By Ralph Calabria
(If you would like to have your DIY project
published in Secrets, please E-Mail Ralph Calabria at [email protected].)
Table of Contents (you can click on the list to go to specific
item)
Introduction
What does the upgrade do?
The "Mod Squad"
The surgery (as performed
on a Pioneer CLD-D703)
Construction tips
Testing your work
How did it sound?
Acknowledgments
Introduction
Wait! Don't throw out or replace your old laserdisc player just
because it doesn't have an RF out for AC-3! There is an alternative.
You can upgrade your old laserdisc player so it can extract the
Dolby Digital signal from the right analog track.
O.K., I know some of you are saying, "But DVD is here, and
laserdiscs are a thing of the past, and I don't want to spend
any more money on it because the laserdisc format won't be supported
in the future......... yada, yada, yada." While I certainly
can't argue with some of those points, the fact of the matter
is laserdisc is going to be in your face for a while, and if you're
like a lot of the laserdisc collectors out there, you probably
aren't going to be tossing out your laserdisc player or LD collection
anytime soon. It will take some time for DVD to catch up with
the 10,000+ titles already available on laserdisc. Chances are
you already own several Dolby Digital encoded laserdiscs (well,
maybe one anyway). Like most of us who've owned a massive collection
of vinyl recordings, it's not likely you'll go out and buy the
DVD version of a movie you already have on laserdisc (at least
not right away). Interested in turning that scratchy, irritating
sound coming out of your right analog track from an AC-3 LD into
something bigger, better, and more dynamic than you've ever heard
before at home? Read on.
What does the
upgrade do?
Suffice it to say that DD completely replaces the right analog
track on the laserdisc. If you try to play a DD encoded laserdisc
in analog, you will hear a fuzzy distorted sound coming from your
right channel. This in normal. In order to extract the DD signal
from the laserdisc, the signal must be extracted before it sees
the audio processing (DAC) stages. In general terms, that's what
this upgrade accomplishes.
NOTE: Keep in mind, performing this upgrade will most likely void
the manufacturer's warranty. Since most older players without
the RF out are two years old or older, the warranty is probably
expired anyway. So, keep reading!
The "Mod Squad"
The modification board was supplied by Charles Triola and Les
Lavin from Houston, Texas (see Acknowledgments). They were responsible
for acquiring the high quality parts that went into the mod board,
as well as getting the board fabricated.
The modification is a generic board that works with just about
every laserdisc player that can play both the digital and analog
tracks of a laserdisc. The kit came with the fabricated mod board,
miscellaneous parts to help with the installation, and complete
custom instructions for installing the board in YOUR player.
The surgery
(as performed on a Pioneer CLD-D703)
When I first got the kit in the mail, I read over the instructions
about 3 or 4 times, stared at the board for about 20 minutes,
and said, "How am I going to pull this off without destroying
a perfectly good player?!" Those feelings were intensified
when I finally built up the nerve to actually open the player.
"Holy Toledo, Batman, those pins on the Printed Circuit Board
(PCB) are awfully tiny and close together!!" Well, when it
was all said and done, performing the mod was extremely easy.
All my worrying was for nothing. All it took was a little planning
(and praying).
I first removed the player's cover. This involved taking out two
screws on each side and three screws from the back panel. The
cover easily slid up and out. I then found a place where the board
would reside. I used an existing screw that held the audio PCB
in place, which was located at the front/center of the player.
I installed the board with the components facing down so the components
would not be protruding when the top was put back on. Following
the kit instructions, I located the pins on the audio board to
which I needed to make the connections. For the CLD-D703, all
the pins were located right on top, so removing the board to access
them was not necessary. The mod board has a strip wire consisting
of four small color-coded wires. The wires are for the +5v, -5v,
ground, and mute. The audio board on the player actually had all
the pins labeled, so it made it that much easier to find the connections.
The mod board also has two sets of 75 ohm cables, RF IN and RF
OUT. The RF IN connects to the audio board, and the RF OUT connects
to the supplied gold-plated RCA jack.
In order to easily install the RCA jack on the back of the player,
I took off the back panel. This involved removing 12-14 small
screws. Taking off the back made it easier to drill the hole for
the RCA jack. This is also a safer way to install the jack, because
if you get metal filings in the player, it could wreak havoc with
the electronics. I drilled a 3/8" hole in a convenient spot
in the back panel. I snaked the RF OUT coaxial cable in between
the audio and video board, installed the RCA jack to the back
of the player, then soldered the wires to the jack (including
the supplied ground capacitor). I then found a grounding screw
on the back of the player, attached the capacitor spade lug to
it, and screwed the back panel back on. After all the other wires
were soldered, I re-installed the player cover. It was that easy!
Construction
tips
The most important aspect regarding the success of the upgrade
is proper soldering technique. Because the pins on the IC are
small and close together, there isn't much room to work. All wires
on the mod board were tinned, that is, a coating of solder was
put on the bare part of the wire. This is critical for a good
solder connection. If you decide to cut the wires to make them
fit better in your player, you must re-tin the freshly cut wires.
Using the proper solder and soldering iron is also important.
The solder used must be rosin core (not acid core), since acid
core will most surely destroy the wires over time. The iron should
be fairly low wattage, about 15-25 watts. The tip should also
be of the pencil variety to get into those close quarters without
touching unwanted connections. Both rosin core solder and the
iron described above could be found in Radio Shack or any other
electronics store. Be sure to tin the soldering iron tip as well.
In between each connection, wipe the tip of the iron free of any
oxidized lead. The tip should have a silvery-shiny appearance.
When making the connections on the board, place the wire parallel
with the board. Place the wire directly on top of the pin to be
soldered, and press the wire down on the pin with the iron until
the solder on the pin and wire melts and the connection is solid.
Do not apply the heat very long, as this may damage the IC. If
the iron and wire are tinned properly, the soldering of each wire
should only take a few seconds. Gently pull on the connection
to ensure that a proper bond was made.
After speaking with Charles Triola about the installation, I expressed
my concern about soldering the big ground lead of the coaxial
cable of the RF IN to the audio board. He stated that this connection
really wasn't necessary, so I opted to eliminate this connection.
If you also opt to eliminate this connection, be sure to properly
shield the ground wire using shrink-wrap shielding material.
Testing your
work
Once everything is put back in place, I plugged in the lasedisc
player. Much to my surprise, there were no sparks or explosions!
I used a volt meter on the AC-3 RF output jack to check that everything
was connected properly. When the unit is on and in stop or pause,
the voltmeter should read 0 volts DC. When the unit is in play
mode, the voltmeter should read approximately 4.5 volts DC. In
my case, it read 4.6 volts DC in play and 0 volts DC in stop and
pause. The reading really depends on the player and how much voltage
loss is incurred, but the voltage should be something less than
5 volts. The range usually falls between 3.6 and 4.6 volts DC.
How did it sound?
The system used to demo the mod was a B&K AVP-2000 preamp,
B&K AV-5000 power amp, Marantz DP-870 Dolby Digital Processor,
the modified Pioneer CLD-D703 laserdisc player, DIY Audax A652
left and right main speakers, Paradigm CC-300 center channel speaker,
and ADP-150 adapted-dipole surrounds, Yamaha YST-SW200 subwoofer,
and Audioquest Quartz interconnect cables throughout.
I guess the first question our readers will ask is, "Does
it work?" First I played a disc using the left and right
digital tracks in Dolby Pro Logic mode, just to make sure I didn't
destroy the audio board. Mission accomplished! No problems so
far.
I selected several Dolby Digital encoded laserdiscs from my LD
collection to audition and switched to Dolby Digital. Discs included
"Twister", "Stargate", "The Mask",
"Star Trek: Generations", "Independence Day",
"Primal Fear", and "Last of the Mohicans"
.
Based on the little red AC-3 indicator light on the DP-870, I
immediately knew that the AC-3 signal was being read and locked
in. But what about the sound? Knowing that volts DC output was
correct, my main concern was external noise. If the board was
not installed properly, there is a potential for generating 60
cycle hum or buzzing, caused by poor grounding and external RF
frequencies. Well, I'm happy to report that all discs demoed were
drop-dead quiet during quiet passages. In fact, there was less
noise during DD playback when I compared it to the Pro Logic soundtrack.
This is an indication that the mod was installed properly, which
included the proper connection of grounding capacitor on the back
of the chassis. Using several key chapters in the demo movies,
I checked the steering of all channels. As expected, sound quality
and steering were right on as well.
If you've heard Dolby Digital before, then I don't have to tell
you what the experience is like. If you haven't given a listen
to DD, I wholeheartedly suggest that you do. It is by far more
dynamic and lifelike than Dolby Pro Logic. If you have a pre-DD-ready
laserdisc player, and you want to get into the DD game, I can't
recommend this mod enough. It will bring your home theater to
the next level.
Acknowledgments
I would like to thank Charles Triola and Les Lavin for making
this mod available and for all the advice given in guiding me
through this project. Unfortunately, Charles Triola is no longer
building these mod boards for sale. However, there are several
alternatives available to you should you decide to pursue this
modification. Check out the Q&A section here at Secrets, #16 June
17, 1997. You might also want to look at a generic schematic diagram
of an AC-3 mod board at http://home.powertech.no/espenb/ac3/output.html
Kevin Nakano has a very nice web page dedicated to modifying LD
players to AC-3. His web site is at http://users.aol.com/knakanoz28/ac3mod.html.
Ralph Calabria
© Copyright 1997 Secrets of Home Theater & High Fidelity
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