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VPG's Through-Hole Z-Foil Resistors for Audio Applications Combine TCR From 0.05 ppm/°C With Low Microphonic noise
MALVERN, Pa. — Nov. 12, 2013 — Vishay Precision Group, Inc. (NYSE: VPG) today announced that its Vishay Foil Resistors brand (VFR) has introduced a new series of ultra-high-precision, through-hole Z-Foil resistors designed to provide low noise and low inductance/capacitance for high-end audio applications requiring distortion-free properties. The conformally coated, low-profile AUR series devices feature low TCR down to 0.05 ppm/°C nominal from 0°C to +60°C, +25°C ref, tolerances down to ±0.01%, and load-life stability to ±0.01% after 2,000 hours at  +70°C.
In high-end audio equipment, careful selection of resistors is one of the best ways to minimize noise and distortion in the signal path. The typical audio amplifier consists of a voltage preamplifier and power amplifier. The voltage preamplifier deals with low-level signals, making the intrinsic noise of resistors critical, while the power amplifier requires high linearity of amplification and minimal dynamic distortion. Bulk Metal® Foil AUR devices meet both of these needs thanks to their cold-rolled metal alloy foil. Their construction eliminates any current noise in the element itself, and provides the linearity that preserves signal integrity with no clipping or roll-off at signal extremes.
AUR devices also feature a special "noise-free" design, with special in-house stabilization, providing an additional dimension for reducing signal distortion and increasing clarity in signal processing. Furthermore, the current in adjacent current-carrying paths runs in opposing directions, cancelling the paths' parasitic inductance. Path-to-path capacitances are connected in series, minimizing the parasitic capacitance of the resistor.
"Many users of precision audio equipment suffer needlessly from unexplained instabilities and drifts due to noise effects and harmonic distortion. They resign themselves to making constant adjustments and troubleshooting, but in fact these can be avoided," said Yuval Hernik, senior director of application engineering for VFR. "Instability is often traceable to a few supposedly fixed resistors, which are not really fixed at all. If these resistors would only retain their original values, there would be no need for costly controls and other compensating circuitry. That’s why Bulk Metal Z-Foil resistors are the only devices for applications such as these."
“Microphonic noise is a parasitic effect mostly associated with surface-mounted resistors. The plane of the mounted resistive element is parallel to the board, by which vibrational movement induces spurious signals in much the same way as a diaphragm in a speaker system," added Hernik. "The horizontal resistor element produces the same microphonic effect, whether caused by physical vibration of the board or by strong sonic waves impinging on it”
The AUR series offers a resistance range from 5 Ω to 120 kΩ. Any conceivable ohmic value within this range, to six digits, is available with no additional cost or lead time effect. The resistors feature rated power to 300 mW at +70°C, a maximum working voltage of 300 V, a rise time of 1 ns with effectively no ringing, current noise of  < 0.010 μVrms/V of applied voltage (< -40 dB), a thermal stabilization time of < 1 s (within 10 ppm of steady state value), and a voltage coefficient of < 0.1 ppm/V.
"Particularly in high-precision audio applications, the best resistor choice is often a through-hole device that is specifically designed to provide higher resistance values, higher power, tighter tolerances, and better long-term stability, while requiring less board space and allowing the clean-up of solvents and resins," added Hernik. "Through-hole devices achieve better stability because they are not subjected to thermo-mechanical stresses from the PCB. And unlike other through-hole resistors, the AUR devices require no added height for stress-relieving bends in the leads, as they feature built-in stress relief."
Samples and production quantities of the AUR series are available now, with lead times of two weeks  for samples, and eight weeks for standard orders.
Further information about the AUR series and other Vishay Foil Resistors products is available at www.vishayfoilresistors.com. Follow Vishay Foil Resistors at http://twitter.com/foilresistor.
About Vishay Precision Group
Vishay Precision Group (VPG) is an internationally recognized designer, manufacturer and marketer of: components based on its resistive foil technology; sensors; and sensor-based systems specializing in the growing markets of stress, force, weight, pressure, and current measurements. VPG is a market leader of Foil Technology Products, providing ongoing technology innovations in precision foil resistors and foil strain gages, which are the foundation of the Company’s Force Sensors Products and its Weighing and Control Systems. The product portfolio consists of a variety of well-established brand names recognized for precision and quality in the marketplace. To learn more, visit VPG at www.vishaypg.com.
About VPG Foil Resistors
VPG Foil Resistors, a part of Vishay Precision Group (VPG), produces the most precise and stable resistors available. Distinguished by the premier brands Vishay Foil Resistors, Powertron, and Alpha Electronics, the VPG Foil Resistors portfolio includes discrete resistors and resistor networks in surface mount and through-hole (fixed-lead) configurations; customized chip resistor networks; precision trimming potentiometers; and discrete chips for use in hybrid circuits. These devices are used in applications requiring a high degree of precision and stability, such as in medical testing equipment, semiconductor equipment, precision measuring instruments, aerospace, and military applications. To learn more, visit www.vishayfoilresistors.com.
Bulk Metal is a registered trademark of Vishay Precision Group, Inc.