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 Caged Frog II-- A Pentode Based Differential Transconductance Amplifier for Headphones

Caged Frog ][

I really like transconductance amps for driving headphones. The first one I built, the Caged Frog, has remained a favorite of mine. Even the Baby Frog is great for what it is. But, since I have a definite preference these days for differential amps, the next obvious thing to do was make a differential gm amp.

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.

The Caged Frog -- A Pentode Based Transconductance Amplifier for Headphones

Caged Frog -- Single Ended Pentode

The truth of the matter is that after years of playing around with all kinds of single ended triode (S.E.T.) amps, I'm not sure that they are really my cup of tea. Sure, they do a some things really well, they have that sweet midrange after all, but some other things just never seem quite there. Indeed, I generally feel like they lack coherence when things get complicated. The usual alternative is push-pull, which certainly has it's place, and indeed a good differential circuit is hard to beat. But, there are other solutions as well.

One solution that is often ignored is the lowly pentode.

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. 

Low Voltage, All Tube, Guitar Amplifier for Headphones

I was browsing though some space charge tubes (these were tubes designed to operate at low voltages -- usually for car radios) recently and happened upon the 12K5 which is designated as a power output tetrode. I thought it might be useful for driving some headphones, and when I went looking, it turned out that others had been here before me.

The Electric Avenue: A Shunt Regulated, Single Feed, Spud Amplifier

I lived with my old single feed headphone amplifier, in one form or another, for a while. However, two events caused me to start rethinking the design.