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. 

D3a Experimenter's Printed Circuit Board

This project is a circuit board which, through various jumpers, can be configured for various circuits. Specifically, it is designed around the D3a vacuum tube, a high Gm, high mu pentode. Additionally, there are several other tubes such as the E180F and E810F that share the pin arrangement with the D3a allowing their utilization as well. 

All 7-pin Tube Based Phonostage

This began as a simple project to build a cheap phono stage for a very old turntable with a cheap cartridge out of parts on hand. However, it turned into a pretty good project that definitely outclasses the rest of my analog setup. Oh well, at least it was pretty cheap to build.

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.