Fullscreen HTML5Med Res (??MB)HTML4

A high-quality stereo DAC for superb sound from your DVD player S ec on d a r t i cl e h as t he boa r d as s em b l y de t a i l s Pt.2: by NICHOLAS VINEN Last month, we introduced our new highquality Stereo Digital-To-Analog Converter (DAC) and described the circuit. This month, we show you how to build the various modules and make the header cables. 34  Silicon Chip siliconchip.com.au TOSLINK Receivers Where To Buy Kits For The Stereo DAC Both Jaycar and Altronics will be supplying kits for this project and both companies will be supplying the Input and DAC Boards with the surface-mount ICs (IC3 & IC6) already soldered in place. This is a real bonus as it will save you the hassle of having to solder these small devices in by hand and risk ruining the boards. The Jaycar kit will be in short form only and will consist of the Input, DAC and Front Panel Boards plus all on-board parts. A kit for the Power Supply Board is available separately (Cat. KC-5418). The Altronics kit will be complete and will include all the modules, the power supply components (including the transformer) and a laser-cut custom steel case with screened lettering. The modules will not be available separately except for the Power Supply Board (Cat. K-5501) and the remote control is not included. A S SHOWN IN the photos, our prototype DAC was built into a 1-unit high rack case with internal rails from Jaycar. However, we recommend against using this case, as the internal rails (used to secure the panels) make it difficult to mount the two main PC board assemblies. In the prototype, these boards were mounted on the rails but it really is an exercise in frustration when it comes to fitting the nuts to the mounting screws. What’s more, once they are in and the case is fully assembled, it’s a big job to remove them again. Another problem is the sub-panel that runs just behind the front panel. This complicates matters when it comes to mounting both the mains siliconchip.com.au power switch and the Front Panel Switch Board because it means that additional cut-outs are necessary. Finally, making sure that all the panels and rails are properly earthed is a difficult and time-consuming task. For all those reasons, if you are not buying a complete kit, we recommend that you build your Stereo DAC into the Altronics H-5035 rack case instead. It doesn’t have internal rails or a sub-panel and so the Input and DAC Boards can be mounted on tapped spacers, making them easy to install and remove for service. PC board assembly As stated last month, the Stereo DAC is built on four PC boards: (1) Jaycar ZL-3003 TOSLINK receivers were specified for this project in the parts list published last month. However, Altronics also sell TOSLINK receivers (Cat. Z-1602) which are pin-compatible with the Jaycar receivers. The only problem is that the Jaycar units run off 5V, whereas the Altronics units require a 3V rail. As a result, we have slightly modified the PC board so that either receiver can be used. This involved fitting a 3-pin header near TOSLINK1 on the Input Board, so that a shorting jumper can be used to select between +5V and +3.3V rails (3.3V is close enough). It’s just a matter of fitting the jumper to select the +5V rail if you are using Jaycar ZL-3003 receivers or fitting it to select 3.3V if you are using Altronics Z-1602 receivers. The two types offer equivalent performance. Check carefully if you buy TOSLINK receivers elsewhere – not only can their supply requirements vary but they may not have the same pinouts. an Input Board, (2) a DAC Board, (3) a Front Panel Switch Board and (4) a Power Supply Board. They are all straightforward to assemble although there are two surface-mount ICs (IC3 & IC6) to consider, one on the Input Board and the other on the DAC Board. The good news here is that both the Jaycar and Altronics kits for this project will be supplied with the surface-mount ICs already installed on the boards – see panel. This is a worthwhile feature that will save you lots of time. However, if you elect not to buy a kit, it is possible to reliably handsolder these TSSOP (Thin Shrink Small Outline Package) parts. The following article titled “How To Hand Solder Very Small Surface-Mount ICs” describes how it is done. Begin by carefully inspecting all four boards for possible defects. Make sure that there are no shorted or broken tracks and check that all the holes have been drilled. In particular, pay special attention to the area immediately surrounding the surface-mount ICs on the Input and DAC Boards, as these have very fine tracks and close track clearances. Having done this, start the assembly October 2009  35 COAXIAL INPUT (BLACK) TOSLINK RECEIVER 2 IN3 2NI 1NI 100nF 100nF 4148 IC1 74HCU04 IC4 D9 D10 4148 C C E GND X1 + - 24.576MHz 100nF 16 15 2 1 IN DETAIL VIEW OF UNDERSIDE OF PC BOARD SHOWING IC3 1 F 1 F 33pF 68nF POWER V5+ NI R EWOP 1 F SOLDER LINK TO CRYSTAL CASE 22 F 100 4.7nF 680 470 F IC3 (UNDER) 100nF 100nF 33pF B REG4 LM3940T-3.3 22 F IC5 74HC14 47k B IC3 DIR9001 E Q2 1N4004 D14 +5V 0V Fig.6: if you buy a kit, IC3 will be supplied soldered in position. If not, you will have to carefully solder it in by hand as shown here. 1nF 100nF Q1 470nF ATMEGA48V 100nF 10k 100 IC2 74HC4052 19090110 100nF 4148 D12 4148 D13 4148 D11 22k 22k 22k 22k 22k 22k 100nF 100pF CON1 Fig.5: the parts layout on the Input Board. Make sure the SMD device (IC3) is installed first (see Fig.6) and be sure to select the correct supply rail option to suit your TOSLINK receivers. 1M 2.2k 2.2k 2.2k 330 330 47k LK1 V5 300 +5V V3.3 +3.3V 3NI 100nF 100pF LK1 = +5V FOR JAYCAR TOSLINK RECEIVERS LK1 = +3.3V FOR ALTRONICS TOSLINK RECEIVERS 47k 47k TOSLINK RECEIVER 1 O/I LATIGID DIGITAL I/O by building the Input Board. This board is coded 01109091 and measures 113 x 93mm. Fig.5 shows the assembly details. As stated, if you purchase a kit (recommended), IC3 will already be mounted on the board. Alternatively, if you’re not building from a kit, the first step is to install IC3. This is a 28pin TSSOP SMD, which has a 0.65mm pin pitch (ie, there is 0.65mm between the centres of adjacent pins). The clearance between the pins is a mere 0.35mm which means that it is almost impossible to manually solder the pins one at a time without bridging them. Fig.6 shows where IC3 is installed. This SMD part is mounted on the 2 1 14 13 LENAP TNORF TO FRONT PANEL BOARD copper side of the board and must be oriented with its pin 1 at upper left, as shown. It’s easy to identify pin 1 – it’s adjacent to a small dot in the body at one end of the IC. Refer to the following article titled “How To Hand-Solder Very Small Surface-Mount ICs” for all the details on soldering it into place. Fig.5 shows how the rest of the parts are installed. Start by installing the 21 wire links (use 0.71mm tinned copper wire), then install the resistors. Table 1 shows the resistor colour codes for this board but check each one using a digital multimeter before installing it, just to make sure. Follow these parts with the diodes. These are all 1N4148s except for D14 DIGI DI GITA TALL I/ I/O O which must be a 1N4004. Check that they are all correctly oriented before soldering their leads. The four IC sockets are next on the list. Install these with notched ends matching the notches on the overlay. In each case, it’s usually easier to first solder two pins at opposite corners, then check that the socket is sitting flat against the PC board before soldering the remaining pins. The two IDC sockets (14-pin & 16 pin) go in with their notched sides oriented as shown (ie, towards the edge of the PC board). Don’t get them in the wrong way around. Alternatively, you can use DIL pin headers (0.1-inch spacing) instead of the IDC sockets Table 1: Resistor Colour Codes – Input Board o o o o o o o o o o No.   1   4   6   1   3   1   2   1   2 36  Silicon Chip Value 1MΩ 47kΩ 22kΩ 10kΩ 2.2kΩ 680Ω 330Ω 300Ω 100Ω 4-Band Code (1%) brown black green brown yellow violet orange brown red red orange brown brown black orange brown red red red brown blue grey brown brown orange orange brown brown orange black brown brown brown black brown brown 5-Band Code (1%) brown black black yellow brown yellow violet black red brown red red black red brown brown black black red brown red red black brown brown blue grey black black brown orange orange black black brown orange black black black brown brown black black black brown siliconchip.com.au NOTE: THE SUPPLY LEADS TO THE FINAL VERSION OF THE INPUT BOARD (FIG.5) ARE REVERSED AT THE TERMINAL BLOCK COMPARED TO THOSE SHOWN HERE. Table 2: Capacitor Codes This close-up view shows the fully-assembled prototype Input Board (it differs slightly from the final version) Take care with component orientation. although these make it possible to plug a connector in backwards, which could damage some components. Once these parts are in, install the 2-way screw terminal block, then install all the MKT and ceramic capacitors. If your 33pF ceramic capacitors have a 0.2-inch (5.08mm) pin spacing they will fit right into the holes. If not, use a pair of pliers to carefully bend the legs out at approximately 45° and then parallel again so that they fit. Follow with the six electrolytic capacitors (make sure they are correctly oriented) and the two BC327 transistors (Q1 & Q2). Just line up the flat sides of the transistors as shown on Fig.5 and you can’t go wrong. TOSLINK receivers The two TOSLINK receivers go in at top left of the board and can only go in one way. They should be installed one at a time. In each case, after you insert the five pins through the holes, gently push the module towards the middle of the board. This will ensure that the plastic feet correctly sit near siliconchip.com.au the edge of the board and that the face is parallel with the edge. Solder the two thicker pins closer to the PC board edge first, then check that it is sitting flush against the board and is correctly aligned. Adjust it if necessary before soldering the remaining three pins. The 3-pin header (near TOSLINK1) can now go in. This header allows you to select the supply rail for the TOSLINK receiver using a shorting jumper. Place the jumper in the 5V position (as shown on Fig.5) if you have the Jaycar ZL-3003 receivers. Alternatively, fit the jumper to the 3.3V position if you have the Altronics Z-1602 receivers. A black RCA socket is used for the coaxial input and this can be a little tricky to fit. You may have to press it fairly hard into the holes to get it to sit properly. Note that the six plastic posts don’t actually go down very far into the holes – the metal flange on the centre pin usually limits this. Adjust it so that it is at right angles to the PC board, then solder the two pins on either side. That Value 470nF 100nF 68nF 27nF 10nF 8.2nF 4.7nF 2.7nF 2.2nF 1nF 33pF 22pF µF Value IEC Code EIA Code 0.47µF 470n 474 0.1µF 100n 104 .068µF   68n 683 .027µF 27n 273 .01µF   10n 103 .0082µF   8n2 822 .0047µF   4n7 472 .0027µF   2n7 272 .0022µF   2n2 222 .001µF      1n0 102 NA    33p 331 NA    22p 221 done, recheck the orientation before soldering the third pin. Next on the list is the 24.576MHz crystal. Once you have soldered its leads to the board, cut a length of 0.71mm tinned copper wire and bend it into a U-shape. Insert the ends of this wire into the holes on either side of the crystal and push it down so that the “U” sits flat against the top of the crystal case. Finally, solder both ends of the wire to their PC pads, then solder the top of the “U” to the case to ensure good electrical contact. Doing this grounds the metal case October 2009  37 The DAC board is mounted in the rear righthand corner of the case. Use a white RCA socket for the left output and red for the right (not red & black as fitted to the prototype). and reduces RF interference. The Input Board assembly can now be completed by installing regulator REG4 and by plugging the ICs into their sockets. Note that REG4 goes in with its metal tab towards diode D4. Push it down onto the PC board as far as it will comfortably go before soldering its leads. Take care when fitting the ICs – they must be fitted with the notched ends oriented as shown. Be careful also not to get IC1 and IC5 mixed up, as they are both 14-pin devices. Building the DAC Board Refer now to the diagram of Fig.7 to build the DAC Board. This board is coded 01109092 (94 x 110mm) and is assembled in exactly the same manner as the Input Board. Once again, if you buy a kit, the DAC Board will be supplied with the SMD IC (DSD1796) soldered into place. If not, you will have to install it as shown in Fig.8. As before, this device is mounted on the copper side of the PC board and is installed in 38  Silicon Chip exactly the same manner as IC3 (see following article). Make sure that it’s mounted with pin 1 at lower left, as indicated by Fig.8. That done, install the wire links, resistors, IC sockets and capacitors. Diode D15 (1N4004) and regulator REG5 can then be installed, making sure they are oriented as shown. Follow these parts with the 16-pin IDC header and the two RCA output connectors. Be sure to follow convention and use a red RCA socket for the right output and a white socket for the left output. Check that the RCA sockets sit flush against the PC board and are aligned at right angles to it before soldering their leads. Finally, complete the DAC Board assembly by fitting the ICs to their sockets. OPA134 op amps are recommended for ICs7-12 but you can also use NE5534s for slightly reduced performance. Front Panel Switch Board This board is coded 01109093 (103 x 34mm) and carries only a handful of parts: the three pushbutton switches, two 5mm LEDs, infrared receiver IRD1, a 100nF capacitor and a 14-pin DIL header. In addition, you have to install two wire links. It should only take you about 15 minutes to assemble but note that the switches, IRD1 and the two LEDs are all installed on the copper (track) side of the PC board. Fig.9 shows the details. Begin by installing the two wire links, the IDC socket and the 100nF MKT capacitor on the non-copper side of the PC board. Be sure to orient the IDC socket correctly, ie, notched side towards the top of the board. Once these parts are in, temporarily install an M3 x 10mm tapped spacer at each corner, with the spacers on the non-copper side and M3 machine screws passing through from the copper side (you can use the spacers that will later be fitted to the Input or DAC boards). This will ensure that the assembly will now sit level on your workbench and will make it easier to install the pushbutton switches. siliconchip.com.au DETAIL VIEW OF UNDERSIDE OF PC BOARD SHOWING IC6 STEREO AUDIO OUT RIGHT (RED) LEFT (WHITE) 22pF L R TUO 100nF 100nF 8.2nF 200 200 27nF 220 22pF 22pF 100nF IC11 OPA134 NE5534 820 820 47 F 10 F 29090110 IC6 (UNDER) 47 F 100nF 16 15 2 1 O/I LATIGID 2.2nF DIGITAL I/O 4148 REG5 LM7805T D15 100nF 2.7nF 47 F 100F 100F +15V 0V -15V + 10k - TPOWER UPNI V5IN 1-/+ Fig.7: the DAC/output Board is easy to assemble but again make sure that the SMD (IC6) is installed first. Installing the three pushbuttons on the copper side of the board is the next step. These have angled pins at each corner plus two straight pins for the integral blue LED. The anode of the LED is longer than the cathode and must go into the hole marked “A” on the overlay (ie, towards the DIL header). Once the pins are inserted through the holes, press the buttons down gently. Because of the way the corner pins are bent, they should not go all the way through. If one of the buttons doesn’t sit parallel with the board, its DIGI DI GITA TALL Fig.8: if you don’t buy a kit, then install IC6 on the copper side of the PC board as shown here. 820 2.7nF 2.7nF 47 F IC7 OPA134 NE5534 IC8 OPA134 NE5534 100nF 2.7nF 100nF 820 22pF 100nF + IC10 OPA134 NE5534 PUTT PU 220 – 22pF 8.2nF 200 180 180 180 180 8.2nF 27nF 220 220 IC6 DSD1796 + 200 8.2nF 100nF 2.2nF 100 100 22pF IC9 OPA134 NE5534 IC12 OPA134 NE5534 pins have been bent, so adjust them using needle-nose pliers and try again. Having fitted the switches to the board, place the flat face of a ruler along the top of the buttons and check that they all line up. That done, carefully solder two diagonally opposite pins for each button without disturbing them, then test fit the board to the front panel on 6mm spacers to make sure the buttons are all correctly aligned. Adjust them as necessary, then solder the remaining pins. Next install the two 5mm LEDs. These are also inserted from the copper side with the green LED closest to the edge of the board and the yellow LED nearest the centre. The tops of the LEDs must sit 11mm above the board, so that they will later protrude through the front panel by about 2mm. In practice, this means mounting the LEDs 2mm proud of the board and this can be done by pushing them down onto a 2mm-thick cardboard spacer (slid between the leads) before soldering them. Make sure they are correctly oriented (ie, cathode to the left). The last part to install is the infrared receiver (IRD1). This must be oriented as shown in Fig.9, with its domed lens facing outwards and in line with the switch centres. The rear of its body should sit about 1mm above the board. In practice, all you have to do is bend its leads down through 90° about 2mm from its body, then push it all the way down onto the board against a 1mm-thick cardboard spacer to set the height. It’s then just a matter of checking that its lens lines up with the switches before soldering the leads. Power Supply Board As mentioned last month, the power supply board used in the Stereo DAC Table 3: Resistor Colour Codes – DAC Board o o o o o o o siliconchip.com.au No.   1   4   4   4   4   2 Value 10kΩ 820Ω 220Ω 200Ω 180Ω 100Ω 4-Band Code (1%) brown black orange brown grey red brown brown red red brown brown red black brown brown brown grey brown brown brown black brown brown 5-Band Code (1%) brown black black red brown grey red black black brown red red black black brown red black black black brown brown grey black black brown brown black black black brown October 2009  39 was originally designed for the Studio Series Preamplifier described in October 2005. Fig.11 shows the parts layout on the PC board (code 01109052). Install the low-profile components first, starting with the single wire link, resistors and diodes. To aid heat dissipation, the two 5W resistors should be mounted about 2mm proud of the board surface. Take care with the orientation of the electrolytic capacitors and be sure not to interchange regulators REG1 and REG2. Note also that they face in opposite directions! It’s not necessary to fit heatsinks to either of these two regulators, although they were fitted to the supply in the prototype (they came with the kit). 14-PIN DIL HEADER* 100nF* K A A K K K S2 S3 K BUTTON/LED S1 K IR RECEIVER LINKS* A K A A A K IRD1 A LED5 LED4 A BOARD IS VIEWED HERE FROM COPPER SIDE 01109093 * NOTE: IRD1, SWITCHES S1-S3 AND LEDS 4 & 5 MOUNT ON COPPER SIDE OF THE BOARD. THE 100nF CAPACITOR, DIL HEADER & WIRE LINKS ARE ON OTHER SIDE. Fig.9: the Front Panel Switch Board assembly. Note that the infrared receiver (IRD1), switches and LEDs are mounted on the copper (track) side of the PC board. The header, links and 100nF capacitor go on the other side. Take care with the switch orientation (see text). Installing Reg3 These photos show the completed Front Panel Switch Board. Be sure to mount the IDC header with the orientation shown (ie, notch towards the edge of the PC board). Unlike REG1 & REG2, regulator REG3 mounts horizontally and must be fitted with a heatsink. Bend its leads down 90° about 5mm from its body and trial fit it in position to verify that the hole in the tab lines up with its hole in the board. Adjust as necessary, then slide a TO-220 heatsink between the regulator and the PC board after applying a thin smear of heatsink compound to the mating surfaces. Secure the assembly to the board using an M3 x 10mm screw, flat washer & nut. Don’t solder the regulator’s leads until after the screw has been tightened, otherwise the PC board tracks or 16-WAY IDC SOCKET 16-WAY IDC SOCKET (270mm LENGTH OF 16-WAY IDC RIBBON CABLE) CABLE EDGE STRIPE 14-WAY IDC SOCKET 14-WAY IDC SOCKET (200mm LENGTH OF 14-WAY IDC RIBBON CABLE) CABLE EDGE STRIPE Fig.10: it’s important to orientate the header sockets exactly as shown when making up the two IDC header cables. You must also leave about 15mm at each end so that it can be looped back and clamped with the locking bar. 40  Silicon Chip siliconchip.com.au A close-up view of the Altronics infrared receiver module (the Jaycar version doesn’t have a metal shield). Bend its leads down at right angles before mounting it on the PC board. the regulator package (or both) could be damaged. Making the ribbon cables Now for the two IDC cable assemblies. Fig.10 shows the details. Start with the 16-way cable. First, cut this cable to a length of 270mm, then clamp a 16-pin IDC header socket (rectangular locating tab facing inwards) to one end, with the red strip going to pin 1. You can do this by sandwiching the assembly together in a vice or by using a crimping tool such as the Altronics T-1540. Be sure to leave about 15mm free at this end so that it can be looped back and clamped with the locking bar. That done, fit a 16-pin header socket to the other end. This header must go on the opposite side of the cable, with the red cable strip again going to pin 1. As before, its locating spigot should again face inwards. Basically, it’s just a matter of orienting the headers at each end exactly as shown in Fig.10. Note that pin 1 on the header sockets is indicated by a small triangle in the plastic moulding. The 14-way cable is slightly different – see Fig.10. Begin by cutting the cable to 200mm and attaching a header socket to one end with its spigot facing inwards. That done, fit the second header socket to the other end of the cable on the same side. It should be The power supply board should only take a few minutes to assemble. All connections are made via screw terminal blocks. Fig.11: here’s how to build the Power Supply Board. Don’t get the 3-terminal regulators mixed up and note that REG3 is fitted with a heatsink. oriented the same way as the first, with its locating spigot facing outwards. Having completed the cables, it’s vital to check that they have been properly terminated. If they are not crimped correctly, then some of the pins may be open circuit because the “blades” in the header sockets haven’t fully pierced the cable insulation. The best way to check them is to connect the PC boards together and then use a multimeter to check for continuity between the correspond- ing header pins on each board. If you do find any open circuits, then that cable should be discarded and a new one made up. This procedure will also reveal if any of the header sockets has been incorrectly oriented. That’s it for this month. Next month, we’ll show you how to assemble the modules into a steel case and get it all going. We’ll also show you how to customise the remote control codes and the various software options. SC Table 4: Resistor Colour Codes – Power Supply Board o o o o o siliconchip.com.au No.   2   2   1   1 Value 1.1kΩ 100Ω 330Ω 100Ω 4-Band Code (1%) brown brown red brown brown black brown brown orange orange brown brown brown black brown brown 5-Band Code (1%) brown brown black brown brown brown black black black brown orange orange black black brown brown black black black brown October 2009  41