The owner scored this amp for free . . . some guys have all the luck!
It was designed for 7189A tubes, which are basically rugged EL84s with a tad more power. The amp had EL84s installed when I got it, and a plate voltage of 480V! Biasing them properly brought it down to 440V but that's still way too high for EL84s, especially considering the high screen voltage due to the ultra-linear output stages. I stuck some Russian EL84M tubes in the amp and they should hold up a little better. Hopefully they do as NOS 7189As are VERY expensive. I also installed a 3-prong cord, a progressive power switch, and replaced the electrolytic capacitors and a couple leaky coupling caps and noisy resistors.
It's a stereo amp, each output amp powering a 12" Jensen. It has the famous Magnatone vibrato (in stereo or mono) and an unusual reverb circuit with en "echo" control that modulates the amplitude of the reverberations. The echo circuit required some work to repair but it's a cool effect.
I love this amp!
