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Supra EFF I & 25 Years limited Edition - interconnects

The Sound of Silence

[Italian version]

Product: Supra EFF I - interconnects
Manufacturer: Jenving/Supra - Sweden
Approx. price: 180 $ (1+1 m with RCA's)
Reviewer: Lucio Cadeddu
Reviewed: June 1999 - updated June 2001

[Supra EFF I]

Supra (Jenving) is a well-known HiFi manufacturer that built its fame upon a series of speaker cables which were very popular during the Eighties, when audiophiles started to consider seriously the problem of cables for HiFi use.
During these years Supra has developed new cables, using some quite interesting ideas and a pretty scientific approach (you may have a look at the very interesting Inter.view with Tommy Jenving, owner and chief designer of Supra cables.
The EFF I interconnects cable is not the latest model from Supra but it is still a very interesting design, which makes use of some special technique to minimize the skin effect of the cable.
Considering the materials which have been used and the (real) research behind the EFF I design, the price has to be considered low, especially when compared with fancier and higher-end cables.
EFF stands for Equalized Frequency Flow and it refers to the particular technique used to fight the dangerous skin effect. As a result the cable consists of two tubular silver-plated copper conductors with a 0.75 mm2 total cross-section and a PE inner core. Each conductor is individually shielded with an aluminium foil. See the picture below for more details.

[Supra EFF I - inner view]
Since the guys at Supra take into serious account the electrical parameters of a cable here are some tech infos about the EFF I: Anyway, I prefer to leave the measures and the numbers to the techno-weenies out there, and I'll try to give you an idea about the sound of this cable.

The Sound of Silence

I know quite well the sound of the Classic speakers cables from Supra (the 2.5, the 4 and the 10) since I've used them for many years in various HiFi systems.
So, as I hooked up the EFF I, I suddenly had a flashback: the sound I was listening to reminded me the well known one of the Classic speakers cables. Well, in some sense, actually.
The big plus of the EFF I is the mid-high range which is very open, clear and refined. It is also extremely revealing, so if there's something recorded into your discs you can be pretty sure the EFF I will reveal it to your ears.
The tonal balance is slightly in favour of the mid and high frequencies as the bass is on the light side. Hence the "body" of some male voice is a little bit thin while the female voices are crystal clear, just sometimes too many sssss-sibilants can be heard.
The high range is well extended and detailed so that it can rival even with much more expensive cables, at least with respect to this particular aspect of the reproduced sound.
The mid bass is tight and well articulated, sometimes light and dry.
The introspection capability of the EFF I is very good and certainly the efficient shielding technique is the main responsible here: this is one of the most silent and quiet cables I've ever tested: keep the noise (RFI and EMI) down and the detail will pop up naturally. This is why I've decided to use the The Sound of Silence (Simon/Garfunkel) subtitle for this review.

Dynamics and soundstage

The dynamic performance is quite good: excellent for the mid range and fair for the bass. It is a very fast cable and sometimes you'd prefer a more relaxed performance.
The soundstage is wide and surprisingly deep. With such a tonal balance one can reasonably expect a very precise soundstage but with a limited sense of depth.
Clearly the large amount of micro informations this cable can easily transmit is useful to recreate a realistic and bright scene, with well focused contours.

Some advice

This is a shielded cable. A well shielded one, indeed. It works very well even as a phono cable (i.e. with a turntable) as the extremely low output of a cartridge can travel safely through the EFF I. With respect to the RFI and EMI shielding properties the EFF I is one of the best cables I've ever tested: silent and quiet as the best cables in the market.
It is even quite flexible so it won't interact with floating sub chassis. It can be used successfully with turtables, preamps, CD players and power amps.


The particular tonal balance makes this cable sound quite bright and dry so the bass range isn't as powerful and punchy as one may desire. Anyway, I can easily forgive this, given the performance in the mid and high range and the very good level of introspection.

25 Years annivarsary Limited Edition

[Supra EFF-ISL 25 Years Limited edition]

In 2001 Supra celebrates its 25th year of activity in the field of special audio & video cables so the Company has decided to build a limited edition version of their best-seller and multi-awarded interconnect cable, the EFF-I SL.
So here it is: cool adjustable RCA connectors, new outer jacket, a classy and precious solid mahogany wood box and a certificate of authenticity with a serial number (only 1000 cables made) and Tommy Jenving's own signature.

The 25 Years EFF-I SL confirms the already good performance of the original cable, while the price, despite all the bells and whistles, remains low (around 160 Euro/$ pair / 1 meter).
I don't know how easy could be finding and buying this "special version" of the cable, considering only 1000 of these have been made and that in some Countries Supra products aren't widely available.

Anyway, if you're looking for an exclusive interconnect...you should start searching - NOW! - for one of these 1,000 rare cables.
Actually, the 25 Years Limited Edition EFF-I SL is a perfect "gift" idea for any audiophile who needs a serious interconnect cable and a collectors' item.


The Supra EFF I is an extremely serious cable, designed and built with something in mind and a very interesting and appealing quality/price ratio.
If your set up sounds dark and dull and it feels like it may need some extra clarity and introspection, the Supra EFF I may be the cable to consider.

© Copyright 1999 - 2001 Lucio Cadeddu - http://www.tnt-audio.com

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