Time to mod: 15-20 mins.
Whilst I totally agree with the Monster's comments above, the clock is a potentially simple fix to improve the DVD performance with little effort and reasonable cost.
The LG player I have is an excellent unit, using one of the C-Cube Ziva decoder chips, and uses a 27MHz clock. The intention was to mod it without taking the whole thing apart as the main motherboard runs the full length of the unit and needs a total dismantle in order to makes changes to the PSU side of things.
As is common in most commercial players they all use switching supplies, followed by some linear regulation. The LG uses a large number of 4-terminal Fairchild reg's, the fourth terminal being a logic-level input to disable the main regulator output in standby mode.
These reg's have pretty poor specs, and will no doubt benefit from some improvements (in particular line rejection is some 30dB worse than even an LM3x7). To implement super regs will require extensive modification since many of the reg's run close to dropout so there's not enough 'head' for this technology at present. Since I have no desire to add external boxes for PSU's a more elegant solution will proabably be to use some low-dropout adjustables, later on.
Anyway the existing clock is a classic Pierce oscillator design, built with a seperate buffer chip, that then feeds the decoder.
There's loads of room inside and the existing crystal and its support components were removed in a few seconds, and the clock was able to be located right next to where the crystal was removed from. This allowed very short output wiring from the clock to the main decoder board (literally a few mm).
A quick scan of the board found a 12V regulator I could tap to provide power to the clock board. With the SMPS technology involved there is likely to be some residual switching noise on the raw supplies, so tapping a regulated supply will help reduce this and reduce noise induced jitter in the clock. The on-board regs will further attenuate this. The power feed runs the full length of the DVD player, so some additional decoupling in the form of a 120u Oscon was added at the clock PSU input, the long feed acting as an inductor to make the input filter, in effect an LC filter circuit. This will further help attenuate any high frequency noise and ensure the 12V reg doesn't 'see' the Oscon and suffer as a result.
In order to determine the correct input for the clock I connected a 1K resistor from the clock output to one of the vacated crystal holes - this limits the current so that if I feed the clock into the output of the buffer chip it won't do any damage. The SMD technology used in the LG is tiny, and component ID's hard to read in order to work out the correct connection from first principles.
Upon powering up I was greeted by a distorted picture indicating that my luck on the 50:50 chance of getting the right input had run out today - obviously I was trying to feed the clock to the output of the buffer chip.
A quick swap to feed the clock into the other input and all was well, so the 1K resistor was removed.
Was it worth it?
Well, yes, athough I must admit the sonic benefits seem much greater than the visual ones. There is more detail within a good DVD (a totally digital production like Monsters Inc. is a good example of this) and there is more tonal detail in some elements. I'm not sure if it's just a question of limited TV performance, whether we are less sensitive to subtle visual improvements compared to sonic ones, or some other factor, but I wouldn't have said it was an astonishing improvement, although it is better. Maybe the difference will become more apparent with time?
The sound though is dramatically better, the DVD player wasn't a patch on the CD5, to the point where I couldn't listen to a CD for any period of time. Post modification the sound is better across the board, to the point where it's very enjoyable. The bass is tighter and better controlled and treble is so much more detailed and less splashy.
Music DVD's sound much more engaging too, the copy of Muse 'Hullabaloo' I have on loan is much better, bass lines that where previously a little muddied by the live acoustic are easier to follow, drums are more dynamic and subtle cymbal work becomes more apparent within the acoustic of a live gig.
It falls down still, on CD's, in terms of low-level resolution, the CD5 digs way more detail from the CD, with subtle changes in the acoustic surrouning a recording being laid startlingly bare. The DVD by comparison misses this totally, but get's the heart of the rythmic elements right, allowing one to tap and sing along easily.
Worth £60 in my opinion and it's made me VERY interested in looking at more music DVD's as the audio/visual combination can prove very engaging, in a way I'd not thought possible, previously.
Andy.
