Become a Site Supporter and Never see Ads again!

Author Topic: Tweaks for the toshiba sd4950 player(DIY content)  (Read 10897 times)

0 Members and 1 Guest are viewing this topic.


  • Guest
  • Trade Count: (0)
Tweaks for the toshiba sd4950 player(DIY content)
« on: July 03, 2005, 12:25:48 PM »

Tweaks for Geeks

By Robert McNeice

Buffed up with US $100 in replacement parts, a $150 disc player can challenge players that cost ten times as much. But forget about your warranty...

When those of us who are into "gadget porn" look at the latest state-of-the-art home entertainment gear, and then check its prices against our dwindling bank accounts, we can't help but feel embittered. Our technolust is bust.

But we want that US $1500 DVD player; we crave the best audio and video that money can buy. Lucky for us, much of the good stuff in the top end components has trickled down into very affordable equipment. Digital processing chips, which are the brains of audio and video players, are relatively inexpensive and universally available. But if a DVD player is selling for $150, the manufacturer's costs were probably not much more than $30, and that cost includes labor. So manufacturers skimp wherever they can: on the cases, the capacitors and resistors, and connectors—common components that they can purchase for pennies.

Free of their mass-marketing imperatives, you can spend dollars, rather than pennies—and hear and see the difference. That's the basic strategy of a thriving if somewhat esoteric group of hobbyists who take such affordable electronic equipment and modify, or tweak, it to perform at levels that reach far beyond its meager beginnings. These upgrades replace cheap components with better-quality and lower-tolerance parts, and the results are often startling. Take a $150 DVD player. Add less than $100 in boutique parts, perform a bit of simple soldering, and the resulting sound and video can compete with that from DVD players costing hundreds of dollars more in retail stores.

Some have made a business out of such upgrades—charging three to five times the cost of the added parts for labor, knowledge, and experience. But if you can read a schematic, are willing to tinker a bit, have basic soldering skills, and are willing to spend about $250 altogether, you can cut out the middleman and get a disk player that will be the envy of all your gadget-lusting friends.


THE TOSHIBA SD4960, also sold as the Samsung DVD-HD841, is the inexpensive universal disk player I chose to modify. It has received good, if not spectacular, reviews in video and audio magazines and e-zines. It uses the same digital processing chips found in considerably more expensive players and its laser mechanism is well regarded, though packaged in a flimsy plastic support. Best of all, it will handle almost all disk formats: DVD Video, DVD-R, DVD-RW, CD-R, CD-RW, SACD (Super Audio CD), DVD-A (DVD Audio), MP3, and digital picture CDs with JPEG. Toshiba licenses the design from Samsung, but most of the parts in the two models are identical. To my eye, the Samsung unit is more pleasing; it also has an HDMI video output connection that the Toshiba lacks. The Toshiba's street price is about $100, while the Samsung sells for about $120 (but prices may be even lower by the time you read this).

The first time I listened to a CD on the unmodified Toshiba player I noticed some distortion affecting the high-pitched sounds like cymbals, bells, and harmonica. Also, there was not a lot of life to the sound. It was a little congested; complex passages in the music were not entirely clear to the ear. Tonally, however, the Toshiba player does well, making instruments sound like instruments, not plastic facsimiles.

The player's video capabilities were similarly solid. Images were free from obvious grain. Colors seemed correct and contrasts were distinct and without shadows, but in the video as well as the audio, there was room for improvement.

To perform an upgrade, you'll need a few things. One of them is the service (not owner's) manual from the manufacturer, which contains the schematic. You can get a copy for $22 plus $7.95 shipping and handling from J&J International at +1 800 627 4368; ask for the Samsung DVD-HD841 service manual. Another thing you'll need is a 25- or 30-watt soldering iron and some rosin core solder.

If it's been a while since you had a soldering iron in your hand, spend a little while practicing the art of making a good, swift solder connection. To avoid damaging delicate microelectronics, touch the tip of the hot soldering iron for a second or two to one of the leads that connects the component to the board, then touch the tip of the solder to the now-heated connection point. The solder should flow freely to the component lead and the board connection. Pull the solder away from the joint, then the iron, leaving a shiny, rounded connection. Before you start, tin the iron's tip and keep it shiny and clean—wipe it with a damp sponge between tasks.

The instructions below are written for the Toshiba and Samsung players, but you can apply them to just about any of the vast array of universal disk players priced under $200. If you're willing to spend a little more, the Marantz CD5400, with a street price of about $300, is a good choice. Just be sure to plan your upgrade carefully before ordering parts.


THE THREE PLACES where tweaks to an inexpensive player can make the most difference are the power supply, the power supply, and the power supply. Okay, that may be a slight overstatement, but it's a fact that the power in your home is often corrupted by air conditioners, dimmer switches, halogen lights, and other noisy appliances—yours and your neighbors'. Cleaning up and filtering out this noise on the line will help any player perform better.

Essentially all low-cost DVD players these days use a switching power supply. It converts the line's ac voltage to dc, at, for instance, the 3.3, 5, and 12 volts needed by chips, motors, and other internal components. Switching power supplies use switching transistors and other devices to, in effect, chop the 50- or 60-hertz line frequency into an ac signal at tens or hundreds of kilohertz. The advantage of this higher frequency signal is that it can be filtered, and its voltage changed, with small and light capacitors and transformers. The high-frequency transformer also easily provides multiple output voltages and isolates the dc from the input voltage.

The supply consists of a power-input receptacle, a bridge rectifier to convert ac to dc, capacitors for smoothing the resulting pulsed dc waveform and for storing the energy needed by the other sections, MOSFET transistors to chop up the dc into the high-frequency ac, and the high-frequency transformer with multiple secondaries to produce the various desired voltages. For each secondary coil, there are rectifiers and filter capacitors to yield the desired dc output. Besides being smaller and lighter, switching power supplies are typically more efficient than other types. The tradeoff is that they tend to generate more high-frequency noise on the power line. Sufficient filtering becomes important—especially in audio circuits.

Before you begin, a few words of caution. You will be playing with a system that runs on real ac current, so make sure the unit is unplugged while you are working on it. If you are new to the world of building and troubleshooting electronics, read this excellent guide before proceeding: Be careful and patient. Oh, yeah, this will definitely void your warranty, too.

To open the Toshiba SD4960, remove the three screws on the back panel; then slide off the lid. Snap off the front panel, being careful not to break the fragile plastic clips that hold it in place. Unplug the ribbon cables where they attach to the main printed-circuit board and unplug the wire running from the electrical cord to the board. Unscrew the board, and lift it gently out of the case.

On the board (See photo, "Inside the Toshiba SD4960"), you will notice lots of insectlike components, their bent leads splayed like little legs on the surface of the board. You will be leaving these surface-mount parts alone. They are too small to fuss with, and their would-be replacement parts too big to fit in their place. Also, they have been machine-soldered to the top of the board and would be hard for you to remove and replace without damaging other circuitry.

Starting with the power supply section (indicated in yellow), first identify all of its capacitors and their values. You should replace all of these capacitors with higher-quality capacitors with the same voltage value but about 20 percent more capacitance. (See table, "Replacement Parts Selection.") There are various measures of a capacitor's quality; one is ESR, or Equivalent Series Resistance. A low ESR means low resistive losses inside the device, and therefore better ability to deliver power to the sort of fast-changing loads presented by the clock and other high-frequency digital circuitry. There will also be one relatively large capacitor just after the rectifier or diode bridge (indicated in pink); you can double the capacitance value of this one, from 82 microfarads (µF) to about 180 µF, or whatever you can fit in the available space.

Basically, by using better-quality parts, like Sanyo Oscon, Panasonic FC, or Nichicon UHE or FG/KZ capacitors, and increasing their values, you will improve the power delivery to the other circuits. That in turn will increase the dynamic range and enhance the all-important bass performance. Besides low ESR, such high-end capacitors have tighter tolerances and use better materials (the Nichicon leads, for example, are copper, not steel).

The one constraint you'll face in replacing capacitors is the space on the board—capacitors with larger values are bigger, so make sure you have enough real estate for them. And don't forget to note the polarity of the capacitors you are removing so you know which way to solder in the new ones. Polarity is usually indicated on the board, but go slow and be cautious.

To take your upgrade a step further, replace the diode rectifier bridge with "soft" recovery FREDs (fast recovery epitaxial diodes) or Schottky diodes. These fast-action diodes have what is known as soft recovery. What that means is that when the voltage across them changes polarity, causing them to go from forward- to reverse-biased, the plot of current versus time slopes smoothly back toward zero current, rather than overshooting the zero axis and wobbling briefly around it, or "ringing." Basically, the lack of ringing means less noise.

Buy replacement diodes with higher amperage ratings than the original ones. The original diodes are designed to tolerate high-peak surge currents, which occur when the power-supply capacitors are charging (and don't forget, you added more capacitance!). Chances are, your replacement diodes aren't designed for high current surges; in my case, replacing the specced 1-ampere 600-volt diodes with the same value FREDs smoked them. So I used 4-A 600-V diodes and they worked fine.

You may have to be a bit creative with the installation of these replacements, because diodes with this increased rating are usually only available in a TO-220 type package instead of the original DO-41 package. Note that the TO-220 package has a metal tab at the top; this tab is generally connected to the cathode and should therefore be insulated with heat-shrink tubing to avoid any shock hazard.

Again, be very, very careful of the orientation of these diodes. By putting a faster, soft-recovery rectifier in the power supply, you will allow the power supply to respond more rapidly to the demands of the downstream circuitry with less switching noise.

Taking the modification yet further, you can also replace both of the X-rated capacitors (indicated in orange)around the transformer with 0.47 µF 600-V Auricaps. These will set you back about $13 apiece. X-rated capacitors are standard components that meet Underwriters Laboratories Inc. (UL) standards for use on ac mains lines. These capacitors are designed to be self-extinguishing in the event of a big surge on the power line. They're potted in fire-retardant compositions, and are designed to fail open, rather than closed, so components up- and downstream will be protected. Auricap capacitors, a brand of high-end capacitor favored by audiophiles, are not rated against UL standards for ac current.

While this tweak is widely used in audio modification circles and no problems have ever been reported on the audio tweak Web sites (as far as I know), it could potentially lead to damage in other parts of the system, so you might say it's risky. But, to my ears anyway, it does noticeably improve audio quality. If you're squeamish about replacing the X-rated capacitors, you might try a compromise, such as replacing the stock X-rated capacitors with a good-quality safety-rated polypropylene capacitor, such as the MKP series from Illinois Capacitor (part number 474MKP275K).


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 (see ) 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

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.


THE OFF-THE-SHELF Toshiba SD4960 I modified had good tonality, which remained after modification. The tone had been slightly light. Modification increased the body of the tone—for example, a guitar sound that previously was all string now includes the wood of the instrument. The stock unit had a bit of congestion on dynamic passages, especially evident on massed strings. Not anymore; the top and bottom ends are detailed, extended, and inviting. The soundstage, that is, the virtual placements of the instruments that you hear in front of you, was originally very good—definitely not an in-your-face kind of sound that you would normally expect from a cheap player. Nevertheless, modification added an ease and presence to the sound; a liquidity that was not there before. This is the kind of sound that makes you smile, sit back, and really enjoy what you're hearing. You'll notice that the video presentation has improved also. The colors seem more vibrant and more sharply defined than before, and the contrasts are better, especially against black backgrounds.

In all likelihood, you'll agree that the project was well worth the effort. Maybe it was even a learning experience. There are certainly lots of other things that you could do to go even further. But, for now, there are probably a few discs you'll be falling in love with all over again.



RSS | Mobile
Page created in 0.037 seconds with 25 queries.
© 2002-2024
Powered by SMF