The Sphinx Guitar build

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The Sphinx Guitar build

Postby chrisp » Tue Dec 04, 2018 9:12 am

Just finished a kit from Pitbull Guitars, junking the hardware and substituting a Q Pickups A3 in the neck and a Sliders '52 Nocaster in the Gotoh InTune bridge. Added in custom etched control plate and neck decals for effect.

TR Sphinx.jpg


The wiring is also different from a typical tele setup -

TR Wiring.jpg


* Lindy Frahlin wired 4 way selector (neck, neck/bridge parallel, neck/bridge series, bridge)
* Fezz Parka tone wiring using a 15nf orange drop tone cap
* Push/pull switch on volume to unload the pickups
* 630V DC safety cap separates hardware from cable negative

Fired it up for the first time yesterday, sings like a duck - that's a joke tele users will understand.
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Re: The Sphinx Guitar build

Postby Chris H » Tue Dec 04, 2018 12:49 pm

Great to play a guitar you have built yourself. Look like a fine instrument!
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Re: The Sphinx Guitar build

Postby Ausrock » Mon Dec 10, 2018 8:32 pm

Hey Chris, is the top standard or an "add on"? Oh and who did the inlay work.......love it.

My son just received the same kit from Pitbull today and is already planning some customising.........great job BTW.

Edit........:

BTW.....is your's pretty "weighty" because my son's is surprisingly heavy.
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Re: The Sphinx Guitar build

Postby chrisp » Tue Dec 11, 2018 4:31 pm

Hey there Ausrock

The quilt maple top is an add-on spec at time of ordering. It's not that expensive BUT the veneer is very thin (1mm) and so needs care when sanding and finishing.

The 'inlay' is bit of a cheat - check out Neck Illusions. In essence, they are vinyl stickers that cover the frets. No damage to the fretboard, they are removable and re-stickable, and they actually give the neck a very smooth feel when playing. I bought a pre-finished neck with the frets already levelled and polished, and then conditioned the rosewood and let dry before applying the decals. The inlay design itself is my own design which they made up as a custom deal.

Small Neck The Sphinx.jpg


Yes, it's weighty - mine is ash, which I think is the default. That said, offset guitars so tend to be heavier than others, so it's not out the park compared to others I have played.

So good luck to your boy. The only real issue I had is that the stock bridge routing is too far back for most third party bridges - with the Gotoh bridge I had to route the bridge cavity about 5mm towards the neck to get the scale length to sit within the saddle adjustment range. Other than that, the key really is to take time with the finishing, remembering that the finish you get is with you for life. I also really love the pickups I used in this build and the non-standard tele wiring gives great tonal options.
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Re: The Sphinx Guitar build

Postby Text_Edifice » Wed Dec 12, 2018 2:43 pm

That looks great!

I put a 4 way in my tele and the series position is the best thing ever.

I didn't put in the safety cap though and am thinking maybe I should?

I assume it stops your body acting as a conductor in case of a short?
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Re: The Sphinx Guitar build

Postby chrisp » Thu Dec 13, 2018 8:10 am

Text_Edifice wrote:I assume it stops your body acting as a conductor in case of a short?


Yes, exactly that. Most guitar wiring muddles up the signal negative (a reference voltage) and ground (RF shielding) circuits - how many times do you see a pot lug bent back and soldered to the pot body. And in most cases it works fine, as both signals end up at the jack socket sleeve in any event.

The issue is when things go wrong at the amp - especially older tube amps, when the HT (300-400V) can end up on the sig neg circuit if the tube fails the wrong way. If you have mixed up the earth and neg wiring in the guitar, that means the bridge, controls, machine heads and strings could all be at 400V!

By keeping the two paths separate and isolating them with the safety cap, any DC voltage from the amp will be blocked while the RFI can continue to be grounded. Something else will likely blow rather than you getting fried. The way I think of it, it's a 20c bit of insurance against something that is not likely to happen, but then again I do play some older tube amps from time to time .....
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Re: The Sphinx Guitar build

Postby Text_Edifice » Thu Dec 13, 2018 8:32 am

I play older tube amps too and am very conscious of removing death caps etc. and making sure they're properly maintained. But...

Do you do this with all your guitars or is it just in cases like this where you use series wiring?
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Re: The Sphinx Guitar build

Postby chrisp » Thu Dec 13, 2018 9:28 am

Text_Edifice wrote:Do you do this with all your guitars or is it just in cases like this where you use series wiring?


It's so simple and cheap that I do it on all my guitars. That way I don't have to think when plugging in, I know they all have the cap in place. It does mean rewiring non-DIY guitars, but I tend to do that anyway. I don't think I have 'standard' wiring in anything except my Ovation semi-acoustic, and that has no earth circuit connection to the strings anyway.
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Re: The Sphinx Guitar build

Postby Text_Edifice » Thu Dec 13, 2018 5:36 pm

That's a really good idea - do you need to use 470nf to hi-pass(?) DC or can the (farad) value be smaller?
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Re: The Sphinx Guitar build

Postby chrisp » Fri Dec 14, 2018 10:43 am

I use 470nf 630V simply because you can buy it as a greencap from Jaycar that doesn't take up too much real estate in the control cavity routing, and the value is large enough to soak up a bit of power and allow something else to blow up first. Actually, a 330nf 400V MKT would be a good if you can find one.

The original idea is from the discontinued guitarnuts forum - forgive me if I post a longish quote that explains it all -

Guitarnuts wrote:I've had a few people ask why I specify a 400V capacitor when guitar circuits usually only have a few millivolts on them. The reason is simple, that capacitor is what stands between you (via the grounded strings) and your amplifier. Some vintage tube amps could fail such that they put a potentially lethal DC voltage on the "ground" side of the jack. This type of failure is extremely rare, but why take the chance? The 400V capacitor won't break down like a 35V capacitor would in the admittedly extremely unusual case where you might plug into a "killer" amp. A 250V capacitor is also acceptable as it will probably stand up to 300V or so for at least several seconds. Note that the OEMs don't seem all that worried, most guitars have the strings grounded directly without any isolation.

On most guitars, the jack is a non-insulating type which means that the jack plate will be directly connected to the negative side of the jack even after this modification. Metal control knobs may also still be directly connected to the negative side of the jack even with the isolation capacitor in place. Finally, even with the capacitor, a high DC potential failure will give you a nasty "bite" while the capacitor charges – but the capacitor serves to limit the duration and severity of the shock.

You can omit the capacitor entirely (replacing it with a piece of wire) if you're confident you'll never plug into a malfunctioning vintage amp and if you check the house wiring religiously everywhere you play.

Note that the .33uf capacitor recommended here is really intended for protection from DC from a malfunctioning vintage amp. It will only provide minimal protection (though more than most stock guitars provide) from an AC shock caused by improper house wiring. See the very important article on electrical shock.

The .33uf designation is not critical. You could easily get away with a 0.47 or 0.22uf capacitor. The larger the value the better, up to a point (except that larger values will provide less protection from AC shock). If your control cavity is tighter than normal, you might want to go with a 0.1uf 400V because it will be physically smaller. I wouldn't go much lower than that though or you will start suffering noise.

You can also isolate only the bridge and strings by tying the shield ground directly to the signal ground, but isolating the bridge ground wire from the shield by an 0.1uf 450V capacitor. That capacitor will be much smaller and furthermore it can be mounted in the bottom of the body cavity. This method provides a little better protection from AC shock (still not foolproof) via the strings. However, if you use metal knobs on the pots they will not be isolated. Also, the metal shaft on the switch and all the pickguard mounting screws will not be isolated either. Still, this method provides good isolation for the bridge and strings, good noise performance, ease of construction, and it's still safer than most factory guitars.
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