Zesto Audio Announces Tube Stereo Power Amplifier with 3-Position Bias Switch

Zesto Audio, the Californian company founded by George Counnas, announced the launch of a new Class A amplifier design that offers an impressive 100 watts per channel (8 ohms) plus a unique feature of a three-position "Auto Bias Select" switch. In order to achieve its power rating, the new Bia 200 Select Stereo Power Amplifier is sold with four 12AU7 plus four matched KT150 output tubes. Thanks to the new auto bias switch, the amplifier is ready to safely accommodate KT88, KT120 and KT170 tubes, delivering options for all preferences.

Denon announced two new hifi components, the PMA-600NE Integrated Amplifier and DCD-600NE CD Player, enabling music aficionados with new options that deliver higher fidelity and improved connectivity at an accessible price. With carefully chosen components and reflecting Denon's more than 100 years' experience in the design and engineering of premium hifi products, the latest 600 series integrated amplifier with Bluetooth built-in and CD player are great options to begin building a system.

This simple single-ended amp project by Pete Millett is a great performer and a very well documented project that was immediately adopted by many DIY'er's. The amplifier achieves good power output and low distortion by employing “E-linear” feedback in the output stage. This article was published in audioXpress, April 2005.

Accurately setting the bias level for push-pull output stages is important to maximize amplifier performance and tube life. This circuit measures error relative to the target bias current and error relative to a balanced condition in the push-pull pair. The meter is compact, low-cost, simple, and accurate thanks to the use of a window comparator IC - a Linear Technology LTC1042. This article was originally published in audioXpress, July 2012.

When Noguchi, a Japanese audio transformer manufacturer, released its FINEMET core transformer FM-5P for less than $200, the author decided to try it in this four-parallel push-pull amplifier project. This article first appeared in the Japanese magazine Radio Technology, December 2011. It was published by audioXpress in March 2013.