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Post by flateric on Dec 12, 2007 16:13:31 GMT -5
Blend pot from Axes R Us: I have this wired up in a new bass build with jazz bass pups, used to blend between neck and bridge position. It has a centre detent which does what it says. I've wired it as per std seymour duncan type schematic: www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=jazz_bass_blendHowever, the signal is really weak in the centre position and volume is far lower than either full neck or full bridge position, so it's virtually unusable in a gig situation. It's like the blend pot has overlapping resistance in the centre and both pups are hushed by about 30%. Is it a duff pot, wrong choice of pot or my choice of schematic? Do I need to get a blend pot which is truly zero resistance on both tracks at th4e centre position? (which is what I thought this one was going to be...) Trouble is, I really like this type of ctrl layout - far more user-friengly than separate vol controls for neck and bridge.
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Post by sumgai on Dec 13, 2007 0:24:11 GMT -5
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Post by flateric on Dec 13, 2007 2:44:58 GMT -5
Nice one, thx sumgai;)
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Post by ashcatlt on Dec 13, 2007 10:27:35 GMT -5
I read this last night, and found myself wondering are you positive that you haven't inadvertently reversed the phase of one of your pickups? I guess that would cause a noticeable change in tone as well as a drop in volume, but it's certainly worth a check.
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Post by flateric on Dec 13, 2007 10:52:28 GMT -5
well yes I am positive, however it will only take me 5 minutes to reverse one pair of wires and test it so I have little to lose. Been delving more into the blend pot residual resistance and it seems fairly common, with both cheap and mid-range (stew-mac) blend pots. Will get the soldering iron out when I get home.
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Post by flateric on Dec 13, 2007 13:14:21 GMT -5
OK, I reversed the bridge pup wires, it goes thin and tinny in the centre blend pos'n so the original wiring is ok, it has to be the blend pot.
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Post by ChrisK on Dec 13, 2007 19:06:15 GMT -5
NOPE, it's that DANG PAN pot that they'all sell as a blend pot!
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Post by flateric on Dec 24, 2007 10:30:17 GMT -5
John East has been really kind helping me out with a TRUE blend pot for this on-going wiring saga. Now I want to revert to the jazz bass pickup blend wiring, ditch the separate vol ctrls for the neck and bridge pups but retain the series/parallel switch I installed as it has a great tone in my bass build. I've been trying to work out if the wiring is possible with this but have been going round in circles. Can anyone help please with a suitable schematic? 2 JB pickups, one master vol, one blend pot, one master tone, and a DPDT series/parallel switch which (of course) in series mode would render the blend ctrl inoperative but still leave me with a master vol and tone?
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Post by flateric on Dec 24, 2007 16:33:48 GMT -5
I came up with this over a couple of whiskies: Not sure if it's correct.....any one able to comment?
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Post by JohnH on Dec 24, 2007 18:49:00 GMT -5
Hi Eric - looks like it would work, but there may be better ways so the belnder is either fully out of circuit in series mode, or working properly to mix. Are you interested in having blending in both series and parallel? - can be done and theres a few different options.
John
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Post by sumgai on Dec 24, 2007 22:16:23 GMT -5
♭eric, It may be time to move up to a better grade of booze, that whiskey made you blind to an obvious shortcoming...... Check the upper wire of the Neck pup...... it goes directly to the blender, eh? So if the S/P switch is in Parallel, then the lower wire goes to ground, and the Neck is controlled correctly. But, when the switch is thrown, the Neck is now in series with the Bridge, yet it's still going through the blender. You now have essentially two volume controls in the path, not just the master. That's gotta hurt, I'm sure of it. In short, you'll need a 3rd pole to your switch, and it will route the Neck's upper lead either to the blender (in parallel) or directly to the Master vol (in series), thus bypassing the blender entirely. These switches exist, look for a 3PDT unit. All of us here know that you Englanders have the Debil's own time trying to get American supply houses to ship small quantities to The Continent for any amount of money, let alone something realistic. I just checked Maplin, they seem to be disinclined to show the needed part. I know there are other electronics purveyors over there, it stands to reason that the part should be available somewhere. If not, ask one of us, and I'm sure you won't be disappointed. Or you could just use a 4PDT (more common), and not worry about the wasted section....... Or you could do as John suggests, and consider using the blender in both series and parallel, that's doable. Just some thoughts. HTH sumgai
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Post by flateric on Dec 25, 2007 5:58:22 GMT -5
If you could use the blender in both S and P that would be better than I could imagine. How would the schematic go for that? Merry Xmas guys!
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Post by JohnH on Dec 25, 2007 14:55:42 GMT -5
ChrisK has a module for using the true blend pots (ie, each pot half goes 0k, 0k at centre, 500k - in opposite directions) in series and parallel, with a dpdt switch: Im thinking for a bass, and to get smoother blending, a 250k blend pot might be better than a 500k one - what does anyone else think? John
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Post by sumgai on Dec 25, 2007 17:13:32 GMT -5
ChrisK has a module for using the true blend pots (ie, each pot half goes 0k, 0k at centre, 500k - in opposite directions) in series and parallel, with a dpdt switch: ............. Im thinking for a bass, and to get smoother blending, a 250k blend pot might be better than a 500k one - what does anyone else think? Well, all I know is that we constantly bandy about a lot of numbers, and some of them fairly often. But one thing I'm sure of is that Leo used 1MΩ pots for everything, volume and tone, on both guitars and basses. The only thing that changed was the capacitor value itself, and that was probably due only somewhat to "tinkering with the sound". It could have just as easily been "what kind of deal can we get on 6 gross of these" thinking, i.e. saving a few bucks here and there. And for all that 1Megger is considered "too high" a value today, I have to wonder, why is it that nearly every last one of us refers to those years as having the best sound ever? And we thought so too back then, not just now in retrospect. I think it was the CBS engineers who reduced the pot values, but I can't be sure of that, I've never thought to look into it closely. In the long run, a larger value will simply mean that more high-frequencies are available at the output, when the control is at full clockwise rotation (max volume, for you lefties ). It's a given that the lower the value, the less the highs that get through. One should be able to tailor his/her sound with ease, keeping this in mind. In regards to a blend circuit, the same thing applies - after all, it's a complementary volume control, that's all. If one wishes to consider the master volume as part of the overall resistance, and the blender another part, and if one were to desire only a 1MΩ resistance in the circuit, then one could easily split the difference, probably with no ill effects..... or so I would guess. Them's my thoughts, hope that's what you were looking for. sumgai
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Post by flateric on Dec 26, 2007 4:44:30 GMT -5
Thx for the schematic. As for the pot restsance, after all that has been said, its 250's I have and thus 250's I will be using! If John says they may be smoother then that will keep me happy figuring out which wires to solder where. This is what I've come up with based on the above schematic. Does this look correct? A couple of things I'm not totally sure about: 1) The mneaning of the Upwards and Downwards arrows. 2) The dotted line joining the 2 sweepers on the centre lugs of the blend pots - I would assume this means they are physically joined together...? 3) The dot by one end of the pickup coils - does this denote North end or hot output for example? Merry Xmas all!
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Post by sumgai on Dec 26, 2007 12:52:05 GMT -5
♭eric, All of your suppositions are correct, as is your drawing! Chris's up and down arrows are simply connection points where this "wiring module" will make contact with the rest of the circuitry. (You'll see this a lot in the Modules section of the Forum, where John found the drawing.) In your drawing, you correctly surmise them to be Hot (the upper arrow), and ground. The only "sorta" catch would be some of the terminology. We don't ordinarily denote a single coil as having a North (or South) lead - North/South usually refer to an entire coil within a humbucking pickup. Start/finish is also more often used within the humbucker context because we want/need to align the two coils correctly (electrically speaking) in order to get the desired effect. One could refer to a single coil as having a Start, and intend that it be the same as the Hot, but that's also not a common usage. We prefer to use either Hot or positive (and ground or negative), or the simple + and - signs. But all that aside, your meaning is clear, and your grasp of what's going on is also obvious. I think it's time to warm up your iron! ;D Oh, and as I've said before, always use what you've already got in your parts box first - no point in letting it go to waste! HTH sumgai
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Post by flateric on Dec 26, 2007 16:06:02 GMT -5
Thanks chaps, I'm off to chip the ice off my solder. Will let you know how it goes.
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Post by ChrisK on Dec 26, 2007 18:20:51 GMT -5
Neither.
Phasing as in wire winding direction (and only if one wants the coils to be hum canceling relative to another coil).
Now as far as north starting and south finishing and eastern star and west-ward ho, you can take all of that hooey and ship it to Kansas.
Did I mention that it was hooey?
By simply reversing the two wires from a coil, one can effect hum cancellation or hum enhancement in respect to another coil.
Hence, only the magnet polarity matters (and matters greatly if you can't reverse it).
If you can't reverse the wiring, stuck is.
If one was to take a SSS Strat and connect all of the pickup "hot" leads to "ground", and all of the pickup's "ground" leads to the places where the "hot" leads were, the guitar would work
.............................................................................................................EXACTLY THE SAME.
Relativity, it's not just for time travel.
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Post by sumgai on Dec 26, 2007 21:49:17 GMT -5
Chris, I think I see where you're going here, let me recapitulate........ If a coil is laid on a bench with the bobbin oriented horizontally, and the feed spool of wire is to the left, then it doesn't matter if the first wrap starts along the bottom side or the top side, eventually it will make a full wrap around the bobbin. At this point, if I mark the end of the wire that lays along the top as + (and the end of the wire that lays along the bottom as -), then I have a coil with markings, which can be used in reference to another pickup built the same way. So, let's build a coil, one wrap long. (!) We'll start along the top, and end by traversing the bottom part of the bobbin, back to the left side, OK? Voila, one coil, marked + at the end of the winding where I went along the top, and - at the end of the winding where I went along the bottom. Check so far? Good. The next coil we'll build starts out by traversing along the bottom side, going around the corner, and heading along the top side, toward the left end. Great, let's mark it...... Hum, which way is positive? Wait a minute here............ .............. What the hey, this wire has two ends to it, and since electricity flows in both directions, I can mark those ends in any way I want, can't I? Yes!! This is brilliant - I can, with the stroke of a pen, make what was the + become the new -, and nobody will ever know the difference!! Mwuhahahaha! ;D And so it goes, the winder doesn't have to make any changes (hence, the paycheck was the same at the end of the week, and the union never got to file a grievance), and depending on how the magnets were inserted (or are added later, for a really cheap pup), the markings become a matter of convenience, not one of relation to direction the coil was wound. In summary (pay attention folks, there'll be a test at the end of the period), the winding goes in both directions..... at the very same time!!! If the winding starts in the top-left of the bobbin (viewed from the end, not from the top downwards), or the top-right, or the bottom-left, nor even the bottom-right, it all doesn't matter. Or as Chris will next propound, it's all 100% dependent on the 'right hand rule' of electro-magnetics. Right, partner? ;D Shouldn't that be "guitar would still work"? And not to be mean or anything, but that statement's a bit of a red herring, no? May I assume you had a point to make, and that I'm too densefull of Christmas cheer to able to see it? HTH sumgai
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Post by flateric on Dec 27, 2007 4:07:47 GMT -5
....and should it always start in a clockwise wind direction if you're living in the northern hemisphere? Or is that only if you are facing the north pole when you are doing the winding?
;D
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Post by flateric on Dec 28, 2007 8:28:23 GMT -5
I am pleased to report that after a little fiddy soldering, this mod is a resounding success. As was warned, the blend pot is a little sensitive in the central region - gives a lot of tone variation for a small movement, but there is no appreciable drop in output, the 2 s/c jazz bass pups work together in humbucking mode and you get a really wide range of usable and impressive tones from just one series/parallel switch and a little turn of the blend pot. Very pleased, it has been a bit of a struggle getting here but thanks to all who helped nudge me on my way.
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Post by JohnH on Dec 28, 2007 14:06:52 GMT -5
congrats! +1!
Lets get as much info out of this as we can. If your 250k blend pot goes from 0 to 10, with 5 being centre, between what settings would you say the tone variations occur, in series mode? and parallel mode?
cheers
John
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Post by flateric on Dec 29, 2007 4:25:29 GMT -5
I'll give you some more tone info on this when I've had chance to explore more. Roughly, the main tone difference happens between 0 - 1, 4.5 - 5.5, and 9 - 10. This holds true for both series & parallel modes. However, the series modes mid positions are very 'filtered' almost nasal in tonal quality. But the series modes at 0-1 and 9-10 are superb.
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Post by flateric on Dec 29, 2007 19:00:29 GMT -5
...in the meantime I got myself a better multimeter, and in the interests of science I carried out a few quick readings of my own on the "standard guitar issue 'blend' pot".(Allparts/StewMac/WD/AxesRus, etc.) For the top track I got resistance going from 0 at far left travel to 80k/400k in the centre, to 480k at far right. The lower track gave me 530K resistance at far left thru to 440/105k in the middle to zero at far right. So the centre 'neutral' detent position would effectively give you an 80k resistance for the neck pup and a 105k resistance for the bridge pup. Surprising to see even the variance from upper to lower track, but I guess the real question is: is this sonically/tonally significant? I know now from my own experience that 80 to 100k resistance at the centre detent is significant enough to render these 'blend' pots useless for wiring mods, as the combined pickup output is significantly reduced; the volume difference between centre blend positions and full left or right is too much to be of practical use in a live performance situation.
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Post by ChrisK on Dec 29, 2007 20:10:01 GMT -5
My statement is a superset of yours (i.e. "still work").
My point is:
Relativity (as in a phase relationship to another) is.
Hence pickup "ground" and "hot", arbitrary are.
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Post by ChrisK on Dec 29, 2007 20:13:25 GMT -5
Indeed! Variance? Tolerance is! 500K +/- 20% is 400K to 600K Defective not. However, they do make dandy flexible pots with both RH and LH curves. If one wants to blend in a pickup to another that is fully selected with a series (2 terminal rheostat mode) variable resistor, the pan pot can be used, with its reverse taper element being of best effect since the normal RH taper pot, in this mode, at the wiper to RH CW terminal changes resistance much too quickly. As I had noted, JohnH has stated, and was empirically determined herein, a value of perhaps 100k is the best maximum value for a series 2 terminal blender. This occurs about mid-rotation for a 500K pan pot and a little farther south on a 250K. ?both series & parallel modes? Are you using a true blend pot (as you had indicated that you'd found a domestic source for) or a pan pot for these results? My results with a true blend pot were that the parallel blending effect was best between 3 to 7 and the series blending effect was best between 0 to 2 and 8 to 10. This makes sense in that in parallel mode, "3" correlates to a 300K parallel resistance across the blended out pickup and a 200K series resistance to the output. Conversely, "7" correlates to a 300K parallel resistance across the other blended out pickup and a 200K series resistance to the common. In series mode, "0" correlates to a full shunt and "2" correlates to 200K across said pickup. Conversely, "10" correlates to a full shunt and "8" correlates to 200K across the other pickup. I can see how your results were limited to a lesser rotational range in that a bass and its pickups have considerably less in discernible harmonics (the first to "suffer" the effects of blending as in series loading leading to shunting, and parallel "voluming" since the action is near identical to the reverse LP volume mode). I would expect that the results with my Fender bass 250K blend pot would be nearly ideal since it was, uh, designed by Fender for blending bass pickups. Again, this was with a true blend pot. I had initially tried the pan pot some years ago, but found it FuGoofy (GeFooey-bar/Minnie Mouse). These findings were based on tests with a Fender SCN Tele pickup set in My Proper TeleCopy . Note that the blend pot is only in circuit in the normal and reverse phase blending positions on the super switch. This allows unfettered (no additional resistance loaded) tonal response in the "normal" Tele positions (bridge, both in parallel, neck). ?Series modes mid positions? Not that I've ever seen with a true blend pot. Series modes at the ends of travel, ya, you betcha! Again, my question as to which pot you are/were using.
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Post by flateric on Dec 30, 2007 3:50:03 GMT -5
Reputedly a M/N stamped 'true' blend pot as supplied by John East - with zero R at centre detent. east-uk.com/jrhome.htm
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Post by JohnH on Dec 30, 2007 15:14:46 GMT -5
I'll give you some more tone info on this when I've had chance to explore more. Roughly, the main tone difference happens between 0 - 1, 4.5 - 5.5, and 9 - 10. This holds true for both series & parallel modes. However, the series modes mid positions are very 'filtered' almost nasal in tonal quality. But the series modes at 0-1 and 9-10 are superb. The unusual part about what you have reported is that it implies there is tone variation in all three of those ranges, in both series and parallel modes. Expectation would be that in series mode, the variations would be 0-1 and 9-10, with everything between 1 and 9 being approximately a blend of both pups and nothing particular happening around 5. Conversely, in parallel mode, one would expect 0-4.5 to be one pup, blends happening at 4.5-5.5 and 5.5 -10 being all the other pup. So if thats right, I wonder what is happening in those series modes around 5? John
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