Need Wiring Help

[nexis]

Hello I need help wiring up 3 single coils to a switch with the following configuration.

1: Neck
2: Middle
3: Bridge
4: Neck->Bridge (Series)
5: All (Series)

In that order...

I'm thinking a 5 way 4 pole switch is needed. And can complete some of it but can't get it working right.

Also... 1 Vol and 1 Tone

Please Help. Thanks!

[UnklMickey]

hi Nexis,

Welcome to GN2!

i'm not certain that a superswitch is needed, but probably it wouldn't cost much more than a 5 way 2 pole anyway.

in the simplest form, you would want to "stack" the pickups with the neck on "top", the bridge next, and the middle on the "bottom".

then use the 2 poles to determine what part of the stack to use.

the problem with this is: it's "dirty". the unused coils would be "hanging from hot".
(or in another style they would need to be shorted).

i try to avoid either of those things when i can.

so it would be worth seeing if that could be cleaned up.


you said you could complete some of it. if you have an image of your drawing, post it, and we'll start from there.

if not we can just start with a blank sheet.

if Jimplaysguitar is around, he hasn't been too active lately. maybe we can convince him to grab this puzzle and run with it.


unk


EDIT: Nexis, i've looked at this for a little while, and it can be done, completely clean, with a 5 way 4 pole.

unless you are in a huge hurry, i prefer to let jimplaysguitar, or someone else, have some fun with this one.

[jhng]

Can't see a way of doing it without the four-pole superswitch unless you are happy to have shunted coils (where a pickup is short-circuited rather than disconnected).

Using a superswitch it is definitely doable without shunted coils. But I think there is still going to be one coil that is always "hanging from hot" (to Unk's dismay).

As a starting point the common poles of the superswitch will be connected to (e.g.) Neck Hot, Middle Hot, Middle Ground, Bridge Ground.

If you want I can do you a pic.

Hastings

[JohnH]

I think it is do-able - and I'm betting on a 4P5T to avoid the hanging from hot issues- while also avoiding shunts:

Heres a description - I hope its not too cryptic, I'm not set up to do diagrams today, so this is a clue rather than a a total answer:

First using, just 2 poles:

all pickups joined in a series chain, end to end, B to N to M

Note N (rather than M)is in the centre of the chain, since you want NB as an option

Pole 1 selects which is the ground connection, pole 2 selects which is hot, between them, tapping into different parts of the chain

With that, you can get all the sounds, no shunts, but sometimes a coil or two hangs from hot.

Now with four poles:

The hanging coils can be snipped off if there is a switch pole to break the series chain between N and B and another between N and M. This can be done with the other two poles, then it would be all OK.

Another suggestion: since you are wanting NB rather than NM, you may want to put a reverse wound pup as the N, rather than the usual M, to get humcancelling in that combo. it doesn't affect any other ones.

John

[nexis]

Thanks for the replies. Heres what I came up with. I think it's how I wanted. Maybe you guys could check it for me.

4 Pole 5 Throw Switch

Position 1: Neck Only
Position 2: Middle Only
Position 3: Bridge Only
Position 4: Neck->Bridge (Series)
Position 5: Neck->Middle->Bridge (Series)

[UnklMickey]

Nexis,

i usually don't have net access on the weekend, but i happened to get a few minutes.

i'll look at your drawing on monday when i have more time and get back to you then.

i'm sure someone else will have time this weekend to check it over, but worst case, you'll have an answer monday.



John,

good call on moving the RWRP to the neck for this application. that one got right past me.




now, it's back to the party. see y'all monday.



unk

[CheshireCat]

nexis said:

Thanks for the replies. Heres what I came up with. I think it's how I wanted. Maybe you guys could check it for me.

4 Pole 5 Throw Switch

Position 1: Neck Only
Position 2: Middle Only
Position 3: Bridge Only
Position 4: Neck->Bridge (Series)
Position 5: Neck->Middle->Bridge (Series)

Very nice looking graphic. Is that one of ours? (The SS bit, that is?)

Incidentally, I'm not sure if that wiring's straight, but I like the way you think. I'll look at it.

BTW, Unk, could you expand a bit on "hangin' from hot"?

Chesh

[nexis]

The switch graphic is from guitarelectronics.com My drawing on paper was messy so I just erased their connections and added my own.

[CheshireCat]

nexis said:

The switch graphic is from guitarelectronics.com My drawing on paper was messy so I just erased their connections and added my own.

Ah.

[JohnH]

Nexis - I think your diagram would work! well done - I can't see any problems with it.

cheers

John

[jhng]

Looks good to me. Avoids shunting coils or having coils "hanging from hot" as well. Very nice. I stand corrected!
Hastings

[UnklMickey]

cheshirecat said:

...BTW, Unk, could you expand a bit on "hangin' from hot"?...

sure.

if you wire 2 coils in series, and then have a selection where the "bottom" coil is connected to the output, the upper coil will be "hanging from hot". acting like an antenna for hum and noise.

sometimes you just don't have enough poles to disconnect the upper coil. then you just have to accept it. but, when you can, i recommend avoiding it. i also avoid shunted coils wherever i can.



unk



EDIT:

Nexis,

i've gone through the totally unnecessary exercise of verifying your drawing. (Hasting and John have already proofread it.)

it looks quite different than what i had in mind, yet accomplishes all the goals. you have gone from asking for help, to solving the problem! good work!

+1

consider posting to schematics page.

[nexis]

Anyone think It might help to put a diode on the bridge pickup ground and if so what kind/rating?

[JohnH]

nexis said:

Anyone think It might help to put a diode on the bridge pickup ground and if so what kind/rating?

Not usual to put diodes in guitars. What would it be for?

Ive played with putting in a Schottky diode to get a distortion effect, but the sound was nothing like as good as a proper active overdrive circuit, and it soon came out again

John

[sumgai]

John,

Not usual to put diodes in guitars. What would it be for?

Ive played with putting in a Schottky diode to get a distortion effect, but the sound was nothing like as good as a proper active overdrive circuit, and it soon came out again

John

You wanted to use a generic germanium diode (or more properly, a pair of them). A Schottky diode is a specialized type that has an almost instant transistion from off to on (and back to off, when appropriate), something that would cause a very raspy fuzz effect, provided it worked at all. A germanium diode has a much slower transition rate (aka the 'slew rate') from off to on to off, imitating a sinusoidal waveform much more closely. Much fewer offensive harmonics that way.

The only problem with diodes is that they are voltage sensitive. Silicon diodes (or transistor junctions, for that matter) turn on at approximately 0.65 volts, plus or minus a few hundredths of a volt. Germanium junctions turn on at about 0.4 volts, sometimes even lower. Sure, most pickups can drive both diode types to turn on, but that won't get you a tone that most players consider to be desirable. Pretty much, if you don't use an active amp, you're stuck with no control over the sound of the diodes..... until you go back inside and start changing things around again.

If you want to pursue this avenue again, let us know, or seek out any of Craig Anderton's books, he has published several circuits that show exactly how to do this type of thing, and they're simple (and small) enough to install directly into a guitar.


sumgai

[JohnH]

sumgai said:

You wanted to use a generic germanium diode (or more properly, a pair of them). A Schottky diode is a specialized type that has an almost instant transistion from off to on (and back to off, when appropriate), something that would cause a very raspy fuzz effect, privided it worked at all. A germanium diode has a much slower transition rate (aka the 'slew rate') from off to on to off, imitating a sinusoidal waveform much more closely. Much fewer offensive harmonics that way.

The only problem with diodes is that they are voltage sensitive. Silicon diodes (or transistor junctions, for that matter) turn on at approximately 0.65 volts, plus or minus a few hundredths of a volt. Germanium junctions turn on at about 0.4 volts, sometimes even lower. Sure, most pickups can drive both diode types to turn on, but that won't get you a tone that most players consider to be desirable.

Thanks for your advice, but I don't agree that I wanted germanium diodes!.

When I was testing this idea, I tried silicon, germanium and Schottky, singly and in pairs, wired via a pot as in a tone control. It was interesting, and I tested them all first for current v voltage characteristics. All the diodes show a logarithmic response, where current and voltage have a relationship such as

V = A.log (I+B)

With A and B varying with type. The forward voltage that is often quoted (0.4V, 0.65V etc), is just one point on this curve, relating to a 1mA current.

Placed in a guitar, the real action occurs at much lower currents and voltages. Looking at the slope of tha I/V relationship, you can derive a 'resistance' value. As voltages get very low, during the guitars decay, the 'resistance' of the silicon diodes rises very high, and hence it has little effect at low volume. but the Schottky's were in the range 70k, to 40k, continuously changing, as the voltage drops through zero. This is a very significant range when applied to a guitar pickup, and so you get a tonal action from the diode right through the decay phase. The germaniums howeverwere too soft - with too low a resistance, they squashed the sound too much to my ears, but better than the silicon.

In all cases, I found one diode sounded better than two - more asymmetrical clipping and better volume.

However, in spite of all that insight - its not as good as an active circuit, so I moved on to JFET designs.

John

[sumgai]

John,

In all cases, I found one diode sounded better than two - more asymmetrical clipping and better volume.

Your observations about the volume being greater with only one diode are correct, of course, but the part about asymmetrical clipping being more desirable (to you) is something that I've no one else say before. Not to say that you're wrong or anything like that, but perhaps we could agree that you hear things differently, hmmm? <attempt at humor>

Your point about germanium diodes being too soft also puzzles me. Generally speaking, and I mean that in the loosest terms possible, the slower the slew rate, the lower the amount of offensive harmonics in a signal. But of course, not everyone agrees to what is offensive, and what is acceptable. You say to-may-toe, I say to-mah-toe......

The rest of your post is inarguable, so I'll sign off on that note. But for the sake of the rest of the members here, would you care to post a schematic of your final solution, please? ;D


sumgai

[ChrisK]

There are some new FETs that have gate thresholds (?well) under 200 mV. If'n I remember the next time that I see them in the trade rags, I'll post.

One is correct in that diodes are not hard switches at threshold, but indeed have a logarithmic/exponential transfer curve (after all, this effect is the basis for analog log/anti-log multipliers).

Schottky diodes are fast, have a low threshold (knee), and are crappy regarding reverse leakage current. But these can be good things....

Asymmetrical clipping is more single-tube output stage like.


Your best results may well be with higher output pickups, perhaps.

[JohnH]

Sumgai - The test arrangement that I used was simply replacing a cap with a diode (or two in parallel back to back), in a conventional tone control arrangement.

My belief is the the 'BlackIce' gadget that you can buy for about $30 is just such a pair of back to back Shottkys: Here's a link to someone who has drawn up the equivalent circuit:
www.projectguitar.com/tut/blackice.htm

Chris - interesting that Schotkys are known for leakage - and yes, I think that is what helps keep them effective at low amplitude as a clipper circuit. Sometimes a bad thing is good. It's like the guy who discovered a glue that didnt stick very well, and ended up inventing the post-it note.

Hot pups are best for these passive clippers - I used three singles in series, but it worked with any combo. I found one diode, with the pot set to about 50-70k gave the best effect, adding a bit of grit but nothing too nasty.

cheers

John

[sumgai]

Chris

.....

Asymmetrical clipping is more single-tube output stage like.

Now that's an interesting thought. I'll have to cogitate over that one for a few days, but at first blush, it does have a certain attraction.


sumgai

[sumgai]

John,

.....
My belief is the the 'BlackIce' gadget that you can buy for about $30 is just such a pair of back to back Shottkys: Here's a link to someone who has drawn up the equivalent circuit:
www.projectguitar.com/tut/blackice.htm

John

John, I hate to pound on a dead horse, but I'm dying to know, where did you get the inference from your site (or from Stew-Mac) that Schottky diodes were used, either in the substitute circuit, or in the Black Ice project?

And I believe you said earlier that it's not a diode's 'nominal' turn-on voltage that counts, it's the shape of the transfer curve. I heartily concur. But the shape of the knee on that curve is what determines the usefullness of a diode in a project like this. Remember, we're talking passive here, not active. As you further mentioned, you went to active circuitry, and I presume you did so to overcome some of the deficiencies of a passive circuit. (Given the relatively high impedance of our signal source(s).) Was I wrong to make that inference, did you actually "go FET" for another reason?

I am curious about all this.... I wouldn't mind a little bit of controllable "let your hair down" dirty right under my fingertips. ;D

Thanks.


sumgai

[JohnH]

Sumgai - I first read about it on the project guitar forum, where it seems to arise quite regularly. let me go and find a link......

...back again, here is a couple

projectguitar.ibforums.com/index.php?showtopic=11549&hl=black+ice

projectguitar.ibforums.com/index.php?showtopic=12491&hl=black+ice

Also the one in my earlier post

My feeling about it was that the passive diode added a nice bit of grit, but I soon wanted more drive.

JFETs, driven hard in class A mode have quite a smooth tube-like response. I've been developing a kick-butt circuit that will make my fortune one day! (dreaming again).

I have a circuit built into a Strat, but the traditional location in a stomp box is easier to deal with. I have also found JFETs to be great for a simple on board buffer.

John

[sumgai]

John,

Let me do this, before I say anything else.....

As it happens, this weekend I was planning on popping the hood anyway, so I'm gonna do a little experimenting, know what I mean? ;D Good thing I've got locking tuners so that I don't have to hassle with the multi-wrap coil on the string ends - I can lift the pickguard quickly and repeatedly.

Wish me luck.


sumgai

[ChrisK]

My feeling about it was that the passive diode added a nice bit of grit, but I soon wanted more drive.

The anti-parallel Schottky's although adding grit, in effect are really an under drive (clipping is).

I guess I'll have to try it, but a series diode (or two in anti-parallel) w/ hot PU's might be interesting (OR not).

Before one gets too "adventurous", the use of diode breakpoints and FETs (as well methinks) had been patented back in 1992 for tube emulation (again, methinks). I don't remember the guy's name, but he lived in Berkley Springs West Virginia. I remember this since I'd used diode breakpoint circuits in the late 70's to emulate non-linear functions (to fix the design error of one yahoo who used a square root module on bipolar signals (uh, like negative, ya know).

How does one represent "i" (sqrt[-1]) electronically?

[UnklMickey]

anti-parallel?

[ChrisK]

Anti-parallel:
Components in parallel, but of opposite polarity/phase.

Anti-series:
Components in series, but of opposite polarity/phase. (Note that regular perfect diodes are fairly meaningless, but zeners aren't)

[UnklMickey]

i think i follow you now.

so you're going to experiment with a couple of diodes, anti-parallel with each other, in series with the "signal path"?


unk

[ChrisK]

Aaaaaaaannnnndddd,

I remembered something from the dark ages (ok, the 50's). Old electric organs used biased diode switching from the keyboard. In essence, the music signal (AC) was about 50 to 100 mVAC in amplitude. It was conveyed thru a diode (capacitivly coupled on both sides) when the diode had a current (from a DC offset voltage) injected thru it via keyboard action. The conveyed signal was 100mVAC (a small AC current really) riding on the DC current to "get over the knee" of the diode.

If'n we had a means (simple is it) to bias the diodes in all structures, we could "tailor" the curve to fit the PU's afoot. All we need is an isolated bias means (coin cell, energy/vibration harvesting [check out EnOcean.com], solar cell) and proper capacitor locating and sizing.

Simple is...Riding on the curve!