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Post by jacklthornton on Dec 26, 2007 20:28:47 GMT -5
I've got a p-bass copy - I swapped out the stock pickups for Dimazio split-p and shielded the cavities and pick-guard. Now the bass is quiet until I play - then I hear hiss/white noise at maybe -30db until I mute the strings again, then it is quiet. Noise consistently returns when I play a note. Imagine running a somewhat noisy source through a gate - that's what the sound is like. Before I strip and rewire everything, does anybody have an educated guess as to what I might have done wrong? Other maybe related symptoms - the output is a lot lower than I expected (way lower than the stock pickups) such that there is very little travel in the volume pot before the signal becomes inaudible.
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Post by sumgai on Dec 26, 2007 22:12:03 GMT -5
jack, Hi, and welcome to the NutzHouse! ;D Weaker sound usually indicates a phasing problem, and on a bass such as yours, an out-of-phase signal will drop the output noticibly. Swap the leads on one of the two pups. Next, you did wire them in series, right? If you put + to +, and - to -, then you goofed. The connection between the two pups should be + to - (it doesn't matter which pup goes where, only that the phasing is correct). But be aware that even with quality pickups like yours, it's possible that something got mis-marked somewhere along the line between the coil being wound, and delivery to your door. Take nothing for granted, check it out personally, before you take it out on the road for a spin. The noise is another issue altogether, I don't think it's related to the lower output, so I don't expect the above change to fix it. Noise gate, eh? This might be a combination of things, but the first thing to do is eliminate the easy possibilities. Swap the two leads on the output jack, and report back what happened. HTH sumgai
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Post by jacklthornton on Dec 28, 2007 20:00:56 GMT -5
Thanks for the quick answer.
Before I switch, a couple of things:
(a) I don't remember the pickups being marked + and -; each had colored leads; the installation instructions said to solder the black and white together; the red lead from one pickup was hot and the green from the other was ground.
(b) each pickup of the split-p design is only wide enough to cover two strings. I can see how wiring two complete pickups out-of-phase would almost cancel the output; but these are two halves wired in series. The center two strings might cause some vibration in the "other" pickup, but I don't see how the G could be seen by the upper pickup nor the E by the lower.
Something else that occurred to me: what would a cold solder joint sound like?
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Post by ashcatlt on Dec 29, 2007 0:44:19 GMT -5
1) "Theoretically" the installation instructions from the pickup manufacturer would be correct, but like unk said, sometimes they goof.
2) You may be correct about the out of phase thing not causing the cancellation we would expect if both coils covered all the strings. Unfortunately, if one of the coils is wired backwards from what was intended then you haven't got a humbucker anymore. In fact, you should get substantially more noise than you would otherwise.
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Post by warmstrat on Jan 2, 2008 6:18:35 GMT -5
As far as i know, a cold solder joint would sound like nothing at all. It wouldn't be connected. It is of course possible that in my part of the world, the expression means something different though.
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Post by sumgai on Jan 2, 2008 18:27:46 GMT -5
jack, Cold solder joints don't "sound", they either operate correctly (not very likely), they operate at reduced efficiency (added resistance where one would expect to find zero ohms, the usual case), or they don't operate at all (seen only occasionally). What they look like is a dull grey, often mottled. That discoloration is rosin that didn't get completely heated, and didn't get out of the way of the solder itself - some of it is still trapped inside the joint. Thus we say 'it's a cold joint', because not enough heat was applied, or it was applied for too short a time. Rosin is not electrically conductive. The usual fix is to simply touch the joint with a hot iron for a moment. When the solder starts to smoke, the rosin is pretty much gone, and the heat can be removed. The results should be shiny, and should remain so for a long time to come. Sometimes a joint will look good from the outside, but underneath, it's still a cold joint. Re-heat it anyways, if you are suspicious, or when no other obvious reason presents itself as to why something doesn't work right. It's been known to happen that when I see more than a few bad solder joints, I'll reach into my bag o' tricks and pull out the "shotgun" method......... I simply re-heat every solder joint in the vicinity. Not the scientific way to troubleshoot and fix a problem, but ya know, there's times when you can use brute force like this, and there's other times when you pretty much have to stick to the straight and narrow path they teach you in school. The reason I get the big bux is because I know when to take the shortcuts, and when to stay on the path. ;D HTH sumgai
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Post by gumbo on Jan 3, 2008 0:00:20 GMT -5
..acherly, the reason yo get the big bux is 'coz we love you so much......
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Post by sumgai on Jan 3, 2008 13:42:44 GMT -5
[glow=red,2,300]Danger Will Robinson, Danger!![/glow] Warm and fuzzy feelings ahead! Great Danger!
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Post by jacklthornton on Jan 7, 2008 17:17:09 GMT -5
Thanks for all the input guys. Asked about the solder joint on the theory that the decreased output might be due to increased resistance if my soldering job wasn't good enough particularly where I soldered the ground side of the pups to the case of one of the pots. In any event, I decided to replace the pots with mil-spec and the cap with a paper-and-oil variety and completely rewired the bass this time. Also took advice from first Guitarnuts pages and made a single common ground point (used the ring connection from the jack). The bass is now quiet, with no perceptible noise whether being played or not. Output is still less than the stock pups, but perhaps the stocks were just hotter in terms of voltage output. I do like the way the DiMarzios sound, so guess the preamps will just have to do more work. Ironically, the worse issue I had was with the size of the parts. The new pots were significantly larger than the old, and first time I saw the cap my reaction was "dang - that's bigger than my whole guitar!". Managed to barely fit it all in without re-routeing the body, though I had to apply liquid tape to the cap leads (and wrap the body in electrical tape) as they kept shorting out against the shielding. Also, even though the old and new pots both had 1/4" shafts (new ones brass, old appear to be aluminum), the old knobs would not go on. Dang - guess I'm going to have to buy a set of those chrome-and-shell knobs I had my eye on
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Post by ashcatlt on Jan 7, 2008 22:48:50 GMT -5
My rick's knobs will fit a 1/4" shaft*. Can't get strat, tele, or LP's to fit without reaming them. For the plastic ones, you can sometimes just enlarge the hole by hand with a 1/4" drill bit. The metals ones needed real power. They need to be clamped to something, and a drill press probably would have helped...
Then I had a "probably too obvious to mention" question re: the output volume. Have you adjusted the physical height of the pickups? Just asking 'cause sometimes we get all excited and overlook these little details.
* Come on! how often do you get to use "knobs" and "shaft" in the same sentence? And then follow it up with "reaming"? This board is cool! Huh-huh, huh-huh...
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