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I thought there were different compression settings for MP3. When I played with it, the highest compression sounded crappy, with a sort of echo to it. The lowest sounded just OK. MP3 does seem perfect when you're just crusing around in the car, or for background "fill."

I've always wanted to do an A/B comparison of MP3 with original CDs, but there is no easy way to do it on my system because when I play CDs, my CD player simply sends the bitstream into my receiver (Yamaha DSP-A1) for decoding. With MP3, my computer's soundcard does not have a digital output, so I'd be sending analog in, which would get redigitized, which is not a fair comparison. I suppose I could convert some MP3s back to WAVs and put them on CD and play them on my system for the comparison. I use 256kbit/s for better quality.

Dolby digital is 360 bits/second in theatres, right? That encodes 5.1 channels of information, so I would think that the sound quality of a 5.1 Dolby Digital soundtrack would be equal to the sound quality of a 70 kbit/second mono track (140 kbit/second for stereo). It seems that the MP3 rate needed to beat DD in fidelity for stereo music would have to be above 140 kbit/second, assuming the algorithms are roughly the same in quality. DD at home is usually 448 kbits/second, so it seems you'd need 175 kbits/second to beat the sound of that for regular stereo music.

Evans

12:1 compression (typical)
All main channels- full range
LFE channel- 3hz to 120hz

It looks like the actual bit rate changes, depending on the use. For example, the bit rate when used in theaters is 320kbs, but the rate is 448kbs with a DVD.

Also, I don't think many people realise that AC3 provides several extra features not used in a theater. For example, from a DVD at home, the AC3 provides a "smart-mixdown" depending on the format. When you switch the DVD player audio settings from, "5.1 channel" to "mono" the actual mix can be changed. If the director feels that a person listening in mono should not hear what was in the surround channel, he can remove it. If a person with poor hearing is listening, they can switch to a pre-approved mix that has dialog-only. There's bits in there to tell the listener what kind of room the sound was mixed for, (large dubbing stage or smaller recording studio) that the surround channel is or is not being used, a karaoke mode, copyright protection, etc.

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And I've heard some excellent Dolby Digital, too. Crystal clear, well mixed, and well planned.

You mentioned that you also have CP500's there... do you mean CP500D's (with the Dolby Digital cards instatlled)? If so, all cards in that section of the CP500D are identical to the DA20 except one. Your tech could then use these common cards for swapping, if necessary. Your description of warbling is interesting. There is a projector speed tolerance of +7 to -11% in the DA20... one could try swapping the Cat. No. 670 card (video preamp). I also wonder if you may be hearing 'block repeats'. If the DA20 cannot read one Digital block and cannot correct for it, then it will repeat the previous block up to 4 blocks in a row where it will revert to SR. There are other algorythm's which look for patterns of bad blocks which may not meet the 4-bad block rule. Anyway, block repeats may sound like a robotic type effect in the audio. If that is what you are hearing on a consistent basis, then perhaps something is up with your reader alignment (or the reader's light source). Your tech should be able to verify this with proper test equipment (an oscilloscope for video amplitude and DRAS for fun).

ken

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