Solomon Posted September 13, 2012 Share Posted September 13, 2012 Hi guys I recently bought a Stellah bass guitar as a bit of an experiment - I heard you got a lot of guitar for not much money so I thought I'd give it a bash. Indeed, I'm really impressed with the aesthetics of the instrument - it looks great and sounds pretty good too for a passive bass. It could do with a good set up but that's to be expected really - even my Warwick Corvette $$ benefited from a decent set up when I bought it new. Anyhow, this Stellah bass's wiring leaves a little to be desired - there's even a bit of masking tape holding a splice together in the electronics cavity. I'm thinking about giving it a going over but I haven't had any real experience of this before so I'm just looking for a little advice really. The bass has 2 pickups (1 single, 1 humbucker), a volume for each pickup, and a tone for each pickup too (I think). The main problem, though, is that the volume pots basically appear to do nothing for 90% of their rotation and only really come in at the top end of their travel. My first assumption is that these were log pots, not linear... then after a little research I reaslise that Log pots are deseigned to respond like the ear so, counterintuitively, log pots should [b]sound [/b]linear... is that right? Does that mean that the current pots are probably linear and I could replace them with log pots to get a better response? There are no obvious markings on the current pots that I have noticed without necessarily dismantling the electronics. I've also been considering changing how the thing is wired up - I don't really like the two volume pots thing - I'd rather have a pickup blend, center detent pot to balance the two pickups, and a tone control, but if I wired it up like that it would leave me with two unused holes... I guess I could still have a tone control for each pickup, but what configuration could I go for to give me four controls (at least to fill the available pot positions) that wouldn't be too hard for an amateur electronics dabbler like myself? The bass has no active circuit and the humbucker has just a couple of wires coming out - I assume this means it cannot be coil-tapped? Thanks!! Quote Link to comment Share on other sites More sharing options...
brensabre79 Posted September 13, 2012 Share Posted September 13, 2012 Hi Solomon, welcome to BC You're right LOG pots are usually used for volume. And the reason for the unlinear response is probably down to cheap pots (you get what you pay for eh?) Luckily its a simple upgrade and not too expensive. I would recommend you look for CTS or Alpha brand pots - these are really smooth. Also, the pot value will determine the smoothness of the sweep and if you have the wrong value it can also make 90% of the turn do bugger all! Generally speaking 250K LOG pots are used for single coil volume and 500K LOG pots for humbuckers. As you have one of each its likely you might need one of each value - Stellah probably have used the same type for both as its cheaper. You can put a blend pot in, these are usually stacked volume pots (i.e. one on top of the other operated by the same dial). They are wired just like a volume pot except that one is reversed so as one turns down the other turns up. There are pots specifically designed for this purpose and again, a good brand will get the best results. You might well need a stacked 250k / 500k for this bass though which are harder to find. As for the extra hole... you could put a rotary switch in there that puts the two pickups in series (huge sound with a slight volume boost), or out of phase (thin, nasal sound that can be good for solos up at the dusty end), or both!.. Or you could have a tone control for each pickup - but beware that with both pickups on even turning the tone down for just one pickup may well make the other pickup lose treble too. You could go active, Artec make a cheap 2 band EQ thats actually not bad. So you could have VOL. BLEND. TREBLE. BASS. controls. There's loads of possibilities to be honest! And loads of wiring info on here! Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 13, 2012 Author Share Posted September 13, 2012 Hi Brensabre79 - thanks for the feedback! I've looked into the blend pots and they seem to make a lot of sense - I've got them figured out OK. I'm pretty used to active basses to - and I tend to prefer the sound... my basses over the past 20 years have all been active. Is it a simple enough job to add active circuitry then? I've read elsewhere that (forgive me if I've got this the wrong way round...) 500K pots strip more off the top end of the sound because there's more resistance to the signal and the top end gets lost - does that mean it's purely down to taste or is there something more to it than that? it's funny you mention the double tone control - on this bass I have noticed that the tone controls seem to behave a little unpredictably - the effect one has seems to depend on the positions of the other volume and tone pots... not a very nice character really. I have just about managed to find a sweet spot with the settings but, because I'm dealing with "90% nothing" pots, if I accidentally tap any of the pots at all it can lead to a radical change in timbre. Oh, and yeah... a volume, balance, tone = 3 pots... I forgot to add a volume to my thinking! Duh! I've dug around various electronics sites to find wiring diagrams - I haven't quite found anything that fits my need just yet... I'm a reasonably bright guy... perhaps I'll try and design something myself and bring it here for some feedback! Quote Link to comment Share on other sites More sharing options...
brensabre79 Posted September 13, 2012 Share Posted September 13, 2012 Is it a Jazz Bass copy then? 3 controls? I would go with Master Volume, Blend and Tone in that case. So each pickup would go to its relevant stack on the blend pot, the outputs of the blend pot would go to the volume and on to the tone before going to the jack socket. I can do a diagram but there should be loads of these on the net, its probably the most common jazz bass mod - although personally I hate blend controls - I have a 5 position rotary switch on my Jazz. I think with the pots and treble its the other way around, the 250k ones are darker 500k brighter. Hence 250k for brighter sounding single coil pickups and 500k for humbuckers... There's a handy article about it [url="http://www.stewmac.com/freeinfo/Electronics/Pots/w101-controlpots.html"]here[/url] Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 13, 2012 Author Share Posted September 13, 2012 Sorry - I've confused you No. there are four pot positions as you correctly deduced from my initial post... but in trying to decide which way to go with rewiring I forgot to count a volume pot... I reckoned on 2 unfilled holes whereas going with Vol/Blend/Tone would leave only one hole to fill, so to speak. I do like the idea of vol/blend/tone, but perhaps if I look into adding an active circuit I could take the route you suggest of vol/blend/treble/bass. I could even go with a push/pull on the volume to bypass the active (for those times when the battery chooses to die mid-gig!)... would I be biting off more than I could chew by doing that? So the 250K pots can take the edge of a pickup that leans towards being too bright, whereas as 500K pot allows more of the pickups natural brightness to come through? I'm not massively into my top end and my sound is quite retro souly funky so taking the edge of a bright pickup would be preferable. The bass itself is Jazz-esque in shape, with its asymmetric hips, but it has four pot positions. If you're interested it's actually one of [url="http://www.adverts.ie/jazz-basses/stellah-sjb-750-5-string-jazz-bass-guitar-new/1161737"]these[/url] - TBH, I would recommend it... I haven't used it in anger yet but I reckon you get some pretty good raw elements if you're prepared to work on it a little... it's certainly a good bass for a beginner. Quote Link to comment Share on other sites More sharing options...
mart Posted September 13, 2012 Share Posted September 13, 2012 [quote name='brensabre79' timestamp='1347538667' post='1802105']...You can put a blend pot in, these are usually stacked volume pots (i.e. one on top of the other operated by the same dial). They are wired just like a volume pot except that one is reversed so as one turns down the other turns up. There are pots specifically designed for this purpose and again, a good brand will get the best results. You might well need a stacked 250k / 500k for this bass though which are harder to find.... [/quote] Warwick put blend pots in all their basses, including ones with a single coil / humbucker pup config. I don't know what pots they use, but you could find out from their website, and if they do use 250 / 500 blends then you should be able to buy them from their web shop, or from Thomann. As for the wiring, yes, it's just like two volumes as long as you go for the Jazz vol/vol wiring, not the traditional Gibson wiring. Finally, yes, with a V/V/T/T setup you will find the controls all interact with each other, especially the tones. That's just the nature of treble need circuitry. Some people would see it as an advantage! Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 13, 2012 Author Share Posted September 13, 2012 I've got a Warwick Corvette $$ - I've opened it up before but only the change the battery - never with a view to see what's going on in there... I'll have a looksie - thanks Quote Link to comment Share on other sites More sharing options...
mart Posted September 14, 2012 Share Posted September 14, 2012 Well, the $$ is a little bit more complicated because of the two three-way switches for series/parallel/split on each pup. But the rest of the circuit would be quite close to what you need. But hit the Warwick website and find the circuit diagram for one of their Jazzman models, and I think that'll be exactly what you need. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted September 14, 2012 Share Posted September 14, 2012 [quote name='Solomon' timestamp='1347545898' post='1802254'] I've read elsewhere that (forgive me if I've got this the wrong way round...) 500K pots strip more off the top end of the sound because there's more resistance to the signal and the top end gets lost - does that mean it's purely down to taste or is there something more to it than that? [/quote] It's the other way round with impedance (resistance) MORE impedance will deliver MORE top end. Here's a useful resource for wiring guitars and basses that I stumbled upon the other week, should be easy enough to follow. http://www.artecsound.com/wiring/wiring_book01.pdf Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 14, 2012 Author Share Posted September 14, 2012 Thanks for all your help guys - it's appreciated! Quick question... kind of related in an unrelated kind of way. I've got a Seymour Duncan humbucker kicking around so I've been looking at playing with that on an old bass I've been working on. Amongst other things I've been looking at coil splitting for a humbucker. I've been studying a couple of diagrams that seems to effectively send both the start and finish of one coil to earth, whilst from the other coil it sends one end to hot and one to earth. I appreciate that this effectively drops the earth/earth coil out of the equation, leaving the other coil connected earth/hot. (for example, [url="http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=1hum_1vol_split"]this[/url] and [url="http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=1h_1v_1sas"]this[/url]) My question arises when I look at another when I look at another coil split solution that uses an on/off/on mini switch that allows you to choose which coil gets through whilst leaving the centre position for humbucking configuration, [url="http://www.guitarelectronics.com/product/WD1H10_03/Guitar-Wiring-Diagram-1-Humbucker1-VolumePull-for-South-Single-Coil.html"]here[/url]. I understand what happens in the central position. Also, in the bottom "on" position on this diagram I can tell that all of red/green/white are sent to earth (so far so good - we have an earth/earth coil and an earth/hot coil like the examples above). However in the up "on" position it looks to me that green is sent to earth but red,white and black are all sent to hot (forgive me if I'm not using quite the right terminology here). This means we have a hot/hot coil and an earth/hot coil. Am I right? So, if we do have this situation, is sending both ends of a coil to hot the effectively the same as sending both ends to earth? In other words, it's not that the coil needs both ends sending to earth to drop it out, rather it is the fact that there's no potential difference between the ends of the coil that drops it out - sending both ends to earth or hot doesn't matter? Quote Link to comment Share on other sites More sharing options...
mart Posted September 14, 2012 Share Posted September 14, 2012 [quote name='Solomon' timestamp='1347656274' post='1803785']... My question arises when I look at another when I look at another coil split solution that uses an on/off/on mini switch that allows you to choose which coil gets through whilst leaving the centre position for humbucking configuration, [url="http://www.guitarelectronics.com/product/WD1H10_03/Guitar-Wiring-Diagram-1-Humbucker1-VolumePull-for-South-Single-Coil.html"]here[/url]. I understand what happens in the central position. Also, in the bottom "on" position on this diagram I can tell that all of red/green/white are sent to earth (so far so good - we have an earth/earth coil and an earth/hot coil like the examples above). However in the up "on" position it looks to me that green is sent to earth but red,white and black are all sent to hot (forgive me if I'm not using quite the right terminology here). This means we have a hot/hot coil and an earth/hot coil. Am I right? So, if we do have this situation, is sending both ends of a coil to hot the effectively the same as sending both ends to earth? In other words, it's not that the coil needs both ends sending to earth to drop it out, rather it is the fact that there's no potential difference between the ends of the coil that drops it out - sending both ends to earth or hot doesn't matter? [/quote] Yes, that's exactly it - the coil is being shorted either way, so cannot contribute to the sound. Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 14, 2012 Author Share Posted September 14, 2012 [sharedmedia=core:attachments:118368] That's great - thanks. Now, with a little fear that I've gone slightly off my original topic, I've been working on a schematic for getting my Seymour Duncan humbucker into my old bass. I'd really appreciate it if you could give it a once over and let me know if I've made any dumb mistakes or how I might be able to improve it. Please excuse my shonky diagrams - I have no real idea how to draw these things - I've just done it in a way that helps me make sense of it all. The plan is to have a 4-way switch for North / series / parallel / South, followed by a standard Volume and Tone control. The Seymour Duncan [color=#000000][font=Arial, Helvetica, sans-serif][size=1]SMB-4D has the following colour legend...[/size][/font][/color][list] [*]Green = beginning of adjustable coil (South) [*]Red = finish of adjustable coil [*]Black = beginning of stud coil (North) [*]White = finish of stud coil [/list] Beyond that, there's another couple of questions... [list=1] [*]How do I tell which coil is which in my SD pickup? Naturally, I would prefer to toggle the fourway switch neck-wards to select the neck-side coil, and bridge-wards to select the bridge side pickup. [*]I've noticed that volume and tone pots have the input at one end and not connected to the middle (is this called the "common" connection?) - is there a difference between doing that and connecting it to the centre of the pot? [/list] Thanks again Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 14, 2012 Author Share Posted September 14, 2012 Oh... and could you point me in the direction of a 4-way switch that would perform this task for me? I'm not entirely sure of the differences between them all! Quote Link to comment Share on other sites More sharing options...
mart Posted September 15, 2012 Share Posted September 15, 2012 The diagram looks fine for what you want to do. The surest way to tell which coil is which in your pickup is to just connect one coil to your amp (e.g. by holding the wires to the end of a guitar lead) and tap the pole pieces on each of the coils in turn. You'll get a loud click when you tap the coil that is connected, and not when you tap the other. The way volume pots and tone pots are wired is effectively quite different. The tone pot only uses two of the tags because it simply needs a variable resistance. You could use the centre tag and either one of the others, but you'll find the pot works backwards one way round, and may have a strange taper too. On the volume pot all three tags are used because the hot signal is being split into two bits effectively, with only part getting sent to the output. With a single volume control it's logical to wire it the way you've done, but if you have two volume controls (for two pups) wired like this then you get very interlinked controls. In particular, if you turn one control to 0 then the other pickup is also earthed and you will get no overall sound - this is the traditional wiring for Les Paul's. But you can get round this by swapping the "input" and "output" hot tags, as is done in a Jazz bass. The resistances are then operating in a slightly different way, but they still do what you'd expect, but now more independently (and you can solo a pickup this way). Sadly I'm no expect on finding electronics parts, so I have no idea where you'd get the sort of 4-way switch you need. Quote Link to comment Share on other sites More sharing options...
brensabre79 Posted September 15, 2012 Share Posted September 15, 2012 Check out Maplin or RS for the 4 way. You can get a rotary switch which is adjustable for the number of clicks from 2 to 8 from Maplin. Its a bit plasticy but it works. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted September 15, 2012 Share Posted September 15, 2012 http://www.doctortweek.co.uk do everything you'll need for guitar/pedal related stuff. tons cheaper than Maplin and he'll steer you in the right direction via email if you're not sure of component values/types. Good quality parts too. Quote Link to comment Share on other sites More sharing options...
brensabre79 Posted September 15, 2012 Share Posted September 15, 2012 Good link! Nice one Paul Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 15, 2012 Author Share Posted September 15, 2012 Indeed - an excellent link! I've dropped the chap a line - hoping to get a bit of advice about the right selector switch to use Another adaptation to thin about is something I've fancied for several years - a Tom Morello style kill switch! I'm just scratching my head to figure how this would work in conjunction with this north/series/parallel/south selector. I guess it should go after all the other electronics, just before the signal hits the jack... I fancy perhaps an on-off-on SPDP switch where on side is momentary - the switch in "up" position will give me the straight through sound, whereas knocking the switch into the "down" position will allow it to bounce back up, being "on" when I press, "off" when I don't. Feels like this would be a more natural response. My question relates to Mart's answer previously when he mentioned shorting things out of the circuit...assuming that the switch gets wired onto the hot wire, if I've got a kill switch in the central "off" position wouldn't the hot signal simply terminate at the switch? Is this safe? Should I try and send it to earth somehow, if so how so? Thanks for humouring all my noob questions by the way Quote Link to comment Share on other sites More sharing options...
mart Posted September 15, 2012 Share Posted September 15, 2012 [quote name='Solomon' timestamp='1347706057' post='1804160']....My question relates to Mart's answer previously when he mentioned shorting things out of the circuit...assuming that the switch gets wired onto the hot wire, if I've got a kill switch in the central "off" position wouldn't the hot signal simply terminate at the switch? Is this safe? Should I try and send it to earth somehow, if so how so?... [/quote] No, it's not a problem at all. In a two pickup instrument with a 3-way selector switch, if you solo one pickup, then often the other pickup is effectively just left dangling. The circuit (involving the unused pickup) is not completed, so there is nothing to worry about. Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 15, 2012 Author Share Posted September 15, 2012 ok - cool... so you wouldn't end up completing some kind of circuit up your arm then? Another couple of daft noob questions I'm afraid, both relating to my SD pickup... see the attached picture of the back of it... [sharedmedia=core:attachments:118378] Firstly, the pickup has no earth/bare wire coming from it but it does have this copper shielding. Does it look like the earth wire was there but has been removed? Do I need to solder on my own earth wire and bring it into the electronics cavity? Secondly, in my hand you can see two magnets which have always been stuck to the back of the pickups... this is probably a really daft question... but they aren't meant to be in the final, wired up instrument are they? Are they there for some kind of temporary protection until the pup is fitted? Thanks as usual Quote Link to comment Share on other sites More sharing options...
mart Posted September 15, 2012 Share Posted September 15, 2012 It does look like an earth wire is missing; what is that stray wire in the middle of the pickup (at the top of the bottom pickup) ? Anyway, yes, I think you should earth that copper shielding. I think you'll find those magnets are fairly essential - they provide the magnetic field whose flux is dragged by the movement of the strings thereby inducing a current in the wires in the pickup, enabling your instrument to produce electricity which can then be amplified to a nice stadium filling thud. Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 15, 2012 Author Share Posted September 15, 2012 [quote name='Solomon' timestamp='1347706057' post='1804160'] Indeed - an excellent link! I've dropped the chap a line - hoping to get a bit of advice about the right selector switch to use [/quote] Just thought I'd mention that I've had a response from this guy, Steve, at doctortweek.co.uk... on a Saturday as well! Friendly chap and clearly knows his stuff. Sadly he doesn't have the component I need but has offered to get hold of one for me if I struggle elsewhere... thanks for the recommendation! Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 15, 2012 Author Share Posted September 15, 2012 (edited) [quote name='mart' timestamp='1347731432' post='1804453'] It does look like an earth wire is missing; what is that stray wire in the middle of the pickup (at the top of the bottom pickup) ? Anyway, yes, I think you should earth that copper shielding. I think you'll find those magnets are fairly essential - they provide the magnetic field whose flux is dragged by the movement of the strings thereby inducing a current in the wires in the pickup, enabling your instrument to produce electricity which can then be amplified to a nice stadium filling thud. [/quote] sweet... shows how much I understand the principles of these things... I figured the metal rods in the pup were magnetic themselves... I've just tried touching the pups with a ferrous thing with and without the magnets on the back and you're absolutely right... not that I doubted you! So I need to route out a deep enough pup cavity to accommodate these magnet too! I have no idea what that wire is... it does look a little out of place and doesn't seem to be doing anything. I bought this thing from a local guitar shop some 15 years ago and never got round to doing anything with it - I guess it was in this state when I bought it. So I'll connect the two copper surfaces together and then bring an earth wire through into the electronics cavity. It's funny, I've got a good understanding of physics and generally well fettled logic skills, but this is a whole different way of thinking - my questions seem reasonable when I ask them but when they are answered so elouquently and simply by you guys I generally feel the question was quite dumb You do know there's another question coming, don't you?.... Do I need to be careful as to which way round the magnets go on the back of the coils? Or is it enough to know that they are simply magnetised? Edited September 15, 2012 by Solomon Quote Link to comment Share on other sites More sharing options...
mart Posted September 16, 2012 Share Posted September 16, 2012 I always thought the pole pieces were magnets until I opened up a humbucker just a year or so back. And I've lost count of the number of people that I've had to explain that it's not the case that electricity comes from the wall socket into your guitar! But, now I'm at my limits. I think your magnets will need to both go on the right way round, both relative to each other and, I think, relative to your overall wiring. (If they're the wrong way round with respect to each other, you won't get a hum cancelling pickup, you'll get a hum-enhancing pickup, and if they're the wrong way round in relation to the coils wiring then you'll get an out-of-phase sound when you have both pickups on, which is an acquired taste). However, I don't know, and can't think, of any way of working out which way they need to go, except by trial and error. Maybe some of the other electrics gurus around here will be able to help on this - there are plenty who know a lot more than me. Quote Link to comment Share on other sites More sharing options...
Solomon Posted September 16, 2012 Author Share Posted September 16, 2012 (edited) Glad to see I've pushed you to the edge my questions clearly aren't that dumb then I'm prepared to try a little trial and error... I'l cross that bridge when I get to it I guess. I knew pickups worked by induction and I understand that you need magnets to make that work... I just assumed the pickup rods themselves were magnetic Tell you what though, I've been e-mailing [url="http://tweekdoctor.co.uk"]Steve at tweekdoctor.co.uk[/url] and he's been super helpful and done loads of research for me! I really can recommend him. All this help and, when it comes down to it, although he's certainly going to get my business, I'm hardly going to make him rich for his efforts... a good guy! With your (and Steve's) help I'm beginning to refine my wiring ideas now for my SD humbucker involving this 4-way rotary switch, vol, tone and, just for fun, a kill switch. Now I'm just thinking about whch direction to go on the volume pot... 250K or 500K. No, I appreciate conventional think tells you to shove a humbucker through a 500M pot, however due to my lack of experience in these things and to my predisposition to play old-school funk and soul music I feel I might quite like a "bottomy" sort of sound that a 250K might be able to give me. So, here's my idea... if I take a stacked 250K/500K pot and wired it up like the attached picture, would I end up with two volume controls? Basically, if I rolled off the 250K pot the 500K would take over, and vice versa? And if both were fully open I'd just get a normal, straight-through effect? If this did work would the effect be essential the same as a tone control? [sharedmedia=core:attachments:118523] Edited September 16, 2012 by Solomon Quote Link to comment Share on other sites More sharing options...
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