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Selling a Harman/Kardon HK725 Ultrawideband Stereo Preamplifier. This unit has been a part of my hi/fi system for some time until recently replaced it with a newer system. Its’ condition is excellent. I just had the power button replaced as the old one felt loose. It was checked out and deemed in perfect health.The Harman / Kardon hk725 Ultrawideband Stereo Preamplifier is renowned for its superior sound quality and timeless design. This preamplifier unit is perfect for audiophiles seeking exceptional performance.This is a high-end Japanese made amp from 1980 designed by Finnish audio guru Matti Otala, and putting into practice his research into transient intermodulation, and intermittent impulse modulation - the result is a sophisticated ultrawideband pre-amp that produces beautiful and dynamic sound - able to articulate complex tonal and harmonic information with superb stereo imaging and separation. A slightly more compact preamplifier than others - a matte silver front panel with an array of square button controls. These employ fixed resistors for tone controls rather than the standard design approach of potentiometers - this allows for true bypass in the defeat position.The phono stage is comprised of 8 stages - the phono signal is equalized to match the RIAA curve - an inverse process required to restore the signal for accurate reproduction. The record cutting lathe magnifies treble information and minimizes bass information to meet physical constraints of vinyl real estate on a record. Many phono stages roll off this curve below 20Hz and above 20,000Hz - here the equalization curve is met above and beyond audible range - ensuring absolute fidelity with deep controlled bass and transparent highsKey Features:Pristine Sound: Enjoy crystal-clear audio with an incredibly low distortion rate.Versatile Connectivity: Multiple input options to connect all your favorite devices.Robust Build: Durable construction ensuring longevity and consistent performance.Specifications:Frequency Response: 1Hz to 150kHzTotal Harmonic Distortion: 0.005%Input Sensitivity: 2.3mV (MM), 145mV (line)Signal-to-Noise Ratio: 90dB (MM), 106dB (line)Dimensions: 385 x 72.5 x 320mmWeight: 4.2kgNumber of Inputs: Phono MM, Line, Tuner, AUX, Tape Play 1, 2Number of Outputs: Tape Rec 1, 2, Tape Rec DIN, HeadphonesTone Control: Bass ± 8 dB at 100 Hz, Treble ± 8 dB at 10 kHz, Loudness + 10 dB at 50 Hz, High Filter 6 kHz, Low Filter 15 HzSpecial Features: DC coupling, specially designed phono stage, ultrawideband response
# Harman Kardon HK725 Preamplifier – Buyer Notes
The HK725 is a solid mid-tier preamp from Harman Kardon's golden era, built to integrate well with vintage separates systems. Asking USD $300 sits comfortably at the median of your own comparable listings (USD $208 median, USD $117–USD $480 range), landing it squarely in fair-market territory. Vintage preamps of this caliber—assuming clean output and functioning phono stage—typically hold value around USD $250–USD $350 in working condition, so this isn't a steal, but it's not inflated either. The 1983 vintage means solid engineering but age-appropriate wear; condition and cosmetics matter here.
Before committing, verify the output levels haven't drifted (hum and noise floors should be nearly silent), test all input selectors and the volume pot for crackling or dead zones, and confirm the phono preamp (if equipped) tracks properly across both channels. Ask the seller for the original manual and whether any capacitors have been recapped—a 40-year-old unit almost certainly needs attention to coupling caps and power supply electrolytics. Confirm all RCA connectors are present and undamaged, and that it's been stored in a non-humid environment.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Harman Kardon traces its origins to 1953, when Dr. Sidney Harman and Bernard Kardon, both engineers frustrated with conservative audio manufacturing at the David Bogen Company, invested $5,000 each to launch their venture in Westbury, New York. Their debut product, the Festival D1000, became the world's first compact AM/FM hi-fi receiver, blending breakthrough technology with sleek design to make high-fidelity sound accessible beyond technical enthusiasts. Pioneering innovations like the 1958 Festival TA230 stereo receiver, the 1959 Citation II ultra-wide bandwidth tube amplifier, and the 1970 CAD5 hi-fi cassette recorder with Dolby noise reduction cemented their legacy in simplifying premium audio for the home.
The brand focuses on integrated receivers, amplifiers, tuners, and speakers that emphasize performance, reliability, and elegant industrial design. Over decades, it expanded into home theater systems and automotive audio, powering systems in vehicles from Land Rover and BMW to Volvo and Polestar. While not delving into turntables, DACs, headphones, or cables, Harman Kardon prioritizes cohesive hi-fi components that deliver warm, detailed sound without unnecessary complexity.
Harman Kardon holds a solid mid-tier position in the hi-fi market, renowned among knowledgeable buyers for its enduring quality and value rather than ultra-high-end exotica or vintage collector status. Now part of Harman International, it appeals to discerning listeners seeking dependable, stylish gear that echoes its innovative heritage without commanding boutique premiums.
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