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Jack Bruce (ish) EB3 / SG Bass


Andyjr1515
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OK - I think we have a workable solution for the three pointer. I've got a bit more filing to do, but basically it has gone like this:

On average, the bridge was 4.5mm too high. Being a fixed neck, the standard solution of adjusting the neck angle is clearly not an option. Sinking the whole bridge into the body - a la Warwick - was a non-preferred option because it would be really tricky to do without it looking like a bodge. A new bridge? Yes, possibly, but if possible I wanted at least a passing nod to the original - especially since so much else is nothing like it (cue me passing the finished bass to Pete, "Here is your Jack Bruce replica, Pete (based on Pete's non-comprehending look, tries to stifle sniggers). No - trust me....the old photos are a bit misleading...it was JUST like that in real life!") :D

So the first approach to try was to slot the saddles 4.5mm deeper. I used a triangular needle file and appropriate sized nut file, rounding off the corners with a round needle file



The next challenge is break angle. I filed an appropriate angle onto the back of the saddle, but with the standard clasps, there would be almost no back angle. I could drill it for back loaded ferrules, but thought I'd try the extender that John (our very own 6feet7) very kindly sent to me 'just in case' (and wouldn't even take the postage for it...what a forum...what a great guy :) )

I haven't filed the back of the bridge yet to relieve the strings - and so the strings are still too flat in this shot - but I can already tell that the extender bar is in the right position to give it the required angle :)


It's a lovely piece of machined steel, too - thanks again John!

The action has been transformed and the strings are ringing out clear and beautifully :D I think it's a goer. I also think it looks fine:


Don't worry that the strings seem to be a bit offset - the positioning nut isn't glued in and was a bit skew with the differential pull of the strings.

This evening's jobs will be filing that bridge relief angle and fret levelling. It's all starting to get quite close :D

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Hard to tell from the pictures, Is the extender bar pulling firm against the metal of the bridge and not indirectly into the body? I found I had to be careful with my home made one, it seemed very easy to ding the body with the bar and the ball ends (mine were not significantly countersunk). It was a wise move not attempting the recessed bridge approach, in that route (pun intended) lay potential disaster.

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[quote name='3below' timestamp='1476391793' post='3153979']
Hard to tell from the pictures, Is the extender bar pulling firm against the metal of the bridge and not indirectly into the body? I found I had to be careful with my home made one, it seemed very easy to ding the body with the bar and the ball ends (mine were not significantly countersunk). It was a wise move not attempting the recessed bridge approach, in that route (pun intended) lay potential disaster.
[/quote]
No - I had a brief flash of clarity and set it so it's level with the bottom :) The one good thing about the three pointer (there had to be one good thing!) is that the front can still be screwed right down so the action was still low enough.

Yes - sinking the bridge would have been,,,,er....bold ;)

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Onto fret levelling, crowning and polishing - and a mystery solved ;)

The levelling and crowning is pretty standard stuff.

I straightened the neck (nice to confirm that the truss-rod works :) ), then levelled with a combination of a full length beam and a shorter diamond file and finishing off with a radius block with 800 grit on it:



Then crowned with a hosco crowning file, wrapped in various grades of micro web from 1500 to 12000 grit:



The mystery solved is that, having missed out the zero fret from the levelling, I expected the levelled frets to balance out the 1st fret buzz. Nah..........and on further investigation, the zero fret is at least 0.5mm lower than the levelled first fret.

All the frets are fully seated so I suspect that when I was sanding the fretboard radius, I fell into the 'rocking either end' error in my sanding motion technique. The impact of this at the nut end is greatly exaggerated because it is that much thinner. 2nd schoolboy error on this build :rolleyes:

I have a choice to either replace the zero fret with a very tall one (if they do them that tall!) or just fit a standard nut. I'll have a ponder on that one - only really went for zero fret because the slot was already there and in someways, as you need a string positioning nut anyway, it would be easier to fit a standard nut now that I have to change it anyway.

Despite the (fairly usual) batch of de-snagging issues, I'm still pleased with this build and I know Pete is going to be very happy with it. Going to try to sort the electrics this weekend :D That'll test pretty comprehensively whether Andyjr1515 knows his choke-based notch filters from his elbow! :lol:

(and the answer is probably a resounding NO! ;) )

Edited by Andyjr1515
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Not much you can do about the zero fret. You can't put wood back on the fretboard, and pulling all the frets and re-shaping the board is a bit extreme. I think the conventional nut is about the only practical option. It's not the worst thing that could have happened though. Fabulous build so far!

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[quote name='Andyjr1515' timestamp='1476358434' post='3153582']








[/quote]

[color=#282828][font=helvetica, arial, sans-serif]Witch...WITCH!!! Burn the witch!![/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Another amazing piece of work Andy...that finish is beautiful...I'm sure that if Pete isn't happy there'll be a queue of BCers happy to take it off your hands.[/font][/color]

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Alternate zero fret / nut thought. You could widen the zero fret slot to (3mm? 1/8" ?) and fit a Fender type nut at the zero fret. Not in keeping with the EB3 vibe but probably a simpler solution. If you used black acetal (aka Delrin) it would not stand out much and could be followed by whatever nut you were originally planning. Other alternatives to acetal could be nickel silver or brass plate. If this was slotted (and probably glued) in it could be levelled and crowned. Apart from the side view in the fingerboard it would present as a higher fret, same frontal profile and appearance.

Edited by 3below
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[quote name='3below' timestamp='1476552764' post='3155180']
Alternate zero fret / nut thought. You could widen the zero fret slot to (3mm? 1/8" ?) and fit a Fender type nut at the zero fret. Not in keeping with the EB3 vibe but probably a simpler solution. If you used black acetal (aka Delrin) it would not stand out much and could be followed by whatever nut you were originally planning. Other alternatives to acetal could be nickel silver or brass plate. If this was slotted (and probably glued) in it could be levelled and crowned. Apart from the side view in the fingerboard it would present as a higher fret, same frontal profile and appearance.
[/quote]

Decent thought but I think I will just go for a nut. As I say, if the fretboard slotting hadn't had the zero fret datum, I'd have done that happily enough anyway. That way I can also ignore that the fretboard itself is probably lower than it should be and fit it in the time honoured way of measuring the gap at the 1st fret when fretted at the second :)

On that basis, I have ordered a brass nut that should be with me early next week. I've tru-oil slurry and buffed the neck, I've smoothed, oiled and buffed the ebony fretboard and I've final-polished the body and so I THINK it's just the electrics to do now... This coming week should see completion :D

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[quote name='TheGreek' timestamp='1476552561' post='3155177']
[color=#282828][font=helvetica, arial, sans-serif]Witch...WITCH!!! Burn the witch!![/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Another amazing piece of work Andy...that finish is beautiful...I'm sure that if Pete isn't happy there'll be a queue of BCers happy to take it off your hands.[/font][/color]
[/quote]
:lol:

It's turned out not half bad hasn't it, Mick :D

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Phew - nice to have a sit down ;)

I've been standing up in my cellar / workshop pretty much all day. Some of these 'little jobs' take so long!

Made decent progress, though. The c****d up tuner positions have been corrected with only a modest angle of the E and G strings (ignore the cobbled up nut - waiting for the brass nut to arrive):



Control and pickup chambers have been screened and earthed:


The wiring diagram has been redrawn in component form:



...and all but the p/ups themselves have been wired up:


I've got to insulate the couple of veroboards with the notch filter components, but then just solder the pickup hot and grounds in

Everything here is earthed via the copper screening - including the bridge. It makes for a much tidier control chamber!

I've got grave doubts that I have the correct value of capacitor in the notch filter (I think I may have mixed up my nanos and picos) but that is a 5 minute swop of components if it's wrong).

I should be able to try out the sounds tomorrow :)

Edited by Andyjr1515
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[quote name='3below' timestamp='1476651374' post='3156058']
Choke capacitor 0.02 uF which translates to 20nF. I wonder if a 20pF would have any audible effect (it is too late in the evening to do the maths out and work it out ). Soundclips awaited :)
[/quote]
Thanks, 3below

Glad you posted this. The 0.02uF is one of the 'standard' tone values? I thought the one I'd put on the board was the same (pretty sure it was out of a PRS), but looking closely, it's marked 0.22uF. Weird! Anyway, I'll swop it for a 0.022uF orange drop in the morning just in case :)

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I suspect the 0.02uF is a consequence of the Gibson notch filter design intention rather than a 'standard' tone capacitor. Do you know what the inductance of your choke is?. I would be interested in modelling what the circuit is intended to do.

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[quote name='3below' timestamp='1476684551' post='3156182']
I suspect the 0.02uF is a consequence of the Gibson notch filter design intention rather than a 'standard' tone capacitor. Do you know what the inductance of your choke is?. I would be interested in modelling what the circuit is intended to do.
[/quote]
The full primary is 1.5H (I have the data sheet and will look at the other coil and option details also). The resistor is 100k

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As expected, looking fantastic.
You wouldn't believe how many comments i get about the birds that you use on the headstock.
People ask me what they are, and as i cant remember what you said (Swifts or Swallows??) i make a new one up everytime :D
I do always point them in the direction of your website though

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[quote name='FuNkShUi' timestamp='1476694665' post='3156268']
As expected, looking fantastic.
You wouldn't believe how many comments i get about the birds that you use on the headstock.
People ask me what they are, and as i cant remember what you said (Swifts or Swallows??) i make a new one up everytime :D
I do always point them in the direction of your website though
[/quote]
Thanks, Kert! :)

They're swifts - my favourite bird and one which, to our family, hails summer. We have had swifts nesting in the eaves since we moved in here (30 odd years ago). We were bothered in the last couple of years because we were down to two nests of which one was abandoned. This year, though, we've had four :D If you've never been close to a flock of swifts when they are tearing round the buildings at crazy speeds screaming away (probably scaring themselves s******s) then it's something to put on the bucket list. Nearest natural thing to the sound of a full and fast rollercoaster :lol: Sometimes they miss you so close you feel the waft of air as they go past :D

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Well, I award myself the honour of Andyjr1515's neatest wiring job ever :D (you need to see some of my others to realise how significant this is :lol: ). This is it, fully wired up and ready to play:



OK - that's some of the good news out of the way :)

But wait! There's more good news. It works! Moreover, the Model One neck pickup is unbelieveable! The 'cheap as chips but looks right' Artec also is really and seriously not bad at all.

OK - hmmm - the notch filter. The good news here is that it does make three different sounds. But the volume is c 10% of the clean pickups. I'm not sure whether that is how I've wired it up or the values of components I've used. I'll double check the I've actually wired it to diagram and then consult with folk (3below springs to mind ;) ) what understand these things a lot better than what I do...

Overall, though, with a month to go before Pete's birthday and just the notch circuit and nut to sort (plus I might re-dye and finish the neck), well pleased.

I'll post a few 'almost finished' shots soon :)

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