Heretical Digital Cable
75 Ohms? Nope...and only $129

Mad Scientist Heretical Digital Cable (HDC) also uses carbon fiber for the main conductor. But why "Heretical"?

Every digital cable makes an attempt to be "75-ohm", whatever that actually means. There is a very good reason for this - it's written into the SPDIF standard. But the HDC makes no such claim. In fact, it has around 37ohms of actual resistance in the main conductor, about half of this "75 ohm" value. Most digital cables strive to be lossless, to have zero resistance - you have even maybe read about how crucial low resistance is, and that is why silver is often used.

But this is not heresy for the sake of it. No, this is a different approach, and judging by the sound, it works really well.

We've had the most amazing feedback from HDC customers. The thing we hear over and over again is "I used to use a high priced cable but the HDC is much better and is now my reference". We started keeping note of the prices of the cables that HDC was replacing. I won't name names here, but contact me and I can let you know. But I can reveal the prices of the cables that HDC replaced: $2450 (!!), $1400, $900, 600 euros. $350. See the Reviews section for more

So Why 75ohms?

The 75-ohm figure refers to the characteristic impedance on the cable. Suffice to say this is a fairly technical concept and you cannot just measure it with a meter. If you have a system that is meant to be 75 ohm, and some part of it is not actually 75-ohm, you get reflections - imagine shining a light down a mirrored tube. In some cases these reflections can bounce from one end of the cable to the other dozens of times.

Problems occur because these reflections interfere with the detector in the DAC - this is the fundamental cause of cable jitter. For a more detailed discussion of this, please see this post on the Mad Scientist Audio Blog

Heretical Digital is Different.

Using carbon fibers as the signal conductor has some beneficial effects that far outweigh the lack of 75-ohmness:

Resistance : an HDC cable has around 37 ohms of resistance. A reflection that bounces off the DAC's input socket will travel the length of the cable and back again, thus experiencing around 75 ohms of resistance. As the DAC's input must be loaded with 75ohms, this causes the reflections to be strongly attenuated. What's more, reflections will not have the chance to bounce up and down the cable multiple times, as they will be simply turned to heat by the effect of the resistance.

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. And the higher harmonics are responsible for accurate bit transitions.

Heretical Digital Cable

Compatibility

Heretical Digital Cable works with the vast majority of sources and DACs, but there are a few combinations that it doesn't work with. It's very obvious - you either get no sound or clicks/pops. If this happens to you, please return the cable for a refund. Or alternatively, you can consider using as an analog interconnect (like the Heretical Analog Cable). Contact us if you run into problems with your system.

The reason that HDC doesn't work with some systems is due to the voltage loss. Because of it's high resistance, HDC consumes around one third (1 meter cable) to one half (1.5 meter cable) of the voltage that the source sends.

Normally this is no problem. The SPDIF standard is 0.5-0.6V output, with 0.2V min input voltage. However, not every device strictly adheres to this standard, so there are some combinations of source and DAC that do not work. We are working  to compile a list of combinations.

Prices and Options

Heretical Digital Cable is available in 1 meter and 1.5 meter lengths. They both sound the same, so no advantage to use a longer cable than needed.