Two volumes, one master tone, series/solo switches

Here's the design I was thinking of, courtesy of JohnH and Runewalker:

Strat with 2 volume controls

The "Plus" version seems pretty close to what you have in mind.

Thanks for your quick replies.

First, I must have been very tired when I wrote "phase switch." Obviously there is no phase switch.

Newey, cheers for your digging out, that's really helpful.

Ashcatlt, I see what you mean about the bridge volume becoming a variable resistor to ground. Thanks for the heads-up. Redundancy in certain selections isn't a problem for the goal of this setup, I just naturally associate "short-circuit" with the words "very bad things." Things like "frying electronics." I like a fry-up as much as the next man, but I don't want to spark my guitar out.

Unfortunately, I don't understand half of what else has been said. "Hanging from hot" means nothing to me, nor whether they're "hanging by their ground ends." I see what you mean about "leaving it's full resistance parallel to the output," but I only understand some rudimentary science behind it, and I've very little idea what you mean by "loading the pickups."

See, it's a shameful admittance, but I'm drawing this circuit up like a water system. In my mind, I'm seeing it easier to imagine the circuit as "power comes from pickup, bridge acts as a sluice gate, resistor lets only so much through, water travels to output, etc." OBVIOUSLY this isn't the way electricity works, but it's certainly the way my mind comprehends it.

I've googled basic electronics, but my knowledge still falls short. If someone has a spare five minutes, would they be kind enough to post some kind of explanation, or at least an introduction, to where and why I'm going wrong. I'd be most appreciative.

Okay, let's see if I can clear up some of the questions you've raised.  It'll probably lead to more questions, but that's okay.  It's what we call learning, and that's always a good thing.  Lucky for you I'm not an EE, so I wont be getting too far into the technical specifics.  There are some EEs around, who might step in to correct or expand on what I have to say.

So let's start at the very beginning.  Ohm's law.  If you've read much of anything about electronics theory, you've likely come across it, but we'll restate.

Voltage (V or E) = Current (I) x Resistance (R)

If we assume that Voltage remains constant (pretty safe for this discussion) we can rearrange to say:

Current = Voltage / Resistance

From this we can see that for a given Voltage, a greater Resistance will demand less Current.  A lower Resistance will draw more Current, and that's basically the source of your (quite reasonable) fear of short circuits.  As R approaches 0, I approaches infinity.  The source will supply as much Current as it can, and if that exceeds the current carrying capacity of some component along the way we will see sparks and smell smoke.  Luckily out passive pickups are incapable of sourcing enough current to harm themselves or anything else in the circuit, so we can short them with impunity.*

When we talk about the load on a circuit, we're referring to that current demand.  A large resistance at the "receiving" end will draw a smaller current and be a smaller load.  A smaller resistance therefor will be a larger load.

If you've been poking around a bit, you may have come across the formula for calculating the value of parallel Resistances.  Its laid out quite nicely here, if you need it.  The gist, though is that for any two or more resistances in parallel, the total resistance seen by the circuit will always be less than any of the individual resistances and therefor a greater load.  

What's this got to do with your Volume control?  Well, without any controls, just the pickups and the amplifier, the load is determined by the resistance between "hot" and "ground" at the amp.  Typically this value will be between ~500K and 1M Ω, let's go with 500K for now.  Now, when we add the resistance of that pot from hot to ground, I think you can see that it is parallel to the amp input.  If that pot happens to be a 500K pot, the total resistance seen by the pickup will be halved, and the current load doubled.

But what does that mean?  Well, honestly this is where it gets a bit over my head, so I'm going to gloss over some of it. Let's just say that on top of these resistances, we also have quite a bit of inductance in the pickup coil and significant capacitance across the cable.  This all creates a low pass filter which doesn't do a very good job of letting high frequency signals (treble) through.  A lower resistance - or higher load - means even less treble gets through.  This is partly how a tone control works, and why I said that Bridge Volume would act like a tone control when "bypassed".  It's also the reason we usually use bigger value pots for humbuckers - they're already darker (thanks to greater inductance) and we don't want to lose much more.

Like I said, kind of glazed it over, but smaller pots or more pots means less treble.

Then there's the "hanging from hot" thing.  It's as simple as seeing that one end of the pickup is connected to the jack tip (the "hot output") while its other end is not connected anywhere.  What's the big deal?  Well, the pickup is a big long coil of wire, and acts as an antenna.  It collects all the Radio Frequency/Electromagnetic noise flying through the air and pumps this straight through the amplifier.  This post has already gone on quite long enough so I'm not going to go into relatively poor explanation of the why, but leaving a pickup connected to "ground" (the jack sleeve) is usually not a big noise problem.  It's standard procedure in the vast majority of guitar wiring.  Hanging from hot is to be avoided, though.  Shielding might help, and humbuckers will still tend to buck hum, but we still generally prefer to avoid this situation.

If we look at your scheme in its Series mode, we see that both M and N pups have their "bottom ends" (which would normally be connected to ground) connected to the "top" of the B pup.  In the B only position this is connected directly to jack tip, and both M and N are thus hanging from hot - albeit "upside down".  In B*M mode, the N pup is hanging kind of halfway between hot and ground.  This will probably also be a noise issue.  Something similar happens in B*N position.

I hope some of this helps.  If you've got more questions, or if anybody's got anything to add, don't hesitate to speak up. 


*ChrisK used to point out that while we won't actually hear anything out of a shorted coil, it still tries to generate current, and that energy has to come from somewhere.  "Conservation of Energy is.". We talked about that most recently here.  Based on that discussion and (more importantly) practical experience I'm convinced that this effect is negligible and not any real concern.

Well, newey's Strat plus was pretty close, but I didn't want an out-of-phase switch, so I changed it to a "solo switch" for the bridge pickup.

Old schematic

I'm aware about the weird things that will happen when I used the series switch with this as well, but I'm excited to try it. I think this is all kosher. Yes?

Yes, John! Yes!

Old schematic

I'm very excited to get this all soldered together. Thanks for your help, everybody. Really appreciate it. I'll be sticking round here for certain.

Asmith-

JohnH's discussion of this scheme, in the link above, answers the question of why to use a dual-gang pot- the tone control needs to be on the pickup side of the vol control (as in LP wiring) to avoid interaction with the 2 volume controls- at least that's what I understood John to mean.

Earlier, Ash asked an unrelated question about numbering the positions on a 5-way switch, and whether there was any convention on how to do so.

The short answer is that there doesn't seem to be any uniformity. Certainly, there isn't any on this Board!

Fender, in its diagrams, consistently calls the bridge position "1" and the neck "5":

support.fender.com/diagrams/stratocaster/0131002B/SD0131002BPg4.pdf

Since Leo introduced this switch to the world of guitars in the first place, I think we should try to stick with that numbering. But I'll admit to doing it the other way myself on occasion.

Somehow, the opposite way from Fender seems more "natural", designating the neck as "1". Maybe because we read from left to right, and so look at the switch , as mounted in the guitar, as being 1 to 5, left-to-right.

With Fender's way, it's more like a NASA countdown, with the bridge as "blast off".

(mini-rant over)

I liked the dual-gang tone pot better, for its consistency of tone as you reduce volume, as I wrote previously, but what you have shown is not too bad. Youll still be able to get the solo/series max-bridge - neck-with-tone turned-down sound that Im talkin' about. With one tone and 2 volumes, when not in solo mode, its not worse than a Gibson Explorer which sort-of works that way.

All good! but please dont stop having eureka moments.

The design you have settled on is likely to be a killer. Id also like to post your graphic on the 2Vol Strat schematic thread for future reference, maybe with some pics when you have it built

John

That greasebucket circuit is kind of popular so I drew my own. The values are based on what I've seen at other websites. If nothing else, I think this shows the circuit more clearly.

I wouldn't get too excited about that greasebucket gizmo. Its easy and cheap to try, but I would not expect too much from it. At max tone it will make no difference, (the 0.1 cap is bypassed and the 4.7k resistor is negligible). At medium tone settings maybe a tiny differencemeasurable in a lab. At low settings, the two caps combine to effectively act like a slightly lower value cap, and the resistor acts to stop the tone control going to zero. That part might be worthwhile. Sometimes there is a nice sound to be found with the tone control almost at zero, just before all treble is lost, but it is difficult to set being so close to the end of the turn. This could make it easier to find.

On your diagrams - I agree with newey. Also, the schematic diagrams that you have been posting are not really the place to figure ot how you arrange the wires physically. Its better to think that through with a more pictorial wiring diagram - see the scheamtics post for the 2Vol Strat for example.

cheers

John

Okay, newey, I made the changes and added a volume control:

Due to size restrictions in the cavity and my complete refusal to do some routing on the body, I'm using stripboard instead of a breadboard. Flippity flop again. I'm less decisive than... I can't make my mind up.

I apologise for bringing up my shortcoming in the knowledge here again. But here it is.

I was just about to buy the pots, and then somebody looked at the guitar as it is now (standard Strat) and said, "these are 250k pots." I was sure they were 500k. Turns out they're not.

This isn't a problem on the push-push switches - the volume controls - as the two resistances are both available; I can purchase 250k switch pots for the volumes instead, and Bob's your uncle. But I don't seem to be able to find a dual-gang 250k. A concentric 500k/500k pot is the immediate option.

I've done some preliminary research and Googled and the like, and the difference seems to be that should I use a dual 500k/500k pot, my tone control would be 'brighter' at full whack. I don't mind this at all, as I'm usually playing at full on the tone. Indeed, I like the idea of playing at a mid-level, with the option to blast the treble up if I wanted. (If I'm playing through the bridge and middle pickups, a split humbucker if you will, with a high treble setting, I'd probably start channeling Edward Van Halen. Bitchin'.)

Is my reasoning correct? Can I use 500k pots for the tone, playing them at a mid-level setting for the Strat tone that I'm used to?

Brilliant! Thanks. The only questions now are, which resistors to use in the treble bleed circuits, being that I'm using 250k pots instead of 500k ones, and which resistors to use in the tone circuits, being that I'm using 500k ones instead of 250k ones?

Or are they changed at all?

Well, the guitar is a second-hand Squier Silver Series Stratocaster. A nightmare for this fella. The headstock says "Made in Japan," but the series number begins with a K, indicating a Korean-made model. I've narrowed the production year down to about 1989.

The pickups haven't been changed since the guitar was purchased, so I'd assume that they're standard Squier ones. Indeed, Squier doesn't give much more information on their website than the description '3 Single-Coil Pickups.' Nothing is written on the pickups at all, so I can't indicate any specific model. To cut this long answer short, I'd hazard at stating they're 'fairly normal single coils.'

I have used all sorts of cord lengths but the longest and most frequent I use is about four metres. I expect my gig-hit-count to rise soon though, so I'll be investing in a wireless system before too long.

I use full volume most of the time, cutting down to anywhere between 1 and 4 for 'cleaner' overdriven playing on the fly, similar to what Ed Van Halen does live for 'Hot for Teacher.' I used to touch down to 8 or 9 when playing rhythm and riffs with a band, nipping up to full for lead parts and back down to 8 or 9 afterwards, but I expect I'll probably use the series switch more for that after I wire this all up.

Read into that what you may... I'd say I use reasonably limited areas of my volume control, but I'm the subjective player. A more objective mind might say I'm using a lot of the range.

I'm sorry my answers are much vaguer than optimally so, that's really as much information as I can give you and it's as clear and concise as can be made. If you've got any more questions please don't hesitate to ask and I'll scarper off to have a second look at the instrument. Thanks for your help.