audioXpress May 2023. Tubes, Amplifiers, and Audio Electronics!

In this Glass Audio special issue, Menno van der Veen brings us his latest Vanderveen TRANS-PP80 Valve Amplifier, Tom Perazella remakes a famous (Z)OTL amplifier with 300Bs, and Peter Dieleman debunks recurring myths in tube circuit designs. Stuart Yaniger reviews the Hypex NCORE NCx500 amplifier module, while Burkhard Vogel expands his article on Vintage Op-Amp Noise Simulations, and Bruce E. Gillingham concludes its unique MB1 Monoblock Power Amplifier with Precision Bias Control.

Schiit Audio is promoting the 10-tube Folkvangr, its first limited-edition headphone amplifier. The first DC-coupled, output transformerless (OTL) and output capacitorless (OCL) headphone amp, Folkvangr also includes an 8X impedance multiplier to increase versatility with low-impedance headphones. Limited to a 250-piece run, the Folkvangr headphone amp is priced at $1799, including a full complement of input and output tubes.

More than a decade since the original publication by audioXpress, many readers still actively search for information and share the schematics of this OTL tube project. Tim Mellow's design explores a different output stage using a novel combination of local feedback and current drive in order to achieve good symmetry and cancellation of even harmonics. This article was originally published in audioXpress, February 2010.