Author: Karsten Hein
Tag(s): Power Amplifiers
Looking at some modern amplifier designs, one might think that the process of signal amplification is infinitely complex and requires lots of patented electronic components and integrated circuits for signal enhancement and sound shaping. It may therefore seem counter-intuitive that some of the best-sounding amplifier designs have taken the opposite approach, following a less-is-more philosophy. Audiophile listeners believe that each additional part in the signal path leads to a deterioration of the original signal. It was out of this understanding that the developer of the Sanken Class-A/B amplifier presented here started his project.
Sanken have an excellent name for building quality transistors and contributed to some legendary amplifier designs, such as the Japan-made Luxman L-10 model of 1976-1982. The Sanken 2SC3519A therefore came as a natural choice and are able to handle currents of 15 amperes and maximum operating temperatures of up to 150° centigrade, just in case the operating temperature should ever be an issue. This project's aim was to build a powerful and tonally correct linear amplifier that delivered lots of clean power with ease. An optional three-band parametric equaliser was to allow for exact tonal adjustment to accommodate the room and the loudspeakers, if doing so should become at all necessary.
The Aschaffenburg, Germany based developer was neither new to the industry nor was this his first amplifier design. On the new Class A/B design, he started out from a generous 250 VA toroidal transformer paired with high-quality capacitors as power supply. There was one amplifier board per channel with each holding four Sanken 2SC3519A transistors. In the amp's prototype version, the transistors were mounted on two overly large heat sinks that were a total of three rack slots high. While the amp itself would also have fit into a two-slot housing, starting from the larger cabinet was more practical when making last-minute changes to the design. Given the size of the heat sinks, the amplifier did not become warm, not even in combination with our 83dB low-sensitivity 4 Ohm Epicure 3.0 speakers.
11 Nov 2022 — Listening Test 1:
Turning on the Sanken Class-A/B amplifier for the first time, I immediately noticed that it provided far stronger amplification than our existing Hafler, B&W, and Dynavox power amplifiers. At 160 WPC, the Sanken was also the strongest amp in our range, offering 15 watts per channel more power than our Hafler XL280 amplifier. The Sanken’s input sensitivity was set at 1.4 volts, and its ultra-strong amplification reminded me of amplifiers from Quad which similarly appeared to be brimming with energy. Bass was exceptionally tight, and this reminded me of the H&S Exceptional tested some time ago. Indeed, the developer confirmed that the damping factor should be near 800:1. The Sanken amp provided lots of effortless control which worked well with our power-hungry Epicure 3.0.
There was lots of attack and crescendo. The music was able to free itself from the speakers better than with our Hafler amp and was thrust more deeply into the room. The resulting musical experience felt more intense and immediate. The sound was dry and, in combination with the Epicure, maintained a solid centre image. The sound was tonally rich with sufficient but not overly presented high frequency resolution. The sound was captivating and easy to listen to over long periods of time. The parametric equaliser had not yet been connected, but I did not feel the need to make any adjustments during my test.
Although I enjoyed listening to the amplifier a lot, its strong amplification served to highlight a weakness in our Dynaco PAS-4 preamplifier. Some weeks earlier, the Dynaco had begun producing a mild hissing sound. This proved to be borderline unbearable in combination with the Sanken Class-A/B amplifier, and has led me to have the Dynaco serviced. On occasion I noticed distortion that sounded like overdrive-clipping. At first, I thought that the clipping might have been present in the music, but when it appeared again, I was not so sure. And, upon restarting the amp without giving it a longer break, I noticed a recurring inner vibration that seemed to fade in and out. This might have been caused by the large transformer. But as I was not sure this was a strictly mechanical effect, I thought it best to list it here.