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Boost Effect Builds My Designs

Building a Simple Op Amp Booster – Assembly

After the introduction, analysis and breadboarding of two op-amp based guitar boosters, I’ll complete the pedal.

I’ll do the final schematic and bill of material, then do the soldering layout for a protoboard. I’ll plan out the enclosure, do some artwork and finalize the enclosure. I’ll finally assemble it and do test and demo.

Final Schematic

The base schematic did not change, it is exactly the same I used for breadboarding:

Schematic of Thunder Booster
Thunder Schematic

To complete the pedal I need the rest of the paraphernalia:

Schematic of the rest of the necessary components
Jacks, power, LED, Stomp Switch

The only difference from my previous builds is that I wired footswitch slightly differently (I simplified it a bit), but other than that everything else is the same.

If you followed closely, you might’ve noticed that TL072 has two op-amps, and I only used one. Proper way to wire-up the unused op-amp is (see The Signal e-book):

Schematic showing how to wire unused op-amp
Connecting unused op-amp

This minimizes current consumption and cross-talk and improves performance. Since this is not really a critical application of an op amp, I would guess the effect of leaving it unconnected would be most likely minimal 🙂. Just being pedantic, that’s all.

The real shame is leaving it unused. Alternative would be to use TL061 or TL071 for example, they carry a single op-amp, but price difference is minimal and pinout is different from TL072. I also have loads of TL072s, and in more complex designs the extra op amp will come in handy.

Bill of Material

Here’s the final list of components:

DesignatorsComponentNotes
27969PSLA
(1590A Hammond)
Enclosure
ProtoboardSBB170 solder-in breadboard by Proto Advantage (fits into the enclosure … nearly)
Jumpers and wires24 AWG solid core wire and 28 AWG stranded wire
J3Cliff FC681473DC Power Socket
J1Switchcraft 112BX (or ACJS-MVS-3S Amphenol)In – stereo Jack (alternatively use mono jack since I don’t use ring connector)
J2Switchcraft 111X
(ACJM-MVS-2 Amphenol)
Out mono Jack
RV110K Linear PotALPHA RV16AF-41-15R1-B10K-3
KnobKnob that fits 6.35mm straight shaft
S1SF17020F-0302-21R-LTaiwan Alpha 3PDT latching foot switch
C1100pFCeramic cap (NP0/C0G)
C2100nFMetal film PET cap
C31uFElectrolytic cap 25V
C422uFElectrolytic cap 25V
C5150pFCeramic cap (NP0/C0G)
C647uFElectrolytic cap 25V
C7100nFCeramic cap (X7R)
C8100uFElectrolytic cap 25V
R1, R6100 ohms1% 250mW metal film
R2, R32.2M
R4, R5680 ohms
R7, R8, R910K
R101KLED current limiting resistor
D1Led3mm Orange-Red, 2V forward voltage
U1TL072IPTL072 in 8 pin DIP package
DIP-8 SocketSocket so I don’t solder the chip directly
List of components for Thunder

I decided to use a socket for my chip so I don’t solder it directly to the board. Once the socket is in place I can simply pop in the chip.

The potentiometer I have is supposed to be mounted on a PCB. Solder lugs would’ve been preferable for this build since I’m not going to mount it on the PCB (RV16AF-10 model instead of RV16AF-41). But I got to work with what I have. Note – the model I have has shaft width 6.35mm, so some 6mm knobs might not fit.

Here are all of the components before I started assembling them:

Photo of spread out components for Thunder just before assembly
Prepared components for Thunder just before assembly

Board Layout Plan

It gets a bit crowded with this many components, I found a nearly perfectly fitting proto-board (or solder-in breadboard, eh):

Photo of SBB170 solder-in breadboard fitting into enclosure
SBB170 solder-in breadboard fits (after light sanding)

I very lightly sanded it (about 1mm or so but I did not need to cut it).

Here’s one way to lay the effect out on it:

Diagram of Thunder effect on protoboard
Thunder on protoboard (Click for full size image)

Here’s DIY layout file as well:

Lots of wires (I hate wires) but unfortunately, with small board, sometimes this is inevitable.

Enclosure Planning

Here’s an excerpt from the SVG I used for planning:

Excerpt image of enclosure drilling plan
Enclosure drilling plan

In order to properly print it, I used SVG format since I could draw everything in actual millimeters for example. Using Inkscape I could plan this and print it exactly as per measures on the drawing. Here’s the SVG:

I prepared pdf version as well, it has to be printed without scaling (so scaling 100%, I was printing it on A4 paper)

Enclosure Artwork

I’m going to do decal for artwork, directly onto the “natural” finish. Same thing as with enclosure planning, I used SVG:

Thunder artwork
Thunder artwork

I used a public domain photo for this, here’s the full SVG for this:

Prepare Enclosure

I got into more details on how I do drilling in one of the previous articles, as well as on how to apply decal with inkjet decal paper.

I did not paint the enclosure, I just washed it with some dish soap after the drilling and applied the decal:

Photo of Thunder enclosure after drilling and applied artwork
Thunder enclosure after drilling and applied artwork

Final Assembly

I did soldering exactly how I planned it in the diagram above. Similarly like before – I soldered them based on height, from smallest (jumpers) to biggest (electrolytic caps and LED).

One note: I soldered socket for the TL072 in place first and I just popped the chip in. I don’t do that all the time, but benefit of doing it is that it saves the chip from being burnt from too long soldering.

Here’s how it looks like, practically 1-to-1 with the diagram:

Photo of soldered Thunder board
Soldered Thunder board

Btw, Sparkfun has a good guide on soldering.

Since I had only PCB mounted pot, I had to cut it’s legs and solder wires to it:

Photo of Thunder pot with cut-off legs and soldered wires to it.
Pot with removed pins and soldered wires

Once I had the board soldered and pot attached, I could do some testing before the final assembly:

Photo of the board with attached crocodile clips for testing
Test the board before final assembly

I hooked up crocodile clips to the wires coming out of the board and attached them to the jacks I used for breadboarding so I can try this out. I attached battery as well and everything worked as expected.

Photo of how everything fits into the enclosure
Everything fit into the box

Despite more components and more complex board, everything fit more neatly than before 😉, looks like after few attempts at this small enclosure I’m getting there. I can probably make it neater if I put everything onto a PCB … there’s an idea!

Here’s the finished result:

Photo of finalized Thunder pedal
Finalized Thunder

Test Ride

Here’s the pedal in action:

Trying out Thunder

Pedal in action:

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