Product Review - True Dimensional Sound (TDS) II Analog Audio Processor - November, 1997

By Ralph Calabria


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TDS-II Analog Audio Processor; Frequency response 10Hz - 50 kHz; Dimensions: 8"W x 1.25"H x 4.5"D.; Weight: 1 pound 9.4 ounces; $295.00 US. True Dimensional Sound, 1450 Madruga Avenue, Suite 404, Coral Gables, Florida 33146; Phone 305-668-9198; E-Mail [email protected].

Can you say ..... tweak? Sure you can. TWEAK. If you're in the market to tweak your A/V setup, there are line conditioners to "tweak" the 60 cycle hum right out of your system. There are processors that can "tweak" a 2-channel stereo setup to make it sound like a surround sound system. To entice you to buy a receiver or preamp, many manufacturers include such "tweaks" as digital signal processing (DSP), and various sound-enhancement modes such as JAZZ, CONCERT, HALL, and ARENA, just to name a few. Most of these sound-enhancement modes use some sort of time delay or phase shifting to give you the illusion that you are in a hall or arena. While this may be fine for watching a football game, these modes just don't cut it when it comes to reproducing accurate, live music. I haven't heard one yet that I've really liked.

Enter True Dimensional Sound (TDS), a relatively new company. TDS has been around for about seven years, concentrating mostly in the professional audio market. Over the past year they have been focusing on the consumer market as well. They offer a consumer product called the TDS-II (II as in the number 2) analog audio processor, an audio enhancer of sorts, but unlike any other on the market to date. The TDS-II is said to restore harmonic loss that occurs during recording or playback of an electronic audio signal. (Harmonic loss is one of those unavoidable things that happens when a signal is reproduced from an original source, i.e., the live music as it is being played.) The TDS-II does not use any time delay functions or phase shifting to accomplish this. Because the TDS-II is an analog device, to use it for Dolby Digital playback would require three processors to accommodate the six discrete channels. It is however, fully compatible with Dolby Pro Logic. It is an active processor, which means it provides its own power and does all of its processing at the line-level stage before amplification of the signal.

The TDS-II is a very compact, simple black box. The front panel has an on/off toggle switch and a green indicator light that tells you when the unit is activated. The back panel has a pair of gold-plated RCA inputs as well as a pair of outputs. The unit uses a 12 VDC power supply. The unit comes with a DC adapter that plugs into a conventional AC plug. Also included with the TDS-II are two pairs of RCA interconnects.

The TDS-II is very simple to hook up. There are two basic ways to connect the TDS-II to your system. You can connect it to a single source in your system by connecting the audio outputs of an audio source (CD, laserdisc player, VCR, etc.) to the inputs of the TDS-II, then connecting the outputs of the TDS-II to the appropriate inputs on your preamp/receiver. If you have a tape loop with a tape monitor, you can connect the outputs of the tape loop to the inputs of the TDS-II, then connect the outputs of the TDS-II to the inputs of the tape loop. Using this configuration enables you to use multiple audio sources without switching wires, since the tape monitor is always active.

After hearing that the TDS-II was used to enhance soundtracks of CDs, and more recently, the soundtrack of the film "Jerry Maguire", I was eager to see if the TDS-II would "Show me the music".

For this evaluation, I connected the TDS-II between my laserdisc combi player and preamp. The equipment used for the tests was a B&K Components AVP2000 preamp and AV5000 power amp, Audax A-652 DIY speakers, Yamaha YST-SW200 powered subwoofer, and a Pioneer CLD-D703 combi player. For movie playback, I added a Paradigm CC-300 center channel speaker and ADP-150 adapted dipole surrounds. CD playback was done with the preamp in direct mode (stereo that bypasses the processor) and the combi player in CD Direct mode. Movie playback was performed in straight Dolby Pro Logic mode. All interconnects were Audioquest Quartz and speaker cables were Audioquest Indigo.

Before beginning the tests, I replaced the audio cables that came with the unit (the standard cables that come with most audio equipment) with Audioquest Quartz interconnects. Then I listened to a variety of music CDs and laserdisc movies with the TDS-II off and then again with the unit on. (When the TDS is off, the audio signal bypasses the enhancement circuitry via a PC board). I immediately heard a noticeable difference in the sound. It was louder. SPL readings indicated a 3 dB increase with the TDS-II on. After speaking with Art Garcia, co-inventor of the TDS, he stated that the 3 dB increase is normal, and that the increase is not due to just making the volume louder, but due to increasing the amount of information reproduced (harmonic loss is regained) , translating into increased amplitude. I checked to see if the change in sound was due to this change in volume by increasing the volume by 3 dB with the TDS-II off. Even at the higher volume, I still noticed a difference in the sound quality. I should note that I really enjoy my audio/video system. The combination of the A-652s and the MOSFET design of the AV5000 amp provides a very smooth, clean sound with no harshness at all. However, with the TDS-II in line, the sound became......well......cleaner. The highs were slightly more detailed without being too "forward" and brassy, and the mid-bass and bass frequencies had more punch without being "boomy". I became "more aware of ALL the music" around me. It truly sounded like the music was being played live, but without the acoustic reverberance associated with halls and such. When I played back CDs through the TDS-II that had been recorded very well, it made them sound even better. Very crisp recordings such as Spyro Gyra's "Dreams Beyond Control" had a more spacious, open sound, with each note sounding "articulate". On music that was not recorded well, such as the title track on Tears for Fears: Raoul and the Kings of Spain, the TDS-II really made the track sound very enjoyable, cutting out a lot of the raspiness in the recording. Orchestral music with a lot of string instruments really came alive as well as certain percussion instruments such as piano and xylophone.

To check out how the TDS-II affected imaging, I played a track from Steely Dan Gold, "True Companion". This track has an electric guitar that is recorded out of phase. This creates the illusion that the guitar is coming from the side of the room rather than the front, as if the guitar is coming from the surround channel speakers. The TDS-II handled this track with great finesse. The guitar was now almost coming from behind me!

I selected a few movies that had a lot of information in the surrounds. The opening scene of "The Abyss" proved to be a good test. When the submarine starts crashing into the ocean floor, there is a lot of different sounds going on in ALL the channels. I found that with the TDS-II on, surround information was much more noticeable, enough so, that the envelopment of the soundstage was significantly enhanced. I then compared the Disney film "Pocahontas" soundtrack in straight Pro Logic, Pro Logic with the TDS-II activated, and Dolby Digital (DD). Voices in Dolby Digital sound so much clearer compared to Pro Logic, so I wanted to see if the TDS-II approached DD quality. I used the scene where Pocahontas sings "Just around the River Bend". There is a lot of action in the scene as well as the dreaded "female voice singing". It's very easy to inaccurately reproduce female vocals, but the TDS-II clearly did a better job when compared to straight Dolby Pro Logic. Dolby Digital was still much clearer and well defined, however, when I compared it to the TDS-II in Dolby Pro Logic.

Now for the quirks. One thing that annoyed me was the green indicator light. It's too bright! I found this distracting when watching movies in a dark room. But that's just me picking nits! When I played a CD that was not encoded in surround sound with the preamp set to straight Dolby Pro Logic and the TDS-II on, there was a significant amount of distortion coming from the front left/right and center channel speakers. I then played "Tchaikovsky's Greatest Hits", a CD that is encoded in surround sound. I found the same distortion on this CD as well. When I played the cannons from the "1812 Overture", they sounded like someone was sitting on a whoopie cushion. Not a pleasant sound at all! The same track, however, played flawlessly in stereo direct mode, even at 105 dB. This was very perplexing, since all the movies I auditioned at this point in Pro Logic performed well with not a hint of distortion. I later found some laserdiscs that produced the distortion as well. I then connected the TDS-II to my video cassette player. I also found that some tapes played with distortion and some did not, no matter how loudly they were played. Over 2000 of these units have been sold, with no complaints of this happening to anyone else. I then tried setting up the TDS-II in the multi-source configuration using the preamp's tape loop. Unfortunately, the B&K tape loop cannot access Dolby Pro Logic. In the tape loop, the TDS-II performed well in direct mode. This phenomenon proved to be a system-specific problem, i.e., the B&K preamp. I connected the TDS-II to two other Dolby Pro Logic sources, a Pioneer and a Sony receiver. Playing the same CDs that caused clipping with my system played fabulously on the other receivers. This brings to mind the analogy of the patient who goes to the doctor and complains that "my arm hurts when I do 'this'" (raising his shoulder), and the doctor, in his infinite wisdom says, "Well then, don't do that!" I would only recommend playing CDs or movies using the B&K in Pro Logic mode with the TDS-II on if you have tried it at lower volumes first, then slowly increase to desired volume.

In summary, True Dimensional Sound has a real "live wire" in its TDS-II. Music has never sounded better on my system. The audio reproduction of music and movies has just been "tweaked" up a notch. True Dimensional Sound will be coming out with a passive unit using the same technology as the active unit. I can't wait to hear what it sounds like. I think TDS should seriously consider changing its name to Totally Different Sound (TDS). In the case of the TDS-II, that's a good thing.

If you would like more information regarding True Dimensional Sound and their TDS-II, link up to their web site at

Ralph Calabria

Copyright 1997 Secrets of Home Theater & High Fidelity
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