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CBG Pickup home made, Help required

Posted by hocuspocus on February 17, 2013 at 2:04pm in Building Secrets, Tips, Advice, Discussion

Hi to all. I'm working on my first CBG and so far I'm pretty happy. Cohiba box, maple neck, all fretted. Now comes the pickup. I've made a 4 poles pickup. 9000 turns, the load is near 5K. That's a start. I have potted the pickup and ready to try.

So I've just hooked the pickup directly to a pair of wire, through a jack, and connected to the amp. Ita a Fender Super champd XD tube amp. My problem is that I hear this feedback every 10-15 sencods and it lasts a few seconds. Any idea why ?  I have attached a sound clip, take a moment to listen to the whole 50 seconds of it.

Many thanks for your help.

Sound Pickup.mp3

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Replies

  • BrianQ. March 5, 2013 at 6:27pm

    I would recheck yer Ground Connections

  • HotBox Guitars March 4, 2013 at 5:10am
    Did you put any insulation between your mag poles and the wire? Like Scotch tape. Or is the wire directly against the mags? You waxed it for about 20 min?
    • hocuspocus > HotBox Guitars March 4, 2013 at 7:40pm

      Yes I used teflon tape, for about one to 1 and a half turn between the alnico and the wires. Also the potting lasted about 30 minutes, until I would not see any air bubbles anymore. Finally, I installed the pickup in the CBG and the noise was less present. Still there but very light. 

      The middle strings are pretty well amplified but not the lowest string. I rechecked the polarity of the whole pickup (installed) with a compass and there is not much pull on the needle. I had magnetized the mags before winding the pickup. Now my next plan is to remove it and re-magnetize it again and recheck polarity. 

      Having fun !

  • hocuspocus February 18, 2013 at 8:37pm

    well I tried shielding the pickup only to the common ground and no changes. So now I tend to think like Mark. I even get the hissing when I touch the tip of the cord jack with my finger. Maybe I'm just discovering something that always existed. So I will put all the bits together in the cigar box and we will see. 

    Any other thoughts from anyone is still welcomed.

  • hocuspocus February 18, 2013 at 5:44pm

    So far, I'm progressing. I moved the amp in the basement and the louder hissing coming every once in a while is not there. Before I was in the living room, right next to the TV set. Who knows. I did not have this problem before with my electric guitar so I didn't know.

    Its fun learning, right ?  Anyway, I still have a continuous hissing, much lower (high frequence, but less audible), that may be surrounding static waves picked up by the pickup. (that why we call it a pickup, right ?). Just the amp, with the guitar extension cord, I hear nothing. As soon as I place the pickup at the end of the jack, holding the wires manually, then I hear the hissing. I even tried without the pickup, but just holding the 2 feet long cable I was using with a female jack that I am supposed to install in the cigar box, and it picks up the noise also !  So it looks like I am in for a shielding job on the pickup and also on all the wires that will be installed in the Cigar Box.

    Does any of you know if all those shields must be connected to the negative side of the jack ?

    Thanks guys.

    • The Phrygian Kid > hocuspocus February 18, 2013 at 5:54pm
      Yes. Ground it to the sleeve on the jack. I often use the foil that frozen apple pie or Danish comes in for shielding, works great
  • hocuspocus February 18, 2013 at 4:44pm

    What was I saying, refering to 4.8 Khz of the pickup. Is that confused or what ?  Anyway, I'll come back with tests results.

    • Mark > hocuspocus February 18, 2013 at 5:44pm

      Yeah, I think you're getting confused there. The 3kHz to 5kHz is a reference to a frequency within the sound you're hearing. I think what you're referring to when you mention 4.8k is the resistance of your pickup, ie. 4.8k ohms - a different thing entirely. No connection between the two.

      Most important thing is, don't worry about the pickup. It sounds as if that's fine and dandy. So go on ahead and finish fitting it in the guitar.

      Sorry if I've confused things at all. I was just hoping I might help you track down the source of the noise - because I've had experience of these types of things getting really annoying.

      • hocuspocus > Mark February 19, 2013 at 6:54pm

        Mark, don't worry. I get everything you mentioned and its very helpful. I just got confused alone. Your analysis is exactly what I was hoping for, since that is usually the right way to approach this kind of problem. Looking at the frequency and trying to match something in the environment that induces this. Many thanks again for your help.

  • hocuspocus February 18, 2013 at 4:04pm

    Thanks guys, all your inputs are extremely welcomed. Actually, the noise is not there with the amp turned ON, and the cable connected. But when I connect the pickup, then it starts after, say, 10-20 seconds. The wavelenght from 3 to 5 Khz respects the 4.8 kHz of the pickup, but whatever it tells, I'll make some more tests tonight. I'll place the setup at different places in the house, and maybe outside.

    It is also true that the pickup itself is not shielded, but that will be my next series of tests, if I don't find anything else before. But again, many thanks for your help.

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