A.F. DOUBLE TRIODEECC82 is 12AU7 medium gain pre-amplifying double triode. Provides a very smooth sound with well-defined tones suitable for audio and guitar amplifiers.
R.F. DOUBLE TRIODEECC81 is 12AT7 medium gain pre-amplifying double triode. Can be also used as replacement for 12AX7 in many applications. Very smooth and warm sound. Very low microphonic. Good for phase inverters or reverb drivers.
A.F. DOUBLE TRIODEECC83S is 12AX7 high gain pre-amplifying double triode. Thanks to its design it also peforms with very low noise and microphonics. Harmonically rich, with a detailed low end and a warm high end.