[Hirsch]

The TDS passive audiophile is a black box, roughly six inches square and two inches high (I didn't measure), with a single switch on the front that engages the unit, and a single set of inputs and output in the rear. In theory, it restores harmonics of the live performance that are lost in the recording process. Whatever. It claims to be a passive inductor. Hmmm...someone dissected one of the MIT network boxes once, and found an inductor circuit. Does this unit use a similar technology to the MIT/Transparent passive networks? I have no idea, but the idea had me curious. I bought a used TDS, and hooked it between my DAC and MF X-Can v2...then let everything burn in as I got used to listening to it. The bypass switch is nice, as it's possible to listen with and without the unit, without having to move wires.

The first thing you notice is gain...about 3 db is claimed. My DAC is an ART DI/O, which has way too much gain to start with, but the X-Can didn't really care, and I got better at very small movements of the volume control. (I also tried this unit with a Theta Chroma 396, but most of my listening is through the DI/O). Rest of system: Senn HD-600 cans, Homegrown Audio Silver Lace interconnects, Elco DC-32 digital interconnects, Rotel 955 CDP, Theta TLC, Monster HTS-2000 power conditioner.

At first, with the unit on, the volume at which things sounded tonally correct was too high, IMO, for headphones. I found that I was using the amp louder than I liked, not because I wanted more volume, but because the music sounded wrong at my usual listening levels. This would have made the TDS a poor choice for headphone use, and could have been a risk to the ears. However, the effect was only present during initial burn-in, and disappeared within a couple of days, as volume levels went back to normal.

So what does it do? To tell the truth, I'm not sure. However, I can't take it out of the system. With the TDS in place, everything seems more vivid. Part of me is wondering if some kind of dynamic range enhancement is going on. If so, it's not bad.

Instruments take on a much more three dimensional aspect. If I use the bypass mode, and volume match to the previous level, everything sounds relatively flat and lifeless. The instruments seem smeared. With the TDS on, in the opening cut to Laurie Anderson's "Big Science", when David van Tiegham's drum beats snap. You can feel the percussive effect, and the later decay. With the TDS off, the drum beat is present, but the impact is reduced. Anderson's voice is very focussed and dynamic with the TDS present. Turn it off, and her voice seems to lose coherence. Instead of standing out vividly, it blends back into the mix. These effects are not subtle.

The TDS seems to bring out a lot of detail in recordings. This is not always good. Eva Cassidy's "Time after Time" is a wonderful CD, but not particularly well recorded. With the TDS on, Eva's voice becomes even more vivid, and there is greater presence. However, you can also hear all of the flaws in the recording process...studio noise is also enhanced, and is distracting when it occurs. Problematical, but IMO the problem is the recording, not the TDS. The TDS seems to make everything more vivid, and brings out detail you just didn't know was there. There may be a slight reduction of this effect at the highest and lowest frequencies, but I'm not certain.

If you can find one of these used, I'd recommend it highly. I normally don't like the concept of signal processors, but this one is doing some very nice things. I find my headphone system much harder to listen to when I use the bypass. As it is, this is rapidly becoming a permanent fixture in my system.

I don't really know what it does, but I like it!

 

[jude]

Thanks for the nice review, Hirsch. How much are these things?

 

[Hirsch]

They're out of production, but I found one at audiogon for $200 (original price was $400). Another one appeared for $175 after I bought mine, but the person took it out of the classifieds and it's now being auctioned. The person ended the classified ad by changing the price to 99999999.00...I suppose if someone actually offered that, they'd risk negative feedback by pulling out of the auction...

 

[dhwilkin]

Any chance of you opening the thing up temporarily, and posting some pics of the insides? That way, all the DIY'ers could figure out just what it does.

 

[DarkAngel]

Hirsch are you describing sound difference for TDS while using headphones? I think you will hear much greater results in main system using full size speakers. The added detail/enrichment
you describe translates to better 3D soundstage perception
in full size system, some CDs it is quite dramatic, this is the main reason I use it. It somehow enhances frequencies that allow you brain to perceives things as more 3D and real sounding.

I tried a couple times to remove TDS from main system, but after couple days couldn't wait to put it back. I also saw that TDS for $175 at Audiogon and almost bought it for my second system.

BTW aren't those HG Silver Lace fabulous ICs for the price.

 

[Hirsch]

DarkAngel,

Yes, that was the headphone system, and yes, I can tell that the 3D soundstage enhancement is going to be good with speakers. Even with headphones, the 3D effect was apparent. On the Laurie Anderson CD, drum placement was stable and precise. Rather odd, having van Tiegham set up a drum kit in your head, particularly when he brought out the rototoms and tympanis

In addition, though, the quality of the instrument was brought out better...you can hear the tonality of the drum as well as I've ever heard it (I'm focusing on percussion, because it's relatively easy to describe, but this is true of everything going on. At the same time, small detail is also enhanced. I'm noticing that background instrumentals and voices are much easier to follow. If this were happening with a dark curtain hiding the equipment, I would have thought someone was substituting the next level of headphone amp.

I was thinking about that second unit also. I'm still thinking about bidding on it...hmmm...none of the little smilies seems to convey the right sense of pure equipment lust

I'm up to three pairs of the Silver Lace, and getting pretty good at putting the kits together

It's a great interconnect for the price. One of my hypotheses about the TDS is that it works in a similar way to the network boxes (MIT/Transparent). This would allow MIT/Transparent to skimp on interconnect wire quality (at the lower levels, anyway, and put the detail back with the network. If the TDS is doing something similar, but allows you to choose the interconnect you're using, then you can get the benefits of the box, but choose better quality wire....hmmmm...(these are just idle speculations, and may have no bearing on reality).

dhwilkin,

I'll check later and see how securely it's sealed. If it's easy to open, I'll take some pics.

 

[Hirsch]

Hmmm...there will be a pic of the innards here as soon as I can figure out how to do it...adding an attachment didn't work.

 

[Hirsch]

OK, let's try this again:

 

[jude]

Hirsch,

Thanks for the pic. Any chance you can make it bigger? If you have no place to put a bigger file, let me know.

 

[dhwilkin]

Any idea what those four objects all the wires are running into are? Maybe this should be double-posted in DIY or something?

 

[skippy]

there was a big debate about this thing back on headwize.

http://headwize.powerpill.org/ubb/sh...num=2&tid=1234

 

[skippy]

Quote:

Any idea what those four objects all the wires are running into are?

they look like transformers.

 

[Hirsch]

Quote:

Originally posted by jude Hirsch, Thanks for the pic. Any chance you can make it bigger? If you have no place to put a bigger file, let me know.

I'll upload a larger version. I had reduced it, as the posting instructions seemed to indicate that I could add a file attachment to a post if it was less than 25K or so. Didn't work, so I linked from my web space. Let's see if this is better:

That's about as far into the unit as I can go, and still be certain of getting it back together. I don't think I want to dissect one of the assemblies

 

[jude]

Hirsch, thanks for the bigger pic. I'm interested in reading the comments of those who better understand the insides of things like this. Looks quite simple.

 

[Audio Addict]

I couldn't agree more with you evaluation. I have 2 of them in my headphone system. I bought them for my 2 channel system but I ran into too much hum in the system with them in. The 3db gain was just too much. I could not eliminate the hum so the TDS was move to my headphone amps and now they appear to be a perfect match. From TDS's website, they used to license the design so I had emailed HeadRoom they should consider it in their design but I don't remember them responding to my email.

Another product to try is the SCE HRS. I use one of these in my 2 channel system and they sonic improvements was pretty great. I actually had the TDS and the HRS in my system at the same time but the 6db gain was just too much with the hum.

Thanks for the review.