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“I have completed the kit and am using it glued to the end of a slinky. On the other end is a piezo that I send sound into.
A lo-fi spring reverb so to speak :-)”— Einar, Oslo, Norway”
Brach and I see a number of possible sources of noise.
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The resonator. As we discussed, the higher the density & mass of the resonator, the more likely it will create a mysterious white noise. In my experiments. the best resonators also picked up ambient noise like crazy, so I couldn’t even isolate this source until I moved into a decent studio space.
The fine leads from the piezo are unshielded.
How are those fine leads attached to the squirly cable? Neatly soldered, I hope, not twisted.
You commented elsewhere that the shielding on your cable may not be great. It’s important.< The grouinding inside the box, which box, by the way, is terribly cool. You have the input jack, output jack and the board all grounded to the copper foil shield. Brach suggests you ground the 1/4" jack to the board, ground the board to XLR pin 1, then ground XLR pin 1 to the copper shield. This gives any errant electron exactly one path to ground, with the shortest, most direct path at the input source. Your current arrangement allows for a few ground loops, which likely accounts for the difference in noise between the two cases.Try fiddling with some of those, especially the ground loops, and let us know if there is improvement.
I am going to move this conversation over to “Product Mods”.When suspended in this harness (hula mic), we got the best results from a small styrofoam bowl, styrofoam dessert plate, and styrofoam clamshell, with or without food compartments. On a shape like the bowl or compartmental-clamshell, the piezo placement has an enormous impact on low end: if you have the option of partially extending the piezo off the back of the resonator, into space, it can add dramatically to the low end and increase the naturalness of the sound. Leaving it dead center gives the narrowest response, and the best “old time broadcast” sound.
Great write-up, Solarbird (below). We are thinking same-same regarding resonator elements for a neo-crystal mic. Very soon we will publish a new instructable on building the Hula Mic: a crystal mic built from bungee cords, binder clips, a hula hoop and a clock face — and of course a Cortado contact mic. A companion article will detail our own research, which led to similar conclusions: the performance of the resonator depends on not only its mass, but its density and rigidity. Guess what material wins that contest?
Here’s a sneak peek.
Shaggyfreak sent us this sample from his Tin Can Mic.
Shaggyfreak Tin Can Mic TestAnything in contact with either side of the piezo is going to affect frequency response. You will always get the best response when the piezo is tightly coupled to the instrument. This is why our “start here” design calls for the piezo wrapped in one smooth layer of electrical tape, one thin layer of copper, and then bonded tightly to the sound board with the provided piece of very-sticky double-tape. Beyond that, everything is an experiment. When using clamping pressure from above, instead of adhesive from below, everything counts. We think you will generally achieve best coupling when the clamp pressure is distributed uniformly across the back of the disc. We once used a piece of thin, dense foam, then a disc of 032 aluminum between the disc and the clamp.
The board-under-the-bridge idea sounds great! Would this “paddle” extend over a sound hole, or off the side of a narrow-bodied instrument? Obviously, the material will strongly affect the tone. Ideally, the paddle should be the same material as the sound board. That’s easy if you are making your own instruments. Otherwise, I would recommend 1/16″ thick basswood, such as from Midwest Wood Products, distributed through Utrecht Art Supplies and many hobby shops:
Basswood from Midwest at Utrecht
This cuts with a very sharp X=Acto knife or a micro-coping saw. Experiment with shapes and sizes. I think the length of freespan tab (or tongue) would influence resonant frequency response. Let us know what you find out!“I do some lo-fi recording at home and I have an acoustic bass that the pickup quit working. I will primarily use this mic for that bass, both live and when recording. Of course, now I can mic just about anything! So I think this will open quite a few doors while recording.”
-Cj, Richmaond, Mississippi“I just wanna use it on a cactus, dry ice, sheet metal, balloons, plank of wood, maybe throw it in an altoids tin with some rocks and maybe attach some springs to the tin, you have any other cool ideas?”
-T.L., Las Vegas, NevadaEspresso Portable Phantom Power Supply First rendering of an upcoming product. Run your Cortado anywhere with a 9V battery.
“I have an old plate reverb, but the original amplifier is long gone. So I’ve been looking for a phantom-powered high impedance buffer circuit to drive a reasonable length of cable without too much noise. I came across your kit at wiki.diyrecordingequipment.com, and it’s exactly what I was imagining–except that you guys have already done all the hard work.”
Patrick, Fair Oaks CA“I am working on an art installation for a holiday event in midtown Detroit- we will have five 10 foot tall musical sculptures and…we wanted to…amplify them, which is where the piezos came in. I’m wiring up the first one the this weekend, to try out the set up (…we’re tying together 3 piezos to send into the Cortado). If things go well I’ll have an order coming for 4-5 more next Monday.”
– A.M., Detroit, Michigan
Shipping one Percolator, kit or prebuilt, to UK (or most anywhere in EU) costs about $60 USD. The Combo costs about $68. Customs situations vary widely and I’m afraid we do not keep very well up on this. Perhaps a UK customer can comment?
Our dealer in Paris, Woodbrass Deluxe, has Percolators, Cabs and Combos (ready to play, no kits) in stock at woodbrass.com. Please check them out! You may find their pricing (and quick availability) makes more sense than trying to buy direct.
