Audio Research Reference 75 power amplifier Specifications

Sidebar 1: Specifications

Description: Tubed power amplifier. Tube complement: four KT120, two 6H30. Maximum output power: 75Wpc continuous, 20Hz–20kHz (18.75dBW into 8 ohms). Total harmonic distortion (1kHz): typically 0.6% at 75W, <0.05% at 1W. Power bandwidth: –3dB, 7Hz–60kHz. Frequency response at 1W: 0.7Hz–75kHz, –3dB. Input sensitivity: 1.4V RMS, balanced, for rated output (25dB balanced gain into 8 ohms). Input impedance: 300k ohms, balanced. Slew rate: 10V/µs. Risetime: 4µs. Power-supply energy storage: ca 520 joules.
Dimensions: 19" (483mm) W by 8.75" (222mm) H by 19.5" (495mm) D. Handles extend another 1.5" (38mm) forward. Weight: 47 lbs. (21.3kg) net, 63 lbs (28.6kg) shipping.
Finishes: Silver, Black.
Serial number of unit reviewed: 22306601.
Price: $9000. Approximate number of dealers: 55.
Manufacturer: Audio Research Corporation, 3900 Annapolis Lane N., Plymouth, MN 55447-5447. Tel: (763) 577-9700. Fax: (763) 577-0323. Web:

Audio Research Corporation
3900 Annapolis Lane N.
Plymouth, MN 55447-5447
(763) 577-9700

volvic's picture

I have gone to a lot of shows and heard a lot of equipment costing hundreds of thousands but the one system that still sticks in my mind was an all Audio Research back end complete with CD player and Verity Audio speakers at the Montreal Hi-Fi show several years back.  The 3-D effect, seperation of instruments, transients, etc, etc wasn't matched by any other equipment including the venerable MBL's.  Reading Mr. Reina's excellent review last month confirmed my experience but also brought me back to that day in Montreal.   

lambrostuff's picture

An "Ultra-linear" Ciruit using KT120 beam power pentodes --  AKA, a Williamson Circuit design, these amps have the screen grids fed from a primary tap on the output transformers as opposed to fixed screen grid voltage.  The biggest enemy in these AB biased amps is Crossover Distortion and heat.   

Interestly many years ago, there had been listening challenges comparing the sound of the Harmon Kardon Citation II against the highly efficient Class B Unity Coupled circuit McIntosh MC-275.  The even-order harmonic distortion of  the ultra-linear Citation II was so pleasing to the ear, it presented a more lively musical experience than the low distortion MC-275.  Most listeners may have loved what they were hearing, but a graphic test sweeping the 20 to 20 khz audio spectrum at full output power showed the Citation's Ultra-Linear circuit to be a "Train Wreck" compared to the clean, cool running Mac Unity Coupled circuit.  Judge for yourself!