ecp & Pickett Furniture Guitar Amplifier Prototype

This is another partnership with Pickett Furniture. The circuit uses a pretty standard 12AX7 based gain stage. It then uses a FET source follower into a 1:1 transformer as a phase splitter, and a fixed bias push-pull EL84 triode output stage for a couple of watts of power. Case is solid walnut. Speaker is AlNiCo from Weber.

DSHA-2 Headphone Amplifier

The DSHA-2 Headphone amp is almost ready for production, so I thought I'd post a few pictures.

Black Diamond Headphone Amplifier, Part 2

In Part 1 of this article, I detailed the theoretical background to the design. This part will detail the practical build process of the circuit as well as the enclosure.

The Circuit

The idea of the circuit is to use an input buffer, a step up interstage transformer for gain, and an output buffer. The circuit used for both buffers is a modification of the so-called Diamond Buffer that utilizes a servo to control for output DC offset. Everything is DC coupled.

Black Diamond Headphone Amplifier, Part 1

There are basically three methods of increasing signal voltage in an amplifier. The two most common are using transistors and tubes. Within those, there are obviously myriad different topologies and circuits. However, the third method, step up transformers, is much less commonly used. The only place they commonly show up are after moving coil phono cartridges, and low output microphones. And then only in quite expensive systems.

The Baby Frog -- A MOSFET Based Single Ended Transconductance Amplifier for Headphones

As I mentioned in the article about the Caged Frog pentode based transconductance amplifier, in a lot of ways, a pentode is pretty similar to a depletion mode MOSFET.

Modding the Melos SHA-1 Headphone Amplifier

 It was Corey Greenberg’s Stereophile review of the Melos and hearing an all Melos system at my local dealer that first piqued my interest. Indeed, a desire in the early 90’s to own one of these is part of what got me into headphones in the first place. At the time, unable to come up with the cash, I bought some Grado SR-80’s and a Headroom Little instead. I finally bought my Melos in 2003. But, it has been sitting unused in a closet for a number of years.