In the digital - and video-processing sections (indicated in red), there are lots of surface-mount components. Leave them alone, along with the various chips that are soldered to the board. The capacitors, however, are all fair game. You can again use the Sanyo Oscon, Panasonic FCs, or Nichikon UHE or FG/KZ series. The Sanyo Oscon capacitors are harder to find, but you can buy them from Capacitors Plus Inc., +1 800 422 7758. The Panasonic parts listed in the sidebar [see table, "Replacement Parts Selection"] for both the power supply and digital circuits should run about $25 for the whole set, and equivalent Nichicons about $5 to $10 more. Replace capacitors with those of the same values and watch your polarity. The capacitor values can be critical here and should not be changed as we did in the power supply. This swap will improve the power delivery to the ICs.
Next, you will protect the player's oscillating clock crystal from outside vibrations. This clock provides the timing reference for the various circuits, such as the digital-to-analog converter chip. Basically, the output of the clock is a square wave. Ideally, the "on" and "off" portions of the square wave are all of identical length. In reality, there is some variation, which is known as timing error, or jitter. Jitter introduces small but audible errors in the analog output. It comes from several sources, such as mechanical vibration of the crystal, and also from spurious voltage variations in the power supply and elsewhere on the circuit board.
It's easy to reduce the jitter that comes from mechanical vibration. Press a small piece of heat-resistant rope caulking, like Mortite, firmly over the chip and to the board on both sides (see photo, " Tick-Tock"). To go further than this in reducing jitter would mean a rather more significant outlay of funds. Several companies sell sophisticated clock circuits meant to replace the stock clocks in disc players. Two examples are the Superclock3 from Audiocom International Ltd., Pembroke Dock, Wales, and the LClock XO3 from LC Audio Technology in Holstebro, Denmark. These replacement clocks cost between $200 and $300 and will require more technical knowledge to implement than I can give you here. They can, however, very dramatically improve the performance of a digital player.
For more information, see http://www.audiocom-uk.com/store/product.asp?P_ID=129and http://www.lcaudio.com/index.php?page=4.
In the analog-signal processing section of the board, the analog output sound signal from the digital-analog converter chip is filtered and amplified before it goes out through the RCA jacks to your amplifier. This is a very critical area that distinguishes different player designs; often the hardware designer will have included circuits in this section that alter the signal as it passes through. My view is that the audio signal should get to the output jacks in as pure a form as possible. There are a few options here.
One is to replace the op-amps and surrounding capacitors. Whether you will actually be able to do this may depend on factors beyond your control. If the op-amp chips are surface-mounted directly to the board, and if you don't have a lot of soldering experience, you may want to skip to the second option.
The op-amps in inexpensive players cost pennies and sound like it. Many different op-amps are available over quite a range in price; different choices will create different flavors of sound. Like so many other things, it all comes down to taste and budget. However, you will need quite a bit of knowledge before you attempt to substitute op-amps. There are many different types, and you need to understand the circuit to make the right choice. Do you need a dual or quad op-amp? Does the D/A chip have a current or voltage output? What are the impedance or filtering characteristics that are required? There is also the price to consider. Many audio tweakers consider the Burr Brown OPA627 to be the best of its type; however, they can cost $20 each and may not get you substantial improvements over midrange op-amps. Counterintuitive though it may seem, in the world of audio, components that have the most impressive specs don't necessarily result in the highest quality sound. This is where the art comes in, and this is where professional modification installers earn their money. I simplified this complexity in my player by bypassing the op-amps completely and using a set of coupling capacitors. More on this later.
As far as you are concerned, this is a good time to decide whether you want 5-channel surround sound or are content with 2-channel stereo (CDs play in stereo only; SACD and DVD-A are either 2-channel or 5-channel). If you want the full 5.1 sound experience ("point one" is the subwoofer), you'll need to address all 6 channels. With stereo, you'll need to address only two.
Replace the op-amps on the board with your op-amps of choice, or experiment with different op-amps, or leave the stock ones alone (recommended if you don't know what is required) and improve the surrounding components. The small capacitors surrounding the op-amps are critical to the resulting sound and should be replaced with higher-quality ones--of the same capacitance--like the Black Gate NX series capacitors. These small Black Gates may cost as much as $2 each, but they are considered to be the best you can buy for this application.
"Less is more" is the philosophy of a second method to tweak the analog signal processing of your DVD player. Here, you'll take the signal directly from the digital-analog converter (DAC chip, pass it through coupling capacitors, and route it directly to the RCA outputs, resulting in a smoother musical sound that is a little less punchy than what you can get with upgraded op-amps. This option works only for disk players that, like the Toshiba SD4960, have voltage-output DAC chips. It will not work for players that have current-output DAC chips. To find out which type your player has, look at the chip or the schematic to find out which specific DAC chip is installed, and then consult the manufacturer's data sheet for that chip. If you're going with this option, first identify the first set of capacitors from the DAC outputs (see photo, " Totally Tweaked"). All modern DVD players will have a separate set of outputs for 2-channel vs. 5.1-channel surround sound; choose the set appropriate for your sound system. Remove these capacitors and attach a 30-gauge wire to the DAC chip side, labeling each wire for the correct channel and output jack--left, right, front, and back. Leave the subwoofer channel going through the existing op-amps to give that a punchier sound.
Connect the end of each wire to a separate 1.0 µF, high-quality bipolar polypropylene capacitor. Some popular choices of these low-loss high-voltage capacitors are Auricap, Solen, Hovland, and Sonicaps. These can cost from $10 to $50 per pair. Each brand affects the sound in slightly different ways--again, this is where the art comes in. (I used Sonicaps.) Connect the other end of the capacitor to the positive terminal of the RCA output jack. Connect the negative side of each RCA jack to a common grounding point on the board (I soldered the wire to the original RCA's negative connection point).
Put a 300-picofarad silver-mica capacitor across each RCA jack, attaching it from the positive terminal to the negative terminal (i.e. ground). This will help filter any radio-frequency and switching noise that your player may output. Ultimately, the sound is clearer without these, but in some cases they may be critical; it is always a good idea to shunt all possible RF noise to ground to avoid damage to your amplifier or speakers.
There is one more option, a really expensive one. LC Audio Technology makes a circuit it calls the Zapfilter Mk2 that goes in place of the op-amps. It is a high-end solution and a price tag to match: a cool $270 for 2 channels. LC Audio offers a package deal with its LClock unit, at $540.79. Of course, this sum is more than twice what the Toshiba player and all the other parts will cost you all together. But, hey, if you're feeling flush, have lots of confidence in your soldering skills, and really want to go all out, this is a great way to do it.
Regardless of which way you go, replacing the stock nickel RCA jacks with better-quality ones is considered standard operating procedure. Nickel is a ferrous metal and should be avoided in the signal path. Get gold-plated jacks if you must, but make sure they don't have any nickel under the gold (most of them do). Better choices are available from Cardas Audio and Kimber Kable; you can't go wrong with any of the jacks that use silver and rhodium over copper. Whatever you use, be sure to test them after you've installed them to make sure they haven't become grounded to the chassis.
The last thing you'll tinker with is the case and the transport--the mechanical device that spins the disk. Here, vibration is your enemy. Use more of the rope caulk you used to dampen the clock crystal and apply it liberally to the exposed areas of the transport, including the underside of the drawer. Make sure all moving parts still have plenty of clearance. Spread more rope caulk on the case sides, under the main circuit board and on the inside of the top cover. For these latter regions, you can cut peel-and-stick floor tiles to fit under the board and on the inside of the case cover. Again, be sure of your clearance. If you used polypropylene capacitors for the output, use more rope or silicon caulk to fasten them tightly to the case.
Clean your solder connections with alcohol and a Q-tip to remove any remaining flux, carefully screw the board back into the case, reconnect the ribbon cables and power cord, snap the front piece back on and replace and screw the cover back on top. Plug it in and turn it on. No sparks or smoke? Terrific! Put a disk in and test it to make sure everything is in working order. Then spin a disk on auto-repeat for a day or two to "burn-in" the unit; the sound will surely improve during burn-in.