The Last Bass Outpost
Gear Discussion Forums => Bill's Shop: Projects, Mods & Repairs => Topic started by: Iome on January 07, 2015, 04:48:17 AM
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Guy's, i'm moving a Model G from my Fenderbird to an SX jbass.
I had the pickup wired to a DPDT switch to use it in parallel/singel/serie. Now i would do the same on this bass but i'm installing a bridge pickup also, in the hope to archive a J-like sound. I'm not sure of the wiring so if anybody could help me before i get other components i'll be thankfull.
My doubt is that, in the attached wiring diagram, without the second pickup, the hot wire from the Model G goes to the side socket:
(http://i243.photobucket.com/albums/ff101/iomepics/ModelG.png) (http://s243.photobucket.com/user/iomepics/media/ModelG.png.html)
while in the other, with two pickups, it goes to the central...:
(http://i243.photobucket.com/albums/ff101/iomepics/PJ.png) (http://s243.photobucket.com/user/iomepics/media/PJ.png.html)
PS: no tone switch...
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Whether you attach a hot lead to the pot center or (the correct) side will make no difference - all the way left will still be 0 Ohms and all the way right will be 500K Ohms (when wearing the bass). That's all a pot does, the resistance between the outer 2 tabs is constant; the pot's max value (assuming 500K) and the middle is the wiper that moves with the knob action along the resistive track, so as long as the same outer tab and center are used, the result (resistance between those 2 tabs) is the same no matter if center hot or not.
So all you need to do is take the pup and switch harness, as is, out of the bird, and when you drop it in the SX, connect the wire labelled "Output 1" aka hot to the center (vs side on the Bird) tab on the appropriate volume pot, with "Output 2" aka ground, going to the pot casing as before.
Note: this assumes that the way the Bird and SX were originally (currently) wired up has the pups in phase. If, after you do this, it sounds a bit off when you run both pups on the SX, try swapping the hot and ground leads at one of the volume pots (doesn't matter which).
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Ok...so i'll just go with the second diagram.
I have a 500K pot for the G and will get a 250K pot for the J, will i get noticeable more highs when running the G in single with the other PU, or will there be less audible difference since there's no tone pot?
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There will still be a difference between humbucking and single modes (at a minimum, due to the fact that the G will be louder in buck mode so you get less of the J in the mix, but there should be less treble from the G in buck mode vs single as well - never used one of those so no sure what they sound like). Tone pots have little impact on treble bleed compared to volume pots. If you want more treble from the J, use a 500K pot for that as well; might get too clanky though so prepare for some trial and error. Otherwise google "treble bleed mod" - you put a parallel cap (small one) and resistor across the V pots so it won't suck tone as you dial down the volume. ... though to be honest, I am not sure if this treble bleed stuff is really an issue on basses; should only affect freqs higher than what most basses produce unless, maybe you play well high up the neck, but I could be wrong. More treble is not something I have ever needed in a bass so I have never experimented with it (as I have on guitar).
edit: apparently treble bleed may apply to bass. See here for some discussion of that, as well as recomended resistor/cap values:
http://guitarnuts2.proboards.com/thread/3973/bass-treble-bleed-mod
the link in that thread to the larger more detailed discussion is dead; this is correct:
http://guitarnuts2.proboards.com/thread/3797?page=3
I'd try a middle of the road value from those suggestions (250 - 280 K resistor and 2000 - 2200 nF capacitor), and then wire it up like this on both V pots in the SX (ignore these values):
(http://www.strat-talk.com/forum/picture.php?albumid=1195&pictureid=11934)
There's also prefab/adjustable ones:
http://www.guitarelectronics.com/product/CPC500V/CTS-500K-Audio-Taper-Precision-Pot-w-Variable-Treble-Bleed-Circuit.html
You can get it with the pot or without (15.99 or 11.99) they say good for guitar or bass, any type of pup, and either 250 or 500k vol pots. Too bad they don't say what cap value they use; probably not ideal for bass.
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Thanks for chiming in Granny, this is over my head....... :-[
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Wow guys, thank's a lot, you're giving me a lot to think about....i guess thats why i've always stucked with one pickup basses.... ;D
My intention was to dial in the bridge pickup only when i use the Model G in single and try to get a Jazz-a-like tone out of it all. On the bird, in single mode, it sounded more similar to a single coil P than to a J neck pickup, more clanky, nice for sure, just not ......Jazzy
I could try a 250 or 300K pot on the Model G...just to try....
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A 250k pot will darken up the G a smidge.
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I finally got the bass wired and set up. I used a 500k pot for the model G.
Only thing that bothers me is the loss in volume when the two pickups are full on together. I know it's a common problem with all two pickup basses, but the loss here is much more than in the J basses i used to have. Does anybody know if it's because there's a big difference between the wiring in the pickups or did i do something wrong?? :-\
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Try taking the output from the pups straight to centre connection from the jack, just as a short, to give you a true full-bore sound, and that will give you an idea of the imbalance if it is being caused by the control wiring...
Not played with one of these so what are the resistance values of the various coils...? If one of them is substantially higher value that will effect the "balance" of the circuit... it can be an experiment to find the "right" sound that suits "your" ear...
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Try flipping the polarity of one of them and see if volume drop is better or worse.
Not all pickups work good together. Remember that height adjustment really can even out things (on some pickups).
And they can be magnetically out of phase too, it takes a tad more effort to reverse..
I think I have a Rick Turner article on blending pickups somewhere... From mid 90's? If I could find it!
I recall him decribing blend pots to detail and if I remember correctly a 1M volume pot(s) sometimes can help
volume difference issues. Just make a note for yourself what you have tried already.
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Thanks guys,
i've adjusted the pickup heights to have the right sound with them working together. Only problem is a overall volume loss. As soon i lower the volume of one of the pickups the volume goes up.
If i remember correct, the Model G has a resistance around 17 + ohm while the J is less than 8....
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I had a similar problem with my PC and the Mudbucker/RD Artist pup balancing... a lot of it was just the wiring for the pots being the wrong way round and it created chaos with the outputs...
I've split the coils on the MB so it's 30k or 2x 15k coils, run independently in phase, out of phase, single coil or standard, then mix in the RD which iirc is circa 12k, so a tough balancing act...
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If i remember correct, the Model G has a resistance around 17 + ohm while the J is less than 8....
Cool, I love loZ pickups :mrgreen:
Well, resistance is not always proportional with volume, but when two pickups are different in design, they can be tough to match. I made a 28 Kohm mini sidewinder to put in an EB3 bass, just to check if it would match the 28K mudbucker.
It came out much louder than the mud. When using both, the mini takes over although the mud adds some bottom.
Another example is my P bass, I´m doing a stock ´75 split P and a 30K mud at the neck.
I don´t want to add pots, so I stick to one blend pot and a tone pot.
I think blend pots is the way to go, just try flipping the polarity and stick to whatever gives the least volume drop
when both are on.
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damn... ok, then Kohm....
Initially i wanted to go with a blend pot, but i've read a lot about how they never open both pickups at max...probably not true...
When you invert the polarity doesn't it change the sound? would it consist in just wiring the pickups opposite?
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Inverting the polarity (of one with respect to the other) was just suggested so as to ensure that you are not getting any phase cancellation (which is another potential reason for volume drop). I doubt this is the case as you'd notice tonal differences as well, but it's worth checking.
Inverting the polarity of a pup does not change the sound of that pup, but will change the sound of that pup mixed with another.
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Ok, thanks for the help guys. I'll go through the wiring this weekend.
I think i'm going to order a blend pot....
edit.. is it me or do 250/500k blend pots not exist? :-[
edit².. and why the hell can i only find linear taper blend pots? wouldn't that cut out one pick up at once, instead of rolling down it's signal smoothly?
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I know that dual pots with 2 different values exist, but no item marketted as a blend pot is like that. As for the taper, I'm not sure, I can see the reasoning for either being better in this instance but never tried it myself; linear is definitely easier/cheaper to manufacture than dual log/reverse log with matching (though inverse) slopes. Jazzmasters (and maybe a few other offset style Fenders) have a 1 Meg linear volume pot.... and I think some pots on the Lo Z Les Pauls are linear too.
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edit.. is it me or do 250/500k blend pots not exist? :-[
edit².. and why the hell can i only find linear taper blend pots? wouldn't that cut out one pick up at once, instead of rolling down it's signal smoothly?
You will be fine with the linear pot, 2x500k - using audio taper for blending will give you a hump in volume when near full, if I remember correctly.
If the single coil gets too trebly with 500k, you can roll off with the tone, right?
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Right.....then i'll need to install a tone pot too.... but i have no place to put it since i also have the toggle switch....i could use a stacked pot....damn, now i remember why i love basses with only one pickup. ???
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Lose the toggle (pup selector?) - it is superfluous with the blend knob; more than that, mutually exclusive really.
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You really don´t need a tone pot, I just assumed you had one in there already. If it´s spikey, it´s an easy fix with resistors and caps. Of course, rolling off at the amp is even easier. When thinking of it, the only instrument I need to roll of treble on is my rick 4001.
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I've removed the tone controls on every bass I've owned and just "control" that with playing style... ;)
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Me too.Plus i was always bumping the tone pot and wondering what had happened to the sound.
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Tone tones down the tone, poimonointly... :mrgreen:
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Lose the toggle (pup selector?) - it is superfluous with the blend knob; more than that, mutually exclusive really.
It runs the Dimarzio in parallel/single/serie, there's quite some difference in sound.
I too have never used the tone pot, that's why i havent installed one, i was just afraid of all the things i hear/read in the net about using a 500K pot with a single coil.
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It runs the Dimarzio in parallel/single/serie, there's quite some difference in sound.
I too have never used the tone pot, that's why i havent installed one, i was just afraid of all the things i hear/read in the net about using a 500K pot with a single coil.
The 250K/500K singlecoil/humbucker tone-dillemma is no big deal on a bass guitar. Although you might hear it, I think strat or tele bridge pickup might be potentially more spikey through a 500k than a bass pickup. A blend and the toggle will fit the bill.
Again, just flip the polarity on the SC when you hook it up, and stick with whatever gives you most output when using both PU's.
When using the HB in single coil mode, it should be able to balance nicely against your other SC - like a jazz bass.
Just make sure you take notes when you hook up!
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Thant's exactly what i wanted. A jazz like tone with both pickups as single coils. But i still got the volume loss.
Do you suggest to connect the single coil with reversed polarity?
Sorry for all these question guys, but i'm just trying to understand how it all works...
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Yes; whether or not the G is bucked or single, try it with the leads switched to make sure the pups are in phase with each other (loudest and fullest sounding that this combination can be).
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Ok, i'll make some experiments tomorrow....hope i don't blow the house... ;D