This model seems to have changed several times during its production, and also a dual mono version has existed.
We should be sure that the tubes GE and Mazda, are the choice of origin, perhaps with the serial number Shindo is it able of responding ?
The Mazda 12AX7 are extremely famous, have become rare and expensive today.
If it's not a secret, what are the tubes used in the latest limited edition of 8 ?
