Willow Revisited: A Design Celebrating the Enthusiasm and the Creativity of the Builder

audioXpress December 2011 introduced readers to Willow, a “proof-of-concept” project featuring a PMBF4393 JFET and HA5002 buffered preamp, built as a companion to the author's 5002 power amp, and the first to use this typology. After considerable positive DIYer feedback, the Willow was revised and updated, and this article, Willow Revisited was published in February 2016. More recently, audioXpress January 2018 features another revised and much perfected take on this tube hybrid design - the new 6922 Amplifier, where author Robert Nance Dee states he "saved the best for last."
 
But since the first Willow project was already available online, we thought our readers would like to recap the Willow Revisited as well before exploring the author's latest 6922 design.

This original 2011 Willow amplifier project generated great feedback from audioXpress readers. This motivated the author to continue to work on the project, replacing the obsolete HA-5002 buffer with the TI LM49600, improving the power supply and the input to the buffer circuit. “I especially wanted to make the amplifier as quiet as possible and have it be flexible so that those who want to avoid microcontrollers could still experiment with the design. After all, this is an amplifier for the DIY community and I enjoy seeing what can be done with my designs,” says Robert Nance Dee.
 
In its final remarks about the Willow Revisited, Robert Nance Dee writes, "I will say that if you like tube amps give this a try. It has a smoothness but with great detail. Do the changes make a better overall amplifier? Yes, I believe very much so. I could give you a lot of specs but what does that really mean and how does it equate to sound, musicality, or the sheer joy of building something that rivals many amplifiers regardless of price?"

This article, originally published in audioXpress, February 2016, is now available online.

An updated gain display board and new bill of materials (BOM) can be found in the Supplementary Material section of the audioXpress website.