This page is authored by W. Marshall Leach, Jr.
LSR&D: In the latter 1970s, three engineers who worked at the Georgia Tech Research Institute approached me with the idea of forming a company to manufacture and market audio power amplifiers. This was the beginning of LSR&D, Inc. The letters L, S, R, and D were the first letter of the last name of the original four partners. One of the partners soon dropped out, but he was replaced soon after that. Our first product was a stereo amplifier which we called "The Leach Amp." It was rated at 160 watts per channel into 8 ohms. It was based on a circuit which I had published in Audio Magazine in 1976 and1977 in two papers titled "Build a Low TIM Amplifier." The earliest LSR&D amplifiers can be identified by a dark colored E-I core transformer immediately behind the front panel to the right of the switch. We soon replaced this transformer with two round toroid transformers. Although the toroid transformers were lighter, I always thought that the E-I core transformers made a "stiffer" power supply. A mono amplifier was introduced later. We called it "The Leach Superamp." It was based on a circuit I published in Audio Magazine in 1980 titled "Build a Double Barrelled Amplifier." The Superamp was rated at 300 watts into 8 ohms. Our company went out of business in the mid 1980s. The three things that doomed us were financing, marketing, and squabbling among partners. The two links below contain circuit diagrams and servicing hints for the two amplifiers. Unfortunately, I do not have a parts layout for the circuit board. I don't have any of the LSR&D amplifiers, but I work with someone who has managed to collect several of them.
Electronics One: In the early/mid 1970s, a former student of mine who was working part time at the company Electronics One, Inc. contacted me about manufacturing an audio amplifier I had been working on. Electronics One was a very small company consisting on one engineer, one technician, and part-time help when needed. The company offered electronics consulting services and it manufactured small-scale electronic components and systems under contract with customers. I signed an agreement to allow Electronics One manufacture and sell audio amplifiers based on circuits I had published in Audio Magazine. These were stereo amplifiers rated at 100 watts per channel and were called "Leach LNF-1 Amplifier" and "Leach LNF-1A Amplifier." The LNF-1 models were housed in a shoe-box style chassis. The LNF-1A models were in a rack-mount chassis. I don't think that the company was ever financially sound because of the uncertainty of the contract electronics business. The owner was looking for a product, and he hoped the amplifiers would fill that need. But the company failed and the owner sold it sometime in the latter 1970s. It had closed, vacated its building, and the owner had left town before I knew anything about the failure. The drawings linked below are all I have on these amplifiers. There are some modifications that I recommend to improve reliability. I have the prototype Electronics One LNF-1 and LNF-1A amplifiers in my lab and both are still working after all of these years.
I have seen two LNF-1A amplifiers sold on Ebay which had an auxiliary circuit boards mounted inside the chassis to convert the stereo amplifier into a strapped mono amplifier. I never knew that any amplifiers were sold with this modification. I recommend removal of the auxiliary circuit boards and operating the amplifiers as stereo amplifiers.
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