Ground hash

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No, the headline does not reference chewed corned beef or cut up cannabis, but it does refer to that which makes for bad sound in digital audio. Ground and power supply contamination are one of the toughest problems designers face; an invisible killer of sound quality.

The term ground came from the the humblest of beginnings, the earth we stand on. This is because most everything else is in a more charged state. If you drive a metal stake into the ground it becomes an anchor for higher potential electrical energy, like lightning, static electricity, or power from the utility pole. In our equipment, ground is the return path for musical signals. Think of a battery operated device like your mobile phone. Inside is a battery with both + and – terminals. Ground is typically the – of the battery and all things reference to this point. The + terminal is at a higher potential, with power flowing to ground through the circuit inside.

When we design products we use ground to reference everything: the chassis, the input and output connectors, the power supply and circuit itself. We imagine ground as the lowest point in our perfect circuit, but then reality creeps and it isn’t exactly what we had supposed. When ground is contaminated or raised above zero, it changes the musical signal by adding unwelcome noise, hash or modulation.

You’ve read recent news of accessories like USB regenerators? DACs using them sound better because of the superior noise isolation they provide.

Our Digital Lens of many years ago suffered from ground hash; noise from digital circuitry and power supplies in transports leaking through inputs. Like a virus, once inside they spread, wreaking sonic havoc that cannot easily be eliminated. Our first thoughts at purging the invasive noise was to separate power supplies, one for the input circuitry, the other specific to the output. This helped but not enough – because power supplies must all be tied together through common grounds.

The solution came from building separate input and output circuit boards with 100% galvanic isolation – which means no common anything, including grounds or electrically connected signals. We achieved this by using fiber optics with light the only connection between boards. Once we figured out how to make all this work, we had a near perfect digital isolation device that regenerated digital audio and almost eliminated the need for better transports. But not entirely – perfection an illusory goal, even today.