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Post by roadtonever on Feb 17, 2011 7:08:45 GMT -5
Here's a Bill Lawrence diagram for a Jazz-bass I found. I wonder how the blend pot is used and the function of the cap the way it's connected. I bet there are neat tricks but in this one that we'd love love to know about.
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Post by roadtonever on Feb 17, 2011 13:18:25 GMT -5
Engaged in some sleuthing and found this info on a related P/J diagram.
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Post by ashcatlt on Feb 17, 2011 14:58:22 GMT -5
It's an interesting scheme, but there isn't really much new arond here.
Think about the Blend pot as an SPDT on-off-on switch. In center, you've got both pickups in series.
Flip toward the right hand lug and you get J2 only. Both ends of the J1 are connected together go, along with J2's top wire to the V pot.
Flip toward the left hand lug, and it depends on what the other switch is doing. When that switch is connected downward, you get J1 only, with its bottom wire and both J2 wires connected to ground.
Now flip that switch upwards and we get what we call "Broadbucker" or "Half Parallel". The high frequencies from J2 find it easier to take a "short"cut through the cap to get back to the bottom wire than having to fight through the J1's winding and the amp's input first. They never get to the amp. The high freqs from J1 also find it easier to go through that cap than through the other pickup, but they still have to go through the amp to complete their circuit, so they will be amplified. The lower freqs from both pickups find it easier to go all the way around. You get Single Coil treble and Humbucker lows. It can be a very effective sound, though I personally have not (yet) tried it on bass.
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Post by sumgai on Feb 17, 2011 18:50:18 GMT -5
Well, FWIW, I find that this scheme puts about ½ of the Blend pot's resistance between the "series connection" and ground, and also between that point and the hot lead. The fact that I can switch in a capacitor between the ground and one side of the pot is a non-starter for me.
What we're seeing here is nothing more than a simple voltage divider, and while it may not cut down the output drastically, it certainly will affect the overall tonality, particularly when the wiper is in the center of its rotation.
It's a very cunning scheme, very stealthy, but I'd only consider it if I were going active in my rig, but otherwise.....
That second diagram is almost the same thing, only it's not meant to be a blender so much as it's meant to be a more versatile Broadbucker. No blending going on there that I can detect.
HTH
sumgai
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Post by roadtonever on Feb 18, 2011 16:18:43 GMT -5
I quickly wired my bass to this diagram omitting the volume pot for two 470k resistors in parallel. It seems to work well, the sound I get with the blend fully to the right is the best bread and butter sound I've gotten so far, like series with restored highs. Don't know what I think about the sounds with the cap activated. I must digest your responces on the inner working of the diagram further, my mind is shot a the moment. Sumgai, could you elaborate on what you found was the fault with the "blend" in the middle of it travel? I'll look into this half-parallel thing. Heres a link to the official Bill Lawrence wiring archive: s1203.photobucket.com/albums/bb390/wildepickups/Wiring%20Diagrams/Some weekend reading for you guys
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Post by roadtonever on Feb 21, 2011 8:19:06 GMT -5
I should perhaps make a new thread for what I'm about to post but since the digram was "nothing new" and I'm learning as I go along... I made a misstake when wiring up the J diagram initally. Found out after redoing it with a push-pull. Now where did that great restored treble series tone go, I thought. Since I didnt make enough notes I had to find out by trial and error. Finally found it's like a combo of broadbucker and spin-a-split. Closest to the series link is the cap which then connects to a resistor (used 220k)before connecting to ground. Is there a name for this? The resistor seems to give highs back to the neck pickup like the cap. Looking forward to hear what you guys make of this. I really like this tone. Meat, cut and clarity add up nicely. Good enough to play out with Here's a sound clip: www.box.net/shared/tq01tut00qPS: Reversed the order of the cap and resistor in series, sounded better the other way. I realize part of what I'm doing is simulating a hotter bridge pickup. I wonder what difference it would make to use a resistor in parallel of suitable value. And what happens then if I place the cap before and after the resistor. Geez, maybe I should post a new thread after all. I'd call it "101 ways to combine pickups".
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Post by roadtonever on Mar 1, 2011 8:38:04 GMT -5
Just want some clarification on my understanding of the original diagram. 'Blend' is both pickups full on in middle and and each pickup alone at either end. With the cap switch engaged one end is bridge alone plus cap with pot resistance "at 10", turning toward the other end blends in the neck PU while removing resistance to the cap. So in the middle neck is "half up" while cap is against half the pots resistance. Correct or no?
For anyone interested, bass players especially: Half-parallel has me ecstatic on this bass! I prefer it strongly over regular parallel for typical bass work. Recently swapped my bridge pickup for a hotter one and after trialling I did away with the resistor, keeping the cap and it sounds even better. One caution could be it's use with high output pickups, at least on bass the lowest frequencies do take a small hit. Hardly to the extent that the tone gets thin but rather agressive. I use an LCR circuit(Q-filter) to compensate when I want a warmer sound.
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Post by ashcatlt on Mar 1, 2011 17:20:11 GMT -5
With or without the cap, you're going to lose high frequencies first from whichever pickup you're dialing away from. With the cap, pickup #2 will never go all the way off, you'll still get some of its low frequencies coming through.
Ideally, I'd think you'd choose a pot value which would not suck too much tone when set to the center. A 500K(linear) here would be the same as a 250K V and T, which is generally considered a little low for two coils in series.
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Post by roadtonever on Mar 3, 2011 11:46:28 GMT -5
With or without the cap, you're going to lose high frequencies first from whichever pickup you're dialing away from. With the cap, pickup #2 will never go all the way off, you'll still get some of its low frequencies coming through. Ideally, I'd think you'd choose a pot value which would not suck too much tone when set to the center. A 500K(linear) here would be the same as a 250K V and T, which is generally considered a little low for two coils in series. Thanks for elborating. Just trying to get my head around what going on in that diagram, if only for the novelty of it and ultimately cherry-picking anything useful. Based on what you said today I tried reducing the resistive load to my series connected pickups to 500k and was pleasantly surprised by a series tone that wasn't dull and muddy but rather nicely balanced. Then tried this with no load at all and found the tone was still pleasant, not over the top at all. My bass wears hot stacked strat pickups, neck pickup close to a J-bass pickup in output, bridge pickup 50% higher output.
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