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250W into 4Ω; 150W into 8Ω B+ CON1 IN 47F NP NRML R2B R2A 4.7k 1W GND LIFT LK1 10 K 100k 4.7k 1W ZD3 5.6V 1W A 330 INV 1nF 4.3k 68k RF R1 R5 LK2 4.7k VAA IC2: TLE2071CP +5.6V (VAA) +5.6V 7 2 4 100F 25V L/ESR CSH VB 16 15 10k VB R4 47k IN– 560pF 6 IC2 3 3 VAA 100 TP1 850 GND R6 6.8k 560pF 4 Comp Ho 22 G 560pF VR1 2k 2 6 –5.6V (Vss) 1W R3B 4.7k 1W ZD4 5.6V K K S CSD COM D6 1N4004 100  22 7 K 2.2k LK4 VREF K SD D5 1N4148 VCC VREF Vcc 100F 25V L/ESR 1F MMC 5.6k Q3 TIP31C R7 DT OCSET 2012 CLASSic-D AMPLIFIER 10 12 8.2k 8 K 10k 9 R8 2.2k C 1k 1W 4.7k 1N4148 A K E R10 B– SC  G RUN  LED1 10 A A Q2 IRFB561 D3 MUR120 COM Building the CLASSiC-D LED2 A 4.7 K A B R9 7.5 B– 1N4004, MUR120 A K World’s first DIY high-power high-performance Class-D amplifier: 250W into 4Ω; 150W into 8Ω Following on from last month, we now describe the construction of the CLASSiC-D Amplifier and its accompanying Loudspeaker Protector. We also describe how to test the completed modules and show the connection details for mono, stereo and bridged modes of operation. 66  Silicon Chip 1F MM 15V 1W A 5 G ZD2 A LO 11 CSD Q4 BS250P PROTECT 13 10F +5.6V D VS VSS VSS A 220F 10V L/ESR IC1 IRS2092 K 100F 25V L/ESR GND 1F MMC R3A Q1 IRFB561 14 VS 4.7k K A 3.3k 1 4.7k 220F 10V L/ESR D4 MUR120 siliconchip.com.au Z A 10  1W 100k 100 F NP 100nF 470 F + 4004 D1 470 F SPEAKER CON3 C2 100nF 2.2k C1 470nF X2 + 4004 0V F1 5A CON2 D2 +50V 10 1W 22 H 150pF A 100nF L1 D1 1N4004 X2 D S B– K A ZD1–4 K LOW ESR HE CLASSiC-D Amplifier module is relatively straightforward to BS250P on assemble, with all parts mounted LEDS a PCB coded 01108121 and measuring 117 x 167mm. Fig.16 shows the K ZD1 D G S parts 15V layout. A Start by checking the PCB for any IRFB5615 defects, such TIP31C as shorted tracks, undrilled holes and incorrect hole sizes. C D The PCBs to be supplied by the SILIB G CON CHIP CPartshop and kit D suppliers E S will be double-sided, plated through, solder masked and screen printed. These are of high quality and are unlikely to require any repairs but it’s always best to check before the parts are soldered in place. Having checked the PCB, begin the assembly by soldering IC1 in place. This is a 16-pin SOIC package (ie, surface mount) and is easy to solder in place due to its (relatively) wide 0.05-inch pin spacing. The IC is mounted on the top of the PCB and must be orientated as shown on Fig.16 (ie, pin 1 dot at lower left). It’s installed by first carefully aligning siliconchip.com.au LK1 2.2k 330 10 F R1 Rf 4.3k CSD 47 F NP 1nF 100k 10 100 Q5 BC327 7.5k 15V 39V 68V 5.6V ZD6 1k R3B ZD5 4004 5.6k 4.7 2.2k R7 8.2k 220 F TP1 (VR1 TO GND) VSS –5.6V LK3 PROTECT Q9 100 F BC337 10k CON1 INPUT Vref VR1 2k NORMAL INVERT 1k 1W 4.7k 10k D3 560pF R3A ZD4 560pF LK2 GND1 MUR 120 15V 22 ZD2 560pF 1 FMMC 4.7k 1W 4.7k 1W 9.1k 10k 4.7k 1k CLASSiC-D REIFILP MA DAMPLIFIER - CiSSAL C 1 2 1 8 0 1 1C0 2012 10k 63V 220 F 1 D6 47k (CON2) + Q4 A 10 R8 10k LK4 LED2 IC1 IRS2092 R9 100 F 10k 470F 100nF T 5k MUR 120 A –50V 100F 25V L/ESR VAA +5.6V 100 F D5 B– Pt.2: By John F2Clarke 5A B– 4.7k 1W RUN 4148 1W D2 1N4004 4.7k 1W R2B 4.7k 10 R2A LED1 68k K 100 S BS250P X2 PROTECT 100V ZD1 22 1 FMMC 1 FMMC 6.8k R6 ZD3 X2 VCC COM R10 K 100 F IC2 TLE2071 2.2k 100nF 5.6V 150pF 3.3k 1W 470nF TIP31C 100nF X2 R4 D4 Q3 A 10 D Q2 Q1 Vs 4.7k R5 GND TH1 VB 47k + TO HEATSINK 10k OUTPUT CON3 L1 22H 5A 100nF Q6 Q7 BC337 BC327 Q8 BC327 9 63V 100k K F MC 15 470F B+ 100nF 100nF X2 CON2 +50V 0V –50V F1 5A GND LIFT 15 F2 5A 10 F NP Fig.16: follow this PCB parts layout diagram to build the CLASSiC-D module. The component values shown are for a ±50V supply but note that 12 resistors and two zener diodes (ZD5 & ZD6) must be selected to suit different supply voltages – see Table 1 and Table 2. Take care with component orientation. it with its pads and soldering pin 1. That done, check that it is correctly aligned. If not, remelt the solder and readjust it so that the pins all sit on their corresponding pads. The remaining pins can then be soldered, starting with the diagonally opposite pin (pin 9). Don’t worry if you get solder bridges between the pins. Once the soldering has been completed, these bridges are easily removed using solder wick. Once IC1 is in place, the remaining low-profile parts can be installed, ie, the resistors, diodes and zener diodes. Note that the components shown on Fig.16 are for the nominal ±50V supply version. However, as mentioned last month, you can also run the amplifier from lower supply voltages. Table 1 shows the component changes required for the relevant resistors and zener diodes, while Table 2 shows the zener diode type numbers. December 2012  67 Follow with the PC stakes and the 2-way and 3-way pin headers. There are 11 PC stakes and these are located at the TP1, GND1, GND, VAA, VSS, CSD, Vref, COM, VCC, Vb and Vs test points. Note that 2-way header LK4 is a polarised type (it connects via a 2-way cable to the Loudspeaker Protector). The two LEDs, Mosfet Q4 and transistors Q5-Q9 can now go in. Note that LED1 is the blue LED, while LED2 is red. If they come with a clear lens and you don’t know which is which, most multimeters have a diode test facility that will drive a LED sufficiently for you to see what colour it is. At least, this should work for the red LED – the blue LED may not light due to its higher forward voltage. Be sure to install each LED with its anode (the longer lead) towards the heatsink. Make sure also that you use the correct transistor in each location. Q4 is a BS250P Mosfet, while BC327s and BC337s are used for Q5-Q9. Don’t get the BC327s and BC337s mixed up. Leave Q1, Q2 & Q3 (ie, the heatsink transistors) out for the time being. The capacitors are next on the list. Note that the electrolytic types must be orientated correctly, the exceptions being the 100µF, 47µF and 10µF NP (non-polarised) types which can go in either way around. Be careful not to get an NP electrolytic mixed up with polarised electrolytic of the same value. Table 1: Component Values vs Supply Voltages Supply Voltage ±50V ±35V ±25V RF (gain) 4.3kΩ 6.2kΩ 8.2kΩ R2A, R2B, R3A, R3B 4.7kΩ 1W 3.3kΩ 1W 2.2kΩ 1W R4 47kΩ 27kΩ 13kΩ R5 3.3kΩ 2.4kΩ 1.8kΩ R6 6.8kΩ 7.5kΩ 8.2kΩ R7 8.2kΩ 8.2kΩ 8.2kΩ R8 2.2kΩ 1.8kΩ 1.5kΩ R9 7.5kΩ 4.3kΩ 2.2kΩ R10 1kΩ 1W 220Ω 1W 100Ω 1W ZD5 68V 1W 47V 1W 30V 1W ZD6 39V 1W 30V 1W 20V 1W This table shows the resistor and zener diode values that must be selected to suit ±50V, ±35VDC and ±25V supply rails. At ±50V, the amplifier will deliver 150W into 8Ω or 250W into 4Ω; at ±35V, it will deliver 60W into 8Ω or 120W into 4Ω; and at ±25V, it will deliver around 25W into 8Ω or 50W into 4Ω. Table 2: Zener Diode Type Numbers Zener Voltage 1W Type Number 5.6V 1N4734 15V 1N4744 20V 1N4747 30V 1N4751 39V 1N4754 47V 1N4756 68V 1N4760 Use this table to select the correct zener diode types for ZD5 and ZD6, to match the required zener voltages. Table 3 shows the resistor colour codes but you should also use a multimeter to check each one as it is installed, just to make sure (some colours can be difficult to decipher). Note that the diodes and zener diodes must be orientated as shown on the overlay, with the cathode (striped end) of each device facing towards the top edge of the PCB. IC2 goes in next and can either be mounted in an IC socket or directly soldered to the PCB. Make sure it’s orientated correctly, with its notched pin 1 end towards the heatsink. Table 3: Resistor Colour Codes o o o o o o o o o o o o o o o o o o o o o No.   1   2   1   1   7   1   1   1   1   1   4   1   1   3   2   1   2   2   4   1 68  Silicon Chip Value 1MΩ 100kΩ 68kΩ 47kΩ 10kΩ 9.1kΩ 8.2kΩ 7.5kΩ 6.8kΩ 5.6kΩ 4.7kΩ 4.3kΩ 3.3kΩ 2.2kΩ 1kΩ 330Ω 100Ω 22Ω 10Ω 4.7Ω 4-Band Code (1%) brown black green brown brown black yellow brown blue grey orange brown yellow violet orange brown brown black orange brown white brown red brown grey red red brown violet green red brown blue grey red brown green blue red brown yellow violet red brown yellow orange red brown orange orange red brown red red red brown brown black red brown orange orange brown brown brown black brown brown red red black brown brown black black brown yellow violet gold brown 5-Band Code (1%) brown black black yellow brown brown black black orange brown blue grey black red brown yellow violet black red brown brown black black red brown white brown black brown brown grey red black brown brown violet green black brown brown blue grey black brown brown green blue black brown brown yellow violet black brown brown yellow orange black brown brown orange orange black brown brown red red black brown brown brown black black brown brown orange orange black black brown brown black black black brown red red black gold brown brown black black gold brown yellow violet black silver brown siliconchip.com.au Fig.17: this diagram can be copied and used as a drilling template for the heatsink. You can either drill the holes to 2.5mm and tap them to accept M3 screws or you can drill 3mm holes (see text). Use plenty of light machine oil lubricant when drilling and tapping and clear away the metal swarf on a regular basis. The completed holes must be deburred using an oversize drill. CL (TOP) A 30 21 A A A 12.5 25 A 12.5 30 45 ALL HOLES A ARE M3 TAPPED (BASE) ALL DIMENSIONS IN MILLIMETRES INSULATING WASHER Table 2: Capacitor Codes INSULATING BUSH M3 SCREW Q1, Q2 & Q3 PCB Fig.18: the mounting details for transistors Q1-Q3. They must be isolated from the heatsink using an insulating washer and bush. 4mm 6.4mm SPADE LUG MAKING THE NTC THERMISTOR CLAMP FROM A 6.4mm SPADE TERMINAL LUG Fig.19: the thermistor clamp is made from a 6.4mm spade lug, bent to give a 4mm step as shown here. Value 1µF 470nF 100nF 1nF 560pF 150pF µF Value IEC Code EIA Code 1µF   1u0 105 0.47µF 470n 474 0.1µF 100n 104 0.001µF    1n 102   NA 560p 561   NA 150p 151 The heatsink is secured using two 3/16-inch x 20mm-long machine screws which pass up through the bottom of the PCB. siliconchip.com.au December 2012  69 POWER S1 A ~ F1 5A CON1 TERM1 BR1 35A/600V + T1 ~ 4700 F 63V 4700 F 63V 4700 F 63V 0V TERM2 0V 3.3k 5W –57V A 40V 0V N  LED1 K 40V – +57V A TERM3 T1: 240V TO 2x 40V/300VA 4700 F 63V 4700 F 63V 4700 F 63V CON2  LED2 +57V 3.3k 5W 0V K –57V E LEDS 1N4004 SC 2012 CLASSIC-D AMPLIFIER POWER SUPPLY A K K A Fig.20: the power supply is based on a toroidal transformer (T1) with two 40V windings. These drive bridge rectifier BR1 and six 4700mF filter capacitors to produce the ±57V (nominal) rails. A S MENTIONED last month, the Ultra-LD Mk.3 Power Supply described in September 2011 can be used to power the CLASSiC-D amplifier. This has a nominal output of ±57V but is still perfectly suitable for use with the CLASSiC-D and will result in slightly higher output power than from a ±50V supply. Alternatively, you can use the power supply described in September 2008 for the Ultra-LD Mk.2 Amplifier. It’s identical to the supply designed for Mk.3 version; only the PCB layouts are different. Fig.20 shows the circuit details of the power supply. It’s based on a toroidal mains transformer (T1) with two 40V windings. These are connected together to give 80VAC centre-tapped and this arrangement drives bridge rectifier BR1. This in turn feeds six 4700µF 63V electrolytic capacitors (ie, 14,100µF on each side) to provide balanced ±57V DC rails to power the amplifier. Two LEDs are connected in series with 3.3kΩ 5W current-limiting resistors across these ±57V supply rails. These serve two purposes: (1) they provide a handy indication that power is present on the supply rails and (2) they discharge the filter capacitors when the power is switched off (see warning panel). Note that the specified transformer also has two 15V windings and these were used in the original design to drive a second bridge rectifier and associated filter capacitors. Two 3-terminal regulators were then used to derive regulated ±15V sup- ply rails. These rails are not required for the CLASSiC-D and so these parts have been deleted from the circuit and parts layout diagram (Fig.21). Trimpot VR1 can now installed with its adjusting screw towards the heatsink. Follow this with inductor L1, screw terminal blocks CON2 & CON3, the fuse clips and the vertical and horizontal RCA input sockets (CON1). Note that the screw terminal blocks must be installed with their wire entry openings facing outwards. Note also that each fuse clip has an end stop, so make sure they go in the right way around otherwise you will not be able to install the fuses later on. amplifier is to go in a 1U rack case. This can be done using a fine-toothed hacksaw and the job filed to a smooth finish. Alternatively, you can leave the heatsink at its full height if space is not an issue. Before installing the heatsink, you need to drill and tap five holes to accept M3 screws. Fig.17 shows the drilling details and this should be copied (or downloaded from the SILICON CHIP website), attached to the heatsink and used as a drilling template. Use a 1mm pilot drill to start the holes, then drill each one to 2.5mm diameter (all the way through) so that it will accept an M3 tap. Take it slowly when drilling these holes and be sure to clear any metal swarf from the drill on a regular basis, to prevent the aluminium from binding to the drill. It’s also important to use a lubricant to prevent such problems and aid cutting, eg, light machine oil. The same goes when tapping the holes. Undo the tap and remove the swarf on a regular basis and use plenty of lubricant. Alternatively, if you don’t want to tap the heatsink, you can simply drill 3mm holes through the heatsink. The various parts are then later secured using M3 x 10mm screws (instead of M3 x 5mm for the tapped version), with nuts fitted inside the heatsink fins. Carefully deburr each hole using an Heatsink mounting The heatsink is a standard 100 x 33 x 75mm (W x D x H) unit but this must be cut down to 30mm high if the 70  Silicon Chip Power supply assembly All parts except for the transformer and bridge rectifier are mounted on a PCB coded 01109111. Begin by fitting the two wire links using 0.71mm or 1mm-diameter tinned copper wire, then install the two LEDs. These sit flush against the PCB with the flat side of the lenses orientated as shown on the overlay. Follow with the two 3.3kΩ 5W resistors. These should be stood off the board by about 2mm, to allow the air to circulate beneath them for cooling (use a card­board spacer during soldering). siliconchip.com.au +57V + 0V 0 –57V - CAV 5 1 T C ~ 5 1 CAV 0 3 1 tuptu O OUTPUT 1 3.3k 5W CON1 LED2 – + + TERM3 –IN TC CT TERM2 4700 F 63V 4700 F 63V + 4700 F 63V NI+ + + 11190110 uS r e woP reifilpmA 2.k M DL-artlU 01109111 + NI- 4700 F 63V TERM1 +IN LED1 + CON2 OUTPUT 2 2 tuptu O–57V 0V +57V - 3.3k 5W + V 5 1- 0 V 5 1 + 0 V 0 2 + Ultra-LD Mk.3 Power Supply 4700 F 63V TO BRIDGE RECTIFIER BR1 4700 F 63V Above: the power supply from the Ultra-LD Mk.3 Amplifier. The parts associated with the 3-terminal regulators on the righthand side of the PCB are not required for the CLASSiC-D. Fig.21: install the parts on the power supply PCB as shown here. The two LEDs indicate when power is applied and remain lit until the 4700mF capacitors discharge after switch-off. The two 3-way terminal blocks can then go in with their wire entry sides facing outwards. That done, fit the three Quick-Connect (spade) terminals to the board using M4 machine screws, nuts and washers. If you can’t get single-ended chassis lugs, cut one side off double-sided lugs. Finally, fit the six 4700µF electrolytic capacitors. Be sure to orientate them correctly and make sure that they all sit flush with the PCB. The completed PCB assembly, along with the transformer and bridge rectifier should be housed in an earthed metal case (this case can oversize drill. In particular, make sure that the mounting area for transistors Q1-Q3 is perfectly smooth and free of metal swarf. The heatsink can now be fastened to the PCB using two 3/16-inch x 20mmlong machine screws that go in from the underside of the PCB (the screws cut their own threads in the holes). It’s simply a matter of positioning the heatsink on the board and installing the screws. Thermistor TH1 is held against the heatsink using a bracket made from a chassis-mount 45° 6.4mm spade lug. This is bent to shape using pliers as shown in Fig.19. Once it’s made, install TH1 on the PCB, leaving its leads siliconchip.com.au QUICK CONNECT PC BOARD M4 STAR WASHER M4 FLAT WASHER M4 x 10mm SCREW & NUT Fig.22: here’s how the spade lugs are fastened to the power supply PCB. Alternatively, you can use solder spade lugs – see photo. also house the amplifier module). The wiring diagram on page 76 of the September 2011 issue (intended for the Ultra-LD Mk.3 amplifier) gives the mains wiring details. WARNING: HIGH VOLTAGE High DC and high AC voltages are present in this circuit. The power supply uses a total of 80V AC and the amplifier power supply rails are a total of 114V DC. Do not touch any part of the amplifier circuitry when power is applied otherwise you could get a severe electric shock. The two LEDs on the power supply board indicate when power is present. If they are alight, the power supply and amplifier boards are potentially dangerous. Power Supply Parts List 1 300VA transformer with two 40VAC 300VA windings (or two 35VAC windings) 1 35A 400V chassis-mount bridge rectifier 1 PCB, code 01109111, 141 x 80mm 2 3-way PCB-mount terminal blocks, 5.08mm pitch (Altronics P2035A or equivalent) (CON1-2) 3 chassis-mount male spade connectors 3 M4 x 10mm screws, nuts, flat washers and shakeproof washers 4 M3 x 9mm tapped Nylon spacers 4 M3 x 6mm machine screws 150mm 0.7mm diameter tinned copper wire Semiconductors 1 5mm red LED (LED1) 1 5mm green LED (LED2) Capacitors 6 4700µF 63V electrolytic Resistors 2 3.3kΩ 5W December 2012  71 CLASSiC-D SPEAKER PROTECTOR 01108122 R OT CET ORP REKAEPS D - CiSSAL C CON2 0V OUT– OUT+ IN+ IN– NC IN– NO 22 Q10 STP16NE06 10k C 2012 50V 35V 25V 820  5W 4.7k 1W 330  1W 2.7k 0.5W 22  0.5W A K LED3 CON1 CHANNEL1 1LE N NA H C COIL 15V 4004 1k ZD7 1k 47 F 22180110 V+ R11 R12 COM _ PROTECT IN1 ++ 1M 4148 S4313 OUT+ OUT– IN+ 100k OPTO2 4N28 D6 RLY1* D8 OPTO1 4N28 4148 + D7 R12: 4.7k 1W LE N NA H C 2CHANNEL2 V+ 1k + + V 0 +V +TU O -TU O + NI - NI - NI + NI -TU O +TU O PROTECT IN2 R11: 820  5W PROTECT * RLY1 HAS A 24V/ 650  COIL 1.5k 0.5W Fig.23: install the parts on the Loudspeaker Protector PCB as shown here. Note that resistors R11 and R12 have to be selected to suit the power supply voltage, as shown in the accompanying table. The 10-way screw terminal block is made by dovetailing five 2-way terminal blocks together before soldering them to the PCB. about 6mm long, then fit the clamp so that TH1 is held firmly in contact with the heatsink. Transistors Q1-Q3 can now go in. Fig.18 shows the mounting details. Note that each transistor must be isolated from the heatsink using an insulating bush and silicone washer. Q1 & Q2 are both IRFB5615 Mosfets while Q3 is a TIP31C, so don’t get them mixed up. It’s simply a matter of attaching these transistors to the heatsink and tightening their mounting screws, then flipping the board over and soldering the leads. That done, use a multimeter to check that the metal tab of each device is electrically isolated from the heatsink (you should get a high megohm or open-circuit resistance reading). Note that the heatsink is anodised so in order for the multimeter probe to make good contact, it must be touched against a bare metal area. Alternatively, if the mounting holes have been tapped, you can simply test for shorts between the device tabs and the mounting screws. If the meter does show a short, undo the mounting screw for that device and locate the source of the problem before re-attaching it. Finally, the heatsink must be connected to the GND PC stake on the PCB. That’s done by attaching a solder lug to the heatsink at top left using an 72  Silicon Chip M3 x 5mm machine screw, then running a short length of tinned copper wire back to the adjacent GND stake. If the hole isn’t tapped, then be sure to scrape away the anodising under the solder lug. If necessary, this earthing arrangement can later be changed when the amplifier is installed in a metal case. In that case, the heatsink should be earthed to the metal chassis itself. Testing the amplifier module With the assembly now completed, it’s time to go through the test procedure. Just follow these step-by-step instructions: STEP 1: install a jumper shunt across the LK3 (Protect) header, just to the right of trimpot VR1. This places the amplifier in the PROTECT mode, so that it will not start up when power is applied. STEP 2: install a jumper link on LK1, a jumper on LK2 (near the RCA sockets) in the NORMAL position and a jumper on LK4 to allow the PROTECT LED to light. STEP 3: monitor the resistance between TP1 and GND and adjust VR1 to give a reading of 850Ω. This sets the quiescent operating frequency for the amplifier to about 500kHz. STEP 4: insert fuses F1 & F2, then connect a power supply to the CLASSiC-D module, making sure the polarity is correct. As mentioned last month, the Ultra-LD Mk.3 Power Supply described in September 2011 can be used. The circuit and the parts layout for this supply are shown in the accompanying panel. Alternatively, you can use the power supply described in September 2008 for the Ultra-LD Mk.2 Amplifier. It’s identical to the Mk.3 supply version; only the PCB layouts are different. STEP 5: switch on the power supply and check that the protect LED (LED2) lights. Note that high voltages are present on the power supply and amplifier PCBs during operation. Do not handle or touch the power supply or the amplifier module with power applied, otherwise you could get a severe shock. STEP 6: check that the ±50V (or there­ abouts) supply rails are correct at CON2 (note: these rails will depend on the power supply used). If these are correct, check that VAA (near ZD3) is at +5.6V (ie, measure between VAA and GND). Similarly, check that both VSS (near ZD4) and CSD are at -5.6V. STEP 7: check that VCC is around +14-15V (measure between VCC and COM), then check the voltage across the output terminals at CON3 (ie, the speaker terminals). This should be around 1.57V with a 50V supply but will drop to only 6mV or less with an 8Ω or 4Ω load connected. siliconchip.com.au siliconchip.com.au 4004 4004 15V MUR 120 15V MUR 120 4004 +50V 0V –50V 39V 68V 5.6V 5.6V + 4148 TP1 LK1 LK2 CLASSiC-D REIFILP MA DAMPLIFIER - CiSSAL C 1 2 1 8 0 1 1C0 2012 INPUT 0V +50V CLASSiC-D SPEAKER PROTECTOR 01108122 R OT CET ORP REKAEPS D - CiSSAL C CON2 IN– NO NC IN– COM ++ CON1 22180110 C 2012 CHANNEL1 1LE N NA H C COIL 4004 15V 4148 OUT+ OUT– IN+ 4148 IN+ OUT– OUT+ + + LE N NA H C 2CHANNEL2 V+ 0V V 0 +V +TU O -TU O + NI - NI - NI + NI -TU O +TU O The Loudspeaker Protector should now be tested, as follows: STEP 1: connect the supply to CON2 (ie, to V+ and 0V), switch on and check 1 LK4 PROTECT IN1 Testing the speaker protector + PROTECT IN2 The Speaker Protector is built on a PCB coded 01108122 and measuring 76 x 66mm. As usual, check the PCB for any faults (eg, shorted tracks, undrilled holes and incorrect hole sizes) before starting the assembly. Fig.23 shows the parts layout on the PCB. Start by installing the resistors, diodes and zener diodes. Resistors R11 and R12 have to be chosen to suit the supply voltage – see the table accompanying Fig.23. The resistor values shown on the PCB layout are for a 50V DC supply. Optocouplers OPTO1 and OPTO2 can now be installed, taking care to orientate them correctly. Follow these with the 47µF capacitor, LED3 and Mosfet Q10. The five 2-way screw terminal blocks can then be dovetailed together (to make a 10-way strip) and soldered in place. Make sure the wire entry side faces outwards and that the blocks all sit flush against the PCB. Finally, complete the assembly by soldering the polarised 2-way headers and the relay in place. CON3 _ Speaker protector + CON2 + STEP 8: check the voltage between VB and Vs. This should be above 9V but will rise to 14V or 15V when the amplifier is actually running (ie, when it is no longer in PROTECT mode). If any of the voltages in the above steps are incorrect, switch off immediately and check that all parts are correctly placed and orientated. You should also carefully check for shorts between IC1’s pins (eg, solder bridges) and for shorts due to solder bridges on the underside of the PCB. STEP 9: if the voltages are correct, switch off, remove PROTECT jumper LK3 and re-apply power. After a second or two, the PROTECT LED should turn off and the RUN LED (blue) should turn on instead. STEP 10: if you have a scope or a frequency counter, the quiescent operating frequency can be measured at the Vs test point (near Q1). If you are building a stereo or bridged amplifier, the modules should be set to run at the same frequency under no signal conditions to minimise distortion. This can be adjusted using trimpot VR1. – SPEAKER + 4  OR 8  PROTECT Fig.24: follow this wiring diagram to connect a single CLASSiC-D amplifier module and its accompanying Loudspeaker Protector module for mono operation (power supply connections not shown). The loudspeaker can be either a 4Ω or 8Ω type. that ZD7 has 15V across it. The relay should switch on, while the PROTECT LED (LED3) should be off. STEP 2: connect a 9V battery between the two header pins for PROTECT IN1 (at bottom left), with the positive side of the battery going to the “+” input. The relay should immediately switch off and the PROTECT LED should now switch on. December 2012  73 AMPLIFIER 2 CON3 + 15V MUR 120 4004 15V MUR 120 4004 4004 15V MUR 120 15V + 39V 5.6V 39V 68V 5.6V LK4 5.6V 1 5.6V 1 LK4 68V MUR 120 + CON2 4004 + 4004 CON3 +50V 0V –50V + CON2 4004 +50V 0V –50V AMPLIFIER 1 + TP1 LK1 4148 4148 TP1 LK1 LK2 LK2 CLASSiC-D REIFILP MA DAMPLIFIER - CiSSAL C 1 2 1 8 0 1 1C0 2012 CLASSiC-D REIFILP MA DAMPLIFIER - CiSSAL C 1 2 1 8 0 1 1C0 2012 LK2 IN NORMAL POSITION 0V +50V LEFT INPUT NOTE REVERSED POLARITY CLASSiC-D SPEAKER PROTECTOR 01108122 R OT CET ORP REKAEPS D - CiSSAL C CON2 IN+ OUT– OUT+ + IN– NC _ PROTECT IN1 ++ CON1 22180110 C 2012 CHANNEL1 1LE N NA H C COIL 15V 4004 NO RIGHT – SPEAKER + 8  OR 4  IN– + COM OUT+ OUT– IN+ 4148 4148 LE N NA H C 2CHANNEL2 V+ 0V V 0 +V +TU O -TU O + NI - NI - NI + NI -TU O +TU O PROTECT IN2 + LK2 IN INVERT POSITION RIGHT INPUT LEFT – SPEAKER + 8  OR 4  PROTECT Fig.25: the wiring layout for stereo operation. Use heavy-duty hook-up wire for the amplifier output connections and to the loudspeakers. The wiring from LK4 on each amplifier module and the supply leads to the Loudspeaker Protector can be run using medium-duty cable. Note the swapped speaker polarity for the right channel. STEP 3: check that the relay also switches off if the 9V battery is connected to the PROTECT IN2 header. Speaker protector connections As stated last month, the Loudspeaker Protector can be used with a either a single CLASSiC-D module or with two modules connected in either stereo or bridge mode. Figs.24-26 show the mono, stereo and bridge mode wiring configurations. The connection from LK4 on each amplifier module is run via a 2-way polarised header lead. This lead is made up using two lengths of medium-duty 74  Silicon Chip hook-up wire, terminated at both ends in 2-way header plugs. It’s important to ensure that the loudspeaker connections are correct. In mono and stereo configuration, the positive speaker output from each amplifier module (ie, from CON3) goes to an IN+ input on the Loudspeaker Protector. Similarly, the 0V output must go to the corresponding IN- input. This is necessary to ensure that the positive side of the loudspeaker is connected to the 0V rail via the NC relay contact when the relay is off. It also ensures that any arcing between the NO contact and the wiper is quenched when the relay turns off. This arcing can be caused by the high voltage DC that’s applied to the NO contact if one of the Mosfets in the amplifier fails and shorts the contact to the supply rail. Note that for a stereo configuration, the second amplifier is set to INVERT mode and the speaker lead polarity is swapped following the Loudspeaker Protector. This is done to avoid supply pumping, as explained last month. For the bridge mode configuration, the loudspeaker (this must be 8Ω or more) is connected between the positive output of the Amplifier 1 and the OUT+ terminal of one channel on the siliconchip.com.au AMPLIFIER 2 CON3 + 15V MUR 120 4004 15V MUR 120 4004 4004 15V MUR 120 15V + 39V 5.6V 39V 68V 5.6V LK4 5.6V 1 5.6V 1 LK4 68V MUR 120 + CON2 4004 + 4004 CON3 +50V 0V –50V + CON2 4004 +50V 0V –50V AMPLIFIER 1 + TP1 LK1 4148 4148 TP1 LK1 LK2 LK2 CLASSiC-D REIFILP MA DAMPLIFIER - CiSSAL C 1 2 1 8 0 1 1C0 2012 CLASSiC-D REIFILP MA DAMPLIFIER - CiSSAL C 1 2 1 8 0 1 1C0 2012 LK2 IN NORMAL POSITION SIGNAL INPUT 0V +50V CLASSiC-D SPEAKER PROTECTOR 01108122 R OT CET ORP REKAEPS D - CiSSAL C CON2 V 0 +V +TU O -TU O + NI - NI - NI + NI -TU O +TU O PROTECT IN2 RCA-TO-RCA SHIELDED LEAD NC IN– NO _ PROTECT IN1 ++ CON1 22180110 C 2012 CHANNEL1 1LE N NA H C COIL 15V 4004 COM IN– + 4148 OUT+ OUT– IN+ 4148 IN+ OUT– OUT+ + + LE N NA H C 2CHANNEL2 V+ 0V LK2 IN INVERT POSITION + 8 – SPEAKER PROTECTED Fig.26: the bridge mode configuration uses just one relay channel on the Loudspeaker Protector. An RCA-to-RCA shielded lead is connected between the signal inputs of the two amplifiers, while LK2 is set to NORMAL on one amplifier and to INVERT on the other. Note that the loudspeaker must be an 8Ω (or higher) type for bridged operation. Loudspeaker Protector. The 0V output from Amplifier 2 connects to IN- terminal of the Loudspeaker Protector, to break the arc across the relay contacts as before. In addition, Amplifier 2 must be set to INVERT mode using LK2, while Amplifier 1 operates with LK2 in the NORMAL position. The completed modules can be mounted in a metal case, along with the power supply. Make sure the case is securely earthed and be sure to use an IEC mains input connector with an integral M205 5A fuse (see page 76 of SC the September 2011 issue). siliconchip.com.au Where To Buy Kits & Parts Both Jaycar and Altronics will have full kits available for the CLASSiC-D amplifier module and its Loudspeaker Protector. The details are as follows: Jaycar: CLASSiC-D Amplifier Kit (includes pre-mounted SMD IC) – Cat. KC-5514 CLASSiC-D Speaker Protector Kit – Cat. KC-5515 Power Supply Kit (Ultra-LD Mk.2 Supply) – Cat. KC-5471 Altronics: CLASSiC-D Amplifier Kit – Cat. K 5181 CLASSiC-D Speaker Protector Kit – Cat. K 5182 Power Supply Kit (Ultra-LD Mk.3 Supply) – Cat. K 5168 PCBs: PCBs for the CLASSiC-D Amplifier, Loudspeaker Protector and the Ultra-LD Mk.3 Power Supply can be purchased separately from the SILICON CHIP Partshop. December 2012  75