2A3 SE Amplifier
DIY 2A3 in red color

2A3 SE Amplifier

I received a request from a friend who want a 2A3 SE amplifier. Here’s the 2A3 I build for him.

I used 6E6P as driver stage. The 6E6P are long life military tube which is very linear when connected in triode mode, Rp are around 1.2K , suitable for use as driver stage. The gain are around 25+ when using plate choke as a load.

I did some test on most of output transformers in market, either they are too expensive , or not perform well. Thats why most of output transformers / chokes in my DIY vacuum tube amplifiers are hand wound by myself, so that I can take control of quality or suitability of impedance / characteristics etc. I will write a separate post on how to wind an output transformer soon.

For plate choke, I choose 0.35mm CRGO EI66 material stacked to 32mm thick . I wound 5000++ turns in total , all 36 layers with thin paper in between, and leave air gap on EI core using craft paper. It measured around 60H , good enough for 6E6P plate load.

Each 6E6P biased to 2.4+ V at its cathode to get 27mA plate current, and the supply at plate choke measured around 150V.

The power stage is just a classic self-biased 2A3 stage. I’m trying to use filament bias but since my friend refused to put any transistor or mosfet in his tube amp, I used normal DC supply for filaments.

For output transformers, I built a pair of C core transformer for this amp. C core output transformer consist of two identical windings, with each side of 4 sections primary and 3 sections of secondary, all primary are in series and secondary are in series-paralleled.

under view of the 2A3 DIY amplifier, 2A3, amplifier, transformer, single ended, diy,, capacitor, vacuum tube, under side, view,
inside view of DIY 2A3 SE amplifier

testing DIY 2A3 amplifier with signal generator, 2A3, signal generator, DIY, 2A3, Single ended, high end, audiophile, audio, transformer, capacitor, volume control
Test my DIY 2A3 amplifier

I love wood frame chassis and apply beeswax on plain wood for natural look. top and bottom plates are aluminium painted in red.

back side of 2A3 amplifier with speaker terminal and RCA socket and power socket, power, socket, RCA, high-end, speaker terminal, binding post, switch,2A3, amplifier, DIY,
2A3 speaker terminal

As for listening test, I played several type of music, this 2A3 SE amp is much differ from my previous 6SN7-2A3 or 717A-2A3, the plate choke can really store energy and I get more detail, very dynamic, very satisfying bass, and huge soundstage.

6E6P 2A3 DIY amplifier schematic, 6E6P, 2A3, Se, single ended, amplifier,
6E6P-2A3 schematic

Here’s my ugly hand drawn schematic diagram:

A short video here with Fourplay “Chant” :

Here’s another test by request from a few from forum friends, female vocal ( Chinese, because youtube deleted most of copyrighted songs )

I’m waiting for my external microphone, once I received, I will record a video clip again and post it on my youtube channel.

Please subscribe to my youtube channel for more video:


Stay tuned !

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