Can you keep me/us posted on the contact mic preamp project? I need to make a half dozen to amplify some typewriters for live performances.VaticanShotglass wrote: Mon Sep 27, 2021 1:53 amThanks! I'm bookmarking this stuff for the nights I get to plan out projects.
Right now, related projects I have in the pipeline include a little contact mic pre amp and DIY contact mics. Might make it a stereo deal to run two mics at once into my stereo portable recorder. Plan to bang on some fence wires and lumber and stick them to a washing machine, you know, standard stuff to figure out how they work.
Then it'll be one of those instrument to line level deals like you mentioned. That should do me for utility boxes for now until I plan out a nice parallel pedal looper.
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
12Of course. Slow going as I only get a free day here and there, but I'll try to write up what I do. I've looked at lots of designs, but I think I'm following this website pretty closely for my builds. https://www.zachpoff.com/resources/buil ... tact-mics/ The exception is that I'm just going to clone a Barcus Barry pre amp rather than fussing with jfets, and it will be externally housed from the mic. Cheap piezo are all over ebay and amazon.twelvepoint wrote: Mon Sep 27, 2021 3:29 amCan you keep me/us posted on the contact mic preamp project? I need to make a half dozen to amplify some typewriters for live performances.VaticanShotglass wrote: Mon Sep 27, 2021 1:53 amThanks! I'm bookmarking this stuff for the nights I get to plan out projects.
Right now, related projects I have in the pipeline include a little contact mic pre amp and DIY contact mics. Might make it a stereo deal to run two mics at once into my stereo portable recorder. Plan to bang on some fence wires and lumber and stick them to a washing machine, you know, standard stuff to figure out how they work.
Then it'll be one of those instrument to line level deals like you mentioned. That should do me for utility boxes for now until I plan out a nice parallel pedal looper.
Edit: Also this link https://www.instructables.com/Make-a-Co ... icrophone/
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
13Thanks for that info. The ideal situation would be a preamp that was in a small FX box, powered by phantom and had a balanced XLR output, and wasn't like $200 per channel.
One thing I checked out were these $12 guitar pickups that Amazon sells. It's basically the active electronics and under bridge assembly you mount into an acoustic guitar, the whole deal for 12 bucks! It doesn't have an enclosure though so it's not real gig-worthy.
https://www.amazon.com/gp/product/B095J ... le_o04_s00
One thing I checked out were these $12 guitar pickups that Amazon sells. It's basically the active electronics and under bridge assembly you mount into an acoustic guitar, the whole deal for 12 bucks! It doesn't have an enclosure though so it's not real gig-worthy.
https://www.amazon.com/gp/product/B095J ... le_o04_s00
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
14Sorry I've been tied up. (might be moving) So this is what I was thinking to build for the contact mics: https://tagboardeffects.blogspot.com/20 ... mp-eq.html. It is not phantom power, but I'm planning to go directly into a portable recorder so that works fine for me. 9V. Shouldn't be hard to put two in one box for a stereo set up. I think this unit is several hundred bucks, but you should be able to DIY it for under $40.twelvepoint wrote: Mon Sep 27, 2021 3:19 pm Thanks for that info. The ideal situation would be a preamp that was in a small FX box, powered by phantom and had a balanced XLR output, and wasn't like $200 per channel.
One thing I checked out were these $12 guitar pickups that Amazon sells. It's basically the active electronics and under bridge assembly you mount into an acoustic guitar, the whole deal for 12 bucks! It doesn't have an enclosure though so it's not real gig-worthy.
https://www.amazon.com/gp/product/B095J ... le_o04_s00
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
15Bingo, thanks!VaticanShotglass wrote: Fri Oct 08, 2021 1:01 amSorry I've been tied up. (might be moving) So this is what I was thinking to build for the contact mics: https://tagboardeffects.blogspot.com/20 ... mp-eq.html. It is not phantom power, but I'm planning to go directly into a portable recorder so that works fine for me. 9V. Shouldn't be hard to put two in one box for a stereo set up. I think this unit is several hundred bucks, but you should be able to DIY it for under $40.twelvepoint wrote: Mon Sep 27, 2021 3:19 pm Thanks for that info. The ideal situation would be a preamp that was in a small FX box, powered by phantom and had a balanced XLR output, and wasn't like $200 per channel.
One thing I checked out were these $12 guitar pickups that Amazon sells. It's basically the active electronics and under bridge assembly you mount into an acoustic guitar, the whole deal for 12 bucks! It doesn't have an enclosure though so it's not real gig-worthy.
https://www.amazon.com/gp/product/B095J ... le_o04_s00
Ultimately I'd like about 16 of these. My ideal situation would be to have two in one box that sums to mono output. Anything clever needed to do that, or would it be just wiring the two outputs to one 1/4" TS jack?
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
16Um. I don't know for sure, actually. I'm pretty new to this stuff. You might need some buffers or a mixing stage, which should not be crazy. If I needed mono, I was planning to just use my little line mixer. As for having a whole bunch of these summed, the parts in the circuit are not cost prohibitive. Jacks and pots will cost the most. However, I don't know if this is the sort circuit that is best for that many channels. It strikes me as more like what you'd run between a piezo and something else more robust.twelvepoint wrote: Fri Oct 08, 2021 9:51 am Bingo, thanks!
Ultimately I'd like about 16 of these. My ideal situation would be to have two in one box that sums to mono output. Anything clever needed to do that, or would it be just wiring the two outputs to one 1/4" TS jack?
What is the goal again? Keep in mind that you can run a few piezos in series, maybe parallel, without much worry. If you are micing an acoustic instrument, using more than two to four is likely over complicating things for most purposes. My understanding is that there's a few sweet spots and it is worth it to focus on nailing them down. However, if you are going for something more out there, then I don't know.
Depending on what you really want to use these articles about building them into a cable and using phantom power might be useful.
http://www.till.com/articles/PreampCable/
https://www.zachpoff.com/resources/alex ... =alex+rice
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
17Thanks FM VaticanShotglass.
This pile of contact mics is for an ensemble of people who perform with manual typewriters. It’s sort of a percussion ensemble with some elements of improv humor and satire. Anyway, it’s tough to mic these typewriters for live shows just using sm58s and we want to start using contact mics. These will feed into a portable mixer. We’d have around 10 typewriters live, some of which would benefit from having 2 contact mics per typewriter. That blend functionality would help us to keep from eating up too many channels on the mixer.
Hope that makes sense!
This pile of contact mics is for an ensemble of people who perform with manual typewriters. It’s sort of a percussion ensemble with some elements of improv humor and satire. Anyway, it’s tough to mic these typewriters for live shows just using sm58s and we want to start using contact mics. These will feed into a portable mixer. We’d have around 10 typewriters live, some of which would benefit from having 2 contact mics per typewriter. That blend functionality would help us to keep from eating up too many channels on the mixer.
Hope that makes sense!
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
18Oh, super cool! I would suggest that you find one or two (maybe three) sweet spots on each typewriter (diminishing returns accrue quickly), semi-permanently mount the contact mics in those locations (tape, hot glue, whatever), wire them either in series or parallel (I forget which is best) either with all always on or with passive volumes on each (if the tonal complexity is worth it) as though you were wiring guitar pickups. You could wire up a simple preamp or buffer circuit right there on each typewriter. Then you'd have something like ten active pickup guitars on stage, which isn't too complicated to handle. You can figure out the rest with sub-mixes.
Or you could go much simpler. Get a resonant table top (or whatever surface) to put all the typewriters on. Maybe remove or counteract any rubber feet or other absorbent barrier between the typing noise and the table top. You might have to just put a 2x4 between them to connect the typewriter body to the table. Then mount at least one contact mic under the table, maybe as many as there are individual typewriters. Make a little preamp sub circuit like I linked to above for each table top. You can do as many channels as you really want to have control over and mount them together for each table. Then run it out to a sub-mix along with all the other table tops/whatever and send that to the main mix.
The preamp circuit above should let you tame any unnecessary noise. Yet I also recommend you put some padding between the piezo disk and the resonant surface. Maybe a disk of felt hot glued to it. This should help calm down the high end clank which can be excessive with this sorts of mics.
Or you could go much simpler. Get a resonant table top (or whatever surface) to put all the typewriters on. Maybe remove or counteract any rubber feet or other absorbent barrier between the typing noise and the table top. You might have to just put a 2x4 between them to connect the typewriter body to the table. Then mount at least one contact mic under the table, maybe as many as there are individual typewriters. Make a little preamp sub circuit like I linked to above for each table top. You can do as many channels as you really want to have control over and mount them together for each table. Then run it out to a sub-mix along with all the other table tops/whatever and send that to the main mix.
The preamp circuit above should let you tame any unnecessary noise. Yet I also recommend you put some padding between the piezo disk and the resonant surface. Maybe a disk of felt hot glued to it. This should help calm down the high end clank which can be excessive with this sorts of mics.
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
19Cool it sounds like you would be a perfect fit. We jam Wednesdays in Boston - see you there tomorrow?VaticanShotglass wrote: Mon Oct 11, 2021 9:40 pm Oh, super cool! I would suggest that you find one or two (maybe three) sweet spots on each typewriter (diminishing returns accrue quickly), semi-permanently mount the contact mics in those locations (tape, hot glue, whatever), wire them either in series or parallel (I forget which is best) either with all always on or with passive volumes on each (if the tonal complexity is worth it) as though you were wiring guitar pickups. You could wire up a simple preamp or buffer circuit right there on each typewriter. Then you'd have something like ten active pickup guitars on stage, which isn't too complicated to handle. You can figure out the rest with sub-mixes.
Or you could go much simpler. Get a resonant table top (or whatever surface) to put all the typewriters on. Maybe remove or counteract any rubber feet or other absorbent barrier between the typing noise and the table top. You might have to just put a 2x4 between them to connect the typewriter body to the table. Then mount at least one contact mic under the table, maybe as many as there are individual typewriters. Make a little preamp sub circuit like I linked to above for each table top. You can do as many channels as you really want to have control over and mount them together for each table. Then run it out to a sub-mix along with all the other table tops/whatever and send that to the main mix.
The preamp circuit above should let you tame any unnecessary noise. Yet I also recommend you put some padding between the piezo disk and the resonant surface. Maybe a disk of felt hot glued to it. This should help calm down the high end clank which can be excessive with this sorts of mics.
Seriously though these are awesome ideas. We do have some concerns about portability and setup time (there's also a vocal element that's a whole other issue!) and some of our typists aren't as nerdy about this stuff as I am. The tabletop idea is awesome. We tried micing the underside of the tables before, but the s/n ratio isn't great with an SM58. Stuff that works ok with recording just can't get loud enough in a live setting.
I think that series/parallel piezo element idea will be good enough without having to dork around with multiple buffers on each typewriter.
Re: Everything about Impedance, Signal Levels, D.I., Preamps, Etc.
20I'd be down were I in the area! Break a leg.Cool it sounds like you would be a perfect fit. We jam Wednesdays in Boston - see you there tomorrow?
Portability: Just mount everything to a "table top" or two. The typists don't have to do anything but put their TWs down on the marked spots.Seriously though these are awesome ideas. We do have some concerns about portability and setup time (there's also a vocal element that's a whole other issue!) and some of our typists aren't as nerdy about this stuff as I am. The tabletop idea is awesome. We tried micing the underside of the tables before, but the s/n ratio isn't great with an SM58. Stuff that works ok with recording just can't get loud enough in a live setting.
Noise: this is the beauty of piezos, they don't pick up anything from the air.