Hewlett-Packard HP 331A Distortion Analyzer, Vintage EC

Description

Hewlett-Packard HP 331A Distortion Analyzer, Vintage
Excellent Condition
This highly collectible HP 331A Distortion Analyzer is in fine condition and was used periordically up until recently.  It still works well but would require calibration to be within exact published specifications.  It was never used in a "day-in, day-out" commercial situation, but rather was used sparingly through the years -- primarily measuring loudspeaker bass harmonic distortion -- and the instrument has been stored in air-conditioned space since new.  The HP 331 is mounted in an extremely sturdy, machined cast-aluminum chassis with side panels and with stainless-steel Posidriv machine screws throughout.  This cabinet is in nearly mint condition except for a small amount of label glue on the top-right edge of the front panel.  This could be removed if necessary for cosmetic purposes.  Otherwise, there are no scratches or other marks of any consequence.
The instrument includes a grounded power cord.  The 331A is very accurate and easy to use.
The HP 331A:
The HP 331A consists of a high-impedance broadband amplifier, a runable frequency rejection circuit and a metering circuit.  The solid-state rejection circuit utilizes a capacitively tuned Wien bridge network which provides greater than 80 dB of fundamental rejection.  Maximum input sensitivity at 0.1% distortion setting corresponds to 200 microVolt rms for measuring low-level residuals.  Input impedance is one megohm for both voltmeter and distortion operation with a single input terminal being used for both modes of operation.  The 331A has one notable feature: it uses precision Gear-Reduction Tuning.  The standard HP Operating Guide for this instrument is readily available in pdf format on the internet or from the seller
This fine instrument was for many years one of the industry standards for accurate harmonic-distortion measurement, and it has been known for its durable, reliable performance that lasts for decades of dependable operation.
Ref. HP-2101500