Home Forums General DIY Pedal Discussion Could the Add-Verb be used to replace an obsolete circuit in a classic amp Reply To: Could the Add-Verb be used to replace an obsolete circuit in a classic amp

#1069
saransk
Participant

I’m building a UL730 using R. G. Keen’s redesign of the circuit board for the preamp.  He did some updates on the VOX circuit but it isn’t a full replacement for the one using the phono cartridges.  (See http://www.voxshowroom.com/uk/amp/730_hood2.html) for the original setup.

With the new board and clearly laid out Reveb section I thought that I could just set it up as a “daughter board”, use trimmers for the Tone and Volume controls.  I’ve Inserted the updated schematic from R.G.’s manual.   It looks as though it should connect pretty well right into the overall preamp circuit – the hardest part may be getting the voltages right.  The “Reverb In” come right off the “Signal Out” line of the 2nd pre-amp channel and then hooks back into the Signal Out summing to go to the Power Amp circuit.  In a modern amp it would be sitting right at the Preamp out and Power Amp In junction.

Originally I had hoped just to use one of the new “bricks” with the circuit but could not figure how to do it correctly with the very old circuit.  The consensus seems to be that a replacement of the whole circuit is the best way to do it.