ECC83 MG is 12AX7 with Mid-gain, which means fuller and richer mids achieved by medium long plate. It provides a milder sound than the regular ECC83. Very low noise and microphonics.
Our observations: Another 12AX7 variant from JJ. The ECC83 MG is a “Mid Gain” 12AX7 type tube. It utilizes a medium length ribbed plate design that is much like the old Amperex and Brimar European designs. It retains all of the definition and detail that the ECC83S short plate and the ECC803S long plate tubes have but it has slightly less gain than the ECC83S but a bit more gain than the ECC803S
the best way to describe the difference is to say that the Gold pin ECC83MG is a little smoother and richer sounding. These make great V1 tubes in any amp if you're after a smoother and richer tone and I have quite a few customers running them in all positions which is a bit expensive but if you want the best of the best in smooth rich tone these will do it