CATHODE RECTIFIED 2A3 STEREO AMPLIFIER

This affordable amp gives you two distinct flavors at the flip of a switch. Warm, big, full-bodied tone or a more revealing, tighter presentation. This dual personality is made possible by eliminating the cathode resistor normally found in this type of Direct Heated Triode amplifier. In picture #7 you can see the simple switch that resides under the hood, giving you the option to place or remove the low ESR bypass capacitor in parallel with the tube rectifier which provides bias voltage for the output tubes. This unique ability to remove the cathode resistor/cap combo completely is what gives this design a high-end sound using carefully selected affordable components. 

All wiring is point to point utilizing the component leads for connections when possible. You will notice some higher quality parts like Riken and Dale resistors, Solen/Angela and Nichicon "Fine Gold" capacitors along with some well researched, great sounding items such as Sprague "ATOM" caps and a pair of great sounding (read Joseph Esmilla's review here)  Hammond 125ESE output transformers. The power supply is rectified by a vintage Mullard 5AR4 tube followed by 2 sections of choke/cap filtration. The "cathode rectified" 2A3 tubes are cap-coupled by the single triode stage of a 6N1P. Less is more. The amp is wired for 8 ohms and can also be configured for 4 or 16 if desired. Residual hum at the outputs is 1.3mv and is somewhat dependent on output tube brand. A single humpot is used for both tubes to null any heater induced AC.

This all sits in a solid red Paduk frame and there is ample room to splurge and purchase some upgraded output transformers or wallet busting exotic caps down the road, when and if the budget allows. All transformer and choke leads were kept as close to their original length for future use or in the event that things need to be rearranged down the road.

The China 2A3s have logged about 200 hours to date...and sound very good, as do Sovtek's single plate 2A3s. The 5AR4 (which should last many years) & 6BW4 were pulled from a Tektronix scope and the 6N1P is new. An entire set of new tubes will cost just under $80.00. The open framed output transformers could easily be covered with one of Horace Atkinson's nice covers and I will admit that my paint job on the new Hammond power transformer leaves room for improvement when viewed up close.

 Can you find a better sounding amp...Yes. I could never claim that this amp is the last word in fidelity or resolution (who can agree on those subjective terms anyway) but you will likely pay handsomely. 

Have I told you enough? Why did I sell it? To be honest, I built this one to sell so our family will have a few more gifts under the tree this year. Besides, I love to build and learn new skills from every project I complete.

Please feel free to drop a line if you have any questions or interest!