filed in Modifications on Mar.22, 2009
One of the latest pedals to join my pedal board is a Boss TR-2. This tremolo is a classic effect and is probably on many pedal boards around the world. There are two revisions of TR-2, the first one suffers from a volume loss when the effect is on, the second does not. If you intend on buying this effect new you should get the second revision and be all right – should you consider the volume loss an issue; be careful if you get one of these pedals second hand otherwise.
I ordered Monte Allums’s TR-2 Plus Mod Kit the shortly after receiving the TR-2, not because I wasn’t satisfied with the way the TR-2 sounded, but more for the sake of modding it – thing I am addicted to. I made all the mods in the kit appart from extra the volume potentiometer because I didn’t really want a volume control on the effect (and also because the TR-2 I have doesn’t suffer form the volume-loss problem).
Having moded the TR-2 I found quite frustrating that Boss didn’t add a small LED on the pedal in order to visually indicate at what speed the tremolo effect is set.
I found a good schematic of the TR-2 circuit on schematicheaven.com. With the schematic on screen and the pedal opened and then started experimenting with a spare LED and a two pieces of wire around the IC3B op-amp.
I found that the LED works best when grounded on one end [UPDATE: Don't ground the LED straigh away, always have a resitor in series with the LED!] and connected to the jumper J3 (see last picture). This way the rate LED is always on (even the effect is not engaged) and only the rate and wave controls have an influence on the LED blinking. I prefer this behaviour (the depth control has to impact on the LED) since the utility of the LED is to visually indicate the RATE of the effect, even with a the depth control set to a very subtle level.
Surprisingly, I couldn’t find any indications of how to do that LED mod online so, hopefully, I hope it helps!