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.

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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.