I know this has been asked before, but I need help and search results aren't helping

VinKreepo · #1 06-01-2010, 10:05 PM

So here's the deal. I got an SR305 a while back and I had a a GSR190 with this cheap aftermarket preamp installed (sounds amazing btw). So in the GSR it was good, nice and quiet, somewhat of a hum before touching the strings. Well the GSR died (I'm not good with applying veneer tops) and so I thought "Hey, the SR305 preamp SUCKS, why not install this cheapo in there since I like the sound."

So I did... but that annoying hum before I touch the strings is driving me and other musicians insane. I know everyone says SHIELD SHIELD SHIELD, but the deal is the graphite paint is there intact and the control cover touches it. It looks EXACTLY like the GSR did. I have touch different wires EVERYWHERE to no avail and I'm ticked. I cannot get it to stop.

So my question is, could it be the preamp? Or possibly the DX5 pickups? I have an Ibanez K5 and it's ultra quiet with no hum at all with this same amp and cable. And if it is the shielding, could it be that the pickups aren't shielded? Cause like I said, the control cavity looks just like all the other Ibanez basses I've opened up. And sorry if I came across rude in any way, I'm freakin' ticked. I love this bass, I will do whatever it takes to get it right

Stealth · #2 06-02-2010, 09:52 AM

Since there's hum when you're not touching the strings, I'd say the bridge is still ungrounded. Try to remove the bridge and check if there's a wire leading from the bridge to the output jack's sleeve contact - if there isn't, place one there. That'll insure string grounding and the hum should go away.

Grounding this way may be unsafe - if you want to make sure you don't get shocked back by faulty wiring (which might happen), you can use this schematic which makes the string grounding less hazardous.

VinKreepo · #3 06-02-2010, 09:56 AM

Ahhh thanks, but it's taken a while for any replies to show up here and in more diagnosing and internet searches I think I've come to the conclusion part of my problem is the preamp while a small portion is that the pickups aren't shielded. There is a wire going to the bridge to my pickup switch. Hmmm I just thought... maybe it isn't thick enough. I mean it's as thin as mechanical pencil lead.

FunkMetalBass · #4 06-02-2010, 10:03 AM

Or it's a cold solder joint. I'd never rule that out with all of the poor soldering I see in production basses.

Even with the shielding paint, I'd still get ahold of some copper foil and shield the pickup cavity and control cavity. While you're at it, place a strip under the bridge so that the bridge ground wire pokes out and touches both.

VinKreepo · #5 06-02-2010, 10:06 AM

Ok lol I'll admit this solder job wasn't great, considering the junk tip and bad solder... still. When I open the cavity up and TOUCH THE PAINT it reduces the hum. So maybe, just maybe, the Ibanez shop did a bad job of painting it with conductive paint? I mean It's like I'm grounding the shielding... and I can touch the pots and get the same result... or the cable plug, or the metal pickup switch... etc

EDIT: love the display pic btw. And if I do all this, I'll have to get a new preamp anyway as the knobs on this one got stuck on and will destroy the pots if I take them off lol... life

FunkMetalBass · #6 06-02-2010, 10:20 AM

Try fastening a small screw to the inside of the control cavity and running a ground wire to it. If the hum stops when you touch the inside of the control cavity, it's logical that you should put a ground wire there.

If you look at some shielding tutorials, you'll notice that they do this same thing (solder a ground wire to the copper foil lining the control cavity).