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Bench Talk for Design Engineers

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Bench Talk for Design Engineers | The Official Blog of Mouser Electronics

Creating a Sound People Can't Resist: MELF Resistors Paul Golata

At age thirteen, I came home from school after music class and announced proudly, “I want to play the drums.” My parents quickly nixed any notions that I might have had about that idea and declared, “No you are not. They are way too noisy.” So I got myself a job and earned thirty-five dollars to buy an electric guitar and an amplifier. Thirty-five bucks for two pieces of gear, even in those days, did not buy anything but the lowest decile of sonic instrumentation. My parents were fine with my amplifier since it was the size of a small bread box and could hardly be heard. I would go on to save all my money so I could buy some real gear and promptly went out after seeing an Aerosmith concert at a hockey stadium-sized venue to procure 150 watts of rock-n-roll, smash- you-in-the-face, stomp-you-in-the-chest, kick-you-in-the-butt, aural power. My parents now wished they had let me get the drums. Hence, my long love affair with music and the never-ending search for tone.

As a Senior Technology Specialist, I am always interested and looking at the most advanced technologies and applications. When it comes to audio, I recently became aware of something that I had never really spent any time on considering, the ubiquitous resistor. I had soldered oodles of them on to various guitar effects and amplifier repairs over the years, but have never spent much real time investigating their sonic qualities.

Then, I heard about metal electrode leadless face (MELF) resistors produced by Vishay Intertechnology (https://www.mouser.com/new/vishay/vishay-melf/). High-end audiophiles always want to experience the playback exactly as recorded without any distortion. They are willing to go to great lengths and expense to ensure that their audio components are of the highest grade. MELF resistors can help in these high-end applications because they provide unique characteristics that are not found within the most common carbon, thin-film, and thick-film resistor arrangements. High-end audiophiles want their analog-to-digital converters (ADC) and digital-to-analog converters (DAC) and amplifiers to exhibit the lowest noise possible and be ultra-stable. MELFs delight audiophiles because they deliver low noise performance, uniform component design, excellent stability and precision, and best of all, they provide nearly ideal resistor performance – introducing essentially no discernable signal distortion to pass through. Compared to thick film resistors, MELFs typically offer an improvement in spectral density on the order of -40dBV/Hz and relative to thin-film resistors roughly -10dBV/Hz.

The first thing one notices when looking at a MELF resistor is that it is cylindrical. Its cylindrical nature does not cause any problems in the world of modern machinery for production operations; it is simply a matter of proper set-up and adjustments. Inside of the resistor is a homogenous film of metal alloy deposited onto a nickel chromium and aluminum oxide (Al2O3) ceramic body. The combination of materials employed in construction help these resistors perform with excellent long-term stability, reliability and temperature cycling. Nickel-plated steel termination caps are pressed upon ceramic rods, before a pulse-mode-driven Neodymium-Yttrium Aluminum Garnet (Nd-YAG) laser cuts a helical groove upon the metal-film resistive layer. The laser provides a very clean kerf with smooth edges, while not damaging the substrate in any way. This special care taken in the laser trimming process leads to low current noise and helps the MELF achieve its target resistance value with a very tight tolerance. All the advantages of a MELF do not come for free. MELFs cost slightly higher than your typical resistors. But if you are wanting to move on and experience the best that your ears can hear, consider MELF resistors in your next high-end audio design. That all said, I hope you continue to march to the beat of your own ear drums.

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Paul Golata joined Mouser Electronics in 2011. As a Senior Technology Specialist, Paul contributes to Mouser’s success through driving strategic leadership, tactical execution, and the overall product-line and marketing directions for advanced technology related products. He provides design engineers with the latest information and trends in electrical engineering by delivering unique and valuable technical content that facilitates and enhances Mouser Electronics as the preferred distributor of choice.

Before joining Mouser Electronics, Paul served in various manufacturing, marketing, and sales related roles for Hughes Aircraft Company, Melles Griot, Piper Jaffray, Balzers Optics, JDSU, and Arrow Electronics. He holds a BSEET from the DeVry Institute of Technology (Chicago, IL); an MBA from Pepperdine University (Malibu, CA); an MDiv w/BL from Southwestern Baptist Theological Seminary (Fort Worth, TX); and a PhD from Southwestern Baptist Theological Seminary (Fort Worth, TX).

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