curtisa

Have a look at the driver circuit used by Fender for their reverb stages (such as in the Fender Twin Reverb). The cathode resistor used in them is much higher, and the two halves of the 12AT7 are in parallel as per your thoughts on possible changes to the topology.

If you're exploring the idea of using both halves of the 12AT7 as the output driver another option is to configure it for push-pull configuration. The Firefly project used as 12AU7 in push-pull for sub-1 watt output. You could probably sub in the 12AT7 and it would be happy enough to work OK.

Have you tried out the amp side of things yet? 20K effective plate resistor with a 130R cathode R on a 12AT7 at 200-ish volts has the tube pretty much hard on the end stops. I would've thought any overdrive you'd be getting would be pretty 'farty' sounding.

Bear in mind that boosting the plate voltage up using a DC-DC converter still makes it a power-hungry circuit on batteries. All you're effectively doing is selecting 4th gear on the gearbox instead of 1st.

Yes, it's odd. But it does 'work', even if it has the side effects you've found. And by and large it a0ppears to be typical across multiple wiring diagrams for the Jaguar that I've looked at, so I guess it's just the way Fender chose to do it for whatever reason they had at the time.

I would point out that there does seem to be one other variant floating around that shows an extra 56k resistor strapped across the top two terminals of the pot (where you have the red and yellow wires shown in your post). See here for example. This would lessen the effect of the tone pot slugging the output level as it's wound down at the expense of making the tone control less responsive overall. You could try it out and see if it makes the circuit behave a little better.

Or you could always say 'to hell with historical accuracy' and just wire the tone pot in a conventional two-terminal arrangement (who uses a stinking tone pot anyway..?)

A softer board might initially grab a fret OK, but it's unlikely to hold it properly under regular playing conditions or seasonal changes. There's a good chance the frets may start lifting and getting high spots after a year or two of playing. The other thing I'd be concerned about is the way a softer board will wear in between each fret from finger pressure pushing the strings against the timber.

1 hour ago, hittitewarrior said:

I believe it is Tasmanian Myrtle? - https://www.wood-database.com/tasmanian-myrtle/

Then I'd suggest it's too soft to be used reliably as a fretboard - sorry

The 'tiger' bit of tiger myrtle is a kind of fungal attack that happens to the tree as it grows, not unlike spalted maple. It's quite a striking visual effect to look at, but IME it leaves the timber much softer than normal. A clear piece of Tas myrtle is not dissimilar to maple in terms of strength and hardness, but the tiger variant needs to be used more carefully and selectively.

You could possibly try flooding the whole fretboard with some kind of hardening agent (maybe CA or water thin epoxy?) but it's going to be messy and a bit of a stab in the dark as to whether it will work successfully. Do you have any offcuts you can experiment with?

30 minutes ago, Jackson Hole said:

That was the qestion on the nut or on the fret?

Unless the nut is extremely high to begin with it probably doesn't make a great deal of difference. Certainly nothing that can't be adjusted out at the bridge anyway. At a pinch I'd suggest resting the straightedge on the frets only might be preferable as the neck will have a tendency to bend forward under string tension, plus you need inherent clearance between the strings and frets to avoid buzzing, and this will have the combined effect of effectivey increasing the strung-up action higher than the straightedge may initially indicate. You'll need a way to control the action, either positive or negative, so the more leeway you can give yourself to control it at the bridge the better.

Raising a Tune-o-matic to increase the action once the guitar is strung up is generally pretty easy. Lowering it will be limited by whatever minimum clearance you have left underneath it, and this is probably where it's more critical to plan out the initial neck angle to begin with.

If this is going to be a Telecaster in the 'traditional' sense (ie, with a pickguard and bolt-on neck construction), you could always add a tapered shim to the neck pocket to fine tune any required neck angle after the fact. They can generally be made to be look pretty unobtrusive to the casual eye.

The ridges I'm referring to are the minimum stepovers left behind by the tool in its attempts to approximate a 3D surface at a finite 'resolution', if you will. Akin to taking a digital photo with a low pixel depth.

19 hours ago, fabyo said:

Thank you very much for your reply! 

That way I wouldn't have to ground the switch anymore because I already do it with the A2 and A3 right?

You're welcome

Re, grounding the switch: Not strictly necessary as such. However if you want to maintain the integrity of the shielding paint/foil (if any), you could solder an additional short jumper from A2 to the frame of the switch. Normally the volume pot case would be connected to ground and then the shielding grounded by virtue of the pot being screwed onto the cavity wall. But as you're removing everything inside the cavity except for the switch you'll lose that inherent grounding through the metallic case of the pot.

However, as you're using a humbucker with (presumably) some shielded four core conductor cable, and not employing coil splitting, you can probably get away without adding a dedicated ground connection to the switch (other than what is shown on my diagram) and save the trouble of grounding the shielding as well.

Assuming you don't want volume or tone pots, and positions 2 and 3 can be 'pickup off' positions:

I'm using a 3D adaptive with a 12mm square endmill to rough out the rear profile and then a 3D parallel with a 6mm ball end endmill to provide a finer semi-complete surface finish. I'm still left with ridges that have to be hand sanded and scraped out, but I'd rather spend 30 minutes doing that by hand than spend hours on the mill going finer and finer. just to get the surface closer to a finish-ready state. I have to go up the grits in order to get to that point anyway, so it makes sense to get the neck to a point on the mill where the labour trade-offs become inconsequential.

Including tool changes and fiddling with work holdings I think I can turn out a neck profile in a bit under an hour. Note that doesn't include the overall 2D outside profile of the neck or anything else; just the rear faces of the neck that the palm of your fretting hand holds on to.

You're probably largely hearing the tapping sound of the deselected pickup being coupled acoustically back into the selected pickup, which a per-pickup kill circuit probably wouldn't do much to combat. With enough gain you'll hear yourself tapping on all parts of the guitar through any one pickup.

That said, if you want to experiment with the concept, a 3-position 2-pole Tele-style blade switch can be wired to behave as a de-selected-pickup-signal-killer.. Wouldn't work with a Les Paul-style toggle switch though.

Good to see you back again. If you need any tips on that headless bridge assembly just hit me up. I've used it before and it's...quirky, to say the least

Go the 520mm. I use the generic Chinese ones all the time and have yet to have an issue. They're cheap enough to buy several, pick the best of the bunch and still be left over with enough cash to buy yourself a beer.

I've never used Marri. Have you tried searching for some of its properties? Google suggests that Marri has a Janka hardness of 7-8kN. Not as hard as Jarrah but harder than maple, so on face value it looks like it would work OK.

But that's not the only property to look for. You want dimensional stability, straight grain, good crush strength (for holding on to theose fret tangs), free of gum veins or anything that might weaken it etc. Maybe start somewhere like a wood database and compare the properties of Marri with the other well-known fretboard timbers and see where it fits in. There might also be other foibles to consider, such as whether the wood has extremely open pores (which might capture all manner of finger crud and look ugly very quickly) or whether it has any special requirements for gluing (maybe it has a high natural oil content and won't adhever to standard PVA?).

Yes, I can confirm that the older 5-way rotary switching scheme is fully humbucking in all positions, but I'd have to open mine up to verify how it's done and what wire colour goes where. There's probably someone out there that's already done the hard work on reverse engineering the wiring on the older CU22 and 24 rotary-switched scheme.

11 hours ago, mistermikev said:

the goal is to be able to run both screw coils at the sm time, or both slug coils at the sm time... and get hum cancellation.  the additional constraint is that it needs to be inside coils vs outside coils ie a larger vs smaller spread between coils. 

Admittedly there's caveats and trade-offs to any suggestions. My first idea is effectively the same as your option of flipping the magnet in the pickup, but carries the proviso that you need to live with the look of the pickup being upside down. It does, however, save you dismantling the pickup to get to the magnet which may be off-putting to some people. If you're not adept and aware of the inner workings of pickup disassembly/reassembly there's every chance you might write off a perfectly decent Seymour Duncan humbucker in the process. 

The second option should also work, but introduces other phasing issues in certain pickup combinations. Indeed, I had to use it recently on an HSS-equipped guitar, where the split-bridge pickup sound when combined with the middle single gave humbucking performance but not the typical Strat-position-2 'quack' sound I was after. Reversing the coil order and tapping the opposite coil on the humbucker fixed the issue without having to worry about flipping magnets or rotating the pickup around. But as you note, it could have unusual tonal effects on an HH guitar if you also want to retain the 'normal' bridge-bridge/neck-neck humbucker switching pattern in addition to the humbucking inner/outer coil tap positions.

3 hours ago, mistermikev said:

one way to get around this is to take either pickup and physically flip the magnet,

Or if you have enough slack on the pickup cable, can live with one Seymour Duncan logo appearing upside down and the slug/screw polepieces appearing in the same order as the bridge pickup, just spin the neck pickup around 180 degrees. Admittedly that probably only works best if you have a pickup that looks the same if oriented either way up, such as a Dimarzio with hex polepieces and the same colour bobbins.

Another alternative is to swap the connection order of the two coils in the wiring. There's no reason why the start winding of a coil on either north or south has to be the one that feeds the 'hot' wire of the circuit in order for a humbucker to buck the hum. Using SD wiring colours, Black (hot) -> White -> Red -> Green (ground) will work the same as Red (hot) -> Green -> Black -> White (ground), but will reverse the phase of the whole pickup by 180 degrees and allow you to tap the opposite magnetic polarity coil if you want without rotating the pickup or magnet, Again, the limitation here is that if you want two humbuckers to sound a certain way when combined (say the neck+bridge position on an LP) it won't work, but it can be useful if you're trying to split a humbucker in combination with a middle single coil for that inbetween Strat-type sound, and the middle single isn't reverse wind/reverse polarity relative to the humbucker coil you're trying to split with.

Use whatever is most convenient to you (hardware store, scrap metal yard etc), although starting oversize and cutting it down to shape after the holes are drilled will probably make life easier. If one edge is straight from the factory to begin with (say the long edge of an aluminium bar) you'll get a head start on the accuracy of the hole placement using the fence on the drill press.

Kinda. The temporary fence at the back of the table is correct, as it allows the workpiece to slide left-right to prevent any error in the forwards/backwards placement of the holes. But the extra jig with the locating pin she uses potentially re-introduces those placement errors, as there's nothing stopping the jig rotating round the axis of the index pin (at 11:14 for example you can see the second-from-the-right hole is closer to the fence than the other five). Better results would have been attained if the jig with the pin was wide enough such that it too could also be pressed up against the fence at the same time as the workpiece, so that it couldn't be accidentally swivelled around when positioning each hole.

The other alternative is to use the long fence at the back of the table as before, but construct a stop off to one side that the workpiece gets butted up against to prevent it shifting from side to side (similar to those adjustable end stops you find on chop saws). If you can make this side stop adjustable in some way that you can incrementally shorten it in discrete steps you should be able to achieve equally spaced holes without the aid of measuring/marking anything except for the first hole you want to drill. The only trick is finding something that has the same thickness as the string spacing you want to achieve as you add or remove components of this side stop (maybe six Lego blocks, or six holes in a Meccano girder, or six offcuts of some metal bar stacked side-on-side?). Something like this:

6 hours ago, Guitrying said:

I'm assuming that you use the special metal-cutting bits and then manually tap the screw holes shown in your photos

Yes, although you don't have to tap the holes if you don't want. You could just as easily drill the holes in the baseplate all the way through, use longer bolts with nuts on the underside to secure each nut/bridge and route out some clearance in the timber underneath the baseplate to allow the nuts/bolt ends to fit in to. The only drawback then is you have to design your baseplate to be intsallable with all six nuts/saddles already in place. The nut plate in my photos, for example would need to have wider sides to allow me to install some mounting screws to attach it to the headstock.

That's pretty much exactly what I do with mine. Admittedly this is done on CNC, but it doesn't have to be that fancy:

A fabricated mounting plate to fit six tuners (or nuts) would be a trivial thing for a capable machinist to whip up, provided you gave them a decent drawing of what you wanted. It's the sort of thing they might do for a six pack of beer in their lunch break if you ask nicely. Certainly a lot less work and money than fabricating up six custom-made tuners specifically for your build.

If you have access to an OK-ish drill press there are ways of making repeatable, equally-spaced holes in straight lines that don't require a lot of high precision operations.

How about buying the individual headless tuners and attaching them to a fabricated baseplate with the required string spacing? The only part that would then require any real degree of precision would be drilling the mounting holes at the required positions on the plate.

1 hour ago, hittitewarrior said:

Any reason to carve first?

I didn't mean to imply that those items be in a specific order; more highlighting that any potential movement of the neck as a result of material being removed from the blank, frets being inserted etc should be the last thing you address before attempting to level the frets.

Trying to get the neck to 'sit straight' this early on in its construction may be counter-productive if all that happens is that the neck moves again before you get to the fret levelling stage. If you re-sand the fretboard now so that it's flat, you'll end up with a fretboard that is (marginally) thinner at the ends than in the middle. If you start cutting/carving/sanding/shaping the rest of the neck and it moves again, your flattened fretboard could end up non-flat again (maybe lifting at the ends again? maybe bending back the other way? maybe twisting in an odd way?), and you'll have to go back and correct it somehow.

It's possible that the neck blank won't move any more from this point onwards, in which case doing nothing now except making the neck as you would normally will be perfectly acceptable, and all you need to do is tweak the truss rod to get the neck flat again prior to levelling. But trying to force it to appear flat and discovering it changes further down the track will just have you chasing your tail.

10 hours ago, hittitewarrior said:

any other ideas or thoughts from others?  Appreciate the input so far!

Finish the remainder of the neck construction steps (headstock, headstock transition, carve, fretting etc) and then make a decision. There's every possibility it will move some more once you start performing further operations to it, so any corrections you make to it now could just come unstuck as you start making further changes to the neck blank, and you'll have to deal with it again. If you've used a dual action truss rod and you need to correct a minor up/down bow prior to levelling, just use the truss rod to offset it. After all, the primary reason the truss rod is there is to control the degree of relief in the neck.

What are the dimensions of the carbon rods you installed?

Just clarifying - are you still having issues with it or was it just a mistake in your original assessment that the switching wasn't working as expected?

Silicone is fine to use. Just use it sparingy and avoid any contact with sutfaces that must be glued or finished.

A safer alternative may be acrylic caulking filler. It's usually sold at hardware stores and available in lots of different colours for hiding the join between a kitchen countertop and tiled walls. It has similar flexibile and adhesive properties to wet area silicone sealer without the problematic oils.