Replies to This Discussion

Permalink Reply by Scott W on January 11, 2014 at 9:39am

Here is the input jack.

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• image.jpg, 1.5 MB

Permalink Reply by David L. on January 11, 2014 at 10:30am

To be honest you have covered all the usual suspects. 

Could be worth trying a new pot if you have one.  Also this old Bass guitar thread discusses this hum below 10 problem

http://www.talkbass.com/forum/f38/bass-guitar-buzzing-when-volume-k...

the quote :

"it's a problem with bad shielding. Perhaps a cheap guitar cable or amp shielding. 

It's like this. The amount of hum pickup depends upon the impedance of the circuit. This is why microphones use low impedance to keep hum pickup low since their output is low. The higher the impedance the more hum gets picked up if shielding isn't 100% effective." 

points to the problem being the high impedance.

You could add some shielding -copper tape or aluminium foil/tape between the pot and lid (even really cheap strat copies add a bit of foil between the pots and pickguard).

How many piezo discs are there?  I use 2 in parallel as this halves the impedance (2 in series would double it and make the hum worse).

Regards,

David L.

Permalink Reply by Scott W on January 11, 2014 at 10:38am

Hmmmm..... This sounds like you may have pointed me in the right direction. I will check out the link. I have just one piezo disc. I began to wonder if it was the wiring since touching it dramatically increased the volume of the hum. Thanks for the advice.

I'd welcome any other suggestions as well.

Permalink Reply by the anonymous pick on January 11, 2014 at 11:04am

before   ripping your guitar apart  ,  try  plugging it in another outlet  .

  something on the same  line   may  be farking  with it   that    jumps  in   , when the signal's weaker. 

Permalink Reply by Scott W on January 11, 2014 at 11:08am

Tried that, too. No difference.

Permalink Reply by Scott W on January 11, 2014 at 11:10am

I tried foil between the pot and lid, and there's no difference. I also tried shielding the wires. No change.

Permalink Reply by Scott W on January 11, 2014 at 11:18am

I am wondering if the length of wire could be the source of impedance -- I used the 22 ga. wire included in the kit, and I left about 12" of wire between the jack and pot. Thoughts?

Permalink Reply by Rob @ SEG on January 17, 2014 at 2:26pm

If you break the code on this problem, please follow up on this post.  I've had this problem with every single one of my builds.  I've used double piezos in parallel, added extra grounding points onto the body of the box, shielded wires and pots.  Haven't figured it out yet.

Permalink Reply by Scott W on January 17, 2014 at 5:48pm

You and I are in ten same boat!

Permalink Reply by Scott W on January 19, 2014 at 3:20am

SEG: might you and I be in similar situations with a low-power soldering irons? Mine is only 25W and takes forever. I am wondering if I might have a cold joint somewhere.

Permalink Reply by David L. on January 18, 2014 at 1:42am

This one (last post) suggests an amp plugged into a socket with grounding issues could be to blame
http://www.talkbass.com/forum/f38/piezo-pickups-problem-hum-20104/i...
Plugging the CBG into a battery amp would quickly check this.

The other guitars that work fine with the amp (if they are magnetic or preamp piezo) will need a much lower volume to hear the pickup working - if you turn the non humming guitars up to the same volume you need the piezo at to hear it are they still hum free?

Permalink Reply by Scott W on January 18, 2014 at 3:23am

Thanks, David but I tried that, too. I get the same hum regardless of where plugged in and another guitar (with a preamp) sounds great through the same amp and cord. So i have ruled out household wiring, amp, cord.

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