|
Video Asylum TVs, VCRs, DVD players, Home Theater systems and more. |
|
|
|
Video Asylum TVs, VCRs, DVD players, Home Theater systems and more. |
|
In Reply to: Thanks, but... posted by Homer on May 3, 2002 at 00:33:10:
Hello -I'm afraid I can't answer your first question very well. Certainly in the case of A/D converters the resolution falls off as the speed increases. This is because it takes time to determine the level of the analog input signal with precision. However, the D/A converters don't really have the same types of limitations. In the D/A converter, you are just turning current sources on and off. Obviously there must be some upper limit to the operating frequency, but I can't answer specifically if there would be significant degradation going from 54 MHz to 108 MHz. It probably depends on the part itself, and how it is designed.
Analog processing will give better overall results than will digital, at least in this situation. We've already determined that one needs around 12 bits in the DAC to *accurately* retrieve the 8 bits off the disc. If you wanted to do processing in the digital domain without losing accuracy, you would need a 14-bit DAC with a linearity error (specified in LSBs) equal to that of the 12-bit DAC. I don't think that such a DAC exists. The new Analog Devices series has both 12-bit and 14-bit DACs, but I would assume that the 14-bit parts have a greater non-linearity (in terms of the LSB for each DAC). I don't know for sure, because these parts are so new that the full data sheets don't yet exist.
Also, keep in mind that the 12-bit parts are less than $20, while the 14-bit parts are around $100. This is an extraordinary amount of money to pay for this feature. Added to this is the fact that these type of adjustments belong in the display, not in the source device. Putting the adjustments in the source device means that every device will need its own duplicate set of adjustments, adding even further to the cost of the overall system.
The stability of the analog controls are really a non-issue in this application. For instance, you don't worry that the volume level of your stereo changes from one day to the next, even though it probably has an analog volume control.
And unfortunately, you cannot compensate for the non-linearities of the DACs. If the DAC always exhibited the same errors at all times, you could. However, these errors fluctuate with time, temperature, and other factors. This is not really a problem though. The errors I specified in my previous post are guaranteed over the full operating temperature range of the part, and we are still able to achieve 7.9+ bits of accuracy. There really wouldn't be much point to try and achieve 7.95+ bits of accuracy. This is like worrying about the difference between 0.002% and 0.001% distortion in an audio preamplifier.
Hope this helps,
Charles Hansen
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: Thanks, but... - Charles Hansen 08:11:30 05/03/02 (3)
- Accumulating noise - Homer 05:57:32 05/05/02 (2)
- Re: Accumulating noise - Charles Hansen 12:55:19 05/05/02 (1)
- Clearing up a few things... I hope - Homer 23:45:11 05/06/02 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
