In the 1990s, Digitech created a series of effects called the XP series.
It was made up of the:
- XP-100 Whammy/Wah
- XP-200 Modulator
- XP-300 Space Station
- XP-400 Reverberator
I picked up an XP-100 back in the day when I was right into Rage Against the Machine (still am…) for the Whammy octave up effect. Very cool. The XP-300 is also apparently pretty awesome too, and is one of the more sort-after effects. Anyway, it turns out that there is not much difference at all between the pedals in the range. They all use the same enclosure (just painted different colours) and they all have the same circuit board (plus or minus a few components here and there).
This means that it is possible to turn any XP pedal into any other XP pedal – or turn one XP pedal into ALL of them! So, I though I’d have a go at modding my XP-100 to also be an XP-300 (with heaps of help from the people at diystompboxes.com)
Here is my XP-100 completely stock, before doing anything:
The ‘software’ for the XP-100 lives on a chip on the board, so to have other XPs living there too, I needed to install a socket for an EPROM chip (circled in blue below). I bought an 27C256 EPROM and one of the nice guys from diystompboxes.com copied the software on it for me. Next, because the XP-300 is so awesome, it requires more RAM to operate, so I had to install some sockets for extra RAM (circled in red below). The RAM chips are D41464C which I found on eBay. Next I had to install a little 74HC574 (circled in green), which was a bit tricky because it was a tiny SMD IC. Lastly, I removed R38, a tiny SMD resistor (circled in orange).
Here it is, half way there… You can see in this pic I’ve also done the “Output Volume Mod” – it’s a nice easy mod that lets your turn down the output to match your other pedals. It’s just a dual-gang pot connected to the output jacks.
Now it’s just a matter of installing the switch. The switch tells the XP which mode to boot up in. If it is one way, it boots up from the onboard XP-100 chip, if it is the other way, it boots up as whatever is on the EPROM – in my case, it’s an XP-300. The switch has an 100 ohm resistor in the centre pole connected to the hole directly above the “33” marking, and right next to the lower pad of where R38 used to be – this is my blue wire. One side of the switch connects to the hole just to the left of the “U8” marking (my green wire), and the other wire goes to ground (my red wire). Like so:
To change modes, just disconnect the power, flick the switch, and power it up again.
So now I have the Whammy/Wah and the crazy Space Station all in one box!
For more info, and a way better understanding and explanation than I can give, check out this thread at diystompboxes.com and also this awesome documentation: converting-the-digitech-xp.pdf. It talks about creating an “XP-ALL” which is all the XP effects in one… that might be my next challenge…