A Bass Mod, Two Multimeters, and a Lesson Learned
“Work on your timing,” my bass teacher would probably say. While modding a bass guitar, I ended up comparing two multimeters and stumbled across a reminder that measurements alone don’t tell the whole story. A short read about bass mods, practical measurements, and why understanding a circuit still matters.
In fact, that bass I worked on is even called “Bastelbass” (“modding bass”). I also own another bass from Humanbase that I would never touch, as in my view it’s a work of art. The Humanbase is not only a wonderful instrument to play, it is also my safety net when one of my modding ideas goes wrong, like my attempt to improve the neck connection to the body by using machine screws. That particular idea was a close call. If you ever thought about doing something similar, don’t, because maple is very hard and difficult to work with.
My latest research project was the possibility to select different tone caps. Basically, the higher the value of the capacitor, the more vintage the sound. Typical for bass guitars is 47 nF. For normal electric guitars it’s 22 nF, and for the real vintage bass guitar sound some people use 68 nF caps. Combining a 22 nF and a 47 nF cap through an “on-on-on” switch, there is a possibility to select between the values 22 nF, 47 nF and 69 nF. The latter is achieved when both caps work in parallel, which is the middle position of an “on-on-on” switch.
Obviously, I wanted to test whether I have properly soldered the caps into my “on-on-on” circuit. Yes, I could have done this with an LCR meter like HIOKI’s IM3533 or even an impedance analyzer like the IM3570. But a good general-purpose multimeter will deliver the same result as well. In line with the famous dart scene from “Ted Lasso” (“Be curious, not judgmental”), I decided to test the caps with HIOKI’s highest-spec handheld multimeter, the DT4282, and one from the “pocket range” of DMMs, the DT4224.
I wanted to make that comparison because the DT4224 has a voltage input protection. When making a resistance or capacitance measurement, the input needs to be low impedance. However, if by accident the DMM is set to resistance or capacitance measurement and someone tries to measure mains voltage, the RCD of that circuit would certainly trip. That’s not a really big deal in my basement, but imagine if this happens during maintenance work in a production environment.
To avoid this scenario, the DT4224 (like its sibling DT4223) will first check for a voltage with the input in high impedance. Only if there is no voltage at the input will the DMM switch into low-impedance mode for the resistance or capacitance measurement. That check obviously takes time, and I was curious to see whether it’s noticeable.
It is (noticeable). The DT4282 is faster at making that capacitance measurement. I wasn’t curious enough to build a setup to find out how much faster. But let me put it this way. The practical difference was about as much as the difference in measurement results. The 47 nF cap was measured as 48 nF by the small DT4224 and as 47.9 nF by the top-range DT4282. Which means there is no practical difference in everyday use.
What I did not expect, however, was that this small measurement exercise would turn into a reminder of why understanding a circuit matters just as much as measuring individual components. At one point during the modding process, the tone control of my bass suddenly started behaving like a volume control. All component values were correct, the solder joints looked fine, and the multimeter readings were perfectly reasonable. And yet, the circuit behavior was clearly wrong.
The root cause turned out to be neither the capacitors nor the potentiometer itself, but a missing reference: a proper ground connection at the volume pot. Resistance or capacitance measurements with a multimeter use DC test signals, while a bass guitar operates with AC audio signals. Without a solid ground reference, the measurements still looked “correct”, but the circuit itself was effectively floating. Once the ground connection was properly restored, everything behaved exactly as expected again. That was a good reminder that measuring individual components is only half the story. Knowing where and what you are measuring is just as important.
So what’s the takeaway from this post? If you’re looking for a small, high-quality digital multimeter, the DT4224 is a very sensible choice. Especially if you can’t remember the last time you measured current with a handheld DMM. It was not only developed in Japan, but is also manufactured there. And yes, I really should work on my timing instead of writing texts like this.
