Since I’m starting to play Anna’s octave mandolin in concert occasionally, I want to get a pickup of some sort attached. Yeah, I can play into an instrument microphone, and I’ve been doing so, but wow I hate that. I hate being tied down into a single place on stage.

A couple of months ago I ordered a Zeppelin Labs “Cortado” pickup kit. I’d planned to try making it into a boundary microphone/PZM – and I probably will order another kit to do that – but since hey, I need a pickup, I have a kit, let’s see how this works when built as actually designed!

I started working on it during yesterday’s DIY Music Chat on Twitter, mostly because it seemed fitting. It’s a small kit, and one of the easier builds I’ve made. Here are all the parts except for a missing ground wire. I don’t know what happened to it, but I have lots of wire so it was no big deal:

Populating the circuit board was very trivial. They did warn you about the transistors, which is good – I have a grounding strap so I used it. But it really was just insert-into-holes-solder-on-backside work. The instructions do walk you through technique, so if you’re new to this, the detail they provide is nice.

The only surprise was that my serial number was in the series that needed a small mod to the circuit – instructions were in a service bulletin. This was only an issue with some of the units in my run, so this may’ve been optional, but I went ahead and did it. It just consists of adding a second resistor in parallel to the included one.

Assembling the piezo pickup is probably the closest part of any of this to being difficult. First – and I’m a little confused about this – you attach the double-sided tape to the back of the disc, and trim it. This doesn’t seem to have any function and I’m not 100% convinced this isn’t an error in the instructions.

Then the red wires which come already attached have to be removed, and replaced with leads from the shielded cable they provide with the kit. That involves stripping the end of the multi-lead cable, bundling the shield together into a connector, and stripping the ends of the other two wires.

The two central wires get attached to the piezo disc, exactly where these are attached:

Then you put a layer of electric tape on either side of the discs (for electrical isolation, which makes the double-sided tape redundant, which, again – instruction error?), then wrap the whole thing in the provided copper tape. It’s important to make sure the bottom side – which is how it attaches to instruments – stays very flat:

Then that aforementioned shield ground is soldered to the copper tape. Also, you should make sure the joins on the copper tape are nice and conductive, which means lots of weird-looking not-actually-random solder spots.

Shielding is pretty important in applications like this, because you’re dealing with small signals at the pickup, no matter what. So it’s important to get that right, and right throughout. Which is why the circuit board gets mounted inside the tin which is provided with the kit.

Drilling that tin was the biggest problem I had, honestly. You need a 3/8″ drill bit, and I didn’t have one of those, so I had to go buy one. And I bought a nice one that was supposed to be super-good at drilling smooth holes in metal. That did not go well, but since that’s not the kit’s fault, I’ll not dwell on it. Anyway, I managed to hide the damage.

The next step is connecting a ground connection on the board to the tin itself. Again, not difficult, but important – what you’re doing is grounding the entire circuit and pickup, to block radio frequency noise. That connection is in the upper right, here:

Once you’ve done that you bring in the wires from the XLR connector, to attach to the circuit board. Those wires are also shown in the picture above. Then on the other side of the board, you do the same thing with the leads from the piezo pickup, just like that:

…and screw the board down inside the tin. There’s a spacer to keep the board from touching the metal case, which is now a shield housing.

And that’s literally all there is to it. Throw in a couple of tight zip ties to keep cable stress off the circuit board, and you’re done with construction.

Now, use is another matter. For long-term attachments, they say to use the included double-side sticky tape – it’s permanent, though, so be sure you know where you want it before applying. But, as above, they already told us to use that sticky-tape. So… I’m not sure what’s up with that.

For temporary attachments, they suggest things like holding the pickup down with painter’s tape, or poster tack. I don’t have any poster tack, but I tried the painter’s tape, and that didn’t work very well at all. It collected sound, but it sounded really midrange-heavy, really tinny – it didn’t pick up any of the low end at all.

So then I tried poster-weight “command adhesive” strips, the removable ones 3M makes. I didn’t expect that to work well, and it didn’t – though I did pick up some more of the octave mandolin’s low end that way, so it was a step in the right direction.

I was starting to get worried that I’d done something wrong in the pickup at that point, so I tried just holding the pickup against the octave mandolin’s face. That worked just fine (10 second mp3, open strumming) so I think it’s just issues with making a good attachment.

Since the user instructions say that you can try plastic clamps to attach the pickup, and those are cheap, I’ll be buying one to try that. I’ll have to space the clamp off the pickup itself with a layer of foam or something, because of wires, fragile pickup disc, etc., but I hope it works – I really don’t want to be playing into an instrument mic even for one song at Conflikt. And held in place by hand, the pickup really sounds good.

Also, the noise level on this thing is hilariously low – they promise a low noise floor and they really overdeliver. VAST TRACTS OF SIGNALtiny noise floor! Well done there.

I am still wondering if the difficulty I’m having is caused in any way by the double-sided tape being inside the pickup bundle. I know I didn’t get that wrong – there are photos of how to do it in the instructions. But I’m wondering if you’re supposed to skip the electric tape on that side if you use the double-sided tape, and they forgot to mention that.

I’ll drop Zeppelin a support note it. If I was supposed to leave it out, well, I have more copper tape. I could re-do this pretty easily if that’d help. I’ll report on that, too.

Anyway, if the plastic clamp test goes well, this will definitely turn into a recommendation. I’ll try that this Friday, and report back. Given that this kit only costs like $25, it’d be a good addition for very little money, so I hope I can end up recommending it.


 


This post is part of The DIY Studio Buildout Series, on building out a home recording studio and other DIY audio projects.