Myriad Design Altoids Piezo Preamp Construction Guide V2 December, 2014 1. The package should include the following items. If any of the items are missing from the package, please contact sales@stompville.co.uk. Note that an Altoids tin is NOT supplied. Designation Description Marking PCB Altoids 1 Piezo Pre printed circuit board APPV2DS01 R1 1/4W resistor - 10k brown black black-red R2 1/4W resistor - 10M brown-black-blue R3 1/4W resistor - 4k7 yellow-violet-black-brown R4 1/4W resistor - 33R orange-orange-black-gold R5, R7 1/4W resistor - 1M0 brown black black yellow R8 1/4W resistor - 680k blue-grey-black-orange R9 1/4W resistor - 220k red-red-black-orange R10 1/4W resistor - 150k brown-green-black-orange R11 1/4W resistor - 3k6 orange-blue-black-brown C1 22p ceramic 22 C2 470p ceramic 470 C3 47n polyester box 47n or.047 C4 1u0 polyester box 1u C5, C7, C9 100n polyester box 100n or.1 C6 10u 25V electrolytic 10u 25V C8 47u 16V electrolytic 47u 16V D1, D2 1N4148 diode 1N4148 Q1, Q2 PF5102 JFET matched pair PF5102 U1 TC54VN2902EZB voltage detector 54VN2902 LED1 3mm red LED - - Battery Clip - J1, J2 1/4 stereo jack socket CL11155 - - green wire - - card with self-adhesive tape/foam - - self adhesive foam pad - - M3 x 6 pozi pan machine screw - - M3 brass nut - - label for underside of Altoids tin - - template drawing for cutting holes - - quick start guide - 1 Altoids is a trademark of the Wrigley Company. Their rights are hereby acknowledged. 2. It is assumed that you have some experience of soldering and building of simple kits and are confident to build or modify effects pedals. If not, there are many relevant tutorials and videos on the internet. Please spend some time familiarising yourself with construction and soldering techniques. 3. Note that Q1, Q2, D1, D2 and U1 are electrostatic sensitive devices and should be handled with care. If you have an ESD protective wristband, use that. If not, wear clothes made of natural materials (e.g. cotton), regularly touch your finger to an earthed (grounded) metal object (such as a radiator) and do not handle the sensitive devices any more than you have to. In particular, don t remove them from the electrostatic protective package until you are ready to fit them to the board. Page 1 of 6
4. Solder the items to the PCB according to the silk-screen legend, checking and ensuring that you insert each component in the correct orientation. Page 2 of 6
5. Note that if you are not using an Altoids tin as an enclosure and you wish to have a volume control on the output, then omit R5 and LK1 and fit a potentiometer (not supplied) to the VR1 connections. The clockwise end of the potentiometer is marked on the PCB CW. 6. Note that LK2 is fitted after the battery clip has been soldered in - and serves to act as a strain relief. 7. Note that the LED must be connected the correct way round. The shorter lead of the LED is the cathode and is shown by the flat side of the PCB legend. If you have cut the leads of the LED and lost track of which was the shorter lead, look inside the LED the cathode is the larger of the two internal structures (note that this is not a universal rule). 8. There is no compelling reason to cut the green earth wire short and you will find it easier to solder the wire to the enclosure if you leave the green wire fairly long. 9. You may wish to test the board before installing it in the enclosure. The input and output sockets are clearly marked on the board. The battery is not connected to the circuit until there is a plug in the input socket. Connect the input to an instrument with a piezo transducer (or indeed any instrument, including electro-acoustic guitar, electric guitar, bass guitar, or even a keyboard, etc). Connect the output to a mixing desk or a combo amp such as an acoustic or keyboard amp. Enclosure 10. Carefully remove the lid of the Altoids tin by bending back the hinge tabs. Cut out the template and stick it on to the tin ensuring that the template is centred. Cut out the holes for the LED and Jack sockets. Take care cutting the larger holes as a normal 10mm HSS Drill bit will likely tear the thin metal. The use of a stepped sheet-metal drill (Google: step drill) or a Q-max chassis punch (Google: q-max 10mm) is recommended. Refit the lid and drill a 3mm hole half way along the lidflange at the front for the screw. Page 3 of 6
11. Remove the lid again and screw the nut and screw through the tin. Solder the nut to the case. Note that a 25W soldering iron with a 3mm or larger tip is adequate. 12. Remove the brown cover tape from the underside of the cardboard insulator and carefully fit it to the bottom of the tin. The foam pad should be at the end opposite to the holes. There is no need to remove the backing paper from the top of the foam pad if you stick the battery down to the pad, it will be useless when you change the battery. 13. Carefully solder the end of the green wire to the inside of the tin. Note that the accompanying photo shows a black wire in lieu of the green wire supplied. 14. If you have not already done so, carefully clip all the protruding pins on the rear of the circuit board. In particular, the pins on the sockets should be trimmed back as short as possible. You can use the supplied sticky foam pad to stick the board down (as shown in the photograph below), but longterm experience is that you will be better off gluing the board in place with a little hot-glue, silicone or instant-grab adhesive. Page 4 of 6
15. Fit the lid and bend the tabs back in place to ensure the lid stays on at the hinge side. Fit the battery, allowing the battery wire to fall across the top of the battery. Close the lid and fit the screw. Lightly shake the unit; the battery should not rattle around. 16. Carefully apply the sticker to the underside of the tin. Page 5 of 6
17. Note: the reason a stereo jack socket was used on the input side is so that the unit may be switched off when the input cable is removed. A stereo jack socket was used on the output side because it retains the output cable with greater force than a mono socket (and if you are in the habit of keeping the unit in your back pocket, you will find that the output cable is less likely to come out if you inadvertently stand on the cable). 18. Note: the power consumption of the unit is very low at approximately 180uA (microamps). This means that a fresh alkaline battery will last several years with occasional use and - if you ensure to disconnect the input cable when not in use - the battery should last up to two years if you re gigging regularly. Using the Preamp 19. The preamp has very high input impedance. This makes it suitable for passive piezo pickups which may be built-into or added on to stringed or percussion instruments. Generally speaking the cable between the pickup and the instrument should be as short as practical - if you are a violin player you should consider having a lead from your pickup just long enough to comfortably reach the preamp if the preamp is in the back pocket of your jeans or in a pouch slung over the shoulder. The output cable can then be as long as it needs to be to reach the mixing desk or mixer-amp. 20. The preamp may also be used with other types of pickup. For example, consider an electric guitar connected directly to a valve amp (without any effects in between). You may notice that if the guitar is connected with a long cable, the sound is much more mellow that that if the guitar is connected with a short cable. This is because some types of cable have significant capacitance and the combination of the cable capacitance and the relatively low input impedance of the valve amp. will act as a low-pass filter on the signal coming from the guitar. The piezo preamp (with its very high input impedance) will ensure that the high frequencies are not lost. 21. You should disconnect the input cable when the preamp is not in use as this will disconnect the battery and conserve battery life. When the battery voltage drops (from 9V) to about 7.3V (which will likely take several years), the LED will illuminate. If this happens during or just before a performance, don t panic! The power consumption of the unit is very low and you will get through the gig without needing to change the battery. However, having the LED on all the time means that power consumption rises ten-fold, so you should change the battery at the earliest convenient point. Copyright 2012-2014 Myriad Design. All rights reserved. Disclaimer. The information contained herein is provided in good faith. Myriad Design has no control over the standard of construction of this kit, nor any control over the way the design is implemented or integrated into a system. Therefore, Myriad Design offers no actual or implied warranty of fitness for purpose and Myriad Design will accept no liability for consequential loss or damage. This design is not authorised for use in any safety-critical system. Your statutory rights are not affected. Myriad Design United Kingdom www.stompville.co.uk sales@stompville.co.uk Page 6 of 6