The high quality Electro-Harmonix 2A3 power tubes are tubes with direct triode heating by oxide cathode. They are ideal for a low frequency power amplifier in the amplifier output stage. The gold grid of these tubes provides exceptional bias stability. At the base of the tube are 4 gold plated pins on ceramic support.

The two tubes are perfectly matched to obtain exactly the same current, maximizing their performance. The Electro-Harmonix "Platinum" pairing consists of a 24-hour burn-in period followed by a measurement in milliamps of the bias current to ensure the perfection of the pairing.