Standard kit but with many brush sounds added. An immense collection of concert drums and timpani for orchestral-styled music. A collection of sound effects. TABLE 2: DRUM SETS Patch 1 9 17 25 26 33 41 49 57 Note Standard Room Power Electronic TR-808 Jazz Brush Orchestra Sound FX 27 High Q High Q High Q High Q High Q High Q High Q Closed Hi-Hat - 28 Slap Slap Slap Slap Slap Slap Slap Pedal Hi-Hat - 29 Scratch Push Scratch Push Scratch Push Scratch Push Scratch Push Scratch Push Scratch Push Open Hi-Hat - 30 Scratch Pull Scratch Pull Scratch Pull Scratch Pull Scratch Pull Scratch Pull Scratch Pull Ride Cymbal - 31 Sticks Sticks Sticks Sticks Sticks Sticks Sticks Sticks - 32 Square Click Square Click Square Click Square Click Square Click Square Click Square Click Square Click - 33 Metronome Click Metronome Click Metronome Click Metronome Click Metronome Click Metronome Click Metronome Click Metronome Click - 34 Metronome Bell Metronome Bell Metronome Bell Metronome Bell Metronome Bell Metronome Bell Metronome Bell Metronome Bell - 35 Kick Drum 2 Kick Drum 2 Kick Drum 2 Kick Drum 2 Kick Drum 2 Jazz Bass Drum 2 Jazz Bass Drum 2 Concert Bass Drum 2 - 36 Kick Drum 1 Kick Drum 1 Mondo Kick Electric Bass Drum TR-808 Bass Drum Jazz Bass Drum 1 Jazz Bass Drum 1 Concert Bass Drum 1 - 37 Side Stick Side Stick Side Stick Side Stick TR-808 Rim Shot Side Stick Side Stick Side Stick - 38 Snare Drum 1 Snare Drum 1 Gated Snare Drum Electric Snare Drum TR-808 Snare Drum Snare Drum 1 Brush Tap Concert Snare Drum - 39 Hand Clap Hand Clap Hand Clap Hand Clap Hand Clap Hand Clap Brush Slap Castanets High Q 40 Snare Drum 2 Snare Drum 2 Snare Drum 2 Gated Snare Drum Snare Drum 2 Snare Drum 2 Brush Swirl Concert Snare Drum Slap 41 Low Tom 2 Room Lo Tom 2 Room Lo Tom 2 Electric Lo Tom 2 TR-808 Low Tom 2 Low Tom 2 Low Tom 2 Tympani F Scratch Push 42 Closed Hi-Hat Closed Hi-Hat Closed Hi-Hat Closed Hi-Hat TR-808 Closed Hi-Hat Closed Hi-Hat Closed Hi-Hat Tympani F# Scratch Pull 43 Low Tom 1 Room Lo Tom 1 Room Lo Tom 1 Electric Lo Tom 1 TR-808 Low Tom 1 Low Tom 1 Low Tom 1 Tympani G Sticks 44 Pedal Hi-Hat Pedal Hi-Hat Pedal Hi-Hat Pedal Hi-Hat TR-808 Closed Hi-Hat Pedal Hi-Hat Pedal Hi-Hat Tympani G# Square Click 45 Mid Tom 2 Room Mid Tom 2 Room Mid Tom 2 Electric Mid Tom 2 TR-808 Mid Tom 2 Mid Tom 2 Mid Tom 2 Tympani A Metronome Click 46 Open Hi-Hat Open Hi-Hat Open Hi-Hat Open Hi-Hat TR-808 Closed Hi-Hat Open Hi-Hat Open Hi-Hat Tympani A# Metronome Bell 47 Mid Tom 1 Room Mid Tom 1 Room Mid Tom 1 Electric Mid Tom 1 TR-808 Mid Tom 1 Mid Tom 1 Mid Tom 1 Tympani B Guitar Fret Noise 48 High Tom 2 Room Hi Tom 2 Room Hi Tom 2 Electric Hi Tom 2 TR-808 High Tom 2 High Tom 2 High Tom 2 Tympani C Guitar Cut Noise Up 49 Crash Cymbal Crash Cymbal Crash Cymbal Crash Cymbal 808 Cymbal Crash Cymbal Crash Cymbal Tympani C# Guitar Cut Noise Down 50 High Tom 1 Room Hi Tom 1 Room Hi Tom 1 Electric Hi Tom 1 TR-808 High Tom 1 High Tom 1 High Tom 1 Tympani D Double Bass String Slap 51 Ride Cymbal Ride Cymbal Ride Cymbal Ride Cymbal Ride Cymbal Ride Cymbal Ride Cymbal Tympani D# Flute Key Click 44  Silicon Chip siliconchip.com.au 52 Chinese Cymbal Chinese Cymbal Chinese Cymbal Reverse Cymbal Reverse Cymbal Chinese Cymbal Chinese Cymbal Tympani E Laughing 53 Ride Bell Ride Bell Ride Bell Ride Bell Ride Bell Ride Bell Ride Bell Tympani F Screaming 54 Tambourine Tambourine Tambourine Tambourine Tambourine Tambourine Tambourine Tambourine Punch 55 Splash Cymbal Splash Cymbal Splash Cymbal Splash Cymbal Splash Cymbal Splash Cymbal Splash Cymbal Splash Cymbal Heartbeat 56 Cowbell Cowbell Cowbell Cowbell TR-808 Cowbell Cowbell Cowbell Cowbell Footsteps 1 57 Crash Cymbal 2 Crash Cymbal 2 Crash Cymbal 2 Crash Cymbal 2 Crash Cymbal 2 Crash Cymbal 2 Crash Cymbal 2 Concert Cymbal 2 Footsteps 2 68 Vibra-Slap Vibra-Slap Vibra-Slap Vibra-Slap Vibra-Slap Vibra-Slap Vibra-Slap Vibra-Slap Applause 59 Ride Cymbal 2 Ride Cymbal 2 Ride Cymbal 2 Ride Cymbal 2 Ride Cymbal 2 Ride Cymbal 2 Ride Cymbal 2 Concert Cymbal 1 Door Creaking 60 High Bongo High Bongo High Bongo High Bongo High Bongo High Bongo High Bongo High Bongo Door Closing 61 Low Bongo Low Bongo Low Bongo Low Bongo Low Bongo Low Bongo Low Bongo Low Bongo Scratch 62 Mute Hi Conga Mute Hi Conga Mute Hi Conga Mute Hi Conga TR-808 High Conga Mute Hi Conga Mute Hi Conga Mute Hi Conga Wind Chimes 63 Open Hi Conga Open Hi Conga Open Hi Conga Open Hi Conga TR-808 Mid Conga Open Hi Conga Open Hi Conga Open Hi Conga Car Engine Low Conga Low Conga Low Conga Car Brakes 64 Low Conga Low Conga Low Conga Low Conga TR-808 Low Conga 65 High Timbale High Timbale High Timbale High Timbale High Timbale High Timbale High Timbale High Timbale Car Passing 66 Low Timbale Low Timbale Low Timbale Low Timbale Low Timbale Low Timbale Low Timbale Low Timbale Car Crash 67 High Agogo High Agogo High Agogo High Agogo High Agogo High Agogo High Agogo High Agogo Siren 68 Low Agogo Low Agogo Low Agogo Low Agogo Low Agogo Low Agogo Low Agogo Low Agogo Train 69 Cabasa Cabasa Cabasa Cabasa Cabasa Cabasa Cabasa Cabasa Jet Plane 70 Maracas Maracas Maracas Maracas TR-808 Maracas Maracas Maracas Maracas Helicopter 71 Short Hi Whistle Short Hi Whistle Short Hi Whistle Short Hi Whistle Short Hi Whistle Short Hi Whistle Short Hi Whistle Short Hi Whistle Starship 72 Long Lo Whistle Long Lo Whistle Long Lo Whistle Long Lo Whistle Long Lo Whistle Long Lo Whistle Long Lo Whistle Long Lo Whistle Gun Shot 73 Short Guiro Short Guiro Short Guiro Short Guiro Short Guiro Short Guiro Short Guiro Short Guiro Machine Gun 74 Long Guiro Long Guiro Long Guiro Long Guiro Long Guiro Long Guiro Long Guiro Long Guiro Laser Gun 75 Claves Claves Claves Claves TR-808 Claves Claves Claves Claves Explosion 76 High Woodblock High Woodblock High Woodblock High Woodblock High Woodblock High Woodblock High Woodblock High Woodblock Dog Bark 77 Low Woodblock Low Woodblock Low Woodblock Low Woodblock Low Woodblock Low Woodblock Low Woodblock Low Woodblock Horse Gallop 78 Mute Cuica Mute Cuica Mute Cuica Mute Cuica Mute Cuica Mute Cuica Mute Cuica Mute Cuica Birds Tweet 79 Open Cuica Open Cuica Open Cuica Open Cuica Open Cuica Open Cuica Open Cuica Open Cuica Rain 80 Mute Triangle Mute Triangle Mute Triangle Mute Triangle Mute Triangle Mute Triangle Mute Triangle Mute Triangle Thunder 81 Open Triangle Open Triangle Open Triangle Open Triangle Open Triangle Open Triangle Open Triangle Open Triangle Wind 82 Shaker Shaker Shaker Shaker Shaker Shaker Shaker Shaker Seashore 83 Jingle Bell Jingle Bell Jingle Bell Jingle Bell Jingle Bell Jingle Bell Jingle Bell Jingle Bell Stream 84 Belltree Belltree Belltree Belltree Belltree Belltree Belltree Belltree Bubble 85 Castanets Castanets Castanets Castanets Castanets Castanets Castanets Castanets - 86 Mute Surdo Mute Surdo Mute Surdo Mute Surdo Mute Surdo Mute Surdo Mute Surdo Mute Surdo - 87 Open Surdo Open Surdo Open Surdo Open Surdo Open Surdo Open Surdo Open Surdo Open Surdo - Table 1 (at top left) shows the number of drum sound kits that can be accessed with the SILICON CHIP MIDI Drum Kit. Note that older version synthesisers (pre-1995) may only provide for the standard drum kit. Table 2 (Drum Sets) shows the list of instruments or sounds that can be selected within each drum kit. As you can see, there are more than just a few available! siliconchip.com.au November 2005  45 MIDI Drum Kit Controls When first powered up, the MIDI Drum Kit display shows “MIDI DRUM KIT -PLAY-”. This is the display that should be selected while actually playing the drum kit. Pressing the Port/Cal switch displays the current port setting on the top line and ^ CALIBRATE ^ on the lower line. The port setting is changed from < MIDI PORTS > to < SERIAL PORT > using the left or right arrow switches as shown by the < and > bracketing around the words. The MIDI invalid LED lights when the Serial Port is selected. The Calibration selection is normally only ever used once, after the MIDI Drum Kit has been completed. Pressing the ^ switch calibrates the unit so that the quiescent voltage level for each pad sensor input is registered. This ensures that we get the best sensor response for each pad. To exit from the Port selection and calibration, press the Port/Cal switch again. Note that the four switches arranged in a quad pattern below the LCD are labelled with < > ^ and v. These arrows are also shown on the display when the switches can be used to change the item within the two arrows. So a value or wording located within the < and > brackets can be altered by the < and > switches. The values within the ^ and v brackets can be altered using the ^ and v switches. Pressing the SET switch selects one of several modes that are available to make changes to the way the Drum Kit sounds and works. The first press brings up the PATCH mode. This allows selection of the various drum kit patches available using this MIDI Drum Kit. The top line on the display shows the patch number, showing 1 for Standard, 9 for Room, 17 for Power, 25 for Electronic, 26 for TR808, 33 for Jazz, 41 for Brush, 49 for Orchestra and 57 for Sound Effects. These patch numbers refer to the MIDI instrument numbers. The lower line on the display shows the patch type in words, as indicated above. For example, the display shows < Standard > when patch 1 is selected. The patch is changed using the < and > switches. Note that if your synthesiser does not support the MIDI 2 standard, then only the standard drum set will be played regardless of the patch setting. The next mode is Pan and Volume settings, selected using the Set switch. At left, the word Pan is shown and below this is the Pan value surrounded by the < and > bracketing. The value is changed by pressing the < switch to decrease the value and the > to increase the value. The pan sets the soundstage for the drum kit sound to be produced between the left and right channels. 0 sets the sound fully left, 63 is centred (equal left and right levels) and 127 is fully right. Volume is shown at right with the value directly below this and surrounded by the ^ and v arrows. The value can be changed using these ^ and v switches from 127 (full volume) down to 0 for no sound and any value in between. The next mode selected with the SET switch is the Repeat/Threshold system parameter settings. These are provided to compensate for physical factors that affect the sensor pads. With any hard material that is struck with a drumstick or similar object, it is likely to ring or resonate for some time afterwards. The sensor pads have been carefully designed using materials that do not resonate excessively. However, there will always be some resonance in any design. Resonance will affect the rate at which a sensor pad can be repeatedly struck. To cater for variances in the pads and their resonance, we have included the Repeat setting. This can be set to produce the best repeat rate that is possible. Values are adjustable from 0-255 in steps of 4, corresponding to a maximum of 224ms or a slowest repeat rate of 4.4/s. It’s typically set at 100 for a repeat rate of about 9/s. Use the < or > switches to alter the value. In a similar way, when there are several sensor pads attached to 46  Silicon Chip a common frame, there is likely to be a small amount of interaction between sensors. So if one sensor is struck, other sensors can detect the vibration through the frame. The adjustment of the Threshold value will prevent this interaction from happening. Typically, a value less than 5 will be correct. Use the ^ and v switches to alter the value. Pressing the SET switch again will show the Pad Volume setting. The second line will show Fixed, Vary Wide, Compress 1 or Compress 2. You can change from one to the other with the < and > switches. The Fixed setting means that the drums sounds will be always at their maximum volume when the sensor is struck. The other settings mean that the volume will be dependent on the degree that the sensor is struck. The wide variation setting gives the full 36dB dynamic range of control, while the compress 1 and compress 2 settings give an 18dB and 12dB dynamic range respectively. Basically, the compression boosts the minimum volume level for the drum sounds but does not change the maximum volume level available. Pressing the SET switch will return the display to showing MIDI DRUM KIT -PLAY-. Be certain that this is the setting that you use when playing the drum kit properly. This is because this setting is designed to provide the best response from the pad sensors as they are struck. You can use the other display settings when setting up and changing instruments and patches but be aware that the sensors may not react as well as when the MIDI DRUM KIT -PLAY- is shown. To select the PAD settings, press the SET switch or the < or > switches. The display will show for example <PAD 1> v #50 ^ on the first line. This indicates that the setting for PAD 1 is the “drum” selection number 50. This is the Hi Tom 1 in the standard drum set. The second line on the display shows for example PATCH 1, then a speaker icon and a number. The Patch number indicates the selected patch (1 for standard patch). Initial settings are Patch 1 and the Kick Drum selected for pad 1, the Snare Drum for pad 2, the Hi Tom for Pad 3, the Mid Tom for pad 4, the Ride Cymbal for Pad 5, the Crash Cymbal for pad 6, and the Open Hi Hat and the Closed Hi Hat for sensor 7. The pad 7 selections are changed with the footswitch. The pad selections can be changed to your own preferences using the list provided to make your selections. The speaker icon and number is a diagnostic tool to allow checking which sensor pad is connected to which input. Basically, the number after the volume icon shows the detected volume level that is played by striking the pad. All you need to do is to repeatedly strike a sensor pad and change the PAD selection (with the < and > switches) until the number after the volume icon shows higher numbers other than 0 as the pad is struck. The struck pad will be connected to the currently selected PAD input shown on the display. A right arrow appears also to indicate that a sensor is struck but not necessarily the sensor that you have currently showing on the display. Note that this feature is not easy to use if the Fixed pad volume is selected, since the volume does not change but stays at 127. The PAD settings are adjusted using the ^ and v switches to select type numbers from 27 through to 87. These select the “drum” sound required for the selected pad. The PAD selection is changed with the < or > switches selecting PAD 1 through to PAD 7. PAD 7 is shown as either 7a or 7b and is again selected using the < or > switches. The 7a pad “ drum” selection is the “drum” selection when the foot switch is open and the 7b selection is when the foot switch is closed. You can return to the MIDI DRUM KIT -PLAY- display by pressing the SET switch and return to the pad settings with the < or > switches without having to cycle through all the other settings that are available. Note that the pad number seen on the display will change up or down, depending on the < or > switch that is pressed. siliconchip.com.au 1N4004 9V DC IN PIEZO TRANSDUCER A RCA PLUG K 470Ω INTERRUPTOR 470Ω PIEZO PIEZO SENSOR Fig.3: the two types of sensors, as described in the text – the simple piezo sensor (above) and the more complex (but better) optical sensor (right). 9V DC OUT (THRU) 470 µF A C K OPTICAL SENSOR 1N4004 A Set, as shown in Table 1. Output volume level is dependent on how hard the sensor pads are struck. Alternatively, there are settings that compress the volume level or one that only plays at the maximum level. In this latter case, the overall volume is then dependent on the master volume setting and the volume setting for the amplifier connected to the audio signal. The sound duration is fixed and is set by the sample within the synthesiser. The sensor pad designs use readily available components that can be obtained from electronics stores and your local hardware shop. In its simplest form, a piezo transducer can be mounted onto a length of plastic tubing and wired to an RCA plug lead. The tube is then tapped with a fingernail, thimble or drumstick to trigger the sound production. This is an ideal sensor pad for stick, click, metronome, whistle and even cymbals or drums if you wish. A piezo transducer is also used in the percussive sensor. This transducer is mounted onto a semi-circular shaped piece of MDF (Medium Density Fibreboard) and this board is then attached to a light-duty frame using plastic clamps. The pad is ideal for virtually all types of instruments as it can be mounted in space (on the frame), in the positions required for ease of playing. The sensor pad must also be struck with a stick or similar hard object. This type of pad has the advantage that it is very easy to build. The percussive sensor pad does, however, have the K RCA PLUG λ λ OPTICAL SENSOR E SENS1 (TOP VIEW) A E K C disadvantage that it produces a sound of its own when tapped. This is normally drowned out by the actual drum sounds. It may, however, be a problem and so we have added settings that can play the drum sound at a louder level, even when the sensors are tapped very lightly. This keeps the unwanted sound at a low level. In addition, the pad can be covered with some vinyl or similar material to deaden the percussive sound or alternatively, the sticks can be rubberised. Such damping will also mean that the pads will have to be hit harder to develop the same sound level from the synthesiser. High-precision sensors can also be made for the MIDI Drum Kit and are based on optical sensing. They can be operated by palm of the hand, your feet or fingers. The optical pads provide a high degree of play control and good volume variation with different pad pressure. They also do not make any noise of their own. They have the disadvantage of being more complex to build and if they are to be mounted on a stand, it must be of high strength to prevent movement when the sensors are played – particularly if the musician gets a little carried away . . . Next month we will describe the construction of the MIDI Drum Kit, making the sensor pads and setting it up. That will include downloading and installing the required software and SC we’ll also describe how to use it. The two types of sensor: at left is the optical variety and at right the piezo model. The optical type, though more complex to construct, has several advantages. siliconchip.com.au November 2005  47