Why Does an Upright Bass Sound Thin? Top Preamps to Bring Out the Best in Piezo Pickups

I have a friend who is a guitarist with a big sound.
I don’t just mean that he plays loud. His sound always comes through clearly, even when he’s playing in a band.
Of course, he’s a highly skilled player, but I’m also impressed by how well he knows how to get the best out of his amp.
Inspired by him, I’ve been revisiting the settings on my own gear lately. Just for fun, I asked AI to recommend some settings for my equipment, and the sound improved dramatically. I was delighted, but also a little frustrated that it worked so well!

The Misconception That “Piezo = Thin Sound”

I’ve tried several pickups for upright bass over the years.
One well-known staple is the Fishman BP-100 Classic Series Upright Bass Pickup.
When connected directly to a bass amp, it tends to produce a thin, trebly sound with a noticeably reduced low end.
For a long time, IA’m embarrassed to admit, I assumed that this was simply an inherent characteristic—or limitation—of piezo pickups like the BP-100.
But I was completely wrong.

The Cause: An Impedance Mismatch

A typical bass amp has an input impedance (the resistance presented at the signal input) of around 1 MΩ.
By contrast, many piezo pickups, including the BP-100, recommend an input impedance of 10 MΩ.
In other words, one major reason the low end gets lost and the amplified sound strays so far from the upright bass’s natural acoustic tone is an impedance mismatch. *When connecting audio equipment with a cable, the general rule is to feed a low output impedance into a sufficiently high input impedance.
Proper impedance matching is essential to getting the best performance out of a piezo pickup.
Fortunately, the solution is simple: just place an acoustic preamp that supports a 10 MΩ input impedance between the pickup and the bass amp!
With that out of the way, let’s take a look at some preamps recommended for upright bass.

6 Recommended Preamps for Upright Bass

1. ZOOM / AC-2 Acoustic Creator

Features

Equipped with a switch for selecting the pickup type. Setting it to ‘Piezo’ activates EQ adjustments that automatically compensate for excessive high frequencies and a weak low end.

Key Point

It includes a dedicated ‘Upright Bass’ preset, making it easy to dial in an optimal setup.

2. Fishman / Platinum Stage EQ/DI Analog Preamp

Features

The unit has a ‘Guitar / Bass’ selector switch. Selecting Bass changes the EQ frequency ranges—including low-end compensation and adjustable mids—to better suit the upright bass.

Key Point

Higher-end models, such as the Platinum Pro EQ/DI and Aura Spectrum DI, also support a 10 MΩ input impedance.

3. L.R.Baggs / Session DI

Features

Equipped with saturation and compression functions, it adds warmth and cohesion to your sound.

Key Point

It allows you to fine-tune the midrange character and tackle feedback issues that are particularly common with acoustic instruments.

4. EBS / Stanley Clarke Signature Acoustic Preamp

Features

In addition to switching between Channels A and B, you can also blend the two channels.

Key Point

You can blend a piezo pickup with a condenser microphone that supports 48 V phantom power and send the combined signal from a single unit. This makes it possible to achieve an even more natural, acoustic sound.

5. Radial / PZ-Deluxe

Features

Engaging the dedicated ‘PZB’ piezo booster switch on the unit changes the input impedance to 10 MΩ, optimizing the pickup’s output and frequency response.

Key Point

It also features a three-band EQ, a notch filter, and a high-pass filter, providing comprehensive tools for managing pickup sound onstage.

6. Grace Design / ALiX Black

Features

A high-end model renowned for its exceptional clarity and resolution. Its midrange can also be adjusted with great precision.

Key Point

The high-pass filter (low-cut) offers an exceptionally wide frequency adjustment range, allowing you to target and cut the boomy resonances and low-frequency feedback components characteristic of the upright bass.

Conclusion

What did you think of our recommended preamps?
Although the upright bass can sound loud acoustically compared with other instruments, its sound can easily get lost in an ensemble. As a result, players often need to rely on an amp or PA system to make themselves heard.
Piezo pickups are appealing because they’re affordable and easy to work with, but pairing them with the right preamp is key to unlocking their full potential. Try adding a preamp that supports a 10 MΩ input impedance and discover your ideal sound!