A simple buffer for a piezoelectric pickup to mixer connection

Question

so my question is pretty straightforward: what are the ways in which this circuit is likely to fail, and how can I protect against that?

I play music (mandolin and viola) and my instruments have piezoelectric pickups, which sound kind of crap connected directly to a mixer.

I've built this buffer circuit (see image) and it works - my instruments sound significantly better. I intend to build it into a module for my instruments for use while performing live.

It is my impression that, because this circuit is so basic there shouldn't be much that can go wrong. Feel free to disabuse me of this notion - but please explain why as I wish to get a clear understanding of what I'm missing.

EDIT 1: I also attempted to measure the current draw, but it's so low (well under 10mA) that my cheap multimeter couldn't measure it, and the 5V USB power bank I was using to power the circuit kept powering down. For this reason, I presume that the voltage levels will generally remain stable during use ... is that a safe assumption?

EDIT 2: Updated circuit design based on suggestions from @richardthespacecat and @analogsystemsrf

^{simulate this circuit – Schematic created using CircuitLab}

Answer 1

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. OP's Figure 2 has a few odities.

I have a few concerns about this circuit.

• Using the op-amp output as ground is unusual. Normally the 0 V line would be considered ground. This simplifies power supply, debug and, in guitar effects units, for example, allows the battery to be connected into circuit by insertion of the jack plug.
• The piezo pickup will have an extremely high input impedance. That means there is nowhere for IC1a's bias current to go. That means that the bias current will drive the + input to one supply rail or the other.

^{simulate this circuit}

Figure 2. A more traditional approach.

The normal way to do this is to use the mid-supply as a bias for the operating point of the amplifiers. Since you have chosen a non-inverting arrangement then you need to apply the bias as shown via R3.

C2 and C3 decouple the input and output and prevent the DC being affected by external connections.