MadScientistAudio HDC Digital Cable review

Kiwi Cable - Mad Scientist Audio HDC Digital Cable.

On the other side of the world, from my option that is, in New Zealand resides the Mad Scientist aka the audio designer Bob Prangnell. He is in charge of inventing many strange but well thought and good working tweaks for the HiFi connoisseurs amongst us.

He has earlier on created the Black Discus devices. We also testet his Magic Tubes at Mono and Stereo and BlackPod Footers. He has also invented the NEO Power Cord. did a review of the cable here: link.

Now he has created a new digital cable, which knocks my socks off, so to speak. It´s quite different to something I have had my hands on before. This one is made with a carbon fiber. CARBON fiber? I asked Bob Prangnell for more information, and he send me this:

So let me explain the interconnects....

"As you know, HDC is a digital cable. It came about after I tried one of my analog carbon ICs as a digital cable, and liked the result.

So it only seemed natural to try two HDC cables as an interconnect. And you know what? It works real well, so well that I will be releasing these soon.

The ones I sent you come with the cheapest KLE plugs - Copper Harmony. I figured that these are budget cables and this is the sweet spot for them.

Compared to my more expensive interconnects - well the HDCs are not as refined, don't have so much space between instruments, that sort of thing. But they really give you a taste of them. More than that in fact. I'd compare more like Methode vs Real Champagne."

He also informs us that:

Every digital audio coax (SPDIF) cable out there claims that it is "75 ohms" (whatever that means). The Mad Scientist Heretical Digital makes no attempt to conform to this standard. This post explains it all...

What is this "75 Ohms"

In the SPDIF standard (Sony/Phillips Digital Interface Format), the coax electrical interface is defined to have a characteristic impedance of 75 ohms.

Characteristic Impedance however is not so easy to understand or picture as regular impedance, say like a loudspeaker is 8 ohms, or an amp might have an input impedance of 50kohms. These are simple resistances, and you can measure them easily with a multimeter.

On the other hand, Characteristic Impedance is all to do with transmission lines. You also can't measure it with a multimeter. Here is the formal definition, from Wikipedia:

The characteristic impedance or surge impedance (usually written Z0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction in the absence of reflections in the other direction. Characteristic impedance is determined by the geometry and materials of the transmission line and, for a uniform line, is not dependent on its length.

So why does that matter?

The crucial point is this : If you have a 75-ohm transmission line (like a digital cable) and you have some part of the system that is NOT 75-ohms, then you get signal reflections. The signal can bounce up and down the cable, in some cases dozens of times. These reflections can and do alter the original signal in hard-to-predict ways. This mechanism is the underlying cause of jitter in digital cables. And jitter is one of the chief culprits of 'digital nasties'. Not the only culprit, for sure, but a very important one.

There have been articles written about the optimum length for a digital interconnect, making it the right length so the reflections avoid the critical points where the detector is trying to detect a transition. However you need to know things like the rise time and propagation time to figure out the correct length for your system; as far as I can see there's no length that would work for everything. The effect that jitter produces is a horrible mixture of noise and distortion - not easy on the ear at all. But it accounts for the differences in sound of digital cables.


The amount of jitter that high quality digital clocks produce is getting to be very small - measured in a few tens of picoseconds. Now that figure is meaningless to most people, me included. So how's this : Light travels about 3mm in 10 picoseconds. And as you may know, light is really really fast. This small amount of jitter can be dwarfed by other sources like cables.

Heretical Digital Cable

The Mad Scientist Heretical Digital takes a different approach. It does not attempt to conform to a 75-ohm characteristic impedance. It does however have a significant amount of resistance as the main conductor is made from treated carbon fiber.

Two things happen with a carbon fiber conductor:

Skin Effect is very very small compared to metal conductors. The square waves that make up the digital data are sent at a few megahertz - fairly slow by digital standards. However, the harmonics that make up the square wave go much higher, into the tens or even hundreds of megahertz. At these frequencies, copper has a skin depth of a few micrometers. By comparison the skin depth for carbon fiber is still as few millimeters.

This is important as the correct transmission of all the component harmonics is crucial for the correct transmission of the whole wave.

Resistance soaks up the reflections. This is probably more important than skin effect. The resistance of the conductor, being of similar magnitude to the 75-ohm loading means that reflections are not going to be able to do much damage - they will be turned into heat.

If you imagine the digital link being like a light tube, with flashes of light being the data pulses; A normal cable has silvered parts and so you get glare and reflections. Our Heretical Digital is like filling the tube with slightly darkened glass - only the bright flashes get through, reflections are absorbed.

The Heretical Digital Cable has a resistance of about 37 ohms - half the 75 ohm characteristic impedance. But all SPDIF inputs are terminated with 75 ohms. This means that a reflection that reflects off the DAC end of the cable/plug will travel towards the source where it can interfere with the data. But the resistance will tend to turn the energy into heat, so reflections are dissipated very quickly.

What Actually Happened

This all might sound like it was planned. But that's not quite how it happened. As is often the case in science, an ad-hoc experiment showed some interesting results which lead to further research, theorizing, more experiments and so on.

After the carbon fiber interconnects were developed, I thought I'd try one as a digital cable. I wondered whether it would work at all and I wasn't expecting it to sound good.

But it did sound good, which surprised me. So a new project was born. I needed to figure out why this was producing such good results. Also I needed to figure out what the best sounding design was.

It turns out that a much simpler design than YANAM/TORFORB is needed. Out with the multiple bundles of carbon fiber, now just a single, thicker conductor is used. Also a cheaper plug seems to work better.

As with the interconnects, I was trying to make the best digital cable that I could. It would also have been ideal if I could come up with a range to suit all pockets. But the result of the listening and design process showed that the simple one is the best. If anyone wants a "signature" version, I can sign it with a silver pen if you like ;).

How Does It Sound

Usual disclaimer about how I am biased, etc. But those that know me might want to take note...

The Heretical Digital Cable astonishes me. I've tried a good number of digital cables in my time, conventional and not-so-conventional. This one shines, being the best one I've heard. Not "best for $99" but "best for any money". The things that leap out at me are:

analog-like sound but with digital crispness - so a lush sound but the leading edges are still fast
very pure treble with lots of air and very fast top end
wide and fast dynamics
intelligibility - I'm hearing lyrics much more easily. Also makes complex passages easier to parse

Listen and learn

So all this is the Mad Scientists words about the how´s and why´s.

My listening experiences showed me: this is the second best digital interconnect I have ever put my ears to. The best one, and yet to be beaten by any means, is Tellurium Q´s Ultra Silver Digital Cable. did of course a review of it, read it here: link.

But costing ten times the HDC it of course should be in another league.


Mad Scientist Audios HDC digital cable sounds way better then the price tag lets you imagine.

When I listen to string recordings with this cable, I can not only hear the strings vibrate, but also the air around it, soft as a summer wind. Many digital cables come with a harsh sound, maybe due to their lack of the 75 Ohm standard, and they all do the “Wow, I am quite impressed with the sound the first five minutes” stuff. After half an hour though, your ears get tired, the music´s fired and you shut off your system. Long term listening is good! And recommend! My advice to all my HiFi buddies is to keep the same new cable/amp/tweak in your system for a week or two. Remove it after this period and your intensive listening sessions will show and the result is quite clear. And very easy to hear are the differences of the “before” and “after”. Many HiFi lovers (me included) can easily judge if there is any difference with the new thing in the Hifi rig within seconds. But the REAL test is with some long term listening, and the subtle differences will show just as easy as the sun rising in the morning.

When listening to Linn Classical Radio at stream lots of details in the music are shown with this HDC cable. Nigel North´s v. Bach´s Menuets 1 & 2 shows and reveals the fundamentals of the musics (s)core. Norths´ lute is beautifully rendered, even played back through an internet stream. What a dream!

For the bass guys amongst us:

Danish/Mali Moussa Diallo is a bass player out of this world, but he is also a singer with an open heart and mind. His tune “Darling” is one of the fab tracks found this day on my hard disc. As a boy Diallo escaped from his strict father in Mali, and showed up weeks later in Denmark to meet his real mother in the year of 1973. And like in a fairytale he becomes one of Denmark's best bass players. His song: “Thoughts Of You” is truly emotional, and world class when listening to the HDC cable from Mr. Prangnell. The bass player´s instrument is deep and the attack is truly phenomenal.

“Strange Fruit” performed by Cassandra Wilson gives me the shivers (and not the shovers as my text correction software wants me to spell it ;=).

Again the bass and the texture of the singers way to perform just let´s me look even more into this song. The awful lyrics and theme thinking of people “hanging from the trees” is terrible, just terrible. Again I am reviewing a damn HiFi cable, yet the music touches me and I forget all the words normally used when doing a review. More bass, more treble? More resolution? I don´t care; with the Mad Scientist Audio´s HDC cable everything is good, everything is in it´s place. The sound stage is wide, and deep. More important though is the enjoyment factor of this cable. No harsh sound (repeating myself again. I know of very few digital cables that can do no harm to the signal), lots of precise yet smooth high frequency sounds.

Doug MacLeod´s “Black Nights” has some of the same signature or footprint. With the HDC cable the sound stage is wide, deep and joyful. With nothing left to loose. It´s easy to hear the small brushes of the snare drum, things I not always easily can recognize when listening to other digital cables in my system.

And also Bachs Simple Symphony  Op. 4 - Frolicsome Finale with the Trondheim Solistene in 24/96 gives me a big smile on my face. A big and wide soundstage is a joy to listen to. And no hard sound, just soft high frequencies - and the violins are having a ball in my listing room. The sound is VERY precise, and it is very easy to look into the sound picture. The depth of the imaginary musical scenery is quite remarkable - quite addictive actually.

But also “Les Mots” with Mylène Farmer and Gary Jules (TimeLess, Live, Lyon 2013) shows a good sound control, a deep bass and the two voices are easily to discern - yet easy to combine. Mylène´s voice is a difficult thing for many a HiFi system, cable or amplifier. Her s-sounds can be hard to listen to. With the HDC cable from down under this is absolutely no problem. The carbon fiber cable does it´s job, showing the great voice of both Farmer and Jules, and when the song finishes the sound of the audience is very, very realistic!

The track “Mediya” from the album Ya Nass with Yasmine Hamdan is another example of good/bad or harsh/soft reproduction of the music. 

If you are in doubt if your digital system can cope with this kind of music, try it with the Mad Scientist Audio HDC Digital cable. I am quite sure you won´t regret it. 

And as always, the Mad Scientist has a 4 weeks money back guarantee - but I am sure you wont use it. Very sure.

Carbon fiber? I don´t care, this one is a cable that really suits my system, and with this price tag I just HAVE to have this cable.

PS This review was done listening for a month with the most modest HDC cable mounted with the cheapest KLE Copper Harmony plugs - coming in at a $169.

One of my friends, who also is a professional sound engineer working for the National TV and a HiFi lover with some good gear (and trained ears) came today to my listening seat with a similar HDC cable, just mounted with the new KLE Absolute Harmony plugs. And the music was taken to even new levels - levels I was not prepared for considering the entry price of the cable. World-class? You bet! 

Way better then the standard version? Yes, a little bit.  Worth the extra money? If you have the dime to spare then yes. Worlds apart differences of the two cables? No, but it still had the same sound signature, which is absolutely stunning! The slightly more expensive cable came with a to me more analog sound, and a little more softness, where the basic version had a touch more attack, some will describe it as a tiny more aggressive way to present the music. 

Again, if you have the money, go for the one with the KLE Absolute Harmony plugs. No way that you´ll be disappointed - it´s a steal!

The basic one, with the only difference being the KLE Copper Harmony plugs, in my opinion is a bargain too. Which one you choose is strictly up to you. I better call Bob Prangnell to send me the KLE Absolute Harmony version of his cable to do a more long time listening session.

Recommended ? This is as good as ANY cable can be for this price, or even way higher. Order now, one version or the other, both will do wonders on your system!

Price for 1 meter is:

Cheapy plugs: $129
Copper Harmony: $169
Silver  Harmony: $189
Absolute Harmony: $229

Text and photos ©Kurt Lassen 2016