SchlegFace
Active member
When I saw the Coming Soon for the End All hit the site last summer I was pumped. I picked up two different Randall RGs about 10 years ago to have on hand for the guitarist in my band to use instead of his Crate starter combo. Since then I've become quite fond of them and have wanted a pedal preamp version, mostly for funsies I think. I knew I had to have one when the PCB came out. When the build doc came out it was almost identical to the red channel of the RGs, the only differences coming in the clipping arrangement and lack of the Presence knob. As I don't like to make things easy on myself, I knew I couldn't make this pedal as stock, I needed to switch up the clipping, add the sustain feature found in the ES and later models of the RGs, and then also introduce gain makeup for said sustain feature.
The Presence knob was super easy. All that needed to be done was to swap R14 for a B2K pot. Simple. Job well done!
The clipping and sustain feature are a different story. The clippers in the RG are 4v Zeners, so that was an easy swap. The challenge was incorporating the sustain feature, which basically swaps 1N914s in for the clipping instead of the Zeners. This adds a bunch of clipping and compression, and absolutely kills the volume. Randall modified the RG circuit later on to address this in the XP models and with the XP-3 booster pack, which helps to a certain extent, but there are only vague details floating around of how they incorporated their solution. To combat the volume loss I decided to use a GuitarPCB Afterblaster as a signal boost after the 1N914s to get the signal back up to match the signal when the Zeners were being used.
I planned on having all the clippers off board, so lifted the negative leg on C8 and wired that to the input on the Afterblaster. The Afterblaster has a built in 3PDT for switching, so in bypass the 4v Zeners would clip the signal. When active, the signal would go through the 1N914s instead, then through the booster circuit of the Afterblaster. After all that I sent the signal back to the board at D2 and it continued on it's merry way. I populated and wired and boxed and tested and was very underwhelmed. Everything was working, but the Afterblaster just didn't have enough gain to bring the sustain setting up to more than a quarter of the volume of the normal clippers.
Back to the drawing board! I decided I needed more boost. I looked at a few vero layouts and decided on a JHS Mini Bomb boost since I had all the parts, it was tiny, and it claimed to be a very transparent boost. I built it up then spliced it in after the 1N914s and before the Afterblaster boost. Surely 2 boosts would do it, right? Well, it was better, maybe 50% the volume of the standard mode. Dang.
Since the Mini Bomb didn't get me there I decided I'd just build a SHO like I had originally thought, and luckily I found a leftover 9.1v Zener from a different project. I built the SHO, took out the Mini Bomb, and dropped the SHO in instead. I had the SHO set to about 1/2 gain and nothing but a whisper! So I cranked it! I was now too about 75% signal strength. Sigh.
Fear not fortunately, or unfortunately if you're still reading this far, our story doesn't end there! I just needed a bit more oomph and I'd be there. I had done so much work on the whole project I had to keep going so it would work as intended. I started rummaging through my parts to see if I had enough to make the early version of the SHO that used 4148s instead of the 4v Zener. I really was feeling lazy though and didn't want to cut another strip of vero, so I thought why not just run the clippers into the Mini Bomb I had already made, into the SHO, then finally into the Afterblaster. What could it hurt to try? This time I had to redo several wires and drop in the Mini Bomb next to the SHO. One more test and SUCCESS!!! Volume with and without the sustain feature engaged was almost identical. I even downloaded a db meter app on my phone and it was only a difference of 2db at most when playing my hardest. I was finally able to close things up and put knobs on!
Art on the enclosure is an ironed on toner transfer. The scene is a panel from a The Crow comic and the pedal name is also a line from the movie The Crow. The text originally didn't read very well so I added the red layer on top to make the words pop out a bit more. I got really lucky lining the red up on top of the original black. From a distance it looks killer. Up close there are some imperfections, but overall I am please with the look of the pedal.
If you've read this far, thanks so much! I'm really excited about how this one came out and just wanted to share. Oh, and it sounds great too! Like, really really good. (Although I've only tested it on bass my small rig.) I am aware my wiring inside is a mess. I've never been that good at it and am really out of practice.
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