It is my DIY PEN45 amplifier in PP operation.

Driver and phase invert : 6SN7 in long tail  pair (one 6S/N7 is good enough for inverting phase and driving PEN45)

Power tube: PEN45 x 4

Rectifier: UU8 x 2

Voltage regulator: 6G6G and VR150

Output transformer ratio: 6K : 16

Negative global feedback: 2%

Amplification class: A

Bandwidth: 20 Hz to 20kHz, +/-2 dB

Power: 2 x 10 watts RMS at 16 Ω

Input level: <= 1V RMS

Input impedance: 100k Ohms

Signal-to-noise: 50 dB

Noise when no signal: 1mV

My first tube amplifier - 300B SET

It is my first tube amplifier purchased from mainland China in September 2001.

Driver tube: 12AX7 x 2 and EL84 x 2

Power tube: 300B x 2

Rectifier: 5U4G x 1

Volt Regulator: VR150 x 2

Modified to using vintage US capacitors

Light balls in dark night

DIY PX4 and PX25

My PX4 / PX25 project completed in September 2005

DIY 300B and PX25 (in a single chassis)

Chassis: 鈴蘭堂 SL-990
Rectifier Tube: U18 / 274A
Driver Tube: WE437a
Power Tube: WE300B / PX25
Power Transformer: Tango CT-250
Inter-stage Transformer:Tango NC-15
Output Transformer: Tango X2.7

Yamamoto socket fits for either WE300B or PX25

WE437A self bias by using 120ohm resistor

Selector for WE300B or PX25

Selectors' Inside - Cathode resistors with heat sink

Back

Front

My 300B / PX25 project was completed in June 2013

********************************************************************************************************

Because power supply for WE437A is built by using a resistor to reduce the voltage from 450VDC to 200VDC, the voltage will be very high in the beginning.  In mid 2014, I added a timer that lets the WE437A have a soft start power supply.

********************************************************************************************************


Rare WE437A with square-getter and tip top