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I found this fantastic site when googling for my new project. After discovering that seasick Steve played on something called a didley bow I realised I had to build me one of those and now that I'm (almost) done with it I really really must build myself a 3- stringer. My D- bow has two strings, my 3-stringer will have... One string at a time. Don't know where I'll end up!
All I need for finishing my first instrument now is electrification ! In this part I need some help. I've made up a schematic with all functions that I want and I've gotten all the parts. The thing is that I'm not much of an electrician. I'm actually not an electrician at all so i did some copying and pasting to achieve this schematic. It's a mixture of symbols and pictures but I hope you'll understand it anyhow. The big question for me is. Will this work? So, please help mee! Take a glance at it and please, please take a look at all the parts of it. For example is the preamp correctly connected?
As a total rookie I have of course many questions. Here are some more...
What capacitor would be appropriate for something like this?
Is it a bad idea to have conducting steel plate as a pick guard? Will I get electrocuted?
I've read about connecting all ground to one spot. Is that necessary or could I just use shielded cable?
Very very thankful for answers.
It looks like it should work - as Mark said on the main forum normally people tend to use the same value pots for both tone and volume (I don't know what it does if you mix them but if you do it let us know how it sounds :o) )
I have used blend pots on a few builds and personally like how they work - the main difference that I do to your circuit is to send both signals (humbucker/both/piezo) via a 3way switch or a blend pot through the preamp (only because I wanted to see how it would work and liked the result and so have stayed with it). Also by adding switchable jacksockets into the circuit you can get separate outputs for the piezo and humbucker for different amps/effect pedals - if this idea is of interest let me know and I'll post more details if you want them (switchable sockets are cheap and easy to do).
You were concerned about electrocution risks - There is a good account of it and how to modify the ground to the strings http://www.guitarnuts.com/technical/electrical/safety/index.php In theory piezos and humbuckers may not need to have the strings grounded - you could give it a try without connecting the ground to the bridge/tailpiece to the common grounding point (I would still place the wire connected to the the tailpiece/bridge end so it is easier to connect up if you get alot of hum) and see if you are happy with the level of hum the circuit gives. I only play at home but still have a plug in socket tester they are a few pounds off ebay like this one http://www.ebay.co.uk/itm/UK-MAINS-SOCKET-TESTER-POWER-PLUG-13A-tes... If you do an ebay search I should think there is an equivalent for the European plugs.
Capacitors for tone pots - depends upon the effect you want. For a humbucker usually a 0.047uF with a 500K pot or if you are going to give the 250Kpot a try 0.033uF the link is here halfway down http://www.guitarnuts.com/wiring/schematics.php
The advice generally given is to have a single point for all ground to go to to prevent the risk of ground loops (never personally seen one) and the back of one of the pots is usually chosen - when I am doing a circuit like yours rather than try to fit all ground wires to one pot I use a piece of strip board (the ones with strips of copper running the length of the board) as I find it easier.
Are you able to post a picture of the preamp you are going to use?
Thank you for your answer!
The fact that you believe this could work really encourages me. I like the idea of using a piece of strip board for the ground, I´ll use it. The main reason for that I want to use a steel plate for pick guard is that I´ve got it at home and for the aesthetics of it. When mounting pots to a steel plate they will make a ground circuit of their own so maybe it’s a bad idea after all, cause in this way there will be a loop. The pre amp is a ready build piece I bought at a RadioShack here in Sweden (where I live). I have never tried it before. It wasn´t expensive and that’s how I want it. This is to be a low cost project. Picture below.
I read somewhere that the output differed a lot between mag pups and piezos and that it therefore would be a good idea to pre amp the piezo. But of course it’s nice to preamp the mag pup too! The only reason for having a 250k pot for tone is just cause they were out of 500k´s in the store. I´ll give it a try I think.
Once again, thanks a lot for your input!
I have the same preamp in my parts draw - I will be interested to see what you think of it (I have used several of the Kemo 3.5W amplifier modules which work well).
Using the steel plate when grounded will make a good shield for the electrics. This forum suggests all will be okay so long as you star ground (all bits needed to be grounded go to a common point such as the stripboard idea).http://www.tdpri.com/forum/tele-technical/258138-guitar-ground-loop...
It is an old poor quality video I made a while ago but if you turn the volume up it gives an idea of the sound of magnetic pickups and piezos with and without a preamp.http://www.cigarboxnation.com/video/comparing-cbg-pickups sometimes I prefer the raw non-preamped piezo sound.
Keeping it low cost is part of the fun of CBG making I find suntekstore cheap (they ship from Hong Kong/China so the the the wait for delivery to the UK is about 2-4weeks) http://www.suntekstore.com/category-228-b0-Musical+Instruments.html I don't know what the import duty is like for Sweden - in the uk we have to keep below £15. For future builds there are a few links here to cheap preamps with tone controls from an answer I gave previously http://www.cigarboxnation.com/group/class101/forum/topics/another-p...
Now i´m almost done with my project. Ive soldered everything and the instrument itself´s almost done. Unfortunately there are some things that don´t work so now I´m up to troubleshooting. As far as I can see everything seems to be connected right but it looks like a dish of spaghetti. I have to double check once more. The mag pup works all right but the tonepot makes no change to sound. I´ll deal with that later on cause the big issue for me is that when I run the piezo through the preamp it turns silent. Do you guys know if there´s a way to control my kemo preamp to see if it works correctly? It probably does but I want to be sure before dismounting everything. I have a multimeter! The cavity in the instruments body where i´ll fit everything´s quite smalland i´ll have to squeeze everything in.Doesn´t look good so I came up with an idea of using stripboard for all the connections. I´ve made principle sketch (attachment) of how bellow. Don´t know if it´s a good or bad idea, if this would be a hum generator or if the cupper lanes are to thin to conduct properly. All hot wires would be connected via the strip board. All ground wires would be connected to a copper plate placed on top of the strip board with an insulating layer of plastic in between. It ´ll be like a sandwich and there should also be a copperplate on the other side that’s also grounded. If I could do like this it would be a neat and tidy solution. Easy to grip and easy to resold.
…What do you think?
Tone pots have little effect on piezos but if it is having no effect on the magnetic pickup then the cap isn't reaching ground (check the earth to the tone pot), or the cap may have been fried by the heat of the soldering iron (I use a crocodile clip as a heat sink to protect it when I solder) or it is the wrong value (for a humbucker a 0.047uF).
To check the preamp - do you have any photos? Does the piezo work with the preamp off?
First checks would be with the multimeter - check at the preamp there is a 9v supply arriving and that there is a working connection between common ground in the circuit and the ground the 9v negative is connected to.
If you have 2 test test leads (wire with crocodile clip on each end) connect the preamp direct to the piezo hot wire and the preamp output direct to the jack socket so you bypass the switch.
If you do not have a camera to take a photo do you have a link to the type of switch you have used?
I just want to close this thread properly. Now I'm almost, almost done with my project. There are a few details yet to be fixed. A separate battery hatch, some painting and proper frets. The aluminium tape frets that I have right now don't work very well...
I'm more than pleased with my instrument that started out as a two stringed didley bow and ended up as a four string didley steel. Tone pot, balance pot and all the electronics work very well. Though the tone pot doesn't do any effect on the piezo, which was expected. I used a piece of strip board to tidy things up and to make it easy to rearrange the wires. Also all ground cables goes via a length of strip board to the jack ground. I had some hard times getting it to work before I discovered that the pre amp IN and preamp OUT were mixed up in my drawing and in my circuit....Minor detail... So if anyone want to use my drawing as an inspiration for their project, please note that in and out on the preamp should be the other way round.
This forum has been a great help for me so thanks to all of you who answered on my many questions!
Now life starts feelin a bit empty... Must start a new project!!!
Here's a picture of my build. Tuned C C2 G# B
Looks FANTASTIC!!!! Well Done.