LG52x (CDROM) as a transport - diyAudio
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Old 2nd March 2004, 07:21 AM   #1
peakrc is offline peakrc  Canada
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Join Date: Mar 2004
Location: TO
Default LG52x (CDROM) as a transport

I picked up this unit last year to use as a cheap transport. It is an IDE drive
with front panel controls (PLAY, STOP, SKIP). More Info below:

http://www.lgeus.com/Product/CD/gcr_8521b.asp

http://www.lgeus.com/pdf/gcr_8521b.pdf

The actual unit I have is the CRD-8522B


I used a power supply from an old PC that a neighbour threw out to provide 5V/12V and disabled the power supply fan.

Two little pins on the far left of the unit provide a digital output. I
clumsily rigged up a twisted CAT5 cable between the two pins (similar to PC speaker connector) and a old RCA chassis jack so that I could connect my co-axial cable to my external DAC. IT WORKED.

The only problems was that it did not sound the greatest. This could be partly
due to the large amount of vibration. It seemed to be spinning very fast
compared to what a personal walkman CD players run at...maybe 52x? The unit was manufactured in Nov 2001 and only cost me about $20. It is dead simple looking
inside (mechaniscally) and has oly one densely populated PC board with one or two big ICs on it:

A Sanyo LC895300 CD-ROM controller chip containing a built in one-bit DAC outputs and an SP/DIF output.

Bypassing the the 5V/12V incoming supplies with small 4.7uF has already bought some improvement to the sound that has become listenable.

PeAK
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Old 4th March 2004, 01:58 AM   #2
peakrc is offline peakrc  Canada
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Join Date: Mar 2004
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Attached is picture of the drive with the tray removed. Toward the back is the centrally mounted RCA jack with CAT5 cable wired directly to the output. The output level when not connected to the DAC is 5v peak to peak. When attach to a typical 75 ohm DAC termination, the level drops to 1/2 and puts out 2.5V.

The circuit board in mounted on the bottom of the unit toward the back third of CDROM unit.

I think "big" improvements could be made if the disc motor and the servo motors were locally bypassed near the motors. The big jump should be when the spin rate is knocked down to the 1x rate.

Although the castings are made out of plastic (no aluminum here), I can hear significant levels of detail using this unit over my DVD transport. It comes down to minimalist parts count and clean design of the interconnection of subsystems.

I do need someone familiar with firmware to help play with different playback speeds (1x, 2x, 4x and 8x) to hear what works best audibly. The built in RAM buffer may have something to do with the sound as well.

In the ATAPI specification, there is an opcode called "SET CD SPEED" (code BBh) which could be use to limit the playback speed.


PeAK
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Old 4th March 2004, 10:53 AM   #3
peakrc is offline peakrc  Canada
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Join Date: Mar 2004
Location: TO
Default Photo of innards

One more time with the picture....tray removed, magnetic puck/clamp off to left, and RCA jack centrally mounted:
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