|MadSci Network: Computer Science|
Hi, For either audiophile CD transports and CD rom drives the data error rate is very low, regardless of cost of the device. The main issue for audio transports is to get the data out at precisely timed intervals (=keep clock jitter low). Depending on the knowledge of the designer, two techniques are used to insure clock stability: 1. To reduce ripple on the power supply that powers the clock and transport, mechanically stabilise the rotation and minimise vibration such as to keep the servo's from operating jerkily and drawing heavily modulated DC currents from the power supply. This approach is cumbersome and only limited in effectiveness. It is also quite expensive because of the mechanical work. 2. To give the crystal oscillator and the output circuit their own power regulator so that there can be no interaction from the servos. Power regulators cost 10c each and are a much more effective way to reduce jitter. The second option works with any cd drive, including the ones used in CD- roms. I have modified my $50 S*N* player by adding a circuit board containing a clock and a correctly designed S/PDIF output circuit, each with their own regulator. The whole mod cost me $10 and the player is on a par with the most expensive cd transports. Wiser still would be to have the clock generated on the D/A board and feed it back into the CD player electronics. That places the clock where it's supposed to be: at the DAC. Regards, Bruno
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