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|25th May 2002, 03:01 AM||#1|
Join Date: Mar 2001
I've been privately emailed many times over the past few months for my pcb's that I've described. So I've made an attempt to post some of them for those who are interested. I make no claim as to their attributes except to say that they work and seem to sound good. They're laid out using a computer program and it's probably obvious from their appearance that I'm a hobbiest. Keep in mind that I post these for whatever help they may offer. If you don't like them or feel you can make them better, you're welcome, but please keep your comments to yourself as I'm not especially asking for suggestions. However, if you note glaring mistakes, then please post their corrections.
I offer no support for these boards as I have a day job and a family. These boards work as is--I'm using all of them in some fashion. You're free to modify them, but then you're really on your own. If you should use these boards, or derivative thereof, in any commercial product, then give me some written credit; otherwise they're 'freeware'. To purchase the boards, and more importantly to be able to view them, download free software from: http://www.expresspcb.com/. Please note that I make no profit from the boards, nor have any association with ExpressPCB except for the fact that I'm one of their customers.
Most of my boards are 'miniboards'. If you order the basic miniboards they are 3 for about $60, and are 2.5 x 3.75 inches. A few, like the power supply boards, are larger. If you load the file, the program will allow you to calculate costs prior to submission using a menu item. The costs of the regular boards vary with quantity and finish. Read their web site for details or answers to how to use their program. You can print out the images. And if you wish, you can manually re-enter the tracings into another program if you don't like their program but wish to use the design.
I've uploaded a few pcb files onto one of my web sites. You can download the the various boards at: http://18.104.22.168/PCBs/, just append the file names that follow to this URL. The files include: 'STK4048d.pcb', 'Phono7b.pcb', 'PS-20V.pcb', 'PS-50V.pcb', and 'XO.pcb'. Also included are 'XO-in.jpg' and 'XO-out.jpg', which show a basic picture of the assembled XO. (If you're wondering about the web site where the files are stored, and you're probably not, it nevertheless is http://22.214.171.124/.)
These files represent in order: a board for the STK4048XI or STK4044XI power amp module (described in another thread), a phono board I previously described on another thread using an INA103 IC and a AD8610. It is intended for MM, but can interface with a MC using a Jensen transformer. The two inputs are switchable via an on-board relay that may be remotely controlled using a off-board switch. Also, note that the output uses another Jensen transformer to create a balanced signal. This can be left out. (The input to the INA103 uses small inductors; don't leave them out--see INA103 data sheet, otherwise it oscillates...). The INA103 is run at +/-22VDC (with the only jumper on the board) and the AD8610 with a shunt regulated +/-13VDC.
The two PS-* files refer to two power supply boards; the 20V refers to a lower current, lower voltage board I use for the phono pcb and the X/O (or for a preamp). It uses 2 stages of filtering: C-L-C-R-C, resulting in an output that was as noise-free on my oscilliscope as a DC battery. The 50V version is intended for power amplifiers like the STK amp and uses C-R-C filtering. I use two full bridge rectifiers for each power supply, one for the positive rail, one for the negative rail. This voltage can be upped depending upon the chosen transformer and rating of the capacitors. Dual bridges lower noise around 12 dB over a single bridge. The boards will fit the Shindengen D25XB60 (25A rating/bridge) full bridge recitifer, or better still, the lower noise Shindengen LN6SB60 (6A rating/bridge). Both of these are available from http://www.bdent.com.
The XO board is for a 4th order L-R filter. The design is based on that found at http://sound.westhost.com/project09.htm. This active X/O is a very complicated stereo pcb with SMT components on both sides along with rectifier bridge, transformer and in line primary fuse--all on one small board (see jpg images). Two pots are included to control the bass output, but can be jumpered out if not desired. I'm using the AD8610 for all devices, but you may elect to use other SOIC op amps such as the less expensive AD825. I'll later post a stuffing guide--if I can get the scanner to work--since most of the parts are very small and a couple of 0.1 microfarad caps are stacked, which isn't clear on the pcb. Voltage regulation is present on-board for each channel using +/-12V regulators (7812/7912).
On the pcb's I've indicated the values of each component. You may, for substantially greater money, order a silkscreen board. You needn't, however, since you will see the text of component values written in plated copper (a poor man's silkscreen) for almost all parts, as I recall and pray. Virtually all parts can be obtained from Digikey. If there is interest, I can supply a list of parts if I'm put into a full-Nelson (no pun intended Mr. Pass). There are a few other boards I can post at a later date, but this is a start.
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