Roasting for fidelity

Roasting for fidelity

June 24, 2015
Paul Haworth

My dad was a broadcast engineer for 40 years. Today, his workshop looks exactly the same as it always has. There are homemade oscillators plugged into cathode ray scopes, various tube type radios stacked in columns, and tiny electronic components littering every square inch of desk space. He may be retired, but he is still building and researching with the same passion that got him started in radio as a teenager.

Another thing that hasn’t changed is what he pursues in his craft, even in the form of a hobby. Quality in audio modulation, transmission, reception, and amplification is all expressed in one word: fidelity. For the majority of his working life, my dad has been chasing audio fidelity in its many forms. Simply put, fidelity is the measurement of sameness that a reproduced sound has with its prototype.


When I was a kid, I couldn’t understand what my dad had against certain types of music. I learned quickly that he was uninterested in listening to anything that included the electric guitar. What I didn’t get until he explained much later was that his aversion was less about the music and more about the sine wave.

Over the years, he had trained his ears to listen for distortions like square and saw-tooth waves as indicators of serious circuitry problems. When a guitar amplifier is ‘over-driven’ it intentionally produces these types of waveform distortions. This timbre is sought after in rock and roll but can be like fingernails on a blackboard to engineers like my father.


In the world of coffee sourcing, a sample roasted too dark will stain the palate and render a coffee tasting all but ineffective. The qualities of a coffee that make it most noteworthy will be masked and eventually lost when the intense chemical changes associated with dark roasting are introduced. Learning how to develop a coffee’s aromatics without allowing this to happen is the goal. It is this form of fidelity that I decided years ago needed to be included not only in sample batches being roasted for tasting and selection, but also those intended for my customers.

A lot of folks ask me why I don’t roast coffee darker than I do. It is similar to asking my dad why he doesn’t like electric guitar. I generally try to answer the question as graciously as he would, with a statement about how my training dictates my craft. For those looking for ‘over-modulated’ coffee, there are plenty of roasters out there who can provide what you need. At Cartel, however, we have chosen the path of fidelity.