Piezo Pickups Evolve

So, we’ve looked at piezo pickups. We checked out the magic of piezo (hint: it’s not actually magic); we’ve looked at integrated pickups and some of their problems; and we checked out the 800 pound gorilla that is the Takamine Palathetic pickup.

Surely that’s piezo finished?

Well, not by a long chalk. However, I don’t want to drive you completely insane so I’ll not dig too much further into the world of piezoelectric pickups. I will revisit the subject in a while to discuss the important matters of installing and troubleshooting these things but, for now, I’ll wrap up by looking at the way in which undersaddle pickups have evolved since the early days.

Advances in piezo materials changed UST pickup designs

The ‘basic’ UST

A few weeks ago, I described what I called the ‘basic’ undersaddle transducer/pickup. This is a metal channel or housing to hold six piezo elements with a metal strip on top to ‘collect’ the signal. Usually, the while thing will be wrapped — maybe in heat-shrink tubing — to keep things in place.

The construction of a very basic piezo pickup

And this is what some USTs are still like, especially at the budget end of the market. They work fine but, because there are six discrete elements, they can be fussy about placement — if each element isn’t directly under a string, you can easily have output imbalances from string to string. Careful positioning is more critical and they may not be ideal if your guitar has an odd string spacing.

Yeah, Science!

Around thirty years ago, men and women with high foreheads, wearing white coats, and carrying clipboards started doing weird things with various plastics. Through the application of liberal amounts of <airquotes> “science” </airquotes> these boffins were able to make thin, flexible, plastic sheets that were essentially big, flat, piezo elements.

Duuuude. The game’s totally changed.

No more need for housings and individual elements for each string. Now it was possible to make a single element span the full length of a saddle slot.

More possibilities opened up for UST pickup design and, as things have shaken out, we’ve ended up with three main types. Each operates on essentially the same principal — a piezo ‘strip’ is sandwiched between a hot and ground conductor and is shielded all around in some way — but how they achieve this is slightly different.

The Rigid UST

The Fishman Acoustic Matrix is probably the best known and most common of the new breed of UST.

Fishman Acoustic Matrix UST

This is what I refer to as a ‘rigid’ UST. It has a piezo strip between two conductor strips (hot and ground) and it’s wrapped in a (grounded) shielding tape to keep any nasty electromagnetic interference (EMI) away from the internals. There’s a hook up cable at one end.

The conductor strips and wrapping give this pickup an amount of rigidity. It doesn’t bend much (nor should you try bend it). Oh, and you should definitely be careful of the joint where the cable connects — it can be delicate. It needs careful installation in a flat slot with a perfectly flat saddle bottom over it.

The Flexible UST (Ribbons)

Pickups like LR Baggs’ Ribbon don’t employ rigid conductors like the Fishman. All its internals are flexible and the whole thing can be easily bent (don’t kink it).

Because it’s more flexible, it’s not tied to a particular length of saddle or slot. The ‘working/active’ part of the pickup can be made longer and, once the slot is full, the unused portion just pokes though the hole in the bottom of the saddle.

As a side note, be careful of this extra active part inside the guitar. It can resonate with the top’s movement, or the air in the guitar, and cause feedback. If there’s a problem, you might want to clip or secure it inside the guitar.

I actually worked on a ribbon-style transducer a couple of weeks ago and forgot to take a photo. Sorry. ¯\_(ツ)_/¯

Imagine a much thinner, more flexible, pickup than the red Fishman UST above. Sorry again.

The Braided UST

Looking like a traditional electric guitar pickup hook-up cable, this UST uses a coaxial design with the hot conductor at the middle. A flexible piezo layer surrounds the core conductor and the whole thing has a braided wire sheath along its length.

Braided UST pickup

Because the braided pickup has the most ‘give’, it’s a little more forgiving of small unevenness in the saddle and slot. However, you do have to remember that there’s now a somewhat softer and more pliable object between your saddle and guitar top. Some players feel this impacts the instrument’s acoustic tone more than the other UST types.

And many more…

There are dozens (maybe hundreds) of UST pickups but they’ll mostly follow one of the designs outlined here and in previous articles.

I'll follow up these last few piezo-related articles with some related info on acoustic instrument amplification soon.