L-8000 DHT

Description

In the early years of the last century, the directly heated triode (DHT) was invented independently, and almost simultaneously, in the USA and Austria. This simple device, an anode, a cathode and a grid in a vacuum contained in a glass bottle, transformed the world. Over one hundred years later, the very first triode remains a favourite audio amplification device for devoted music lovers worldwide.

Debate about the quality of the DHT’s sound reproduction potential continues even today. One of the interesting aspects of these debates is the degree to which they ignore analysis of common, fundamental assumptions about DHTs. Those assumptions are based on many decades of circuit and mechanical experimentation and compromise. Indeed, because of the difficulty of using DHTs for audio, many circuit design issues have evolved into assumptions about the audio characteristics of DHTs themselves.

Allnic’s Mr. Kang Su Park has spent a lifetime studying and designing circuits and transformers for use of DHTs in audio reproduction. Mr. Park has questioned basic assumptions about DHTs, re-examined variations of DHT circuit designs, and researched and experimented rigorously. His work has resulted in some remarkable audio power amplification devices. For example, Allnic’s 300B amplifiers produce significantly more power than normally expected. They do this without shortening tube life because the power increase is not achieved by increased bias. In conjunction with an increase in power, Mr. Park’s 300B amplifiers also have exceptionally low distortion and wide bandwidth.

Mr. Park successfully combined elements of what he learned and invented over decades to the development and production of a pure, direct heated triode (DHT) based amplifier and preamplifier: the A-5000 and L-5000, respectively. The main breakthrough was the design of a circuit, valve and transformer combination with astounding measured results. The purity of its square wave reproduction – as perfect as anything he had ever seen from a DHT valve amplification circuit – had him questioning what he was seeing! Of course, he replicated these tests many times and recorded them and their results before assuring himself that there was no mistake.

With such an unprecedented superior outcome for the circuit design, Mr. Park could not be satisfied placing a DHT stage after one or two stages using indirectly heated triodes. That approach is used in a number of commercially available preamplifiers using DHTs, but it is a compromise. It does not result in PURE DHT amplification. It introduces the characteristics of indirectly heated triode sound into the circuit. The output DHTs are only amplifying a signal already determined by the initial stage indirectly heated triodes. In contrast, Mr. Park created an amplifier and a preamplifier that use DHTs at each amplification stage. In his design, the output stage DHTs do not merely amplify the signal from indirectly heated triode stages. The L-8000 DHT preamplifier are pure DHT, from signal input to output.

Remote control included.