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What's New
[1.1] Background to Transport Mod
Scene
[2] Transport Related Links
[2.1.2] Toshiba Mods
[2.1.3] Toshiba SD-3990
[2.2] Digital Output Buffer Mods
[2.3] Clock Mods
[2.4] Mechanical Mods
[2.5] Last Frontier: Transport Jitter
[2.6] RFI Reduction
[2.7] Miscellaneous Datapoints
^/\^ What's New in Transports ...
Jan 2, 2007
October 23, 2005
May 21, 2005
May 15, 2004
March 10, 2004
October 2, 2003
February 20, 2003
What if we put a transformer on the very most frontend portion of the read/playback system of a CD player/transport ? With its assortment of motors and control circuits to maintain constant angular velocity, lateral tracking servo and focus servos, it makes sense to isolate the power coming into the transport as best as possible. Two ideas on this front are by Jon Risch and Reference Audio Mods in the form of Jon's SQ&D; (Super Quick and Dirty) Isolation filter and Mod's DMF (Digital Mains filter). I would recommend these changes first before replacing clocks, supply capacitor blanks with black gates, and replacing regulators.
February 22, 2003
1 The Search for a "giant killer" Transport
What the Art DI/O community needs now is a good inexpensive transport with a co-axial output that will complement the the DI/O. As early as 1993, Robert Hartley has reported that the sound of CD players is heavily influenced by distribution of jitter in frequency or the jitter transfer function. Many well heeled audiophiles who have jumped to the DI/O DAC from the more expensive kilo-buck breathen, based upon sound quality alone, have the transport problem solved partly by using a kilo-buck transport already in their possession. Some good names mentioned in various audio forums are:
Chuo Denki Company, better known as C.E.C. was a company that put out some fine belt-driven turntables. They use this expertise to come late into the CD playback scene but recoginzed the major failings in the architecture of servo controlled CD playback outlined in their patent.
What you see in CEC products such as the TL 0 transport offered by C.E.C are paralleled in the re-newed turntable industry today:
One question is what exactly do these well regarded
units have in common?
(Update Jan/2007):
When I began writing these pages (4 years, earlier), it was
generally agreed that the DAC was the prime determinining factor in
digital playback. It is now agreed better results could be
had,
inexpensively, if the internal DAC is of sufficient quality and that
the SP/DIF inteface not be used due to the possible introduction of
additional jitter and the SP/DIF receiver. I would say that
Toshiba have a couple of engineers that really know what and how to
listen to their products. Similar to how Marantz has operated
but
without the traditional and well-earned markup. How they manage to
incorporate these core values at entry level prices that keep
sprialling downward is a minor miracle.
1.1 Background to Transport Mod
Scene
Doug Blackburn, formerly of Soundstage, wrote an article on modifying a
Pioneer
DV-525. In it he theorized that supply regulation, vibration,
RFI, and internal reflections had a lot to due with the sound of a
transport. On the commercial front, Modwright will update the a
transport with a standard set of mods
for succeeding generations of DVD players (DV-414, DV-525, DV-333,
DV343 ) used as CD transports. The mods offered cover the following:
Products Pioneer Transport Mods for Use With an External DAC This mod
optimizes the unit for use as a transport, but in no way disables the
video function of the player or its ability to play music as a
standalone player. Below is a list of mods offered by Modwright.
Level I Transport Mods:
Level II Transport Mods (Including the above mods and the
following):
One unit worth mentioning is the JVC XL-Z232 CD player which earned a garnering of the title "giant killer". in a TNT review from September 2000. The player offered a compelling overall high end sound due to a decent transport, DAC and a decent output filter. The latter two are not needed by DI/O types. What is needed is a co-axial output which this unit unfortunately does not have. For the owners of a DI/O, the basic requirements are:
The CD player is still on sale today in the JVC catalogue
despite the fact that combined CD/DVD/MP3/CR-RW/DTS compatible DVD
decks will probably soon obsolete it based upon the limited real estate
found on stereo component racks. ...hands up those of you who have a
dedicated CD player alongside your DVD player.
2
Transport Related Links
The links below are a first attempt at organizing information that will
form the basis for eventual "giant_killer" transport derived from some
existing player. Keep your suggestions coming in.
2.1
The Short Transport List
I for one am truly dissapointed in the agenda of reviewers and
manufacturers in promoting the next format as the answer to our prayers
of good sound reprodcution from digial sources at the turn of the
millenium. I can only put down here what I perceive as good "vibe"
reproducing machines and hope that competing manufacturers listen to
these units to see what half-way decent sound is like.
The unit has been recommended by user Rosconey on AA. Two users with decent DACs in the form of Vinnie R. and John Swenson picked up on it and added significant fuel to the "3950" fire. This initial buzz increased to a frenzy on Audio Asylum as some claimed that this $60 clearenace item was causing people to consider replacing their CEC belt drive transports, Theta Basic II transport(s), and Cal Ikon transports.
I picked up my unit from Walmart for about $100 in
"black". I have been experimenting with some 8x CD- ROM drives, NEC 6x
CD-ROMS in an effort to unlock more of the sound of my new Ack! dAck
DAC (just had a dAck attack). The skinny from me would be use this unit
unmodified as a transport.
It
also has progressive scan (TV), supports Kodak Picture format (2000
JPEG images on a CD-ROM), and has a great image with an extended black
range to mine detail in the shadows. It has ended my 3 year search for
a decent low cost transport.
The
internal DAC was given a quick listen after a day of
burn-in...not too shabby. More on this later.
Before I put down how it performed in my system, here is some more
reading for those with an itch to know a bit about this player.
Some claim different. different settings are preferred for using the internal DAC versus the external DAC.
I guess with my purchase of my Toshiba 3950, I come to an obligatory review of its sound in my system. I tried it with two sets of speakers (Linaem LX-5 and Axiom M22-ti) and two sets of speaker cabling. The improvements were on the order of the opamp change but maybe more stunning in their refinement. The vocal midrange became lush with tone and warmth. I heard deep tuneful bass and my liliputtin LX-5 (5" woofer in a cubic foot box) seemingly going full range and the Linaeum tweeter working new magic on me. Bottom line, it has somehow created more music in my little room with my system that I have ever had.
Update: I came across two sites that have a slight variation on the above internal mode. One site likes the removal of a 5.2K series resistor between the DAC output and the large coupling cap. This resistor apprently causes a loss of output but I do not see any isses as I measured a healthy 1.8V peak (1.3V RMS output). There is also discussion about removal of a a small yellow shunting the RCA jack to ground near the RCA jacks. These caps made be responsible for the lack of staircase artifacts that I saw on 2 KHz and 20 KHz sine waves. The other post (actually two) seems to be the original source of these ideas and is authored by John Day. One futher note on C903/C905. If you try this and the above procedure, PM me.
2.1.3 Toshiba SD-3990
Below are a bunch of links for you to peruse:
Mechanicals and Reliability: The case is metal with the tray off to the left (versus in the center on the 3950). The old remote works with the new unit but there are some quirks. You can index the beyond the 9th cut but in a different manner from the earlier units: The 10+ button is no longer needed to access cut 11. Now you just press "1", twice, and the the PLAY button. When a song is paused within the first 5 seconds of the start of a track, pressing "PREVIOUS" will skip to the previous track. If you press pause after the first 5 seconds, PREVIOUS will take you back to the start of the track. The numeric display cannot show you elapsed time as on the 3950 and now comes in green.
The DVD drive making up the transport is no longer suspended from "rubber grommets" as was the 3950 drive. This may explain some of the changes in sound as the case was deadened with rope caulking report by some users.
It is early, but weakest link of this amp may well be the op-amps used. Lasts, unit to unit variation is possible as I found in 2004 with the SD-3950. The purchased unit sounded quite different from the one my friend purchased and they were built in the same month.
Reliability is
often a sore point with Toshiba DVD players. This might be a result of
getting what you pay for in terms of design, assembly, and warranty.
The unit may be suspectable to damage from static electricity either
due to weakness in the chips or initial damage incurred during assembly.
This weakening/damage can lead to something called "infant mortality"
where the unit cannot withstand the rigors of everyday usage and fails
early on in its life...given the chance. The best safeguard against
this is to just screen it out is by leaving the unit powered on
long enough to evaluate the weakness. If it passes this period, you can
be assured years of reliable service.
The SD-3990 no longer powers down
by itself after 10 minutes of non-usage with CDs. This was a major issue
before as you really need something like a week's worth of continuous
powering to screen these faulty units. Do not actually play
a CD at
this time but just load it into the tray. Mechanical wear
is another issue that you'll be trading off against should you decide
you also like to spin the CD during this break-in period. . Note: With
DVDs in the tray, the unit will power down after 10 minutes. When
viewing that are short in portrait/vertical orientation, the 3990
correctly displays the thumbnails which the 3050 did not. Lost however
is the ability to remember changes to the orientation which the 3950
had as a hidden feature, so that you could sort out the orientation of
individual JPEGS (ahead ot time) and then run a slideshow, seamlessly.
Below are some
"buyer posts" outlining their experience with the 3990.
Circuit Details: I've put a modifed JPEG image from KH's 3990 page tracing out the schematic of the SD-3990 output stage. Related posts are here:
MODS: Unlike the 3950/3960 generation, the output from the Toshiba is differential and not single ended. This means that a Swenson type passive mode is not possible...unless you happen to have Balanced inputs on your pre-amp, in which case you may implement a balanced version of the Swenson mod.
2.2 Digital Output Buffer Mods
2.3 Clock Mods
These devices have been purported to improve anything from speakers to turntables. The following has been key to keeping my DVD player from becoming a paperweight. More info here.
2.4.1 DIY Roller Block Notes
These are constructional notes from having put together a number of
these roller blocks. Give yourself about 10 minutes to put together one
of these when you get good at it. Accident prone types might give
themselves about 30 minutes for the first effort. My first few resulted
in vertical slits forming from too much uneven pressure during assembly
of the two halves making up the support. Putting a inward curve using a
spoon (Step 7, below) solved the problem. It may take you 3 tries (like
me) before you get the first one right. Good Luck
The cans are getting progressively thinner these days. Some aluminum cans (older) are made from heavier stock and are preferred. Despite this fact, pushing the two halves of the can together will result in a very strong structure that does not ring.
|
Step 1: Take two empty pop cans |
Step 2: Mark a series of dots 1 inch above the bottom of the can using a ruler. |
|
Step 3: Use masking tape to define a cut line over the 1 inch marks. |
Step 4: Cut the can in 1/2 starting from the top opeining |
|
Step 5: Cut a 45 degree line that just touches the masking tape and then use your shears to trim along the masking tape edge |
Step 6: Completed bottom section |
|
Step 7: Use a spoon to curve the edges toward the middle of the can so that the top section can slide over. The edges are curved by adding thumb pressure on the can edge against the inside of the spoon. Rotate can about 10 degrees and repeat until entire edge is curved slightly inward. |
Step 8: Repeat steps 2 to 6 (skip step 7) to form the top. Skipping step 7 should result in the diameter being slightly larger than the bottom so that you can slide the top over the bottom. After fitting top over bottom, slowly push the two halfs together. The top edge should come close to the rounder portion of the bottom (about an 1/8 of an inch). |
You can try different size bearings and materials to get the best sound. I have used plastic balls and mouse balls in different combinations with the metal ball bearings to get the CDP sounding just right.
[2.5] Last Frontier: Transport Jitter
Increasingly, reports about "ripping" CDs to
computers and then using the digital stream (USB, Firewire, I2C) to
non-SP/DIF converters being better than 5 figure d cost no object
conversters have surfaced. The mightly Mark Levinson reference DAC
essentially not being necessarily providing you get rid of the SP/DIF
interface. Why is this so ?
[2.5.1] Background: 1st Generation Redbook
Problems
In the decade preceding the release of the first CD players (1982),the
Personal Computer had captured the imagaination of the public and of
large companies such as IBM which released it's first version at about
the same time. Encoding 16 bits of information for two stereo channels
at 44.1 kHz meant that a bit stream of 2 million bits a second: A
farily high bandwidth of data for the time. This prevented the
possiblity of having the transport detect errors being read and
resending correct data but required data to be corrected on the fly by
an algorithim pioneered by Reed-Solomon.
[2.5.2] USB/Hardrives: Lower Jitter via "Hurry up
and Wait"
[2.5.3] Why DVD make for better transports
[2.5.3.1] 8x Oversampling and Transports slaved to
FIFOs
[2.5.3.2] Low frequency jitter and Big screens =
Better Audio
[2.5.3.3] "Bit Accurate" datastreams
2.6 RFI Reduction
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1. Clark Johnsen (6/03) |
2. DHMC (6/03) |
3. Geoff (9/03) |
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4. JeffereyK on PAUSE / (9/03)JeffereyK on SKIP (6/03) |
5. Jerome (10/02) |
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7. Leisure7 (6/03) |
8. LWR (9/03) |
9. methos (4/03) |
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10.Slosh ;-| (10/02) |
11.Simon@TnT on "Repeat 1" (9/03) |
12.Subhuman (6/03) |
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13.Todd on SKIP (6/03) / Todd on PAUSE (9/03) |
14.ToddB (10/03) |
15.Byteme (6/03) |
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John Crosset (1/03) |
Tomcat (7/03) |
Fiddler (9/03) |
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Jurgen@TNT (10/03) |
Debopriyo@TNT (10/03) |
Hans-Martin@TNT (10/03) |
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RCprince (10/02) |
Sol322 (10/02) |
KRAM (11/03) |
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Allen Wright )(2/04 |
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Prad (11/04) |
Ken B (12/06) |
