Master series/parallel switch [FINISHED]

[Deleted]

Hi everyone,

I've got a les paul style guitar which has the Jimmy Page wiring setup (2 coil shunts, phase switch, master series switch). The series/parallel switch has a few major disadvantages - it only works in two pickup selector positions, the other position being a dead spot, and the volume controls act in a weird way (one is a blend, one is a master).

I found a design on this forum by JohnH that should fix both these problems but I'd like to do it my own way and get it right first time so I've drawn up my variation of the series/parallel circuit for people to check. It should wire both pickups in series and bypass the pickup selector switch so both pickups are always on when the switch is activated. Questions: Will it work? How will the volume controls behave in this configuration (in normal parallel mode, and with switch activated)? And will it work if the tone controls are wired up as standard (johnH's tone controls are modified to do the 'broadbucker' thing)?



Pots in the picture are the two separate volume pots.

Original thread: guitarnuts2.proboards.com/thread/3159/jhs-jimmy-page

Thanks for your help.

[JohnH]

Hello and welcome to GN2 (or have we seen you before?)

Anyway, that switch diagram should work, forcing full series mode no matter where the pickup selector is, which was the idea on my diagram. (btw, I borrowed it from Borsanova, who also did a JP LP variant at the time - jeez, 10 years ago now!)

In series mode, the proportion from each pickup is independently set by each volume pot, which is different to most versions. In parallel mode, it works as a normal LP. But, to get that series mixing to work, it should have treble bleed circuits on each volume pot (150k and 1nF in parallel), between middle and hot outer lugs. Apart from the variations in series mixing, this system has the advantage of less load on the pots in series mode, keeping better high treble.

Id recommend trying the tone pots wired as I showed it, with tone hot where you have it and the tone grounds to the right volume lugs, then you can control tone for each pU separately in series mode. But, if you really need a master tone, take the neck tone ground to ground instead. The bridge tone will still control just the bridge.

Again, in parallel mode, it's like a normal LP.

[Deleted]

Thanks JohnH, I wasn't sure I'd get a reply from the man himself given the age of the original thread! Thanks for the welcome as well, I'm a long time (occasional) reader but I don't believe I've ever posted here before.

I am a big fan of treble bleeds and I do plan to include them - I left them off my diagram for simplicity. On this guitar I currently use 500pF silver-mica caps in parallel with 270k resistors, but I've changed my mind about this part of the circuit so many times over the years that I now have it socketed for ease of swapping.

I'll follow your recommendation for grounding the tone controls to the right volume lugs as that's how I want it to work. I was planning to ground them to the pot body for ease/simplicity but it sounds like your method will work better for me.

I will be sure to post again once I've put it all together - probably asking where I've gone wrong!

[Deleted]

Ok, I've run into what is hopefully a minor problem. I'm using CTS push pull pots with SPST switching for the single-coil sounds in my circuit. The 'middle' wires on the neck pickup are tied together and shunted to hot (left lug of the volume pot), and on the bridge pickup they are shunted to negative (the lug on the phase switch that goes to ground).

This is obviously different to the circuit shown in the original thread, and I'm not sure where to put the negative wire for the neck pickup. I'm thinking right lug of the neck volume pot? This would be ground when the pickups are in parallel and go to the bridge volume pot in series.

Am i way off the mark? Keeping series mode happy really adds to the complexity of this circuit!

[JohnH]

Sounds ok to me. You might check that when you coil cut, in phase, you get a north and a south coil so its humcancelling asa B N combo.

Then when you change to out of phase, the brudge will cut to its other coil, so then you have two coils the same magnetic polarity, also hum cancelling when out of phase.

[Deleted]

SUCCESS!!!!

Thank you again JohnH, I've finally had a chance to spend some time on this project and I managed to get everything working first time. I couldn't have done this without your help and advice. I managed to make the middle positions hum cancelling too.

Here's the before picture:



And now:



I'm quite excited to have finished this and want to talk about it to somebody, but my wife stopped listening to my guitar talk long ago! So here's the full story.

I had 3 things I hoped to achieve:

1. The original mod (top picture) used the series/parallel circuit that has a dead spot on the selector switch and weird control knob behaviour. I wanted to implement the JohnH/Borsanova solution to this. This works really well, with the volume/tone controls as equal mixers in series mode rather than a blend and a master, and rolling one volume to 0 does NOT mute both. When the switch is in series mode the selector switch is bypassed an both pickups are always on, unless the volume is set to 0. I really like this and find it handy in out of phase mode when you want to kick in a bit more output - just pull the series switch.

2. New pots and caps - The original pots were a mix of Alpha push pulls (flimsy from the very beginning, and time has not been kind) and old-style CTS push pulls (steel shafts with stiff action, and the shafts were too long for this guitar). Now that CTS have expanded their guitar-friendly lineup, including DPDT push-pulls, I could finally have those nice brass-shafted CTS pots all round. The PIO caps I originally used are physically bulky and I no longer believe they offer any significant benefit over the Orange Drops, so out they came. I will probably sell them, they were high end copper foil audio caps.

3. I did the Jimmy Page mod to this Tokai Les Paul as my very first soldering/electronics project. In fairness to my teenage self everything worked as it should but it was a hideous piece of work - mods and maintenance were a nightmare and I had some noise issues even with the shielded cavity. My soldering skills, still far from professional, are good enough now that I felt I could sort this mess out. I'm happy with the result and the background noise levels are way down.

I'm sure I'll be back here at some point. Cheers!

[JohnH]

That's great to hear, well done. It's not the simplest puzzle to get all that working with the right phase etc.

But I know how your wife feels with regard to talking about guitars. Probably much the same as I feel about my wife talking about horses. I met her in 1986 and I can confirm that it is possible to talk about such creatures for at least 30 years.