While ripping apart my V1.00 schematic to do a complete redesign for generation number 2, I stumbled upon a nasty little bug that has eluded me through all of the releases starting with V1.00. Apparently, when I drew in the 5 V+ rail, I accidentally connected it to the wrong spot on the schematic.
I don't know how this one could have slipped through, since I have traced my schematic through several times to make sure that everything was where it was supposed to be. In this version, you will find the correction for that little "oops". For those of you have already started constructing the circuit or who have built the circuit, there are two 1 K ohm resistors that I have removed, effectively jumpered across, which you should be able to easily short across. In the incorrect schematics, they appeared between the 5 V+ supply (7805 regulator) and the 5 V+ supply to the DAC0808s (along with everything else).
I apologize for the confusion this bug may have caused. I wasn't aware of the problem until I started to "gut" the V1.00 schematic for the V2.00 redesign. I suppose that I would have found the problem sooner had I actually constructed the trace layouts for my current V1.00 sound board using the schematic. As it happens, I was relying more on logically thinking through the functionality of the circuit more than I was relying on the pre-drawn schematic. This allowed me to swap the data lines around at will so that I could come up with a trace layout that didn't require a lot of jumpers ("antennas" to the electronically experienced).
You will find that PCSTEREO.GIF, PCSTTR.GIF, and PCSTBR.GIF have been modified to reflect that bug correction. I can only speculate as to what would happen with those two resistors in the circuit, but I would think that the circuit would sort of work but that the sound output would be noisy, the power and stereo lights would be dim and flicker, and/or the stereo auto-detect and latching circuitry would be intermittent.
The second bug I came across deals with the V1.50 adapter. In my haste to get a working circuit, I neglected to make sure that it would be universal. This bug popped up when I tested my V1.00 sound board with my V1.50 adapter on my father's computer. While the V1.00 circuit worked exceptionally well, I lost compatibility with V1.50. I think that it was differences in impedances from his parallel port and mine that is causing the problem.
I have corrected the schematic in PCSTADD1.GIF to reflect using two additional inverters from the 74HCT04 as a buffer. This should make the V1.50 adapter parallel port impedance independent. However, I left the 0.001 uF and 0.0047 uF capacitors as they are. In reality their values will have be picked for your particular case.
I haven't had the time to wire up the circuit and fine tune the capacitor values. I speculate that I won't have time this summer to do it either. I am currently working on the V2.00 schematic so that I can purchase the parts and hopefully have a working version by early January.
I should mention that I recently purchased a new computer on which my original V1.50 adapter circuit works fine. So the score is 2 computers with their parallel ports like the original schematic and 1 computer with it's parallel port doesn't like it.
On the lighter side, Triton's FastTracker is. You can check out my full review of it's performance in the COMPAT.TXT file along with all of the latest files that I have discovered that maintain compatibility with my sound board. In short, it allows for a mixing frequency up to 64 KHz, of which my old 386-20 allowed it to do 49 KHz (twice as good as what MODPLAY PRO will allow me to do). I have tested it on my father's 486-50 and my new 486-33 and at 64 KHz it sound totally awesome (Stereo set with loudness on but NO filtering). Not only that, but it also supports the ProTracker 2.2A format which allows for 4, 6, and 8 channel MODs.
Triton just released their sequel to Crystal Dreams a few months ago called Crystal Dreams II. It's 3 meg of sound and graphics like you haven't seen before.
I started working on V2.00 of my sound board over the summer. But, I haven't had too much time to work on it thus far. I plan to spend my free time at Christmas break focused on it and pretty much end the V1.xx series with this last release.
I had suggested in previous releases that I would probably include schematics to allow someone with a V1.xx to upgrade to the V2.00 format without having to reconstruct a new board. However, with the problems experienced with the V1.50 adapter and the band-aid approach as a whole, I am probably not going to do that.
Here is just a preview of what the V2.00 WILL offer:
1) Support for both known Stereo-on-1 formats
2) Mono support
3) Support for the Stereo-on-2 format
4) Auto-detect everything
And here are a few ideas that I have been kicking around that may show up in V2.00:
1) Single sided power supply allowing for battery operation
2) Limited support of DSS (You would still have to purchase
a DSS, you just would have to listen to it's 2 inch
honker)
3) Possible support for a third type of Stereo-on-1 that
Visual Player 2.0 utilizes.
4) Peripheral port to allow further expansion
and a few other ideas that have escaped my mind right now.
In conclusion, this is probably the last release I will do for the V1.xx type sound board. The next version of the sound board you should see from me is the V2.00, which will be out probably in early 1994. If you have built a V1.xx, I would suggest building the V2.00 and giving the V1.xx to a relative or friend that you are having a hard time picking out a Christmas or birthday gift for.
I've cleaned up this file a bit, so if you want to find out specifics about certain versions you may want to download an earlier version. Of course, I have all the versions (somewhere).
COPYRIGHT NOTICE:
All of the schematics and text files contained in this archive are copyrighted as of 1993 by the author, Dave Boyd. These files may not be altered or omitted in any way, shape, or form by anyone other than the original author, Dave Boyd.
This archive may not be distributed or copied in any way that the distributor or copier receives a profit or a fee. Acceptable means of distribution of this archive of files is through BBSs, public domain distributors, CD-ROM public domain file collections, and simple disk to disk copying.
Any other form of distribution or copying of these files requires prior written consent from the author, Dave Boyd.
INTRODUCTION:
This circuit schematic is distributed with the hope that someone will find it of some use. This circuit is intended for people who want their computer to NOT sound like an IBM but are too cheap to buy a commercially available sound board or they happen be avid electronics hobbyists and welcome the opportunity to build something more or less for the hell of it. (like me)
Files included in the PCSTGIF6.ZIP file are:
+ PCSTEREO.GIF (V1.00 Sound Board schematic)
PCSTTL.GIF (V1.00 Top left corner)
+ PCSTTR.GIF (V1.00 Top right corner)
+ PCSTBR.GIF (V1.00 Bottom right corner)
PCSTBL.GIF (V1.00 Bottom left corner)
PCSTPWR.GIF (V1.50 Power supply schematic)
PCSTPWRL.GIF (V1.50 P.S. left side)
PCSTPWRR.GIF (V1.50 P.S. right side)
PCSTADD1.GIF (V1.50 Schematic additions #1)
DELETED PCSTAD1T.GIF (V1.50 S.A. top part)
DELETED PCSTAD1B.GIF (V1.50 S.A. bottom part)
PCSTPIC1.GIF (Picture of the V1.00 board)
+ README.1ST (You are here!)
PARTLIST.TXT (List of parts with prices)
+ COMPAT.TXT (Compatible files list)
FOCUS1AD.TXT (Advertisement)
FOCUS1AD.TXT is an advertisement for one of the companies I work for. If you are opposed to advertisements, don't read it.
A + in front of the file indicates files that have been altered since the last release (V1.55).
Note: The partial schematic GIF files contain some overlap. Refer to the whole schematic when using/assembling the pieces.
The two files that have been deleted are enlarged pieces of the V1.50 adapter schematic. Since I was using my drawing program to alter the schematics instead of my CAD software, it was too difficult to make the same changes on all three V1.50 schematic drawings, so I have significantly doctored the GIF of the complete schematic so that with a decent printer one should be able to make out all of the important text and details.
TARGET AUDIENCE?
I am not sure who all will try to build this circuit so I have tried to make the explanations as elementary as possible. I'm sure I've probably gotten a little to elementary in some places for the people who are most likely to try and build this circuit. Try to bear with me, though.
I've also included the technical explanations where possible for those of you who are interested and are capable of comprehending them.
NOTES ON THE V1.50 FORMAT:
You'll find the entire schematic for this modification in the PCSTADD1.GIF file. There are a few things that should be noted about this modification:
1. This circuitry is only temporary. In V2.00 I
plan to have this circuitry switched in and out
of circuit with some auto-detect circuitry when
needed.
2. I've designed this circuit so that all you have
to do is stick it in-line with the input of the
V1.00 sound board. No modification to the
actual sound board is required, so if by chance
you've already built it, you're in luck.
3. This circuit is impedance dependent, so both
the inverter chip on the V1.00 sound board and
the inverter required by this circuit should be
74HCT04 in order for the circuit to work as I
intended it to.
4. I have tested this circuitry only on my machine
for every mixing frequency allowed by my
machine and it seems to work fine. However,
I cannot guarantee that it will work perfectly
on all systems, as of yet. It is simple enough
though that building it and testing it on your
system shouldn't require much effort. If you
have problems with it: I would like to hear
from you.
5. When I crank up the volume on my amplifier, the
left channel seems to have a little noise on
it. (Of course, this could just be my
amplifier.) I'm almost sure that this is the
result of this "band-aid" approach to making
the original V1.00 board compatible with V1.50
stereo sound, and I'm fairly sure that when I
do a complete overhaul that this problem will
disappear. As it stands, the noise isn't
really noticeable until you turn the amplifier
up to about 20 watts or so. If you can
actually hear it, try fudging with the
capacitor value associated with the left
channel of the V1.50 circuit. If you select a
value that is too low, a clicking noise shows
up. If you pick a value that is too large then
the sound from the left channel becomes less
and less stereo. Chances are, you won't even
notice unless you are looking for the noise.
FEATURES:
1. Stereo and mono compatibility with MOD players
2. Mono compatibility with sound players
3. Auto-detection and processing of stereo signals
4. Auto-fallback to mono when stereo signal ends
5. Compatible with most software supporting Covox
Speech Thing
6. Indicators for stereo and power on
7. Limited compatibility with Disney Sound Source
LIMITATIONS AND COMPATIBILITY:
Now, for a discussion of the limitations of this and all similar designs. This and all other sound boards that reside on the parallel port are no substitute for the Gravis Ultrasound, SoundBlaster, or Adlib type cards. Both the SoundBlaster and Adlib cards contain a dedicated sound processor which allows for the playing of relatively high quality sound during graphics intensive programs such as games. Because this design does not contain its own processor and most types of sound files are highly processor intensive, most software programmers would not even consider making sound files for their programs compatible with this or any similar design. So what does that leave us compatible with? The answer to that question is all programs written for parallel port sound boards that don't try to do a lot of heavy graphics manipulation at the same time.
Basically this comes down to two file types: .MOD and .VOC or .SND. .MOD files are supported by MODPLAY PRO written by Mark Cox whose program also contains the specifications which the core part of the V1.00 circuit is loosely based on. .MOD files are sound files that may contain up to 31 digitized instruments that are played four at a time (2 through the left channel and 2 through the right channel). Since each instrument is only digitized once and the computer calculates how fast to play the samples back to achieve different pitches, each file may only be a few hundred K bytes long yet playback for several minutes. For a more detailed description of .MOD files refer to the documentation files included with MODPLAY PRO by Mark Cox. I have also found some other .MOD file players that support parallel port sound boards. There is a sister program to MODPLAY PRO called MODEDIT by Norman Lin which allows you to edit or create your own .MOD files.
The other type of sound files are .VOC, .SND, and a whole assortment of other file extensions, including .WAV sound files (which are associated with Windows 3.x). These files are digitized so that when t=0 the instantaneous voltage is digitized and recorded. This is repeated for t=1,2,3,... for t equal to some preset constant time interval. Hence, you can have files that playback for only a couple minutes that may take up several megabytes of space. Almost every computer (IBM, Amiga, Mac, etc.) has their own format of this type of sound file and with the right program you can playback all of these file types on whatever computer you have. SPUTTER written by Adrienne Cousins is one such program. It will play just about anything and also includes a text to speech synthesizer.
There is one important note to make about the comparison of a SoundBlaster Pro to my sound board. SoundBlaster Pro can only achieve a maximum mixing frequency of 23 KHz while playing sound files or MODs in its stereo mode. So far, I haven't found the limit on this sound board. I have found programs that will support my board with a mixing frequency of up to 63 KHz. What does this mean? It means that with a fairly decent computer and my sound board, my sound board can sound about 3 times better than a SoundBlaster Pro in the stereo mode. Even my old computer (a 386-20) can achieve about 2 times better stereo sound output. (For comparison, a low end CD player samples at 44.1 KHz)
You'll note that feature 5 says something about compatibility with Covox Speech Thing. Some programs (including a few decent games) support these parallel port sound boards. So far I haven't run into any compatibility problems with Covox Speech Thing except those that specifically require a copyrighted driver file by Covox.
In V1.00 of this DOC file, I said that the sound board can support some Disney Sound Source programs as long as they don't try to auto-detect the DSS card. Well, since then, I have purchased a DSS and some of its supporting software, and found out that this version of the sound board really doesn't support the DSS format at all. (Sorry, about that.) It turns out that there are about three DSS programs, that I have found, that supports my sound board. One of them is MODPLAY PRO. But since the DSS is a mono board and my board is in stereo, there isn't any logical reason to set MODPLAY PRO up in the DSS mode.
So far I am only aware of software for the IBM that supports this hardware design. Although, any computer that will handle a parallel printer should be able to accommodate this sound board (if you know someone who wants to write software for it).
The software listed above will work with any of the IBM models. However, MODPLAY PRO requires at least a 286 at 10 MHz. In theory, .SND files aren't as processor intensive as .MOD files and should be able to accommodate slower machines. Case in point, a friend of mine owns a Tandy Color Computer 3 which can play .SND sound files through roughly equivalent internal circuitry yet the processor runs slower than the slowest IBM PC-XT. (He recently upgraded to an Amiga 500. Unfortunately, he isn't as interested in collecting MOD files as I am.)
FUNCTIONAL DESCRIPTION V1.00:
When a stereo signal is present, pins 1 and 14 on the parallel port are active. (pins 1 and 14 are normally high) Thus, initially when pin 1 or 14 goes low, the 2N3906 is properly biased and the .47 uF capacitor connected to the threshold pin of the 555 timer is discharged to ground. This causes the output of the 555 timer to go high which in turn lights the stereo indicator and also allows the G input on each 74HCT373 latch to follow an inverted signal from their respective strobes (pin 1 for the right channel, pin 14 for the left channel).
When either latch receives a high on their G input the output lines on that latch then change to reflect the same states found on their corresponding input lines. When the signal on the G input falls low again, the output lines remain at the states they were most recently set to. The capacitor connected to the G input serves a double purpose. First, it isolates the signal found at the G pin from feeding back to the inverter driving the 2N3906. Second, it cuts the pulse width of the original strobe signal for the hell of it.
Each DAC0808 then takes the output from their respective latch and converts it into a corresponding voltage below ground.
The LM324 Op Amps take the voltage at the output of their respective DAC0808 and amplify the voltage as well as bring the voltage positive with respect to ground.
As long as pins 1 and 14 stay active the .47 uF capacitor never gets a chance to charge up, thus the circuit remains in the stereo mode. Once the activity stops on pins 1 and 14 the .47 uF capacitor charges up causing the output of the 555 timer to swing low. This causes the stereo indicator to go out and also forces the G inputs on both latches to go and stay high. This results in the output lines on the latches to continually follow the their
corresponding input lines, which allows for mono compatibility.
FUNCTIONAL DESCRIPTION V1.50:
Basically the functional description of V1.50 is the same as V1.00 and in fact it is the same if you are using the sound board in the V1.00 mode. The main difference between the two Stereo-on-1 modes is that the V1.00 mode uses two strobe lines to decode the stereo signal and V1.50 uses only one strobe line. The way that V1.50 decodes the stereo signal is that it latches the right channel on the negative-going edge of the strobe and latches the left channel on the positive-going edge. Thus the data on the bus changes when the strobe line is either a stable high or a stable low. This method is actually more efficient than the V1.00 method, not only with conserving port lines, but also from a programming standpoint. On the other hand, if I had stumbled across this method first, it would be considerably more difficult to adapt the V1.00 method to it.
HOW TO PRINT GIF FILES:
I don't know of any nice, easy ways to print GIF files. I have found a couple of ways to do it, though. Both of which require you to have a program called VPIC by Bob Montgomery which can be obtained from almost any BBS.
The first way requires you to also have a copy of CSHOW which also can be obtained from almost any BBS. The first step is to load the GIF file into VPIC and invert the colors (so black is white, and white is black, etc.) and save the file in GIF format. Second, load the inverted GIF into CSHOW and print it out. Note: Some colors don't seem to print, so you will have to draw in some of the lines manually.
The second way requires you to purchase Dr. Halo. The first step is to load the GIF file into VPIC and convert it to a CUT file. Then load the CUT file into Dr. Halo and print it. (I haven't actually tried this, so I am not sure how well this method works.)
If GIF files are so hard to print, why would I pick them as the format to distribute my schematics in? As far as I know GIF files are the easiest to view. I was originally distributing the V1.00 schematic in AutoSketch and AutoCad formats but I figured that the people most likely to be interested in my circuit probably wouldn't have either of these programs. I could distribute the files in TIF format, but I haven't found any way to display this format.
MISCELLANEOUS NOTES:
I have tested the sound board by replacing the 74HCT04 on the V1.50 adapter with a 74LS04 and verified that my suspicions are correct. The sound board wasn't able to successfully separate the stereo signal. Therefore, from here on in, only construct this circuit using HCT logic as is specified by all of my schematics. Although the basic function of a 74HCT04 and a 74LS04 are the same, they don't appear to be directly substitutable for this application. I am going to assume that trying to substitute all other logic types will result in similar problems. The bottom line is: build the circuit with the parts that I have specified in the schematics. If you've built the circuit using a different logic type and you are having problems getting the circuit to work properly, be aware that this might be the problem.
You should always turn this sound board on before or at the same time as the computer. MODPLAY PRO has trouble detecting the sound board if you don't. If you have a printer also connected to the same parallel port, you will need to turn it on as well. If you don't, sound through the board will sound noisy and distorted.
Trying to operate the sound board on parallel port where there is either a hardware or software printer buffer won't work very well, if at all.
Some computer BIOSs assign different port numbers to each parallel port. For example, on most computers LPT1 is located at hex address 378 and LPT2 is located at hex address 278. At least that's how my old 386-20 worked. With my new 486-33, LPT1 is located at hex address 3BC, LPT2 is located at hex address 378, and LPT3 is located at hex address 278. Since my sound board is on LPT2, if a program asks for the port address, I have to enter 378. However, if the program lists the parallel ports LPT1, LPT2, etc., I have to pick LPT2 to get the sound board to work. Of course there are some programs that just assume that LPT1 is 378 and LPT2 is 278, in which case I have to pick LPT1 knowing full well it actually means LPT2. If some programs don't seem to work with the sound board, you may have to play around with the port configuration.
Although the schematic says that the voltage input should be + and - 12 volts, you can actually get by with anything between + and - 9 to 15 volts, just make sure that the power supply is balanced. I have run this circuit off of two nine volt batteries for over an hour.
SPUTTER by Adrienne Cousins also has a TSR that allows you to play a sound file in place of the system beep, whenever you open or close a file, a certain time of the day, whenever you press a certain key, or just about
anything else on your computer. As an example of what this program does, I have my autoexec.bat set up so that whenever my computer boots up the computer plays a sound file of Data from Star Trek - T.N.G. saying "Sir, I have completed a level one diagnostic. There are no malfunctions." I have the TSR set up to play "Excellent" whenever I open a file and "Bogus" whenever I delete a file. Both of those sound clips are from the movie, Bill & Ted's Excellent Adventure.
Pin 7 on the 74HCT04 should be connected to ground. Pin 14 on the 74HCT04 should be connected to +5 volts. (the output of the 7805) It is an assumption on most schematics that if using gate chips (inverters, AND's, OR's, etc.) that the power and ground lines have to be hooked in order to ensure proper operation even though you may never see anything on the schematic indicating that these chips have power and ground lines. Usually, but not always heres how power and ground pins are connected on a digital I.C.:
Remember, the purpose of decoupling capacitors is to eliminate noise on the power supply lines as close to each chip as possible to ensure reliable operation of those parts. For that reason, I do not show decoupling capacitors on the schematics. Inexperienced people have a tendency when they see them on a schematic to group all of them in the same area on the board or replace them with one large capacitor instead. This completely defeats their purpose. So remember to wire in a decoupling capacitor of 0.1 uF across the power and ground line to each chip as close to the chip as possible. The only requirement on the type of capacitor that should be used is that to stay away from electrolytics, usually disc capacitors work best.
There is one note to make about the V1.50 circuit. If the sound coming from the sound board seems to be distorted, noisy, or missing altogether in one channel, then you probably have the switch set to the wrong position. Try the other switch position and see what happens. Remember that for most toggle switches that when the switch is in the "top" position the "bottom" pins on the back are connected. However, for a slide switch, the pins that are directly under the sliding part of the switch are in contact.
I make it a point on all my circuits to use I.C. chip sockets with all of the I.C.'s. If you've ever had to try and remove a 14 pin chip from a soldered board, you know why. Socketing chips makes it easier to debug the circuit as well.
If you obtain a copy of SPUTTER by Adrienne Cousins, make sure you add the following line to the AUTOEXEC.BAT:
SET SPUTARG=/P378
The above line specifies that the sound board is on LPT1. If your sound board is on a different parallel port, you will have to look in the accompanying DOC files to see what number you should replace 378 with.
On the back of the computer there are two types of ports that look almost identical, but aren't. The parallel port is characterized by a female (one with holes) DB-25 connector. Serial ports can have a male (one with pins) DB-25 connector. Don't connect the sound board up to a serial port, it won't work. And no, using a gender changer on a serial port doesn't convert it to a parallel port.
It is always a good idea to enclose all circuits in metal boxes. However, when circuits are enclosed in a metal box, the box should be grounded in some way. There are a couple of main reasons for this. If the hot wire of the high voltage side should ever come loose (and make connection with the box), the fuse or the house's circuit breaker will blow (if the box is earth grounded) protecting the user from a potentially fatal shock. High voltage wiring and power transformers make good antennas for 60 Hz hum. An earth grounded box will effectively eliminate almost all of this problem. On low voltage circuits, the box should be connected to the circuit ground. This prevents almost all noise (EMI, RFI, AFI, etc.) from this circuit from being transmitted to other circuits. It also prevents almost all noise (EMI, RFI, AFI, etc.) transmitted by other circuits from reaching this one. If possible, it is a good idea to connect the earth ground to the circuit ground. Before making this connection permanent, it is a good idea to test it first. Occasionally, you will run into a situation where the earth ground will feed more noise in than it will take out. (This is usually a result of the earth ground having too much resistance in the line. Be aware that if this is the problem, then that outlet should be considered very unsafe.)
The ZNRs and zener diodes in the power supply are provided for surge protection. They are not "needed" for the circuit to operate. The ZNR on the high voltage side will prolong the life of the power switch. The two ZNRs on the low voltage side of the transformer serve to help keep high voltage spikes from getting across the transformer. (the one on the primary side does most of the work) The two zener diodes clamp reverse voltage and transient spikes that could be potentially damaging to the sound board circuitry or create loud snaps through the audio outputs during power up, power down, and when large appliances "kick" in or out.
The transformer in the power supply schematic is a 25.2 V AC centertapped stepdown transformer. As long as the transformer is centertapped and stepdown (from 120 V AC) the secondary voltage can be anywhere from 24 volts to 30 volts AC.
When specifying capacitor values you will also need to know what voltage the capacitor is seeing. If you are unsure what value to go for, use a 50 volt or above. 50 volts is a little overkill in the 12 volt and 5 volt sections.
For all practical purposes, to identify the pins on a 3-pin voltage regulator, the pin numbers that I have used are as such: hold the voltage regulator so that the pins are pointing down and the part number is visible, then the pins are numbered from left to right. In other words, the leftmost pin is 1 and the rightmost pin is 3. The 7812 is similar to the 7805 in that the input pin is pin 1, the ground pin is pin 2, and the output pin is pin 3. As for the 7912, my linear data book is unavailable right now. I'll have to look up the pin configuration when I get that book back.
SETTING UP YOUR STEREO AMPLIFIER FOR BEST RESULTS:
I thought it was about time I include a section on the recommended amplifier setup. Let me give you an idea as to how I set my stereo up. First, I have a Scott stereo receiver (Yeah, I know, but I got it for free. It has power supply problems among other things.) which produces significantly more power output than my 2-way JBL 40W speakers will handle. I tied the output of my sound board into a passive mixer that I built a while back which is sandwiched in the tape monitor (sometimes called accessory) inputs and outputs on the back of the receiver (basically the mixer allows me to preset the volume from the sound board as compared to the receiver and it also means that even if something is playing on the receiver both the sound from the computer and receiver is output to the amplifier and thus to the speakers.)
As for the controls on the front of the receiver, I have all three tone controls flat (set to 0), the loudness contour on, and the high pass filter activated. I've found that I get the richest sound output from this setup. If you don't have a loudness contour, I've also found that you can get similar results (on some amplifiers) if you set the bass and treble tone controls up about half way and leave the mid band control flat along with activating the high pass filter.
Whether or not you need some sort of high pass filter depends on what you can get the mixing frequency of the software up to. With a really high mixing frequency you shouldn't need a high pass filter. Hiss and buzzing results in the sound when there are frequencies present in a sound which the mixing frequency won't allow for an accurate reproduction of. As for the reason behind the loudness contour, it doesn't matter to me whether the music is from the computer, CD, radio, etc., it can always use a little more bass to make the sound richer.
I'd recommend staying away from those small (3 inch or smaller) amplified speaker pairs (like they sell at Radio Shack for amplifying portable radios). That's like upgrading from a PC speaker to two PC speakers. I also recommend trying to resist the temptation of hooking this sound board into the nearest boom box. As most boom boxes (except for really nice, expensive ones) don't do much better. (Their speakers are usually rated for a maximum of one watt.)
The optimum system should have an equalizer in it. That way you could adjust it to filter out only the frequencies where hiss may occur instead of relying on a high pass filter (which may filter out more frequencies than you want). You could also boost the bass frequencies more to your liking if your amplifier doesn't have a loudness contour button.
It is also nice to have an amplifier with at least a double digit wattage rating. (I mean positive integer double digit.) This allows you to have as much bass as you want. If you like to show off than you'll probably want (if you don't already have) an amplifier with at least a triple digit wattage rating. It's also nice to have at least 2-way speakers (3-way with a couple of satellites and a subwoofer, of course, are preferred). Despite what you may of heard, there are no such things as (single) full range speakers. If the speakers are big, they don't reproduce high frequency sounds well. If they are small, they don't reproduce low frequency sounds well.
WHAT THE HECK IS V0.50?
Somewhere in this file (in this and a couple of past releases), I mention something about a V0.50 sound board, but I don't tell you what it is. Truthfully, it is a sound board that I haven't really designed yet. If the design I have planned out in my head works, it will basically be a super cheap stereo sound board consisting of one DAC and none of the auto-detect circuitry. The design for this board will require about a fifth of the components that the V2.00 will have. The V0.50 will be designed to be appealing to those people who don't want to spend practically anything or those people that feel uncomfortable assembling large circuits.
It will have two major drawbacks compared to V2.00. It won't be able to support the V2.00 stereo mode and you will have to use a rotary switch to select which stereo or mono mode you need. Some sound quality may also be compromised in this design.
The reason it won't be able to support the V2.00 stereo mode is that to make it do so would make it more complex than the V2.00 sound board. (Kind of defeats it's purpose.)
DISCUSSION OF AMIGA AND IBM SOUND HARDWARE:
I thought it would be a good idea to point out what each system is capable of, so you know what we're aiming for. This section might be better off as a subsection of the limitations and compatibility section, but I thought that section was getting a little cluttered.
First, let's take a look at the Amiga. The Amiga has a dedicated sound chip (basically a microprocessor in itself) with two 8-bit DACs (as I was recently informed by someone with documentation for an Amiga, at least the cheaper ones do), one for the right channel and one for the left channel.
Now let's take a little look at IBM. IBM has a one inch speaker connected to the output of a flip-flop (through a little amplifier circuitry). And if you're really unlucky you have a piezo speaker instead of a dynamic one. Piezo speakers have a frequency response ranging from a few KHz on up (Vocal and musical instrument frequencies? What vocal and musical instrument frequencies?). Those small dynamic speakers have a frequency response of a few hundred Hz to a few KHz. All in all, it really doesn't matter what type of speaker you have because realistically the PC's internal sound circuitry is equivalent to having one 1-bit DAC. The "volume" of the speaker is also fixed at a constant. So how do they get roughly 6-bit sound output from the speaker? The programmers can create the illusion that there are more bits by fudging with the frequency and duty cycle they're actually outputing to the speaker. (I don't know exactly how this is done.)
Now let's get down to a little discussion on the quality of sound. How many bits does it really take? By listening to your PC speaker you can tell that 1 through 6 fall short. (I've actually connected a five inch speaker up to my computer just to see if the computer was actually capable of decent sound. It sounded a lot better but it was still noisy.) By comparison, your CD player is outputing 16 to 18 bits per channel.
Now for a discussion of how sound are digitally mixed. When you take two 8-bit sounds and add or average them you get a 9-bit result (When you add you get a 9-bit sum, when you average you get an 8-bit dividend with a 1-bit remainder). In other words, to get the same resolution as if you were outputing each sound to its own DAC, you need a 9-bit DAC for the sum of the two sounds. When your output device is limited to 8 bits then the least significant bit is discarded (it gets discarded when the average is taken).
Well that sums up what happens when playing MODs in stereo, when you play MODs in mono all four channels of sound get converted into one. In other words, it takes 10 bits to fully describe the resulting sound. Of course, you can consider the fact that when you play a MOD file through the PC speaker, you're converting a 10-bit sound to a 6-bit sound. (Yuck!)
Modplay Pro supports a quadraphonic DAC bus card. That means bit-wise you would be getting better sound quality than you would get from an Amiga. However, mixing frequency is the other determining factor in sound quality. I'm not sure what mixing frequency Amigas use (I have a feeling it's around 44 KHz), but I know it's higher than what Modplay Pro will allow. On the other hand, if you want to obtain good quality sound just by getting the best mixing frequency, you are better off using this sound board with a program like HP00A or FastTracker.
TROUBLESHOOTING GUIDE:
Problem:
No sound whatsoever.
Possible causes and solutions:
This could be caused by a lot of things. Is the power on? If you are using batteries, are you sure that they are not dead? Is the sound board input hooked up to the computer? Is the sound board output connected to the line inputs of a suitable amplifier? Is it on? Are you sure that there aren't any hardware or software printer buffers in the system? Are you sure that the program you are using supports the sound board and that the program is setup to use it? Are you sure that the board is wired properly? If your amplifier has a source selector switch, make sure that it is set to the position corresponding to the sound board. If there is a fuse in the power supply, is it good?
If all else fails, try another parallel port. If it is necessary to purchase another parallel port, remember the cheap ones seem to work best. (Cheap multi-I/O cards are typically about $11 mail order.)
Problem:
There is sound, but it sounds like crap.
Possible causes and solutions:
If you have a printer sharing the parallel port, make sure that it is on, or just unplug its data cable. Make sure you use the line inputs on the amplifier, if you use the microphone inputs the signal may sound distorted. Make sure that you have the audio ground hooked up between the sound board and the amplifier. You may need to use shielded patch cords between the sound board and the amplifier. (I always do.) If you are using batteries, they may be almost dead. It could be a loose connection, try shaking the board. (If this temporarily fixes it, then the problem is definitely a loose connection.) It could be that you mixed up the data bus wires going to the 74HCT373s or to the DAC0808s. It could be that you forgot to hook up the power and ground pins to one or more of the chips. Make sure that if the V1.50 circuit is hooked up, that the switch is in the right stereo mode. Make sure that at least pins 20 and 25 on all of the DB-25 connectors are connected to ground on the V1.50 adapter and the V1.00 sound board. (Remember, pin 25 on the input of the V1.50 adapter is not only ground to that board, but it also runs through to the output DB-25 connector.)
Problem:
The stereo light comes on and stays on or flashes, when there isn't a stereo signal present.
Possible causes and solutions:
Something in the auto-detect circuitry isn't wired properly. (The auto-detect circuitry region consists mainly of the KS555, the 2N3906, and the 74HCT04, and pins 1 and 14 on the DB-25.) There also may be a loose connection.
Problem:
The fuse in the power supply keeps blowing every time I turn it on.
Possible causes and solutions:
Somewhere in the circuit a (+5, +12, etc.) power line has been accidentally connected to ground. If the fuse seems to be good up until it starts trying to play sound, then it is likely that the output of a chip has been accidentally connected directly to ground (or power). (The chip in question, may also be damaged.) This problem can also occur if a chip has been placed in backwards.
Problem:
After several hours of the sound board playing perfectly, the sound will start to cut out (and the power LED may dim).
Possible causes and solutions:
If you are using batteries, they're probably getting low. Most likely, though, the power regulators are shutting down because they are overheating. The 7805 and the other voltage regulators have built in thermal protection; when they get too hot, they shut down. This can be fixed by mounting a bigger heat sink on the voltage regulators. The immediate fix is just to shut off the power to the sound board and to let it cool off naturally. (The above problem only happened to me when I was using a logic probe that I was powering off of the sound board's power.)
Problem:
The program that I am trying to run, either says that there isn't enough memory or that I have some memory managers in the memory that need to be removed.
Possible causes and solutions:
Dust off the DOS manual and look up how to make a bootable disk. Once you have the bootable disk, insert it into the floppy drive and reset the computer either by shutting the power off for a few seconds or pressing the RESET button on the computer. (Ctrl-Alt-Delete won't work correctly.) You should be able to run the program now. By booting off a floppy, the AUTOEXEC.BAT and CONFIG.SYS files are bypassed (providing that the boot disk doesn't contain either), and thus all the driver files that normally reside in memory aren't loaded into your computer when it boots. If you need the mouse to work, you will have to find your MOUSE.COM (or similar) file and run it. (If your computer has a bus mouse instead of a serial mouse, then you will need to make a config.sys file on the boot disk containing a statement like: DEVICE=C:\MOUSE\MOUSE.SYS)
If, however, you are one of those unlucky persons that has STACKER (Yuck!) or a similar program running on your hard drive, it is not recommended you boot off of floppy. You'll have to refer to the STACKER manual to determine how to free up memory. If you're feeling lucky and decide to boot off of floppy and your drive is STACKed then accessing the drive (modifying, adding, or deleting files) without the STACKER drivers in memory may cause fatal errors to occur, in other words you would be simulating your own software induced hard drive crash. If you don't know if your hard drive contains STACKER, just ask whoever setup your computer if they installed it. For the most part, only people that have hard drives smaller than 130 Mb actually go out and buy STACKER.
QUICKIE CIRCUIT TROUBLESHOOTING GUIDE:
This section will attempt to point you in the right direction if you come to suspect that something is incorrectly wired on the circuit board. It is impossible for me to predict all of errors that one could make when wiring this board, so here are the most common or most likely.
If you are going to troubleshoot this board you are going to need a Digital Multi-Meter and a logic probe. The logic probe should be set to TTL and the sound on it should be set to pulse mode so that if the signal is pulsing, the probe makes noise, and if the signal is stable, the probe is quiet. The logic probe's power leads should either be connected across the +5 and ground on the sound board or the probe should be connected to an independent 5 volt DC power supply with the ground on the independent source also tied to the ground on the sound board.
Unless otherwise specified, all of the troubleshooting techniques require that the power to the sound board be on and some sort of program should be outputing sound to the sound board. In order to isolate problems that I may not have thought of, it is important to follow the troubleshooting directions in order.
Often times in this guide I will specify that you should be reading a specific voltage AC or DC, this means that you have to set the DMM or volt meter to either the AC or DC range before you try to read it. For example, if I specify that with the meter hooked up in a certain way that you should be reading + 12 volts DC, then you have to set the DMM or voltmeter to read DC volts before trying to read it.
Problem:
The board sounds fine but the power light never comes on.
What to check:
In all likelihood, the LED was wired in backwards. Try removing it, turning it around, and putting it back into the circuit. (You may experience a similar problem with the stereo indicator if it is wired in backwards.)
Problem:
The board doesn't output any sound and the power and stereo lights don't come on or are very dim.
What to check:
Trouble Shooting the Power Supply:
This usually indicates that something is not right with the power supply. If you have a continuity meter handy, verify that the fuse in the power supply circuit hasn't opened up. Next, place the leads of the DMM across the primary side of the transformer, the meter should read about 110 to 120 volts AC. If it doesn't then it is likely that either the fuse, the fuse holder, the power switch, or the cord is to blame.
From here on in when I mention the transformer, I am referring to the secondary side, the low voltage side. Make sure that don't confuse the primary and secondary sides of the transformer. Hooking anything to the primary that belongs on the secondary, whether circuitry, test equipment, or people can cause serious damage to the transformer, the circuitry, the test equipment, and you or any other living creature nearby.
Connect the black lead (negative) of the DMM to the sound board's ground (I suggest the ground pin of a chip). First, check the transformer's ground, by placing the red probe on the secondary centertap of the transformer. The appropriate reading is zero volts AC and DC. If there is a voltage here then it is possible that you forgot to tie the secondary centertap of the transformer to ground or that there is a loose connection at this point. Next, use the red probe to check each of the poles of the secondary side of the transformer. If you are using a 25.2 volt AC centertapped transformer, then the meter should read about 12.6 volts AC on each pole. If it doesn't, then the transformer may be bad.
Next, place the red probe on the positive output side of the bridge rectifier. The voltage should read greater than + 14 volts DC. If it does not, then one or both of the two diodes connected at this point may be in backwards or may just not work. If it is because they don't work, then something else down the line may have caused them not to work. Check the negative output side of the bridge rectifier in the same way, it should read less than - 14 volts DC, numberwise.
Next, test the inputs to the voltage regulators. The inputs of the voltage regulators should test out as follows:
7812 same as positive bridge output
7912 same as negative bridge output
7805 about + 12 volts DC
If you don't then it is likely that there is no connection. Be advised that you should go through all of the testing instructions pertaining to the 7812 and 7912 and then go back and test the 7805.
Next, test the ground pin on all of the regulators. All three should test out to be 0 volts DC. If not, then they probably have a bad connection.
Next test the output of all of the voltage regulators. The output pins should test out as follows:
7812 about + 12 volts DC
7912 about - 12 volts DC
7805 about + 5 volts DC
If not, then the regulator is bad or it has been wired incorrectly.
Check to make sure that the power lines running from the 7812, 7912, and ground actually make it to the sound board.
This just about raps it up for the power supply. You should test for voltage across each of the capacitors and the other components in the power supply. If you aren't reading any DC voltage, then it is likely that there is a bad connection. If you are reading a stable but wrong voltage, then you may have a short between the line you are testing and somewhere that contains that voltage.
Special Case:
There is a special case if the fuse keeps blowing every time the power is turned on. The first thing to do is disconnect the sound board from the power supply, in other words cut the + 12 volt and the - 12 volt line. (You can leave the ground connected.) Turn the power on with a new fuse installed. If the fuse doesn't blow then you have a short circuit in the sound board somewhere. If the fuse blows then you have a short circuit in the power supply.
In either case, make sure you check all of the chips to make sure that one or more of them aren't in backwards. Check all of the electrolytic capacitors to make sure that they have been installed correctly, reversing an electrolytic is like shorting the power to ground. Make sure that all of the diodes are installed correctly. Now, check all of your wires (or traces) to make sure that they all run to the correct places.
Problem:
The power light comes on, the power supply has been checked out and it works, but there is no sound.
What to Check:
The first thing to check is whether or not there is a data signal on the parallel port. You will need to have a program running that is continually sending a signal. (preferably mono) Use the logic probe to check pins 2 through 9 on the DB-25 connector. All of the pins should have a pulsing signal on them, most of the time. If they don't, double check to make sure that the program is sending the data to the parallel port. If the lines are still dead, then try flipping switch on the parallel port card that disables its interrupt. Reset the computer and try this test again. Also, make sure that you have connected the sound board to a parallel port and that you don't have any printer specific programs hogging the parallel port. If it fails the test again, then you probably need another parallel port.
Second, once you've established that there is a signal on the parallel port, the next thing to check is whether or not sending a stereo or mono signal out to the port has any effect on its condition. To do this run a program that outputs mono, then run a program that outputs stereo. If one mode works and the other doesn't then the problem most likely lies in the auto-detect circuitry. If both modes don't work then the problem is most likely to be one of the following:
1. power to the LM324 is not connected.
2. 5 V power to the entire board is not
connected.
3. the data bus is not connected to the
sound board.
4. one or more chips are not connected
correctly or are in backwards
5. the G pins on the 74HCT373s are being
held low indefinitely
If you confirm that the problem is #5 then something in the auto-detect circuitry isn't working properly.
Problem:
There is sound, but its noisy and distorted.
What to check:
Check to make sure the data bus lines aren't crossed at some point. If you are playing a stereo signal make sure the stereo mode select switch is in the correct position. Make sure the negative voltage supplied to the DAC0808 is at - 12 volts DC (if you built the power supply).
Well this covers the main problems. I promised someone I would have this file done by January 10, so I'm gonna wrap this section up kind of early. In the next version I'll improve this section and possibly add a schematic diagram with all the voltages you should test for.
WHAT'S NEXT?
By my next major release I plan to have support for both Stereo-on-1 formats finalized and an auto-detect feature that will automatically determine which type of signal is present and process it accordingly. It'll be a while before I get around to this, so don't expect to see it before the summer '93. At that time I'll release two schematics, one that will be like this modification and require very little or no modification to the V1.00 sound board and the other which will be a complete overhaul of the V1.00 sound board.
Also by release V2.00, I plan to make my sound board compatible with Stereo-on-2 formats. This is actually a simple (and cheap) modification to the circuit itself, but if you already have a V1.00 built, it might be easier to start from scratch. I don't know if this feature will have associated auto-detect circuitry. Auto-detecting this type of signal is a bit tricky. I know of a few programs that use this type of stereo, and it is understandable why. This method is actually easier and faster from a programming stand-point.
I'm not sure if I'll get to my next feature by my next release and I'm not sure how messy it is going to be to integrate it into sound board. I plan to add more Disney Sound Source compatibility. Disney (and Mozer, the company that actually made their sound board,) have several patents and copyrights on their design, so I am NOT going to attempt 100% compatibility. Basically, the principle behind their sound board is that they send out an auto-detect signal on one of the lines and then wait for answer from the DSS on another line. This is how they know whether or not a DSS exists in your system. Then, if they find one, they send out the sound code out on the 8-bit bus with a latching signal. While their sound board isn't looking at the bus they send out a garbage signal to keep people like us from having compatibility with their programs. To keep the people at Disney and Mozer from hunting me down and shooting me, I am not going to fake their auto-detect signal, but only offer an alternative to listening to DSS sound through their board. That means in order to take advantage of this feature you would still have to buy a DSS.
What advantage would this have? Well, I bought a DSS to figure out how they work. So here's what they offer: a maximum of a half watt (1/4 nominal) of power output through their internal amplifier, output through a two inch speaker, not easily adapted to external amplifier circuitry for better sound, a headphone jack that doesn't sound much better than the speaker (I tested it with Sony digital-ready headphones), and a nine volt battery power source that dies every few hours. On the bright side, the DSS is completely portable and easy to use.
Also planned for the next release is a artwork for etching a double-sided copper clad board. I have artwork drawn up right now for the V1.00, however, when I went to construct a V1.00 for myself using the artwork, I found a few minor bugs in it. Included in the version that I built for myself last summer, I added a volume control, a switch that turns the sound off when I want to print something, and the ability to daisychain a printer through my sound board to the computer. I also substituted a blue point source LED for the red power indicator. (yep, it was worth it.) I'll try to include all of these features next time. (except the blue LED, it costs $2.80 through Digi-Key)
Also planned for some future release is the design for a single sided power supply. I'm thinking about using a voltage inverter/doubler chip in place of the negative voltage supply rail. This would make the circuit better suited for battery operation. It would also cut the cost of the power supply circuitry somewhat.
Sometime in the future, I would like to get around to making a sound digitizing board. Right now, I imagine that the board would consist of 5 or 6 chips and various other discrete components. Parallel ports are particularly easy to use when outputing data, however, they don't lend themselves very well for inputing data. Therefore, I would most likely use a serial port. (Actually, after doing some preliminary calculations, the serial port may prove to be too slow. No, I will NOT consider using the game port instead. Contrary to popular belief, the game port doesn't contain any ADCs, otherwise it would be a perfect solution.)
Possible specifications:
- 8 or 10 bit input (depends on the price of
10 bit)
- Stereo input (a must)
- Software selectable sampling frequency
(Possibly better than SoundBlaster Pro's)
- Possible hardware filtering
Unfortunately, there seem to be a few blocks in my way. Currently, I know about 5 different assembly languages, and while one is 8086, I don't have enough knowledge to write adequate code. Therefore, if anyone knows of any shareware or freeware programmers (Assembler or C preferred) out there that would like to write the software for my hardware, have them get in contact with me. Perhaps I can have the hardware schematic release done for it by next year.
Just recently, I decided it was time to learn assembler for the IBM. I am up to the point where I could write a simple program to input data from the keyboard and output it to the text screen via dos INT 21. It'll probably be a while before I can write any software for my sound board. I haven't found any real good books that detail what ports go where and how to successfully program them.
I've been kicking around the idea to sponsor a programming contest. In the next major release, I'll tell you if it's a go or no-go. Right now, I'm not sure that there is enough interest in my sound board or not for it to be an effective way get more software out there to support it. Besides which, I'm a college student majoring in electrical engineering at a private school (M.S.O.E.) and don't have any money to put out for really nice prizes. (In other words, you'd have to be in it for the challenge, not the reward.) If I do go ahead with the contest, the prizes would go something like this:
1 - First Prize - A V2.00, fully assembled and tested
2. The program must be a game (recreational or educational)
3. The program must support VGA (256 colors)
4. It must support my sound board in one of it's stereo
modes, although only programs utilizing Stereo-on-1
will be considered for First Prize.
5. The program cannot exist before the contest begins.
6. You must be prepared to release the program as either
freeware or shareware after the contest is complete.
7. The program doesn't have to be 8088 compatible. It
should be compatible with at least a 386. (a 486 is
highly recommended, a 286 is optional)
8. Don't use extended or expanded memory, unless the
program will function without either.
9. Keyboard control is a must, but feel free to use
joystick and/or mouse.
10. Yes, multiple entries from the same person/group would
be accepted. (1 year usually isn't enough time to come
up with more than one program, though)
11. The program should be written in either Assembler, C, or
possibly even Pascal. (NO BASIC PROGRAMS ALLOWED!!!)
and whatever else I can think up. At the time of the contest, all of the applicants would receive a copy of the official rules, detailed info on my sound board so that they can design the program whether or not they have a sound board, and a copy of the judging sheet so they will know exactly what I am looking for. Like I say though, right now I'm not sure if I'll try this contest or not.
If you or anyone you know is interested participating, please drop me a line. I'm sure the determining factor of whether or not I do this is going to be determined by how many letters (from serious programmers) I get in 1993 saying "Go for it."
SOURCE LIST:
There are two main companies where I buy parts. They are:
JameCo
1355 Shoreway Road
Belmont, CA 94002
1-800-831-4242
and
Digi-Key Corp.
701 Brooks Ave. South
P.O. Box 677
Thief River Falls, MN 56701-0677
1-800-344-4539
Each of these companies has their own idiosyncrasies. Both of them will be happy to send you a free catalog, though.
JameCo:
- has all of the components needed to build this circuit
- $30 minimum order
- component prices are usually better than Digi-Key
- shipping charges: UPS ground $7.25
- offers individual component data sheets for $0.50 ea.
- offers no alternatives to backordering
Digi-Key:
- has most (if not all) of the parts required
- no minimum order: $5 fee assessed to orders under $25
- shipping charges: UPS ground $0.00 (FREE!)
- offers a few alternative parts to backordering
If you find it necessary to purchase an additional parallel port, you can order one from one of the following places:
Net Computers International
13725 Gamma Rd.
Dallas, TX 75244
1-214-386-9310
($14 bfr shipping)
or
AMKA Computer
15342 E. Valley Blvd.
City of Industry, CA 91746
1-818-369-2121
($11 bfr shipping)
or
Cycad Microsystems, Inc.
121 E. Brokaw Rd.
San Jose, CA 95112
1-408-436-4843
($10 bfr shipping)
or
Computer Gate International
2960 Gordon Ave.
Santa Clara, CA 95051
1-408-730-0673
($8 bfr shipping [parallel only])
or
Accessory Connection
3300 Bee Caves Rd. Suite 650
Westlake Hills, TX 78746
1-515-416-5750
($10 bfr shipping)
I'd like to make it clear that I have not actually tested any of the multi i/o cards that I have specified here. The place that I had specified in previous versions sold a multi i/o card that had been tested and found to work perfectly. Specifying replacements therefore was accomplished by referencing the Computer Shopper and looking for places with comparable prices to NCA (since NCA went out of business).
ACKNOWLEDGEMENTS:
I'd like to thank Mark Cox for writing a really good program that makes the IBM sound a lot better than you can ever imagine. I'd also like to express thanks for developing the specifications that I based my V1.00 circuit on.
I'd like to thank Adrienne Cousins for writing a program that can play almost any sound file format.
I'd like to thank Disney and Covox for setting standards that a few programs actually chose to support.
I'd like to thank Apogee, Id, and Sierra in advance for their DSS support. I hope you guys (and gals) will consider expanding your software support to include my and any other parallel port sound boards.
I'd like to thank the SpacePigs, Skyhawks, Twilight Zone, Cascada, Triton, and whoever else for making all of those kick-ass demos that support my sound board.
I'd like to thank DongleWare Publishing for making a decent game with lots of sounds.
I'd like to thank the makers of Adlib and SoundBlaster cards for making their products so damn expensive that it is well worth it to build this circuit.
I'd like to thank Accolade (Paul Reiche III and Fred Ford) for producing one hell of an awesome game. I only hope that Star Control III will support the Stereo-on-1 format.
TESTING:
The V1.00 sound board has been tested and found to work on the following systems:
a 386DX-20
a 386DX-33
a 486DX-33
a 486DX-50 (had to use cheap multi-I/O card, instead of
the one integrated on to the floppy/hard
controller)
The V1.50 circuit has been tested and found to work on the following systems:
a 386DX-20 with added parallel port card
a 486DX-33 with added parallel port card
I have tested the V1.50 circuit on a 486DX-50 with built in parallel port and had it perform poorly which in part prompted me to release this version with a fix for that bug. The 0.001 uF and 0.0047 uF may require a bit of fudging with to get optimum sound quality from the circuit. Because of this "band-aid" approach to adding V1.50 compatibility, the adapter circuit is highly dependent on the input and output impedances that it sees, and thus specific values are impossible to specify.
If you don't have one of the systems listed above, don't worry. This is only a list of what the sound board has been tested on. The sound board should work fine on all computers that have a parallel port, since the parallel port is the most important factor in determining whether or not the sound board is compatible, and there are several guidelines that manufacturers of parallel ports must follow to keep it a standard format.
DISCLAIMER:
Any damage you do to yourself, your computer, your stereo, or anything or anyone else is your own fault, not mine.
To the best of my knowledge there are no errors in the circuit schematic.
This circuit schematic has been given to you in hopes that you will copy it, distribute it, and use it to build this circuit.
Altering this file (like removing my name) or any of the other files in this ZIP file is strictly prohibited and illegal. Selling this file for a profit is strictly prohibited and illegal.
I don't expect any fee for using this file. However, if you find this schematic to be of great use, a donation of $5 would be greatly appreciated. This schematic took me more time to draw up and document than the circuit took to construct and debug.
Send any questions, comments, and donations to:
Dave Boyd
W2740 Rock River Paradise
Watertown, WI 53094
You can also Email me via EXEC-PC BBS at (414) 789-4210. I keep up with my mail on Exec-PC on a daily basis except during the summer.
