Wednesday, April 4, 2012
Making Your Mark: Reviving A Custom Vibrolux Reverb
Every once in a while you come across something that really, as they used to say in the Pepsi radio jingles, hits the spot.
Such are the Mark Moyer mods for the Custom Vibrolux Reverb.
With that said, a Fender Custom Vibrolux Reverb arived here with a really high level of background noise. Incidentally it had a scorched tube socket and failing electrolytics which didn't help anything.
In " The Soul of Tone" Tom Wheeler describes this as a production of Fender's Custom Amp Shop which was designed by Bruce Zinky. As a commercial item it was more or less a flop, because most people didn't like the noise level-you don't see them around much, and when you do, they aren't that expensive to acquire.
Back a decade or so ago, a fellow named Mark Moyer decided to tackle the hiss and noise problem with this amp and he developed a plateful of mods that move the CVR from an also ran to a great piece of gear.
The mods consist of delinking the reverb from the normal channel, installing a negative feedback loop, adding a shunting capacitor to the phase inverter, removing the surge protection diodes, and replacing the ground reference resistors. In addition and highly recommended is installing an adjustable bias control and replacing the 12AT7 reverb recovery tube with a 12AX7.
Don't forget to check the electrolytics for ESR-the power supply capacitors were failing on this amp.
The modifications will take you about an hour of work, after you've opened up the chassis, marked and removed the connecting wires from the board that have spade connectors, and removing the daughter boards from the front of the amp. If you're not handy with a soldering iron leave this to a professional.
You can find the rundown on these mods here.
If you're like me you'll find the transformation outstanding.