TELEFUNKEN / SIEMENS V77 Valve Mic Amps PAIR . Original. Tested
he V77 was a Siemens made supercharged V72 with a maximum gain of 80 dB. It produced sound like a V72 but with the gain of the V76. With an external switch (W77) the gain could be adjusted from 0 to 80 dB. Tube set-up, choke and output transformer are all identical to the V72. The input transformer is wound the same way but with a 1 to 40 ratio, because in order to get the required S/N ratio the V77 needed a different power transformer with two separate filament windings.
The V77b is a V72b that has the V77 conversion mentioned above done to it. It is considered by many to be the greatest mastering tube amp of all time.