I figured that I should probably write an article about an actual technical issue in live-sound, seeing as how Carlos always introduces me as an audio-human. I mean, it was getting a little ridiculous there (my piece about why some audio guys are unhelpful notwithstanding).
Some of you have instruments with non-preamplified pickups. That is, the pickup doesn’t run to any kind of processor, doesn’t need any batteries, and isn’t connected to an amp that you’ve brought along. Instead, the pickup simply turns your instrument’s vibrations into electricity, and that electricity travels down a cable that gets plugged into the audio rig.
…and some of you have had real problems. I have very definitely heard several variations on “When we played at that other place, we couldn’t get any level out of my pickup. I might need a new one.” It hardly happens to me every day, but I’ve encountered people with similar issues often enough for me to think: There’s something out there that needs to be addressed.
Let me start by saying that the news is probably good, actually.
It Probably Didn’t Break Between Rehearsal And The Gig
Yes – sometimes gear does get mangled on the trip to the venue. You can’t discount that possibility. However, if you just recently plugged your pickup into a practice amp, and everything was fine, it’s unlikely that your gear spontaneously killed itself.
Most instrument pickups that I run across are fairly hardy creatures in and of themselves. These days, the actual pickup part of the pickup should be able to withstand at least a bit of abuse before having an internal failure. (I’m not advocating that you do mean things to your pickup. I’m just saying that riding around in a gig bag probably won’t wreck the actual transducer.)
Oh – if you didn’t know, “transducer” just means “a device that converts one form of energy into another, corresponding form.” In this case, we’re talking about taking the energy of your instruments vibrations and turning it into electrical energy.
The actual transducer is usually attached to a cable. That cable, while probably not delicate, is likely to be far more fragile than the pickup itself. For that reason, it’s worth keeping a mental note as to whether or not that cable might have been yanked, bent at a sharp angle (especially near the plug or the pickup), stepped on, rolled over by a roadcase, smashed during transit, or otherwise treated poorly. That’s just due diligence when you have a problem.
But, what if everything seems like it should be okay? What if you’ve connected your instrument to the PA system via the audio craftsperson’s shiny, new, undamaged direct box…and all you get is a “tinny,” weak signal? Do you need a new pickup?
Short answer: No.
You Probably Have An Impedance Problem, Not A Pickup Problem
Impedance is really the “meat” of this issue. So, what is it?
Impedance, by itself, is not a complex idea. It’s the opposition to the flow of current in a circuit where the voltage changes over time. Yes, that’s right: The signal on your instrument pickup’s cable is a kind of alternating current. Sure, the voltage is much lower than the alternating current that comes out of a wall socket. Sure, the frequency content is complex.
It’s still alternating current, though.
The basic concept of impedance is not difficult to make sense of. What gets audio and music folk into trouble is that impedance issues can have profound effects on how our gear works. What also gets us into trouble is that we live in an age where a lot of “impedance matching and bridging” problems have been thoroughly worked out. We just don’t have to think about impedance issues very much (or at all), and so we forget to consider possible impedance pitfalls when a problem occurs.
I know that this is getting REALLY technical. Don’t panic. Yet.
The problem with us pro-audio types is that we predominantly live in a world that thrives on low impedance. Sending signals across “long” lines (like a 100’+ snake), and then applying a ton of gain to those signals are “Very Pro-Audio Things To Do.” The doing of Very Pro-Audio Things is facilitated by having relatively low-impedance signal paths. Low impedance is great for driving long cables. Low impedance is great for keeping noise manageable.
…and low impedance can make your instrument pickup sound awful. Getting into precisely how that happens is a bit beyond the scope of this article, but suffice it to say that low impedance can result in signal loss, unwanted resonances, and the filtering out of either low or high-frequency signal content (depending upon the situation).
But What About That DI Box?
Now, at this point you might be saying, “But at my last show, we plugged my pickup into a DI box. It sounded terrible! DI boxes were made so that my gear would work with pro-audio gear, right? My pickup must be bad.”
Firstly: You’re correct that DI boxes are primarily used to help with getting different kinds of gear to play nicely together.
Secondly: Not all DI boxes are the same.
(I’ve actually written a whole article about this on my own site.)
These days, a lot of the most affordable DI boxes are basically meant to serve one purpose: They take an unbalanced, actually low-ish impedance signal that might be a bit too “hot” for a mic pre, and turn it into a balanced signal that’s at an even lower impedance, and has been reduced in voltage to a mic-pre friendly level.
These DI boxes are passive, meaning the only electricity that they need is what they get from the signal source plugged into their input.
Let’s be clear. “Passive” does not mean “bad.” I myself have a handful of passive DI boxes that are perfectly adequate – when they’re being used for the correct purpose. The issue with passive DI boxes is that they are simply not the best choice for high-impedance devices, like your “stick it in the soundhole” inductive guitar pickup.
Further, passive DIs are a THOROUGHLY AWFUL choice for really, really, really high-impedance devices, like that “no installation necessary” piezo pickup that sticks to your classical guitar/ mandolin/ violin/ whatever.
The reason is impedance. A passive DI box’s input impedance just isn’t that high, especially for a piezo pickup. A magnetic pickup might get by with some “ultimately tolerable yet still disappointing” loss of high-end, but a piezo pickup might seem like it has no output, no “body,” and a rather disgusting sort of “nasal honk” if you can get enough gain applied to hear anything.
On the flipside, active DI boxes and preamps designed for instruments DO have high-impedance inputs. This is why the question of “did your pickup work with a practice amp” is an important one to answer. If your pickup worked with the practice amp in rehearsal, then the problem at the gig might just be DI box’s impedance. Mate your pickup to an active DI, and chances are that your pickup problems will “magically” resolve themselves. Active DI boxes have undergone significant price drops over the years, to the point that they can be had for only slightly more than a passive model. If you’re using an instrument with a passive pickup, you might want to invest in an active DI or preamp of your own…
…because even an otherwise competent audio human might not be aware of the above, just as you weren’t aware of it. Which leads me into a bit of a rant:
We Seem To Also Have An Education Problem
I don’t want to get too “tinfoil hat” about all this, but it seems like the constant drive to reduce packaging and reduce costs has resulted in the death of The Truly Helpful Instruction Manual. Back when I was much younger, it seemed like all kinds of things shipped with thick, detail-oriented instruction books that did more than just tell you how to plug things in. These Truly Helpful manuals had all kinds of background information in them, which helped you to understand how a product actually worked. If the customer actually bothered to read the book, they stood a good chance of understanding enough to know WHY something might be acting up.
Now, as many things have gotten highly commoditized and much more “stupid resistant,” manuals have been reduced to quickstart guides that tell you very little about the whys and wherefores of your gear. In some cases, this is excusable…especially when the manufacturer has truly eliminated most of the guesswork involved in using the product.
The issue with passive instrument-pickups (and other things) is that the informative manual has been eliminated while the uncertainties remain. Active or preamp-equipped instrument pickups can be plugged into almost anything and work acceptably, so a manual that talks about things like DI boxes and impedance issues would be nice…but not 100% necessary. On the passive side, though, it’s troubling as to the lack of information that would help customers understand what affects their gear – perhaps profoundly.
Of course, this lack of education on the part of equipment manufacturers helps folks like me, in terms of giving us consulting gigs and letting us write articles like this. In the case of someone’s live-performance, though, I think that the cost of saving money on the manual might just be a little high.
I dunno. Maybe I’m wrong.
But I do miss informative, well written, engagingly illustrated instruction manuals.
Anyway – your pickup probably isn’t broken. Just remember that impedance is a factor, and be ready to try a couple of different things when the unexpected occurs.