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Hi all! I’m relatively new to pedal building. I’m a musician and engineer, and have built pedals in the past. However those have mostly been kits with components already selected and provided for me. I’ve practiced using the BMPOA board, and now I’m ready to get a little adventurous!
I’ve wanted to make my own DOD Preamp 250 with eq control, but I’ve also just purchased an easy order switch pcb while it was on sale. Now, I’m wanting to combine all three pcbs into a handy little preamp pedal for me!
My question is how would I order the boards and wire this project. My thinking is jack-in to the footswitch board, and its board-in to the easy order switch pcb with each FX connected. I’m wanting to remove the volume control from the Emexar, so I’ll be coming out of Emexar Volume lug 3 to the output of FX1. From there it’ll go to the board out from the footswitch, then to jack-out. I have included an image of how I believe the pedal should be wired.
I also wasn’t sure how all +9 and ground should be connected to this build. Should a single 9 volt supply work for the entire build? Do I connect all FX boards (including easy order switch pcb) grounds and power to the footswitch pcb pads?
Thankful for any insights and advice, I’m just a hobbyist that is looking for a fun way to get the sounds I want! Thanks!
There are instructions in the build doc for the order switching board. (<span style=”font-size: 100%;”>https://guitarpcb.com/wp-content/uploads/2018/06/BD_Easy-Order-Switching-Board-3PDT-Toggle.pdf</span>) Hope this helps.
That link doesn’t word. Try this one. https://guitarpcb.com/wp-content/uploads/2018/06/BD_Easy-Order-Switching-Board-3PDT-Toggle.pdf
I see that in the document it shows how to wire them based on the two FX having independent footswitches. I was planning on having a single footswitch control the on/bypass of the whole pedal. Would I still be able to put the two FX in the order switch loop and have a single footswitch in the way I drew in the diagram? If not, I will just put the two FX in series and forego the order switch.
Hello Maxwell. Your drawing will work as drawn. I would caution the removal of the emexar volume pot though. That would of course allow full volume into the Tweq. For best sound be careful not to overdrive the input of the Tweq by either keeping the volume pot or maybe replace it with a trim pot which can be set, according to the output of the rest of the rig thats before it, to not distort. There is plenty of gain on tap between the 2 circuits. No problem there.
Cheers
I can’t believe someone else is doing what I am currently working on, but I am so busy this summer I won’t be able to finish it until the fall. I’m going a slightly different route and going to use an On-On DPDT switch to add the tone Tweq or bypass it to go to a stock 250 configuration. Got the main boards built but that’s as far as I have progressed.
I would ditto Steve’s response, but Barry I think would be the final say on this.
The only thing I would point out is the connection to the Tone TwEQ, and Emexar needs to be at the (T) pads and not ground at the IN and OUT sections. Make the necessary common ground connections between all circuits including +9v and audio jacks. There are plenty of extra pads on all PCBs to choose from to make that happen. Also the two main boards need to have a +9v connection as well as the 3PDT wiring board assuming that will be your Status LED location.
As Playsforfun points out, particularly when the Active EQ is first in order I would try to keep the overall volume level of the TwEQ at a minimal setting so as you are not creating undesirable clipping. Then TwEQ it from there. Much in the same manner as you would do with any EQ.
Thanks for all the help from everyone! I’ve always wanted a 250 so it’ll be great to build my own, built to my specifications!
I hadn’t thought about hitting the TwEQ too hard when the switch is set to Emexar>Tone TwEQ. I’ll keep that in mind, thank you Barry and Playsforfun for the heads up. I had imagined the TwEQ would allow the ability to hit the Emexar harder and cause more distortion. I might take the suggestion and put a trim pot or permanent resistor in series back to the order switch so as to mitigate too much distortion. I believe since the volume pot for stock Emexar is 100k that I might get away with a 50k resistor or similar trim pot to set how I want, correct?
Again, thanks for the guidance. Big O, you’ll have a badass pedal in no time!
Your last question needs answered as you may not get the 1/2 volume result you seek with just a 50k resistor set before the output. The volume works as a voltage divider and not as a variable resistor. With the voltage divider there is 2nd resistor to ground. The signal remaining is a calculation between the two resistors and comes from the point where the two resistors junction. And the pot mimics this and has resistance on each side of the 2nd lug and 1 side goes to ground. So 2 50K resistors used together as a divider will give you half of the signal. A trimpot swap takes care of all that technical stuff. Just wanted to make sure it was clear. Its worth googling the calculation and keeping note of it for reference. If you just misstated above or already know this, disregard.
Interesting, I did not know that the volume pot functions as a voltage divider. I was actually considering just a resistor in series out of lug 3, so good to know now. I might just end up using a trim pot to set to my preference, but out of curiosity, how would one go about the 2 resistor solution? Would a 50k resistor go between lug 1&2 and 2&3, each? I think by Playsforfun’s explanation, the pot acts as two resistors where each resistance on either side of lug 2 depends on what position the wiper of the pot is in. Am I thinking of this correctly?
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