STEALTH audio cables
STEALTH Sound Technology Enabling Audibly Lucid Transcomponent Harmony


Roberto Petti

The beta Indra cables have been tested extensively in three different (reference) audio systems, including my personal one. The whole process took more than one month, including the break-in periods. The test systems were already deeply optimized (including room treatments, supports and accessories) since they are used to evaluate and develop audio equipment. First of all, let me say the results were fully consistent in the three systems and all people involved in the tests described the effect of the Indra cable on the sound in the same way. I believe this is an important point, allowing a more objective description of the outcome of the tests. In addition, we used many hi-end cables (some of them custom built and optimized for our amplifiers) as control samples. The best word that comes to my mind to describe the performance of the Indra cable is "natural", as opposed to typical hi-fi enhancements and exaggerations. The intrinsic grain usually present in the reproduction vanishes, leaving a smooth and extended sound. The bass range, usually very critical, is as tight and deep as you can expect from your speakers. The interesting thing is that this cable does not change the balance of the systems in any way: it "just" makes everything more liquid and realistic. The soundstage extension and precision and the inner resolution (details) are exceptional, although one does not notice it at first, given the overall life-like presentation. Any of the other (good) cables we used sounded compressed and artificial in comparison. I must admit it was a nice surprise to hear our systems sounding that good. 

The Indra cable makes much more easy to understand the effect of even minor changes in the system, thus providing an effective "tool" to tune the overall musical performance. The choice of supports, cabinets, vacuum tubes or even electrical components like resistors and capacitors becomes then straightforward. If there is a problem anywhere in the system, you immediately recognize it and feel the need to fix it. Clearly, this aspect could turn into a nightmare in either low quality (which is unlikely, given the cost of the cable) or badly assembled systems. For instance we had an interesting experience in one of the test systems, related to this aspect. The whole system was deeply optimized with a given set of (custom) interconnect cables (two pairs between source-preamp and preamp-amp). We first replaced the source-preamp cable with the Indra. Although we obtained a significant improvement, we felt there was a little lack of treble extension (a thing we noticed only because of the very natural overall performance). We then replaced the preamp-amp cable with a second pair of Indra and we went back to the old balance for which we tuned the system. Clearly, there was interdependency between cables and components (probably due to the tuning of the sound). This fact seems to indicate the Indra cable is really neutral and does not alter by itself the overall tonal balance. I wish I could report some flaws, but this is not the case. The only thing I would recommend is to invest some R&D in the study of connectors & soldering (if you have not yet done so). The Indra cable deserves that. From what I've seen you are using Cardas top of the line connectors, which are quite good, but perhaps the use of amorphous alloys or custom designs could further improve the performance. Usually connectors & soldering are the weak point of cables. In summary, the experience with the Indra cable was very positive. None of the other cables we tried could reach its performance and it became our reference. It's very hard to give up such a cable once you have tried it. I'd like to congratulate with you for this exceptional product.

I must admit the more I use those cables and the more I like them. I think they definitely deserve special connectors...

(several months later) ... I had a chance to test the Indra cables with the new STEALTH connectors. The difference with respect to the old Cardas termination is quite clear, although not huge. It's a bit like unveiling further the sound, with enhanced transparency and details. This can be appreciated by switching back to the old pairs. The new terminations seem to strengthen the good points in the performance of Indra cables: lack of compression and life-like overtones and harmonics. I tried to give an extended break-in period to the new cables before the comparison since the old pairs were used for quite a while. I would say the new connectors improve the sound of Indra cables by something like 10-15%, which of course is significant at this level of performance. The mechanical strength of the connection appears fine (the contact with the female RCA is quite firm)...

(more than several months before) The experience with your MLT speaker cables is very positive, they are neutral and natural without specific colorations. They outperformed several different cables we used before, although the gap was not as huge as with the Indra cables. I have the impression all of your cables show a similar behavior, in the sense they tend to a common musical presentation. In particular, I appreciate their ability to match high resolution with warmth and body, keeping an excellent balance throughout the spectrum. Did you ever consider to build a dedicated bi-wiring version of MLT in which the lower and upper frequency conductors are optimized separately (for instance taking into account a typical cross-over frequency of 1k-2k Hz)? Do you think it's realistic to use alloys in ribbon configuration or that would make the price unmanageable?

The M21 power cords were tested extensively. The locking IEC connectors (15A) seem indeed a very good solution from the electrical point of view, in spite of the fact they do not look very nice. It seems M21 is an excellent cord for the preamplifier, providing an improved reproduction of overtones and harmonics and increasing the "body" of the sound. Qualitatively, the effect is similar to a change from digital to analogue source, although not as large. I suspect part of the performance is related to the cryogenic treatment and part to the cable construction itself (it would be interesting to check). The use of M21 on the power amplifier gave more contradictory results. I remind you I'm talking about a single-ended triode design based upon the 845 tubes, which is notoriously a topology very sensitive to the power supply. Note it's not at all an "old style" tube amp since it has a wide frequency response and a very transparent sound. The M21 performance it's good in this application as well, but, especially  if a second M21 is used on the preamplifier, it has the tendency to slightly slow down the transient response and to restrict the soundstage (in particular the height). A Elrod EPS3 (standard) power cord (similar retail cost) provided better overall results (and I wanted the M21 to sound better since it's much easier to handle).  However, I want to add a small note here. As you know, it's always possible to improve a given amplifier or system by using more refined parts etc. Of course this can be done only through listening tests. Usually, if one knows live music enough, it is quite clear the direction to go in order to have a "natural" (and not spectacular) presentation. Now, my comments above referred to the use of M21 in a system which was already quite advanced in that direction. However, if we inserted the M21 in systems using less refined parts it could help to reduce the grain in the high frequency region (which is perhaps the most evident effect of compromises in construction).

I've tested the connectors and cables you sent me. A couple of weeks were needed for break-in, during which the performance improved. Your gold over silver plated connectors offer indeed a very low contact resistance (both NEMA and US wall sockets) and their use resulted in a significant upgrade of the AC filter. Subjective effects include increased dynamics and a reduction of the perceived "grain" in the reproduction. The M21 is very quiet when used as the input cable of the AC filter. The Varidig digital cable was tested against the Illuminations Orchid AES/EBU (+ other digital cables) on the digital front-end. Overall, it provided a better timing information (rhythm) for the music and a more focused soundstage. It is also more detailed and extended (yet natural), although at the very beginning it was a bit bright. Overall, my impression is positive, the only thing that could be improved being the subjective bass extension and body. Roberto