As diodes are highly efficient devices, they would not create the audio compression caused by the voltage "sag" of the GZ-34.
The GZ-34 tube was replaced with a bridge of four IN4007 silicon diodes. These would be replaced with less costly components that would not affect performance. Vox determined that through modern design the GZ-34 rectifier tube and the choke could be eliminated from the AC30C2 power supply. Such pricing would make the amp available to many who could not previously afford an AC-30. Vox hoped to design the AC30C2 so that the street price of the amp might be less than $1000. Many feel that the audio compression created by an overdriven AC-30 is an essential component of Vox tone. These drops in voltage compress the audio output of the amp. The GZ-34 rectifier tube had the tendency to exhibit a momentary "sag" or dip in power supply voltage when an AC-30 was pushed toward the limit. The choke worked in conjunction with two 16 uf 450 volt capacitors to eliminate the ripple in the B+ supply.Ī bit of Vox mojo was inadvertently created by the GZ-34 rectifier tube.
The GZ-34 tube converted AC voltage voltage from the power transformer to rippled DC.
The original design for the JMI AC-30 B+ power supply included a GZ-34 full wave rectifier tube and a choke. This allowed the chassis to act as a heat sink for the tube sockets. While some earlier versions of the AC-30 had tube sockets mounted directly to the main PC board, the tube sockets for the AC30C2 were fastened to the chassis. It bolted to the amplifier cabinet with four large machine screws. The AC30C2 steel chassis had a "C" shaped cross section. It included spring reverb, tremolo, an effects loop and output jacks for extension speakers. The AC30C2 was a two channel amplifier powered by three 12AX7 and four EL84 tubes. Let's take a look under the hood at what makes the AC30C2 tick. It defeated amps from manufacturers such as Mesa Boogie, Marshall, Orange, Peavey and Fender.