quilter overdrive 202

Built-in tuner upgrade for Quilter Overdrive 202 Amplifier

This was a project to make my life a little easier. As a guitar player who has gigged since the 1990’s, I wanted to make some improvements based on the lessons learned over that period of time.

Having a minimal, portable gear set up for gigs is essential. Every extra piece of gear is one more point of possible failure. One of the biggest changes I made was to switch from a standard 50lb, 100w Marshall tube head to a 3lb, 200w solid-state amplifier. The Quilter Overdrive 202 fit my needs perfectly. It has an onboard overdriven distortion that sounds great when played through a Marshall cab. The tone is very close to my tube head and at a fraction of the size and weight. I use it exclusively now, even for practice. I don’t have any other effects or pedals except for my tuner.

In an effort to minimize the set up further, I came up with the idea to modify the Quilter to include an on-board guitar tuner. Frankly, I don’t understand why this isn’t more common -every guitar or bass player needs a tuner, right? Why not built into the amp? I know most guitar players like having a pedal in front of them so they can mute and tune easily on stage. I retune maybe once when playing an entire set live. Sometimes not at all because I tune up beforehand. Still, I see the value in having a tuner on the floor. I just wanted to see how minimal a set up can be.

I experimented with several different types of tuners, but the limited space made it impossible to use anything but the smallest devices. Guitar tuner pedals were not an option. When disassembled they are too bulky -even the “mini” versions. The smallest ones out there are clip-on tuners. Clip-on tuners, as the name states, “clip on” to the headstock of your instrument and use surface vibration to detect the musical notes being played. I will need to plug directly into the tuner’s input (like a tuner pedal) and bypass the transducer/contact mic inside the tuner.

Figure 1: Fender Bullet Tuner

Figure 1: Fender Bullet Tuner

After a few failed attempts to find the right tuner, I settled on the Fender Bullet Tuner as this was one of the most compact ones I could find. It’s remarkable how small this thing is. Especially when you disassemble it (figure 2)!

The tuner upgrade for the amp had the following requirements:

  1. Fit within an existing cavity inside the amp.
  2. Be powered by the same power source as the amp (no batteries and no additional plugs).
  3. Use the instrument input to the amp for the tuner.
  4. Be bright enough and visible when on stage.
  5. Be able to mute/turn down amp without effecting the tuner.
  6. All connections should be hard-wired (soldered) to prevent continuity issues.


Since the tuner is so small, it was important to be extra cautious when disassembling it. I already destroyed one clip-on tuner and at $29 a pop, I didn’t want to break this one.

Figure 2: Disassembly of Fender Bullet Tuner

Figure 2: Disassembly of Fender Bullet Tuner


closeup of tuner element

Figure 2a: Closeup of tuner element

You can see the transducer/contact mic glued to the top of the black plastic disk. There is a red wire soldered to the center of the contract mic (this would be the instrument cable “tip” input) and the battery spring is attached to the negative power input and shared with the plate of the contact mic input (instrument cable “ring”).

Microphone modification

I’ll need to tie into the instrument input on the amplifier and connect it to where the contact mic on the tuner is connected. The transducer cannot remain connected in order to work properly, so I’ll need to take it out.

Figure 3: Instrument input lines inside Quilter Overdrive 202

Figure 3: Instrument input lines inside Quilter Overdrive 202

I found the perfect spot for the tuner (directly behind the “Quilter” logo). It’s also the same general location where the instrument input is. I removed the circuit board and tested the leads to find the location of the tip and ring from the instrument cable (mono). It looks like the instrument input can be used with a stereo cable (balanced input). I’m not gonna worry about that so much since I won’t be using a balanced cable with the guitar. I’ll need to drill a hole here for the tuner display to poke through.


The tuner normally takes 2 x LR44 batteries totaling 3v. Figured the current draw is less than 10ma since that’s all these tiny batteries can handle. Since I’m going to power the tuner by tapping into the main power plug from the amp, I’ll need a power supply that can handle both 110v and 220v just like the Quilter can (so I can use the amp anywhere in the world). I didn’t have a 3v power supply and after looking online, it was impossible to find a small one. All of them where the standard “wall wart” size and would not fit within the amp. I had to get creative.

I started going through my stock of power supplies and found a bag of old iphone charging blocks. These are by far, the smallest power supplies around. Since it’s standard USB power, it’s 5v. But it can handle 110/220v. Perfect. All I need to do is figure out a way to step the voltage down to 3v. I don’t think the tuner has a voltage regulator nor a high tolerance to higher voltages so I won’t risk it as-is.

After another run through of all my electronics, I found some buck converters (DC to DC voltage converters) with a nice little screw to adjust the output voltage to whatever you need. I will have to sacrifice an old USB cable so I can have easy access to the 5V.

In order for the tuner’s power to only be active when the amp is on, I’ll tie into the main switch for the amp (running power in parallel) being careful to shield any exposed metal with an insulator.

Figure 4: iPhone charging block (USB 5V power supply) with buck converter inside Quilter Overdrive 202

Figure 4: iPhone charging block (USB 5V power supply) with buck converter inside Quilter Overdrive 202

Figure 5: Connected USB power supply in parallel to power switch of amp.

Figure 5: Connected USB power supply in parallel to power switch of amp.


Figure 6: Tuner hot-glued into place inside Quilter Overdrive 202 after a hole was drilled so tuner head is flush with faceplate of amp.

Figure 6: Tuner hot-glued into place inside Quilter Overdrive 202 after a hole was drilled so tuner head is flush with faceplate of amp.

The only way I could figure out to secure the USB charging block and buck converter was to use zip ties. Not the most elegant solution, but it’s secure and no one will see it.

Next I had to drill a hole into the faceplate which was the last step on the process. If anything else failed before this step, I didn’t have to cut a big hole in my amp! Of course, everything checked out. I completely covered the electronics with tape and plastic so no metal shavings would get into the electronics and cause shorts.

Securing the tuner in place was challenging. I tried a variety of methods and settled on good old hot glue. Again not the best solution, but I really didn’t have any other option available, so I glued the shit out of it!

The moment of truth

It took some guts to flip the switch and hope it doesn’t blow up in my face. Fortunately, it didn’t.

After thoughts

The tuner has an automatic shutdown feature (after 10 minutes) to preserve battery life. You can turn it back on by power cycling. It’s not an easy thing to disable due to the size of the tuner. I’d end up destroying it for sure, so I decided to leave it be. I’m considering installing a small push button switch next to the tuner so I can easily turn it on/off. For now, I just turn the amp off and on and the tuner comes back on.

I noticed after I installed it how the Quilter logo almost lined up with the letters shown for the key. Perhaps a missed opportunity to have the key letter alter the title. Something like QuiBer, QuiCer, QuiDer, QuiGer, QuiFer. Nothing too thrilling. I wonder what other title I could use for the key letters A-G? Maybe, DI_? DIA, DIB, DIC, DID, DIE, DIF, DIG. LOL! It’s gonna be tough to find a word with one missing letter that will work for consonants and vowels.