After several revisions of my original
lunchbox-reverb
circuit, I arrived at a PCB design that I'm very pleased with. The new LV-100 lunchverb has a re-voiced reverb driver and recovery stage, a new tone control, an input level switch, a 9V battery connection, and it has gained the ability to drive 600 ohm tanks as well as 8 ohm via an internal impedance switch.
By taking readings from a 1967 Super Reverb, I was able to get a clearer picture of how the Fender circuit actually interacts with the tank and surprisingly, I found way more low frequencies than expected. By letting more low end through the driver and compensating with more high pass filtering in the recovery stage, I was able to get exactly the springy attack sound that I was after. I had some PCB's made and worked out a design for the whole assembly to optimize efficiency when building several at a time.
Here's a shot of some boards after being populated. The pots and jacks go on last to ensure a propper fit.
The whole assembly comes together as a stack using M4 standoffs. The spacing of the tank's mounting holes is matched by every other layer. The faceplate is another PCB with solder pads for spring contacts to lock on to the lunchbox and give a strong ground connection while allowing easy disassembly in the future.
One of the biggest updates in this schematic is the elimination of the LM386. I found that by using a current source configuration, an NE5532 can drive an 8 ohm tank just fine. A discrete transistor split rail buffer was added to replace the now preoccupied op-amp half. The new tone control is an active LPF in the recovery stage. Beyond that, the design is functionally the same as the original lunch-verb.
The first batch all ready to be housed in their lunchboxes.
...and if you want to own one, you can
buy one here!
