Intro: Add an Effects Loop to Your Amp.
Does your amp lack effects like reverb (or any sort of echo), chorus, flanger, tremolo, or any of those effects that effect the volume of things? Well, it probably does. But here's the deal, if you buy pedals of these effects then put them before the amp in your effects chain, and you try to do distortion (on the amp), it sounds terrible and your echoes don't fall off, volume boost pedals don't do anything, you get the idea. So how do you get around that? Effects loop. It goes in between the pre amp and power amp stages in your guitar amplifier and when you patch in effects there, they work great.
IF YOU BREAK YOUR AMP, WHICH THERE IS A GOOD CHANCE OF, DON'T BLAME ME! YOU HEARD IT FROM ME FIRST, IT'S BEST TO TRY THIS OUT ON A CHEAP AMP THAT YOU DON'T PARTICULARLY CARE ABOUT IN THE EVENT THAT YOU DO BREAK IT! ALSO, BE ABSOLUTELY SURE BEFORE YOU DESOLDER OR SOLDER.
Step 1: What You Need
Now what all do you need to complete this project?
1 Guitar Amp (I'm using a Kay GA20K, very cheapo)
Some bits of wire
2 1/4" phono jacks, aka guitar jacks.
Some Soldering skills.
Also drilling skills and a drill
Step 2: The Concept
So as I addressed in the intro; this effects loop goes between the pre and power amp stages of your amp. So if you don't know what kind of crazy talk I'm speaking right now, you probably want to go research that. Now, what we are going to do is try to find the division between the pre and power amp stages and splice a send wire and a return wire.
Step 3: Disassembly
The first step is going to be to unplug everything , the cord from the outlet, speaker, ect. Now we need to remove the screws (usually on the top of the amp, and around four or so) that hold in the amp head unit into the cabinet.
Now examine your amps guts, see if you can unplug anything else off of the main amp board thing. It turned out I could unplug the power supply and the speaker outs/headphone jack.
Now carefully remove the knobs (some amps have knobs that just push on, others have a set screw) and their nuts, also the input jack's nut. Then proceed to remove any other screws holding the board down, mine had two on the little heat sync thing connected to that black thing there. Essentially, just get it out.
NOTE: Be careful with your wires, I broke one of the connectors for the power supply, this provided me with much anger/annoyance because I thought it was a problem with something I had meant to do. I think it was when I was testing it that I did this. So be careful! (As you always should anyhow).
Step 4: Finding the Division Aka the Hard Part
Now this is the hardest part. This step is the step where we find where the pre amp ends and the power amp begins. I can't really tell you how to do this because it's going to be different for every amp. But I can give you some tips.
Look for ominous looking chips, then google their numbers. In my case, I found two ominous looking chips that turned out to be two op amp chips, one smaller than the other (smaller one is the pre amp chip!). This made it easy for me, because I just looked up the pin out for my big chip, found the input and that was my power amp in.
Master volume knob. Some amps have the master volume knob right before the power amp in. For example, look at this Pignose G40V tube amp's schematic, you can see (as I've circled it) the master volume pot is pretty much the only connection to the power amp stage (the one with the 6L6 tubes). But I don't recommend following that directly from me, as I haven't tried it! (EDIT!!: I did try it. And it didn't work, I'm in the process of making it though).EDIT AGAIN!!: (I tried it after the master volume and it works, although you can't do a compression pedal or anything like that, because that makes it go full volume! haha and auto wahs don't work.
Be careful! If you find something you might think is it, be careful when desoldering it. Clip an alligator clip onto the component as a heat sync, and try to keep the heat out of it. And when you try to start it up with your wires attached, keep them either hooked up to the pedal, or touching each other when you start it up. I had some times when I didn't and the noises I heard didn't indicate a happy amp. You may not know what I'm talking about with the wires, but we'll get to that in the next steps.
Step 5: Soldering on the Wires!
Now this is the fun part. Desolder the part that you think is the power amp input (I'm sure you can find an instructable on desoldering, so I won't get into that). Now solder a wire on the pcb side and a wire on the pin (or whatever) that you desoldered. The pcb wire will be send, and the other will be return. Now test to make sure you didn't fry anything by connecting the two wires together, plugging in your favorite homemade (or not homemade) guitar in and turning the thing on (plug the stuff you may have unplugged back in; in my case, speaker wires and power supply). You should have it behaving as usual, if it does, AWESOME! If it doesn't, then awww, you did something wrong. Try checking stuff like your solder joints, make sure your wires didn't come untwisted from each other or something stupid like that, etc.
Step 6: Moment of Truth
Now it's time for the moment of truth. You've made sure you didn't fry anything and your connections are good, but did you pick the right input? Here's how we'll see.
Get your least favorite effects pedal (as you might blow it up if you inadvertently picked a place that's like +10248236 volts or something) and plug in two guitar cables to it. Now connect the wire that is coming from the pcb, the send wire, to the tip of the cable that goes in to the "in" hole on your pedal. Connect the wire going into the power amp to the tip of the cable coming from the "out" hole in your pedal. Connect both the "sleeve" parts of the cables to ground. Now strum the guitar and turn it on, you should have effectage! If you didn't (like I didn't) then you picked the wrong place to splice in. Try again! If its an op amp, look over the pin outs that it shows on the datasheet (you can find those via google) and if you're like me, you slap you face with the palm of your hand and realize your mistake.
Step 7: Wiring Up the Jacks
Now this is the easy part. After you've determined that it works with effects, it's time to wire up the jacks! This is really simple, you connect the wire that comes from the pre amp (the send wire) to the positive side on one jack (positive is the little tab that connects to the J shaped thingy, not the one that connects to the sleeve) and the other wire (the return wire) to the other jack's positive side. Now wire both jack's grounds together then solder a wire from there to a good ground. That's it! Your wiring is done! (If it works, otherwise, trouble shoot!)
Step 8: Drill!
Now drill holes in the chassis for the jacks to be mounted in. If you don't know how to use a drill then I don't don't know what to tell you haha. Oh and find a good place to mount 'em before you drill, the warning label was optimal placing for me haha, but seriously, the space behind it was just right.
Step 9: Re-Assembly!
Now just reassemble it all! Install the circuit board, plug in the plugs, mount the jacks and screw on nuts, you get the idea. I also added some little blue plastic labels, because nothing say's classy more than "hand made" labels. Oh also, you might want to put some tape over exposed wires and stuff like that.
Step 10: Plug It in and See If It Works!
Now you need to hook it up and see if it works! If anything doesn't work, go back through the steps and try and find what you screwed up on.
Now there are a few tricks with this thing. The first and foremost is always have something plugged into the loop, otherwise it makes a nasty noise that quickly gets louder and gives me a bad feeling of "this thing might blow" So just play it safe and keep something plugged in. The other thing is, if you want to not have anything plugged in, just plug both ends of a cable into the loop.