Whats the difference between the PGA-04 and PGA-05?
The PGA-04 is a mono speaker simulator with a built-in 8 ohm load box. You can use it with or without speakers–set your tube amp head to 8 ohms. The PGA-05 is a stereo unit designed to use with line level preamp equipment. It does not have a load box onboard. The PGA-05 has a line/speaker input switch on the back of the unit to facilitate the use of a preamp or an amp.
