Nattawut Uamkruea, blogger and audio gear maker who passionate in vacuum tube, audio & music.
Producing electronics projects since high school. Seriously upgrade and modify vintage audio equipment for “Real Sound” concept.
He is a co-founder of Soundaries and Sentimental Studio, all audio solution provider.
Experienced and lively explore the listening rooms & audio shops in Japan as his most favorite to do.

Thursday, November 12, 2015

My new WE tube amplifier with P&C transformer Part 2

Continue from part 1 that has built and tested for a month.

Single ended amplifier from Western Electric tubes and components,

using 421A double triodes tube as power, 418A tetrode tube as driver

and 394A thyratron tube as rectifier.

P609 output transformers with original WE core from P&C Electronics Japan,

Thordarson input transformers, WE 274 type inductors for filter chokes.

Designed for compact size in real wood frame.

Schematic of both channels that use ExpressSCH program for drawing.

WE421A has nice smooth sound, not too sweet but compromise with many kinds of music.

Similar 5998 Tung Sol with more mellow tone.

WE418A with triode connected support WE421A to get more energy

and same bulb & base like WE437A is a valuable appearance. ;)

2 of WE394A thyratron tubes work as full-wave rectifier,

Get both benefits from thicker sound of mercury-vapor & gas filled

and beautiful blue glow of bird cage style grid.

P&C P609 output transformers is a highlight of this amplifier.

They're deliver WE characters from using original core and improved frequency response

to cover music after WE era.

Reasonable price for people who need WE sound characters in their systems.

Flat non-inductive wirewound resistor from CTS with WE patents as cathode resistor of WE421A.

WE 274 type inductor as filter chokes, not hard to find and reasonable price.

Inductance and current rating quite low because of size limit

but enough for low watt SE amplifier or preamplifier.

Main power transformer from old transmitting equipment.

External filament transformer for WE394A tubes because they need more current than

main transformer winding can deliver, and inside area has no space to assembly. ;)

Using "Real" WE cloth wires for all wiring inside amplifier.

PIO capacitor and bleeder resistor across first electrolytic capacitor.

Rectifier area with Sprague oil filled, F&T and Hitachi HL2 capacitor.

West-Cap CPV09 paper & film in oil were selected as coupling capacitor.

Will bring Arizona capacitor "Blue Cactus" to replace this position and test again.

Wet tantalum capacitor as cathode bypass of driver tube for clearer sound.

Let enjoy with music along the night. ;)


  1. That is really cool. I am tempted to start collecting parts for one of these. Thanks!

    1. Let me know if you need any support.

      Thanks a lot for your follow. :)

  2. Your articles are very good, thank you.

  3. Glad to know if someone can take advantage from this.

    Cheer !!!

  4. Dear Natawoot,

    Nice design! How's the WE 418A performing? What's the anode current and anode voltage you got with your schematic?


    1. Hello Heng Gin Loo,

      Excuse me for my lately reply.

      WE418A's sound not too sweet but natural & flat from bottom to top.

      Benefit from using WE418A that it look like WE437A. ;)

      I've got WE418A graph from MJ magazine ; February 2015 issue.

      Please see links below for graph & parameter.

      Thanks for your interest!

  5. Hi Nattawoot,

    Thank you for your reply. I saw the curve. Very linear indeed. I've purchased some WE418A to try. :)

  6. Hi Nattawut,I'm not very good at building, I would like to buy one, is it possible? Hello

    1. I will launch my new amplifier with these tubes soon.

      Will update to you.

  7. Hi, Amp looks very nice are P&C - P609 transformers Permalloy ?

    1. Hi,

      P&C 609 had 2 versions like 171A.

      P609 - Silicon steel core
      PP609 - Permalloy core