Comments on: 20W Power Tube Amplifier with EL34

By: phillip jones

phillip jones — Sat, 05 Aug 2023 13:31:45 +0000

20w? An EL34 operating in single ended mode is only capable of 12w. And as people have said the bias supply is the wrong way around. Also the EL34 operates best at 250v anode supply with 100ma of anode current with a 2k anode load. They sound really nice single ended with those parameters.
Hope this helps

By: Alexsander Bittencourt Vieira

Alexsander Bittencourt Vieira — Fri, 14 Nov 2014 04:02:01 +0000

Only Bias circuit is incorrect. EL34 operate with negative voltage in the grid 5. For correction, invert diode and capacitors polarity in power source: 10uF 100V with positive connector in ground 🙂

Adjust bias corrent 35-45mA range. Caution for plate not stay red.
Good look and sorry… my english is less.kkk

By: karnakstudio

karnakstudio — Thu, 29 Dec 2011 14:21:52 +0000

The schematic diagram is incorrect, in the grid of El34 the bias voltage is negative….the bias circuit is incorrect

By: circuit diagram

circuit diagram — Thu, 26 May 2011 05:43:31 +0000

In reply to Christotech. 12AX in a tube. It has pin which need to be connected to power source. Find the datasheet to know its pin assignment. 1M in a value for resistor. For diode, you may use GBPC102 bridge diode rectifier or 4x1N5400 , 4x1N5401 or 4x1N5402 single diode rectifier

By: Christotech

Christotech — Wed, 25 May 2011 22:30:03 +0000

Pls i want to know wt kind of compnt is this 12AX,1m,5.34 & the number of the bridge retifier.The output,input of the power pack.I wil be glad 4 ur reply