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Taking the Hum out of High Fidelity – Magnetic Shields and Turntables

ITAR Certified Manufacturer April 2, 2018

Some years ago, a client approached us with an unusual magnetic shielding application. The chap was an audiophile. He had just purchased a Riga Planar 2 turntable with a Grado cartridge. As he played some vintage vinyl, his fine-tuned ear detected an audio hum. Noticing the Riga turntable had a direct drive motor under the platen, he correctly assumed magnetic radiation from the motor was inducing an AC current in the Grado cartridge.

Audio Joe (we’ll call him), reached out, and got us thinking about his request. Mumetal Magnetic shielding seemed like it would be a simple fix. So, we laser cut a 12” diameter x .006” thick mumetal with a ¼” diameter center hole to engage with the turntable spindle – much like the platter tray and vinyl records driven by once antiquated, but now feverously popular turntables. Placing the mumetal on the platter under the Audio Joe’s slipmat worked like magic. The hum was gone – and the audio permeating from that system was pristine.

The physics is simple. The mumetal piece absorbed the magnetic interference preventing the induced current in the Grado cartridge.

Following this initial query from Audio Joe, MuShield has since sold a fair number of turntable shields through a now defunct stereo store in the Chicago area. That said, we’ve still got the shields in production and readily available for those experiencing similar audio hums. It’s easy to experience exactly what Audio Joe did because of the mixing and matching of “retro” vs. contemporary components.

The vinyl boom has legs. It’s not a flash in the pan. In fact, as has been the case for the last half-dozen years or so, vinyl sales are on an upward tick sales-wise and have outpaced some of the market’s other formats. Yearly vinyl album sales from 2017 hit another Nielsen Music-era record high, selling 14.32 million units – up 9% from 2016 which registered 13.1 million units sold and 53% higher than 2015. In short – tangible music has become cool again.

With the recorded music industry getting all nostalgic on us and vinyl becoming the go to option, and further, big box stores like Best Buy pushing records over CDs (in fact, Best Buy just announced they’ll be discontinuing the sale of CDs come summer 2018 – but Vinyl will remain – heck even cassettes are getting popular again – up 35% in 2017!), your turntable may be emitting the same annoying hum. If that’s the case, reach out to us about our turntable magnetic shield! We’ll make that rich, warm sound POP (and we’re not talking about the pops that are the product of the grit, grime, and wear within the grooves of all the records you just pulled down from the attic…)


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