MPST Digital Jukebox: Hard Problems

The current enclosure I'm using is a desktop PC painted black, which is actually smaller than the Sony carousel, but still much bigger than it need be and not quite as visually pleasing as I would like. The basic enclosure requirement is to be able to present a CD drive and 4x20 LCD display. Currently, the easiest setup has been a desktop PC with 3 5.25 bays, since the Crystal Fontz display comes in a double bay mounting bracket. There are a couple other possible solutions:

1. A black or silver mini tower with 3 5.25 bays. This will work fine, as long as that format fits well into your stereo cabinet.

2. Forget the LCD, add TV-output for the UI and use a book-pc format. This is fine, as long as you have a TV handy, which I don't want to require. You may also run into ground noise problems again, but they make transformers for this purpose as well.

3. Find a cool case in which a 4x20 LCD and the CD drive can be mounted side by side. This would be ideal. I still need to get a full height sound card in the back in order to get pure digital output from of the
machine, but the LCD could be any type. There may be a high-end motherboard with digital sound, but I suspect that would undermine the price target. So does anyone know where I can find something like this?

So is the band's name "The Who" or "Who", verses "Yes" or "No Doubt" whom you would never call "The Yes" or "The No Doubt"?   Although the FreeDB rules ask everyone not to enter a leading "The" for the artist name, it still happens more often than not. In either case, you want "The Who" sorted in the "W"s and not the "T"s.   Do to the design of Grip and DigitalDJ, it was much easier to solve this problem in the database, rather than write special sorting code in the UI. Hence, I created a MySQL user-defined function called TITLE(). TITLE does two things:

1. It converts all numbers into words.
2. It removes the leading "The"
For example:
        TITLE("The 10,000 Maniacs") == ten thousand Maniacs

This allows the user to continue to have "The Who" and "The Beatles" as the artist name in the database, but all database sorting is done with the TITLE() function.

I'm still considering whether TITLE should remove the leading "A" as well, but it's currently not an issue.

The other problem I'd like to solve is dealing with data tracks.   I'm trying to find a way to quickly identify a data file, prior to ripping and encoding it. This would save time on the rip and disk space on the system. Luckily, mpg123 bails before trying to play a data track, so you don't hear garbage, but the disk space and encoding time is still being wasted.

Most modern stereo equipment use two prong plugs with a floating ground.As you connect each device to the stereo, a larger floating ground is created. As soon as you connect a device which contains a PC power-supply, suddenly the floating ground is now attached to your houseground along with your microware, refidgerator, variable lighting potentiometers, etc... Futhermore, the PC power-supply itself, wasn't designed for a sensitive stereo system. This usually causes a nice 60Hz hum to eminate from your system, as well as many other interesting noises. There are a number of things I tried to solve this problem:

1. Balance the ground
According to most the websites I could find on the issue, one of the problems was that the PC and receiver were sharing ground through the audio-shielding. CheapNoiseHardwareTips recommended connecting the two devices with another thick copper wire such that the grounds were joined outside of the audio system. This did REDUCE the hum, but it did not eliminate it. In fact, I learned that the hum occured as soon as I connected the grounds, whether the audio cables were connected or not. In fact, the hum was present EVEN WHEN THE PC WAS POWERED OFF.

2. Lift the ground.
Do not do use a ground lifter with your PC. The power-supply was designed such that any spare noise or voltage is drained to the ground wire. If you lift the ground, all your stereo components become the destination for that spare noise and voltage. That said, with the PC powered off, I plugged it into a ground lifter. At that point the hum disappeared. What we really need here is a balanced/floating ground PC power supply. This actually exists in many newer laptops. If anyone knows how to wire a laptop power supply into an ATX motherboard, we may have an interesting solution.

3. Go Digital
This is the easiest solution. If your receiver accepts optical digital input (TOSLINK), then use a high end audio card that supports digital out. There is no ground sheilding here for obvious reasons. Note the Creative Labs Optical Digital I/O daughter card for the SBLive series also acts as a ground isolator, so you can use either the direct Coaxial PCM or TOSLINK connection without any ground noise issues. I suspect the higher-end external audio devices do the same, though I haven't tested them. There are also Coax to TOSLINK converters available, but with the added cost, you might as well buy an external audio device.

4. Ground Noise Filters and Isolators
It turns out people ran into this problem before PC audio was invented while they were installing car stereos. The ignition system in a car engine can cause quite a bit of ground noise as well. Hence, for as little as $10 you can buy a ground filter from a car audio shop (or some Radio Shacks). You simply insert this between your PC and the receiver. I experimented with a couple of different models ranging from $10-$20. Both eliminated the hum, but they only work with the standard RCA analog outputs. They do not work for digital PCM. Furthermore, at high gain (with no audio playing) other higher frequency noises can be heard. It's possible these may of been from the processor itself. Note there is a high quality Jensen Ground Isolator which retails for $200. I haven't tried this, because if you're going to spend that much money on the problem, you should simply go digital. In the end, the $10 isolator would be fine for most casual listeners.

In conclusion, I'd love to get more information about laptop power supplies and whether they can be modified to work with an ATX motherboard, or if laptop motherboards can be purchased on the street? I have yet to find them at a reasonable price. The far easier solution is an external sound device with a built in ground isolator. The key here is to insure the digital data is not converted back and forth on it's path to the receiver. For a great introduction of audio issues (even though it's directed at Car Audio) see http://www.eatel.net/~amptech/elecdisc/caraudio.htm