Thursday, January 10, 2013

300B Single End Vacuum Tube Amplifier

Current (new) production 300B tubes like the Electro-Harmonix 300B and the JJ 300B sound wonderful at a fraction of the Western Electric 300B price. A direct coupled driver stage and a low mu triode array are the specific reasons why this design works so well. Good output transformers are the key to good performance. Magnequest FS-030 or XE-60S are good choices.

The schematic for the 300B Single-Ended Vacuum Tube Amplifier is shown below. Using audio output transformers with a primary impedance of about 3000 to 3500 ohms you can expect about 8W of output with at about 2.5% THD. 


Paul said...

Hi there. I'm a newbie with amps and wanted to ask if that's a pot on the grid from the input? If so, what's it for? I assume the pot on the 300b is the volume control?


Anonymous said...

I'm not the writter of this circuit, but the first pot looks to me like it's the volume pot, and the one next to 300B should be tone