Original design 2A3 Class A1 Single-ended Power Amplifier (All stages connected by transformers） for high frequency

Let me introduce my own design power amplifier
（I made this in year 2003, modified in year 2011)
I attach whole circuit drawing below.

Designing concepts of this amplifier are
1) All stages are connected through transformer.
Equip the power tube for 1st stage and drive 2nd (Final) stage through interstage transformer.
2) Use “AC-2.5V” for heater circuit of 2A3.
AC heating sound nicer and no much hum problem because of low heating voltage.
3) Don’t use any Electrolytic capacitors. (As result, I use only one for last part of B+ power supply circuit to reduce hum noise.
4) Operation of 2A3 is following the RCA data sheet (Not 100%)
*Voltage between Plate-Cathode = 250V
*Voltage between Cathode-Grid = -41V
*Load impedance for 2A3 = 6k ohm (Typical use is 2.5k ohm)
Not necessary to get high power for me,
high load impedance has Advantage from the viewpoint of distortion
I chose Tamura PC3003 power transformer. This transformer has 2 circuit of 2.5V output, this is good for 2A3 single “stereo” amplifier. Using 320V high volatage output, Rectifier is 5U4G, 2A3 plate receive DC290V.
Filter type is “Capacitor input pai type” , first capacitor right after 5U4G rectifier is only 5uF from durability point of view.
I used Tamura A4004 choke coil. Input transformer is Tamura TKS50, usually using 600 ohm input circuit only.
First stage tube is triode connected 6F6, interstage transformer is Tamura B5003.
I attach photo of this amplifier.

Year 2011, I made modification to reduce hum noise level.
Tamura Choke coil A4004 has 2 different choice of wiring, one is series connection to get high inductance(10H-200mA), another one is parallel connection to get high current output(2.5H-400mA).
Originally I used this choke coil in series way (10H-200mA). I wanted add capaitor to center point to make double pai type. But this trial doesn’t work as my idea. This idea based on my experience of Hashimoto choke coil used in my preamplifier and successfully done.
You can see copper shield around power supply and Electrolytic capacitors.
Output power hasn’t reach 3.5W, but do not feel any power problem to drive “Altec 288D Driver”