PACO SA-40
Forty watts, fourteen inputs, and a ninety-page manual that assumes you've never held a soldering iron.
Overview
The SA-40 is a stereo preamp-amplifier kit, and it was the first of PACO's component high-fidelity offerings. It puts two complete preamplifier-control sections and two 20-watt power amplifiers on a single chassis, in a gold and satin black case with a satin gold panel. The pitch was simple. Buy the kit for $79.95, or the factory-wired version for $129.95, and skip the stack of separate cabinets. PACO was the kit division of Precision Apparatus Co., a firm with a quarter century of laboratory-instrument manufacturing behind it. Buyers in 1959 were meant to read that as reassurance.
The numbers are respectable for the period, and honestly stated. Each channel delivers a true 20 watts, 40 watts total. The power supply is well-regulated and low-impedance, so PACO claimed the amplifiers would not clip even on sustained high-level passages. The main feedback circuit eliminates phase-shifting components, which helps stability. Distortion is quoted within 0.5% at 20W per channel - High Fidelity (September 1961, p.22) carried the same figure in PACO's advertising - and frequency response runs 30 cps to 90 Kc within 1.0 dB. That bandwidth looks almost absurd for 1959, but it's the number PACO put in print, and the period coverage repeated it.
The input complement is where the SA-40 earns its keep. Fourteen inputs and fourteen panel controls sounds like a typo until you look at the rear apron: Aux 1, Aux 2, Tuner, Phono 1, Phono 2, Tape head, and Mic. The two separate phono inputs are the useful part - one for the record changer, one for the manual turntable, no cable swapping. The auxiliary inputs take high-level signals, and a TV set was the example the period coverage kept reaching for. The mode switch is where the stereo-era thinking shows. Bal Right and Bal Left mute one speaker at a time so you can compare channel volumes by ear, Stereo Reverse flips the channels, and Mono combines the preamplifiers so a mono record played through a stereo cartridge comes out of both speakers. A Contour switch boosts bass when the Loudness knob is run low, compensating for the ear's falling response at low levels. Bass and treble are each dual concentrically mounted controls, adjustable in unison. A two-position equalization switch selects RIAA or old LP and 78 rpm. It also equalizes 3¾ or 7½ tape speed if a tape head is fed to the proper input.
Construction is the other half of the story, and the SA-40 is unusually considerate here. The 90-page manual assumes a rank beginner and devotes a large section to soldering technique, with types of solder, irons, and clear photos. The clever bit is a staged power-up. Wire the two power amplifiers and the power supply first, hook a speaker to the output, feed a signal from a tuner or crystal cartridge to the input, and confirm it sounds good before moving on to the preamplifiers. The reviewer wished that approach were more common. Printed circuits handle the tone and equalizer sections, ground points are deliberately centralized, and shielded cables connect to the chassis at just one end. The same reviewer's listening tests ended in a plain verdict: a Good Buy.
Kit builders were warned to have at least some kit experience before tackling this one. It's extensive even if it isn't difficult. PACO's own advertising ran a testimonial from a Huntington Station, New York builder who claimed the SA-40 took him a third less time than a nearly identical preamp-amplifier from another kit maker. He credited Paco's pictured-and-labelled parts, resistors mounted on cards for identification, and fold-out diagrams placed beside the instructions rather than buried elsewhere in the book. Take the timing claim as advertising rather than measurement. The documentation quality is what keeps turning up in period accounts.
One caution for anyone chasing one today: the SA-40 is a kit, and kit-built units are only as good as the person who built them. Cold joints, miswired grounds, and the occasional resistor installed by someone who didn't read the color code are all part of the used market. The factory-wired version sidesteps that, which is presumably why it cost $50 more. Values on either version are not well documented, so treat pricing claims with skepticism. What is documented is the design intent: a true 20 watts per channel from a regulated supply, fourteen inputs, and a manual written for someone who has never soldered before.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.