K-AMP
Frequently Asked Questions

Q What Do K-AMP Hearing Aids Do?
A K-AMP circuits offer level-dependent progressive frequency response (greater treble boost for quiet sounds). When the K-AMP circuit was introduced in 1989, it was (and still is) the only amplifier that combines wide dynamic range compression (WDRC) with the following features:

  • A single-channel circuit that performs like a multi-band compressor. In the original K-AMP circuit (TILL version) there is a compression ratio of 1.3:1 in the low frequencies and a compression ratio of 2.1:1 in the highs. The programmable K-AMP can be programmed up to 3:1 in the highs.
  • Variable recovery time which provides instant recovery from hand claps and door slams, and slow recovery for normal sounds to eliminate pumping.
  • Clean, undistorted operation even at inputs up to 110 dB SPL. At 90 dB SPL input, the K-AMP has essentially zero-noise and zero-distortion out to 13 kHz (a coherence of 1.0). No other circuit can make this claim.

Q Who Is A Candidate For K-AMP Circuitry?
AThe standard version of the K-AMP is for persons with mild-to-moderate high frequency hearing loss. The K-AMP circuit was developed for those who report that they only need hearing aids when people speak softly. Gain for loud sounds is usually not necessary. However, persons with moderate-to-severe hearing loss may require some gain for loud sounds; these persons are candidates for the higher power, higher gain version of the K-AMP hearing aid.

Q What Makes K-AMP Hearing Aids High Fidelity?
A K-AMP hearing aids were the first (and are still the only) hearing aids to offer the option of a full-fidelity (50-16,000 Hz) bandwidth. This range covers the high frequency sounds of speech like /s/ and /t/ that contribute to clarity, and all the harmonics that give music its characteristic tone colors. A piano trio heard through full-fidelity K-AMP hearing aids sounds like the original, complete with the crisp sound of cymbals.

Q What Is The Difference Between K-AMP WDRC and Other WDRC?
A In order to determine how much gain to provide, all compressors require a level-detection circuit. The K-AMP uses rms detection, which provides a more accurate estimate of signal energy (loudness) than either peak detection or average detection used in other circuits.

Q What About The K-AMP Circuit And Musical Performance?
A At one time symphony musicians would never be seen wearing hearing aids. Now several members of the Chicago Symphony Orchestra wear K-AMP hearing aids full time. The K-AMP circuit will not audibly distort during live performances even if worn by the performer. All other circuits fail (analog or digital and regardless of price) due to overload distortion. Some hearing aids become so intolerable that they must be removed to allow proper musical performance.

"I have been working with hard of hearing musicians for over a decade, and of the last 200 hearing aid fittings on musicians, 180 of them [90%] were K-AMPs. Musicians seem to like the low distortion levels of the K-AMP in high-volume environments. Perhaps it has to do with the high input limiting level of the K-AMP that distinguishes it from other hearing aids, including digital products."
Marshall Chasin
Director of Auditory Research
Musicians' Clinics of Canada

Note: Chasin also asked 65 musicians to compare digital aids and K-AMP aids. Eighty-two percent preferred K-AMP circuitry. Of those, twelve percent noticed no difference but chose K-AMPs based on cost.

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