This one's a real labour of love and is based on my much cherished mid-90s Schaller Tr 316 Tremolo which has been a permanent fixture in my FX lineup ever since I bought it new way back when. Schaller have been knocking these out since 1958, so it must surely be one of the earliest all-transistor trems (as opposed to those weird and great electro-mechanical devices that first appeared in the late 40s). Most likely produced as a cheap, compact and reliable alternative to a vintage amplifier's built in tremolo, it does a pretty good job of simulating those smooth shimmery vintage sounds.
My original unit, great as it is, has always had a few features that have irked me for some time; it's housed in a "metal-look" graphite-laquered plastic box, has a plastic footswtich, and most importantly isn't true bypass and sucks tone like no other. Having built some pretty good fuzz clones, I thought I'd turn my attentions towards improving this old favourite. It now has my standard heavy duty Neutrik jacks, Alpha pots and footswitch, and robust bare aluminium MXR-sized box. I've added a pedalboard-friendly standard Boss-type 2.1mm centre negative 9V DC jack and kept the battery powered option too (it comes with a fresh Zinc-Carbon PP3 installed). Switching is now 100% true bypass, so it won't sap your tone when off.
I love my Schaller original because of its very "vintage" soft-sounding attack, and that's what was hardest to capture - but I got there. The controls are nice and simple - a "Rate" knob that controls speed, a "Depth" knob that controls the tremolo intensity and a "Speed" toggle switch that flips between a slow and a fast speed range. The "Speed" switch has a little extra cleverness in that it changes the oscillator waveform to a more "square" shape for the slow range, and makes the waveform more sinusoidal on the fast range. This works really well and ensures that things stay nice and edgy at slow speeds and don't get too harsh in the fast setting. The "Rate" and "Depth" work in a nicely intuitive and interactive manner giving you access to a nice array from vintage shimmer to more extreme psychy chop.