I recently built the Bass Overdrive from GuitarPCB.com. Here are some pictures and notes following the process. I ordered these last week, and the package was mailed the next day and arrived quickly. Everything was packaged well, and it ben cam with a guitar pick!
I have a lot of parts on hand, so I didn’t place any special orders. This project looked to use very standard and readily available parts. I figured I’d have everything. As it turned out, there were a couple things I didn’t have. So i had to make a few substitutions. I made some notes about the substitutions I used below.
This is a high quality PCB with plated through holes. You don’t need to use much solder. Just a little touch at each connection.
Notes, used 47uf for c5. I didn’t have enough 22µf caps on hand. This shouldn’t make much difference here. A larger cap incases the gain on lower frequencies. The stock value of 22µf is large enough to cover the entire range of bass guitar.
Box caps from futurelec
Others from mammoth if I recall.
Note: I used some sockets here. I always do this on the first build of anything. Also good for experimentation.
Mil max sockets are my favorite. Got these from mammoth. I cut three, three pin lengths.
The PCB has a nice set up with holes for different types of trimmers nice. I used parts I had on hand nothing special ordered. I didn’t have 3 x 5k trimmers so, I used a 10k for TR1 this is fine though, it might be a little harder to adjust.
Not sure where these trimmers came from. Either a grab bag from RS or futurelec.
These pots mount to the board. They need to sit just above the board, with some space. I use another PCB between the board and pots when soldering to get a good space.
I didn’t have B100k pot with legs so I made one. Soldered some wire to the lugs. Then added some heat shrink tubing to stiffen it a bit.
Before soldering the pots I check to make sure that no off board wiring will happen under the pots. In this case not, so I solder the pots now. Double check the values to make sure the right pot is in the right spot.
Cut some 4 to 5 inch lengths of wire I have a bunch of this solid core wire that I’m trying to use up. The length is not important. If you make the length as long as the box you are going to use you can be reasonable sure the wire will reach where it needs to go inside the box when you need to make these connections.
Trim the legs bend them straight. Get the spacing to match the sockets. make sure the height won’t leave these sticking out, above the rim of the box. Q1-2 are MPFA102, while Q3 is 2N5457. Don’t mix these up! Though, in this circuit, it might still work. You might event want to experiment with different transistors in different stages. For the first test it’s probably a good idea to stick with the stock values.
Before boxing things up it’s probably a good idea to test. It’s easier to investigate and fix problems with everything out of the box. I have a test rig with two jacks and a switch. This is wired up like a stomp box, with three wires: in, out and ground.
The holes in the front can hold pots if they are lose. In this case the pots are attached to the PCB.
I use this Heath Zenith power supply for testing. There’s a red and white wire that end in a couple alligator clips.
I use this amp on my desk for testing. It says Webcor on the front, it’s and old tube PA. I got it at a swap meet a couple years ago. It’s got a volume knob on the front. Someone modified it by adding a 1/4″ jack on the back. Sound okay.
Test rig wired up
Using a solder less breadboard I connect the effect to the test rig. Don’t forget to connect ground!
The test guitar
I’m using Squire Sub-Sonic, it’s a baritone guitar. I have it tuned to low B. I usually play guitar. Should be good for testing a bass overdrive. If everything works we’ll break out the bass.
This is a multimeter I bought from RS fifteen years ago. Still works just fine. Set the multimeter to 20v. Time to test and set the bias for the transistors.
It’s hard to take these pictures when you need both hands. Use the panavise as a camera stand.
Take a measurement from each transistor from the leg closest to the trimmer and GND. I use the volume pot, the leg closest to the center of the board for GND this is was easiest to touch with the probe.
First test too low at first. Turn the trimmer and measure again until we get close to 5V.
Bias to 4.95v
Bias up close to 5v. This first trimmer is a 10k I didn’t have enough 5k trimmers so used a 10k it was a little touchy but managed to get it pretty close.
After biasing all three transistors close to 5V. Turn on the amp and test things out.
No sound hmmm. After some thought I check the wiring. Looking closely at the in and out markings on the PCB. There are two wires for each. One is for ground the other is the hot or signal. Quick consultation of the wiring diagram, showed I had the out put leads reversed. Swap these and we have sweet overdrive.
The sound is not “hairy” definitely and over drive rather than fuzz or distortion. I’ll go out on a limb with my inexpert opinion, and say that the over drive sound emphasizes the second harmonic.
Time to box it up
This box came from mammoth electronics/4site. I like these boxes the screws are much better than some of the other 1590B knock I offs, though I suppose this is probably a knock off the Hammond. These screws really make these boxes the best choice in my opinion.
Tape the drill guide on to the box. Make sure to leave a little room for the corner posts inside the box. I just eyeball it. You could break out a ruler and calipers. I’ll put the dc jack next to the switch on the right. I like to put these on top but I was afraid it get afould of the LED since that is top center.
I put a couple marks where I want to drill jacks and switch, see the small black dots.
I drill starter holes with a smaller bit. Then step up to larger bits. I should really invest in one of these stepped drill bits. I hear these work well and save the time of swapping bits.
Some times the holes are a little off, or a little too small. For this I have a round file and reamer I keep on had for small adjustments.
I didn’t have one of those plastic bezels for the LED, I decided to just have the bare LED poking through the hole. This will work well since the LED is mounted to the board directly below the hole. I drilled the hole small and reamed the hole until the LED just fit. I had to adjust the holes a little with the reamer since I don’t have exact bits for each size pot, switch and jack. The reamer lets me get a good fit for each.
Test fit everything in the box
Time to test fit everything into the box. I’m going to use this Fulltone 3DTP switch. I got this switch in 2000 back then it cost $13 and this was the only one. No you can get these all over for less than $3. Back in the “old days” you had to jump through a few hoops to have true bypass and an LED. This switch was the easiest, though most costly method. I think Fulltone wanted these, and couldn’t get them. So he had them custom made. I guess Steve Daniels from Small Bear Electronics finagled a deal with Fulltone to sell these.
Everything fits nicely. Plenty of room for the battery.
Rubber stamps and ink
Now that everything works, and fits in box, time to fix up the box before putting it all together.
First I ash the box off in the sink with some dish soap and sponge.
I always buy a new stamp for a new pedal. I use Stazon ink. This is permanent ink that goes onto any surface seems to be pretty durable. You could scratch it off or sand it off, but doesn’t come off easily. If you put a clear coat over it to make it really durable. I have some pedals I made with just the ink, and they show less wear than painted pedals. It’s quick and easy no spray cans and little clean up. I haven’t tried it yet on a powepder coated box. I like these unfinished boxes they are cheaper, and have an industrial esthetic that I like. I do have an orange powder coated box for a future project.
You really need two sets of the letters to be able to spell things like Fuzz. I have two sets of the small letters and only one set of the larger letters. I should have bought two of the larger. The letters were cheap on amazon.
Fit the LED without solder
To get the right height fit the LED without soldering. I’m using a regular LED make sure the cathode positive pin is in center hold, and the shorter negative anode is on the right.
Add the jacks and switch
I build up the box, everything is hand tight, something might go wrong and I’ll need to take things apart, or I might need to move things around. I leave the switch out for now. This makes it easier to solder the DC jack.
First solder the battery jack. I solder the red wire to the DC jack leaving enough wire to have room to the pull the battery out of the compartment when changing. I run the wire below the other jacks. I measure it and trim a little off to a good length.
Next solder the black wire from the battery jack. I run this wire on the same route, and make sure it has about the same length. Solder to the ring lug on the input jack.
Next solder the ground wire from the PCB to the dc jack ground tab. In retrospect I feel I should have ran it under the input jack.
Now the ground wire from the PCB to the output jack. I route this one under the input jack, and tuck in out the way, I like this better. Neat and clean.
Solder the input ground. I wrapped this under the jack and around. +9v wire from the PCB goes under the input jack also.
Next install the switch. And solder the short wire
Next add three short wires to S4-6. It’s not too difficult to solder them from the top is you leave a small amount of bare wire above the board, just enough to touch it with the tip of the iron.
S4-6 and the in and out solder to the switch. I bent these wires so they ran in a bundle across the center. I’ll tie them together with a zip tie later to keep things neat. Notice the wires from the PCB input and output go to the upper corners on the switch.
Add the final wires to the tip lug of the input and output jacks.
Tighten down all of the nuts. Caution, do not tighten the dc jack too tight, this type strips or breaks easily. Be sure to hold the item on the inside of the box while tightening so the it doesn’t shift. Careful with the wrench on the outside so not to scratch the finish.
Add some knobs.
I always like to make two of everything. If something goes wrong with one I can compare. I can give the extra away to a friend, trade it, bring it to the musicians electronics swap, or sell it on ebay. These two are each a little different. On the left I flipped the PCB upside down. You can see this changed the position of the Volume and Drive knobs and moved the LED to a different spot.
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