Portable Triode Headphone Amplifier

A portable Triode Headphone Amplifier is rather a unique piece of gear for a world which is solid state and integrated chip driven. But this very warm and musical sounding preamp is truly portable relying on two 9V lithium batteries for its energy.

The circuit is based on the Oatley Electronics K272 triode preamp kit. There are many upgrade components added to the original kit. The input comprises two JAN6418 sub-mini pentodes in triode mode. The output is buffered by a PT2803 OP amp driver chip. This chip is a low distortion headphone driver/amplifier but here is used with unity gain. It has sufficient power to drive low impedance headphones.

Coupled with your iPod or more high performance portable player, this Mongrel Dog Audio headphone amp provides a unique and intoxicating listening experience. Compact and not too heavy for daily use and with a battery life of hundreds of hours there is now no excuse not to listen to your fav. music with the full tone it had been recorded.

MM Phono Preamp-Battery powered

Mongrel Dog Audio produces MM phono preamps. These preamps are based on the Jaycar MM kit which has since been discontinued in 2009. The basic OP amps in the kit are upgraded to Burr-Brown OPA2134 types and the cheap chip sockets replaced with mil spec versions.

Silver wire and gold RCAs compliment a quality build. The resonance free and non-magnetic plastic enclosure is lined top and bottom with bitumanised Al foil. The original kit was designed to work with an external AC plug pack. The circuit has been modified to be battery powered.

Three 9V lithium batteries provide a silent power source to ensure no hum or PS noise is passed to the rest of the system. This two stage MM phono preamp gives excellent performance for its low price and simple construction.

Mongrel Dog Audio Guitar Puppy

Mongrel Dog Audio is more about Hi-Fi audio gear than guitar amps. But in this case I made an exception. Here is my version of the Fender Champ 5F1. I Incorporated a lot of the components of the early amp builds by using cotton coated tinned copper single core wire, carbon resistors, valve rectification,vintage 12AX7 valve, vintage 6V6 Black Glass and 5Y3 rectification tube.

To this I added an effects loop, a choke and much larger filtering caps. And a nice touch was the two original Jupiter bees wax and paper, hand made, inter-stage caps.

I called the amp "Mongrel Dog Audio Guitar Puppy". Though low wattage, through sensitive PA drivers, it delivers a lot of sound. The highs are bright and the lows full powered and gutsy. It over-drives well delivery a rich full sound.