Heathkit was a well known supplier of electronic kits from 1947 through the early 1990’s (although no new kits were developed after 1986). An incredible number of kits were offered including test equipment, amateur and SWL radio, audio, televisions, computers, robotics, automotive and other items difficult to categorize.
THD Improvement kit for IG-18 series audio generators
“The meter buffer is a crucial part of improving the THD specification of the IG-18. The non-linear loading of the analog output can create additional harmonic components due to the non-linearity of the diodes used to drive the meter.”
History and Antiquity
In 1947, Heath introduced its first electronic kit, an oscilloscope that sold for US$50 — the price was unbeatable at the time, and the oscilloscope went on to be a huge seller. Heathkit Wiki.
The Heathkit Virtual Museum, a tribute to the Heathkit era-a time when building electronic kits was a favorite pastime for many electronics hobbyists. This commemorative virtual showcase takes you back to the Heathkit age which began in the late 1940’s and lasted through the early 1990’s.
Then you ought to look around at Bill Wilkinson’s Heath Company Page if you want to know more.