Metropoulos Forum

Hello, I bought a pair of JJ E34L tubes for my 2204 type build. The tubes came from a popular online tube and amp parts supplier that sends out their tubes with convenient "bias point" stickers attached. I plugged in this pair and set the idle current to the specified "bias point" and have been pleased with the tone ever since. I probably have 10 hours on the amp, with no problems except occasional minor bias drift due to a lo-res trim pot.

My concern is, from a bit of research after the fact, 56mA seems quite high for an EL34 type. What do you fellas think; reckless bias current=TONE, or is this supplier trying to ensure that I'll need new power tubes sooner than later? No red plating or signal/volume issues at all. Mostly I just don't want to burn these tubes out recklessly because of a possible error in labelling.

That "bias point" is what those tubes draw in the testing machine, most likely a Maxi Matcher. It is not what you're supposed to set the bias to. Bias should be set to not exceed 70% of the max plate dissipation rating, using the plate voltage measurement as your guide.