ECC81 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. The JJ ECC803S is my favorite preamp tube: more than ANOS Telefunken, ANOS Mullard, Ei, Sovtek 12AX7LPS, Chinese 12AX7 etc. The JJ ECC803S is lower gain than the JJ ECC83S and works beautifully, in combination with JJ EL84s, in a VOX AC4/15/30 top boost circuit.
JJ Electronic 5751 Factory Data Sheet: 5751 Our observations: Another short plate preamp tube from JJ which was released to us in January of 2012. The JJ 5751 has all of the qualities we have come to expect from JJ Electronic, a nice tight low end, a natural open mid, a great harmonic structure and a sweet high end that is not brittle. Tube Data Sheet Locator. Warning: Substitutes are given as a guide only - please refer to original manufacturers data sheets to ensure that a substitute is safe and appropriate for your application.