robbiec
Rookie Solder Flinger
Posts: 3
Likes: 0
|
Post by robbiec on Dec 5, 2007 11:37:24 GMT -5
Is it possible to wire a 2 pickup guuitar with
-vol pot -blender pot -tone pot -4 pole 6 position selector switch (pu 1, pu 2, pu 1+2 parallel, pu 1+2 parallel out-of-phase, pu 1+2 series, & pu 1+2 series out-of-phase)?
If so, would anyone know where to find a schematic?
Thanks, RobbieC
|
|
|
Post by ChrisK on Dec 5, 2007 20:25:43 GMT -5
Sure, providing that one pickup is at least 2 wire plus shield (or 2 wire alone with no shield). At least one pickup cannot be single conductor plus shield.
What do you want the blender pot to do (as in "what" in which positions)?
What pickups are you using?
|
|
robbiec
Rookie Solder Flinger
Posts: 3
Likes: 0
|
Post by robbiec on Dec 5, 2007 23:52:44 GMT -5
Thanks for your reply ChrisK!
Two Fender pickups. The volume would be the master volume. The blender would be relative volume. The selector switch in positions 1 and 2 would bypass the blender since otherwise I'd have two volumes in series.
|
|
|
Post by warmstrat on Dec 6, 2007 16:03:57 GMT -5
Sounds interesting... one doesnt often see only two fender SCs together on a guitar... be sure to post pics!
|
|
|
Post by wolf on Dec 6, 2007 17:02:51 GMT -5
robbiecI like to use toggle switches in my rewiring projects. (I'm not a big fan of rotary switches). If you don't mind changing the appearance of your guitar, you could get all 6 sounds with 3 toggle switches (2 SPDT and 1 DPDT for the phase switch). Anyway, this schematic shows how to wire 2 SPDT toggle switches to get those first 4 sounds you described. The positions of the toggle switches easily show which of the sounds you are getting. neck toggle switch down, right toggle switch up - neck pickup only neck toggle switch up, right toggle switch down - bridge pickup only both toggle switches up - both pickups in parallel both toggle switches down - both pickups in series (to eliminate confusion here, when I describe the switch as pointing 'up' or 'down' it depends on whether you are using toggle or slide switches). It would be easy to add a phase switch into the circuit but I don't want to confuse you with too much wiring information too fast.
|
|
|
Post by ChrisK on Dec 6, 2007 17:10:26 GMT -5
|
|
robbiec
Rookie Solder Flinger
Posts: 3
Likes: 0
|
Post by robbiec on Dec 10, 2007 13:35:17 GMT -5
Thanks everyone for your very informative replies...Wolf, ChrisK, Warmstrat.
ChrisK...nice looking Tele...is this a Warmoth neck? Your're obviously going after the 50s look, but have you ever tried the Gotoh 0025 bridge? It's a copy of the Schaller that I use.
I have two 2PU Fender guitars that I'm considering for this project...a 63 Tele Custom and a Jazz Bass. Currently the Tele has a stage setup a la EVH... just a Gibson toggle switch and a volume pot. No tonal subtleties. All the original hardware is boxed of course.
The Jazz Bass is wanting for a better way to blend and switch between pickups (2 volume pots, no switch) as well as a deep Precision kind of sound (series). All the other tones may not be usable but I'd get the Jazz, Rick, & Precision sounds and some special effects.
I understand that at a blender pot's detent center position the both PUs are down in volume but that StewMac has a compensated blender.
|
|
|
Post by sumgai on Dec 10, 2007 15:18:36 GMT -5
robbie, Hi, and welcome to the NutzHouse! ;D That's not necessarily true. In fact, the only way that could occur would be if the job were botched. A properly designed blender (correctly called a balance control) should introduce no reduction of the signal at all, when the control is centered (both pups fully on). Stew-Mac's so-called "compensated" unit is nothing more than a properly designed control that most engineers would specify for use in this type of circuit. I'd use the 500KΩ version, for the reason that when you combine the two pups in series, you'll have the same inductance/reactance as a standard humbucking pickup. Those usually sound better with 500KΩ pots, so the same might apply here. But either one will work, the differences are subtle. Stew-Mac also has a pretty good 4P6T rotary switch, if you're still looking for one of those. ChrisK has more info on that switch, here: guitarnuts2.proboards45.com/index.cgi?board=wiring&action=display&thread=1195501136HTH sumgai
|
|
|
Post by ChrisK on Dec 11, 2007 0:12:16 GMT -5
Well, it's been my experience that a pan pot as used in mixers do indeed have both channels "down a bit" in the center detent position since the purpose of a pan is to realize equal volume/power output as the signal is swept from one side to the other. At the center detent, both are at -3dB?
A true blender pot (in my not so humble description) has both signals at maximum at the detent. Only the Fender linear bass blend pots (in my direct experience) and the StewMac ones (as described by them) are so.
Measuring both 250 K and 500 K pan pots (sold as blend pots) that I bought a few years ago resulted in detent readings of 40 K'ish and 80 K'ish respectively.
|
|
|
Post by JohnH on Dec 11, 2007 1:05:27 GMT -5
I was wondering about these 500k blender pots, that go to full volume on both pups at the centre detent. It would seem to me that, with the pups in parallel through the blender, as you turn the knob away from the detent, that one pup will quickly be pushing through quite a large resistance while the other is still at full. I would have guessed, from some rough numbers, that the faded down pup would quickly become audibly insignificant in the mix as you move away from 5, hence making it difficult to set a particular blend. Is that what happens in practice? I haven’t tried them.
John
|
|
|
Post by sumgai on Dec 11, 2007 5:06:55 GMT -5
John, At something like 5 bucks and change (American), try one for yerself! No, seriously, it's all in the point of view. If a signal coming in is attenuated by some small amount at the center detent, and never rises above that level during rotation, then for all practical purposes, the outgoing signal is at "par" value, for the "neutral" half of the rotation. If one insists on comparing it to the incoming signal, and sees a loss, then yes, there is a loss. But fer kee-riminy's sake, there's a bunch of amplification coming up, so where's the beef? The half that actually does attenuate the signal, intentionally, is made with a taper intended to be smooth, and not jerky. If what Chris measured (at the center detent was only 40KΩ, out of ~500KΩ, then that's nearly 10% of the total claimed resistance. One would have to wonder, is there any resistance at all, in the nominally 'neutral' half of the rotation. There shouldn't be, but one never knows...... But even so, 90% or 100% or whatever, that's a lot of change for only 100 to 120° for rotation, and I can see where it'd be hard to make that usable with any degree of certainty. Manufacturing tolerances, and all that. Bottom line is, what's usable, and what's not. Unless one has to satisfy "golden ears", then one would probably be happy using the control sold by Stew-Mac (or others), and not miss the tiny 0.0001% of whatever's allegedly missing. BTW........ robbie, I've had a second thought on the 500KΩ thing....... It seems that the two coils in series will present about the same inductance/reactance as a humbucker, and for that, a 500KΩ value is good. But these pots (at Stew-Mac) have 500KΩ per section, not for both sections combined. For that reason, you may be just as happy with the 250KΩ pots instead. Why? What John and I have just discussed, above. It's the taper....... the larger the value, the harder it is to make a usable taper within a pot. The lower the value, the better the chances of having the rotation act smoothly on the signal. Plus, in the parallel combinations, that much resistance may make the two pups together a bit harsh, now that I've thought it over some more. Again, it's your choice, but I think I'd go with the lower value offering. HTH sumgai
|
|
|
Post by gumbo on Dec 11, 2007 9:40:01 GMT -5
Hmm..please post the results if you get this up-and-running on the Jazz......been thinking of something similar on one of my Jazz's for some time.. Greetings from South Oz, where the bushfires are now raging.....
|
|
|
Post by JohnH on Dec 11, 2007 17:12:03 GMT -5
My comment was more in the form of a question. I don’t have an application for the blender pots myself at the moment, but I wanted to flush this out since they are being proposed on this thread. With the Stewmac type that go 500k, 500k at centre, 0k, and 0k, 500k, 500k for the other half, then the situation when wired conventionally, is similar electrically to having two volume pots on an LP or SG and turning one down slightly to get a mix of all of one pup and part of he other. I find this quite tricky to do, because you either get all of both pups, or one part audibly fades away as soon as you turn its knob by a very small amount. With a blender pot, the only purpose for it is to create these in-between mixes, otherwise, it may as well just be a switch. So I just wanted to hear if anyone can confirm that they work effectively for those in-between tones.
Cheers
John
|
|
|
Post by ChrisK on Dec 11, 2007 22:55:54 GMT -5
No. This is a Callaham Tele bridge. It's welded from flat stock, is thicker than the Fender part, and is a boutique part (it also sounds reeaal good). Related to the original topic: I am unfamiliar with the pickups on a '63 Tele Custom. Are they two insulated wires or a single conductor with shield (I won't stop asking this question until it's answered!). By looking at the Fender support site for Jazz basses, I can deduce that the pickups are two wire (and hence eminently usable in a series structure). (I will stop asking this question about the Jazz bass pickups because it's been answered for you!). I'm a big fan of the multi-sound bass. So much so that my 4 string one is a Fender Stu Hamm Urge II. It kind of "cheats" in that it has two J pickups and a P pickup and active circuitry. www.fender.com/support/diagrams/pdf_temp1/basses/0191500A/SD0191500APg1.pdfwww.fender.com/support/diagrams/pdf_temp1/basses/0191500A/SD0191500APg4.pdfI do like the Fender Jaguar bass. I'd have one "on the surgical table" under modification if I didn't already have the Urge bass (and if I actually played bass............... ). www.fender.com/products//search.php?partno=0259505515I like the series and parallel modes as well as the active preamp with active/passive switch and the passive tone control that works in both modes. Now, we all here a'board know how to realize bridge, neck, bridge + neck, and bridge * neck with just two DPDT slide switches (binary tree is), freeing the third DPDT slide switch for, uh, you know, like phase reversal or sumpthin'. However, if you scroll down to my series/parallel blender circuit.it works with a DPDT switch to realize both series and parallel blending. Coupled with a push pull (for series/parallel selection) volume pot and a push pull (for phase reversal) passive high cut tone control, you would have a serious series/parallel/blendable/two-phased paralyzing monster on your hands. (I did assume that you have a three-hole Jazz bass, Vbridge, Vneck, Master Tone.) Oh, and you don't need any other switches.
|
|
|
Post by ChrisK on Dec 12, 2007 1:17:46 GMT -5
sumgai, I apologize in advance for using your last post as target practice. You had the unfortunate luck of having summarized things well. In series, each pickup sees 500K. In parallel, both pickups see 250 K (500 K || 500 K). If you use 250 K, in parallel both pickups see 125 K. It's your choice. I've found that with 500 K blend pots (true ones), the best series (shunting) blending occurs from 0 to about 200 K Ohms and the best parallel blending occurs from about 300 to 500 K. This indicates that a linear response is best when doing both series and parallel blending. That being said, I like 250 K pots for Fender SCN pickups (I generally tend to blend/phase reverse only humbucking pickups). General topics: Well, there isn't any jerky response in either a linear or audio (don't get me started....oh, wait, I got myself started...full story at 11:00) taper pot. It's just the jerky'ness of our fingers. Well, 40 K for 250 K and 80 K for 500 K, however................ You betcha! Dang it, I said you betcha'! Uh, no. Having near zero Ohms of resistance is important in both parallel and especially series blending applications. I would state that it's vital. If the detent resistance on both sides is 80 K out of 500 K, while the percentage seems small, the effective series resistance of both pickups has increased substantially. Each parallel pickup is now driving the summing node (at the input to the volume pot) thru its internal impedance PLUS 80 K Ohms. Not only has the effective drive model changed, the normal pickup characteristics' interactions are substantially subdued (since they are isolated from each other by 160 K). The series meta-pickup now has an additional 160 K of internal impedance, substantially reducing its drive capability as well as the aforementioned normal pickup characteristics' interactions. Since most single coil pickups have an internal resistance of about 6 K or so, the additional 80 K is huge. Lastly, manufacturing tolerances apply more variation to absolute values (paste mix and thickness) rather than ratios (screen apertures), which both are a function of the paste screening process. Firstly, while there seems to be a lot of change for half of the rotation, there isn't. Well, no more or less than the pedestrian audio taper volume/tone pot because that IS EXACTLY WHAT BOTH ELEMENTS (one right-hand, one left-hand) in a pan pot are! The only thing special aboot a pan pot, aside from being ambidextrous in a dual personality kind of way, is the mechanical detent mechanism. Which is EXACTLY WHY I preach the use of pan pots in left-handed guitars, since they ARE also left-handed audio taper pots. I also preach using them for blend pots in right-handed guitars since they also have a left-handed audio taper suitable for real parallel blending (related to that there jerky thing). My point is, that for parallel pickups, in the full parallel selection, one wants the effective output impedance of each to be, well, the effective output impedance of only each. Whilst blending ONE of them toward OUT (by effective output impedance increasing), one wants the other, fully selected in parallel one to remain fully in selected parallel. Conversely, for series pickups, in the full series selection, one wants the effective output impedance of each to be, well, only the effective output impedance of each. Whilst blending ONE of them toward OUT (by effective coil shunting so that the effective meta-pickup impedance remains low/goes lower), one wants the other, fully selected in series one to remain fully in selected series. With the pan pot, both pickups in either mode never get to fully "wrestle" with each other, but are confined to an isolated environment. This is also why the Fender blend pots used in basses are true blend pots (and why I use them for blending pickups). Now, part of the problems with pots is the mode that we use them in. In an LP, the pickups are blended by using volume controls. Sometimes we reverse the connections to the volume controls to avoid the interactions of said volume controls near off (to fix a problem that doesn't actually exist, hey Sparky, it's the "both on" position on the three-way selector switch, if'n you don't like the controls interacting 'cuz one of them's dang near zero, use the correct position). But, these are used as volume controls. In a Strat, we often try to blend in a pickup by using a pot as a rheostat (a two-terminal variable resistor). This is often less than optimal in performance. When a volume control type of blend is used (ratiometric), the effective series resistance is less than when a rheostat type of blend is used. For example, if a pot is at half of its value (about "8" on an audio taper Strat), in the series resistance/rheostat mode, the 250 K pot will have about 125 K of resistance in series with blended out pickup. Since parallel pickups average their signals, and the typical single coil is about 6 K, the blended out pickup is already at the disadvantage of 130 K vs 6 K in driving the output node. When the pot is in a ratiometric mode, the output signal contribution to the parallel output node is attenuated by the Thevenin equivalency of the pot. In this case, it's the parallel equivalent of the pot (125 K in parallel with 125 K or 63 K) in series with a generator at half the output voltage of the normal pickup. In this case, half of the signal is driving the output node thru about 70 K against 6 K for the dominant pickup. While this may seem to be relatively equal to the rheostat mode, it isn't since the ratiometric approach not only adds in series resistance; it does it ratiometrically in a controlled manner. Of course, when we use the reversed LP style of volume pot wiring, we realize both a coil shunting control that actually adds in series resistance like the rheostat mode. This is sort of the worst of both worlds. OK, as threatened................ pot tapers. I've known forever that there actually aren't logarithmic/audio taper pots in use in electric guitars. WHAT? Yes Tim, the logarithmic taper pot is a myth. Outside of studio uses where folks WILL pay $40 for a quality linear slide audio taper pot, or military applications where we'all get to pay for.................., in the consumer areas (you know, that crappy low cost market known as electric guitars), most pots are piecewise linear approximations of an audio taper. Now, if one has enough chords (geometric math term, not the sound of the strings), one can, for all practical purposes, effect virtually any continuous/contiguous curve in this manner. (Which goes back to some discussions about modeling tube responses with diodes in the late 80's/early 90's.) Unfortunately, many cheap pots only have two segments which are linear. This is due to the way that pots are made. A conductive paste is screened onto an insulating substrate. One can either change the width of the track, the thickness of the paste, or both. Since these are low cost (we pay about $5 for them so they cost about $0.50 to make), the minimal number of operations is in order. Uh, like two paste applications. Sorry to spring this on the world, but I think that we're ready for the big truths now..................... Here's a typical curve; B is linear, A and D are the two typical "log" (not) curves. C is the reverse-hand of A. If one interpolates at 50% of rotation, one sees that the response is aboot 16% of full scale. This correlates to 40 K at 250 K and 80 K at 500 K. Dang! Here's anotherSo there, I killed the tooth fairy.
|
|
|
Post by sumgai on Dec 12, 2007 4:22:59 GMT -5
............. (don't get me started....oh, wait, I got myself started...full story at 11:00) Are you gonna have pictures? 'Cause if there ain't no pictures, then I'm gonna have to give it a miss, ya know? It's like, I don't have a lot of time to be, like, reading or sumpin', ya know? A summary in pictures would be reel gud fer me, please. ;D sumgai
|
|
|
Post by ChrisK on Dec 12, 2007 11:51:19 GMT -5
OK, I changed one link to a "picher". I intend to add a section to the "Reference" section on potentiometers and their general applications to guitars. Probably ought to do one on switches as well. I'm sort of thinking along the lines of an "Elements" or "Basic Components" thread. There would be simplified explanations (yeah, and my complexer' ones) for a modular approach to building up a wiring scheme based on, uh, basic concepts. And, for the "short of span" ( ), there'll be some pictures too.
|
|
|
Post by flateric on Dec 13, 2007 2:52:47 GMT -5
Thx Sumgai for directing me to this thread. I have a 250k blend pot wired to my new bass build with Jazz bass pickups and because the centre position is at least 3db down from the 0 and 10 position, due to some residual resistance being present in both tracks the mid position becomes unusable - the volume drop is significant. In fact the only practical thing you can do in a gig situation is use the blend pot between 10 and 9 and between 0 and 1 to take the edge off either pickup full-tone position. I really need to find me a blend pot that is truly zero resistance at the centre for this wiring to work propoerly.
|
|
|
Post by flateric on Dec 13, 2007 7:51:56 GMT -5
The kind folk at AxesRus will send me out another blend pot FOC to have a look at - they say its same source as Stewmac so it ought to have zero R at centre. Sorry for hijacking yr thread. If anyone's still interested I'll post my findings and prove the theorists right. Even a small residual resistance at halfway makes such a significant difference to the output for me to want to rip out all the wiring and think again.
|
|
|
Post by sumgai on Dec 13, 2007 15:02:33 GMT -5
eric, No, you haven't "hijacked" the thread, what you've contributed is important and germaine to the whole thing. I also have a Jazz bass (an MIM fretless, in fact), and I've been contemplating giving it a kick in the arse with the series mod. Along the way, the idea of a blender has also been on the front burner......... JohnH, I think it's time to investigate the idea of modifying a pot (or more precisely, a pair of pot elements, tied to a concentric shaft), only this time, instead of cutting a trace, how's about we try gluing in a tiny strip of copper foil over the offending portion of said trace(s)? Your thoughts, if you please. sumgai
|
|
|
Post by JohnH on Dec 13, 2007 16:47:37 GMT -5
Sumgai – interesting idea.
My messing about with track scraping has been based on either single pots, or attacking just the rear track of a dual gang pot. I’ve not been able to find a way to get full access to the inner track on a dual gang without trashing the pot . It must be possible however, since it was created by humans from parts – much trickier though.
Glueing foil to the track would need some testing, and the application of some tiny female fingers. As an alternative, how about using a conductive pen of the type sold for the purpose of repairing pcbs? This might work without full disassembly, and could be applied just around the outside of the track. The contact to the wiper would still be to the carbon track, but the track would be continuously shunted along its edge to this conductive trace.
Now I have not seen a positive statement from anyone based on experience, that these blender pots actually work with zero resistance over one half and full resistance over the other. By working I mean that not only does it allow a transition from one pup, to both pups, to the other pup, but specifically that you can set a blend which is near 100% of one, and audibly a smaller (but not negligible) part of the other, without the setting of it being so sensitive that the whole useful blending range occurs between 4 ½ and 5 ½ on the blending knob. That’s my concern, but I’m sure somebody can reassure me that it works. I can’t buy one to try it without an overseas mail order.
My knowledge of blending systems that do seem to work, is that it is more effective to do blending of series wired pups, using a single 250k linear pot with central track cut. For pups in parallel, I reckon good blending occurs if you introduce a relatively small resistance in series with one pup only, 30k to 50k in series with one pup is enough (yes I tried it!) to make the other pup sound like its at 100% with minimal contribution from the reduced pup. This scheme could be adapted to a dual-gang 100k linear pot, with the track-shunting idea (foil or conductive pen), making each track 50k, 0k, 0k and 0k, 0k, 50k. The two tracks are put in series with their respective pups, with no ground connection to the pot , so that at mid position, both are at 0k and towards one end, one pup is in series with a variable 0k to 50k resistance and the other is at full.
cheers John
|
|
|
Post by ChrisK on Dec 13, 2007 17:02:11 GMT -5
As I had indicated earlier, but with specifics, on my Proper TeleCopy I used a Fender bass blend (yep, blend, not pan) pot. This is where I found that the initial 30% to 40% was effective for parallel pickups and the last 30% to 40% was effective for series pickups, both using my blend module with a DPDT switch. This was with a 500K linear blend pot. This correlates to about 200K in either case. While the best effect occurred with perhaps 10% to 20%, I could still hear the effect up to these percentages. This swamp ash body/maple/maple neck guitar has Fender SCN pickups and was listened to thru a clean model on an amp modeler. This led me to choose the 250K Fender bass blend pot as optimum for these pickups. If you look at my series/parallel blend circuit (scroll down please).......you'll see that a ratiometric/potentiometer structure is in use for parallel and a series shunting structure is in use for series. As I had alluded to earlier, the use of a 3 wire/ratiometric structure will have a different effect than a 2 wire series structure for pickups in parallel. For series, shunting is about the only way to do it unless one can find the equivalent of an "L" pad for pickups. Here I pictorially represent the blend pot as having minimal resistance for half of its travel.Folks will often (well, sometimes) use a 50 to 100K series resistor to add in the other pickup when in a one-pickup only selection. It adds just a hint of harmonic variation. These Fender blend pots were ordered from a Fender authorised repair center by Fender numbers, which I gleaned (?scraped?) from the Mr Gearhead/support (or whatever it isn't called today) link on the Fender site, for basses that used blend pots (pretty much any of the active basses with a master volume, two pickup blend, and some EQ variations). I bought both the 500K and 250K ones. One was $3 and one was $6. I don't remember which, but I got $30 worth of both. If I remember, I'll look on the bags that they came in when I'm in that city next.Hey, let's look together! BOM item #14 here.......indicates that the Fender part number for a 500K one as used in my Stu Hamm bass is.......... 0056097000
|
|
|
Post by flateric on Dec 13, 2007 18:42:07 GMT -5
I gave some thought to shorting out the centre detent position so at least you would not get the volume drop with both pups selected, what you would end up with is a rotary knob doing a bad impression of a 3 way pup selector switch as virtually all the remaining sweep between centre and full will still cause a significant output drop so the whole benefit of having the blend will be lost. I'm thinking of reverting back to 2 separate volumes for blending and stick with the master tone ctrl as the only practical solution before tomorrow night's gig. Pity, as the blend concept is a really neat one and far more user-friendly (if it worked). Surely out there somewhere there must be a source of blend pots with zero R at the midpoint?
|
|
|
Post by ChrisK on Dec 13, 2007 19:03:20 GMT -5
Yes, there is/are. I may have been editing my last post when you posted. ""These Fender blend pots were ordered from a Fender authorised repair center by Fender numbers, which I gleaned (?scraped?) from the Mr Gearhead/support (or whatever it isn't called today) link on the Fender site, for basses that used blend pots (pretty much any of the active basses with a master volume, two pickup blend, and some EQ variations). I bought both the 500K and 250K ones. One was $3 and one was $6. I don't remember which, but I got $30 worth of both."" BOM item #14 here.......indicates that the Fender part number for a 500K one as used in my Stu Hamm bass is.......... 0056097000By looking here, www.fender.com/support/diagrams/one could find other basses that used the 250K blend pot such as this one that uses a 250K blend pot (item #16Also, StewMac claims that their blend pot is an actual blend pot. I've never tried them and they won't/can't/don't_understand_what_the_words_mean verify that "full on" actually means zero ohms (and in the same sentence with "full on" they use the word "panning").
|
|
|
Post by flateric on Dec 13, 2007 19:10:28 GMT -5
I've heard reported that the StewMac blend pots can also suffer from the same problem. Would you like to sell me one of your true fender blenders?
|
|
|
Post by sumgai on Dec 13, 2007 22:38:35 GMT -5
So Chris, Can you do a ratiometric analysis on one of these pots, please? Like you've done for other potentiometers, it'd be nice to see what the readings are in real life, and not just conjecture. Thanks buddy, we'll all owe you one. sumgai
|
|
|
Post by flateric on Dec 14, 2007 13:19:33 GMT -5
Well I ripped out the blend pot this afternoon and hurled it at the cat. It's been replaced by separate neck and bridge pup vol pots, and I threw in a series/parallel mini switch for good measure, which gives a nice boost to the mid range frequencies. When in 'normal' -which I believe is Series for a jazz bass, there is an almost scooped sound to the blended pups compared with the parallel mode, which is also a little louder, a bit more attack on it. It adds a nice extra feature. Sadly my crude multi-meter is not accurate enough to detact the small resistance of the blend pot in centre detent position, so I cannot report any further worthy findings from this project.
|
|
|
Post by sumgai on Dec 14, 2007 14:23:44 GMT -5
⒢eric You've got that reversed......... the normal connection for most Fender guitars, and for all standard Jazz basses is to connect the pickups in parallel. A short study of the selector switch will make it obvious as to why this is so. On the usual run-of-the-mill Jazz bass, the two pups usually have individual volume controls (which you just reverted to), and they are also in parallel. To get a series connection, as you just found out with your switch, requires that one of the pup's ground wires be switched to a new location within the circuitry. That switch is an added expense that Fender won't invest, in their "affordable" series of guitars/basses. It is found on some of their higher end gear (read: players who have money to burn), either as a separate switch, or as part of the pup selector (the S1 and the Tele 4-way come to mind). As a footnote, the P-Bass does indeed connect the two pup sections in series, thus giving the instrument a helluva wallop. But there, we don't have any switching issues, do we? It's that way all of the time, and if you were to put them in parallel, they'd sound thin, unlike a P-Bass should sound. (Yes, I've tried it, and immediately reversed it. ) HTH sumgai
|
|
|
Post by ChrisK on Dec 14, 2007 22:03:21 GMT -5
Hmmm, gotta GeThunk on that one.
In reality, parallel pickups average their contribution, series pickups add theirs.
Actually, the logical representation of combinations contributed to my choice of "+" for parallel (analogous to "OR"ing the signals) and "*" for series (analogous to "AND"ing the signals).
Part of the problem is that pSpice doesn't handle generators that are not all ground referenced. Parallel is do'able, but series will take some thought (I might as well look at a series shunting scheme since I preach it for blending).
Simple frequency sweeps won't help since the individual pickup contributions need to be easily discernible. I think that a square wave and triangle/sine mix might be in order. If I can keep one to just odd harmonics and the other to only even harmonics, it just might work out.
I'll think aboot it.
|
|
|
Post by sumgai on Dec 15, 2007 16:43:58 GMT -5
Chris, No, buddy, not so complicated! Your previous analyis of why a pair of pups in series versus parallel will sound (react) differently with something on the order of 40 to 80KΩ in the circuit, that was sufficient in that regard. But I was aiming my question at a look-see at the pots themselves..... specifically, the percentage of total resistance, plotted against the percentage of total shaft rotation. That was all, truly, I swear it! The obvious problem (for you or anyone else) is the procurement of various pots - blend, pan, balance, whatever they may be called by a given source. Given such a limitation, my request might well find itself on the back burner for some time to come, that's understandable. But it'd be nice to know......... sumgai
|
|