RF noise outside US

[Mario Souza Lima (souza_lima)]

Hi, I am a brazilian bassist and recording technician. When I?m not in studio work I try to get gigs with my bandmates in local clubs. Our CD was released by a big company last year and things are going fine.
 
   I?ve always dreamed about having an Alembic, few years ago I realized it buying a Rogue. It is gorgeous but captures a very loud radio signal interference.
   Although Brazil hasn?t severe laws about radio transmissions and I live near several TV and Radio Stations antennas, it is not conceivable that a fine ( and expensive ) work of art like that bass can?t be used in South America?s biggest city.
   I have two other basses, a AC50F Carvin ( 5 strings semi-acoustic piezzo driven fretless ) and a Corean made 6 strings active Washburn, and they work fine ( not a huge tone but noiseless ). I also have two friends owning a Series II and a Mark King Signature respectively, they are astonishing and... quiet.
   Sometime ago people at Alembic suggested me that I should take the bass to the factory or move myself to another town. Sorry, I love my bass but I just can?t afford a flight to California and is ridiculous suggest me to leave my city ( and gigs ).
 
   PLEASE somebody help me!!! I bought the only useless Alembic in the world!  
 
There is only three way to avoid that ugly noise: disconnect one pick up ( but this obviously kills the tone ), put both hands over them and bridge ( not much confortable playing position ) or use it only in strongly shielded places ( only in recording, never live ).
   I?ve heard about using resistors soldered to the pick up. Could this work?
 
   I apologise about the lousy way I express myself in english but I hope you can understand my point and I?m waiting afflicted for some help from you.

[Paul Lindemans (palembic)]

Hi Mario,
 
first of all: welcome to the club!
It's a sad story you have to tell here.
There must be a way and unfortunately I'm a Electronical Baboon.
Sure you'll find advice here.  
 
Paul
 
PS: Don't apologize for your English. You ought to see my Portugese! THAN tehre is an apologize appropriate!

[Michael Walker (rockandroller)]

I'm not an RF guy.. but i think what you need are very very small value capacitors added to your circuit which will ground out everything above audio frequency - i think these have to go across both the input AND the power supply lines... also adding ferrite beads around the pickup leads and output wires should help. i believe the problem is only found in basses that use high-requency OP-AMPS that have the potential to act as very high-gain amplifiers for any audio that is superimposed on the RF that they are picking up... ground out the RF, and you solve the problem.
 
there was a thread on this in one of the recent archives... try and search for the word ferrite
 
In fact if you do a Google search on ferrite bead RF rejection you might come up with some good basic do-it-yourself info.. i know i saw some out there not long ago!

[Michael Walker (rockandroller)]

by the way ( i just re-read yer post!)
 
if the problem goes away when you disconnect one pickup, then you have likely stumbled onto the source of the problem!
 
try swapping the pickup leads around, and then see if disconnecting the same pickup will still stop the noise... if thats the case.. then you might find that the shield connection to that pickup has gone bad. Checking with an ohmeter is possible, to see if the shield connection is flakey.  
 
I have an AXY on my desk here, and on the bottom, where its encased in epoxy, i can see four tiny spots near the edges of the pickup bottom where the copper faraday shielding protudes out of the epoxy a little... (i can see 4 minute pinpoints of exposed copper) If you can find them too (or just carefully scrape a little epoxy off to expose them) then you can at least test for continuity with the pickup leads.
 
 
The AXY in front of me has some copper shielding exposed just where the lead enters the epoxy, and actually, on this one it looks almost like the shield part of the wire lead isnt connected there by very much! (hanging by a thread, even) I could see this being an area where a problem could occur...
 
also, while you have the ohmmeter handy, compare the resistance reading of the good pickup with the resistance reading of the noisy pickup.. if its different by more than 5% - that could indicate a problem with its wiring lead (or even its internal wiring, though thats very unlikely)
 
If you isolate the problem to one pickup, then you are halfway fixed! IF the shield looks good, i would try ferrite beads on that pickup lead. If that fails, probably ordering a new pickup will be your simplest solution. (assuming the other pickup is noise-free when connected to either position )
 
hope this helps a bit   :-)
 
 
 
 

[Paul Lindemans (palembic)]

Now that's what I call a real  Advanced Member talking. I don't understand 4 words of it ...amazing.
There was once a thread in a local music-magazine called: Geen Muziek zonder Techniek. Litterally translated: No Music without Technic.
I think this is a good example Michael!

[Mario Souza Lima (souza_lima)]

Thank you very much Michael, althought I?m not a eletronic expert I?m sure your advice will help me to find a way to fix these problems.
    I will look for a repair shop right now...
    Thank you, thank you, thank you.