Finished Pics! Ultra Modern Bass

Andyjr1515

A lot of hours make up just a few photos below!

First earthing the tuner block.  I generally solder the earth to a small patch of shielding copper to get a good connection without the risk of a 'lump' between the bridge and its seating:


Then battery clip and pots.  In this shot, two of the pots are installed -  using @Sporky 's excellent suggestion of a threaded bush - with the slimline stacked pot still to install:


And here they are all in.  Still have to do the jack socket and tidy the clearance carves round the knobs, but this is broadly how it will look from the back:


The knobs and tuner block are fully accessible and very easy to use...but everything remains completely hidden from the front:
 
 

paulnb57

Fab-u-lous!

BigMonka

I can't wait to see it finished, having an acoustic style bridge and no (visible) pickup is going to be such a distinctive look!

Are those magnets I can see to keep the control cavity cover on? Nice touch. Do you have to pry it off with a slim knife/screwdriver if you need access?

Andyjr1515

BigMonka said:

I can't wait to see it finished, having an acoustic style bridge and no (visible) pickup is going to be such a distinctive look!

Are those magnets I can see to keep the control cavity cover on? Nice touch. Do you have to pry it off with a slim knife/screwdriver if you need access?

Thanks, @BigMonka

Yes, the main cover and the truss rod cover are held by magnets.  Having said that, I need to take another look at the security and shape of the back cover. It is supposed to follow the curve of the back, but the magnets aren't really strong enough to hold the curve on the very thin and wide cover that - left to its own devices - straightens and curves depending on the weather! So I might have to rethink the best way of doing that.

The cover for the rear-fitted cylindrical magnetic pickup coils will need to be held with conventional screws - I can't use magnets because they might impact on the custom coils and also the hatch, backed with foam, is what will be used to hold the coils in place.

Onto a bit of further progress, the expression 'tight as a tick' comes to mind

...but the cover still fits! :

Perhaps surprisingly, the controls are not impacted. I think it helps that the pot nearest the jack has stacked knobs.  In the playing position, the knobs remain accessible and easy to turn, using the side of finger 'speed knob' approach

From the front, it's all pretty discrete:

I need to make sure there is no shielding anywhere near the hot signal parts of the jack or pot tabs, especially on the cover 

In the meantime, I need to take that all the above electrics out again and do a proper job of the relief channels at the back of the knobs and jack.

Then a bit of re-finishing those areas

Then a bash at installing the pickups! 

Andyjr1515

For those who are interested in such things, by the way, I've been able to do the final weighing. It will be a touch under 7lb 4oz.  That's pretty light for a long-scale bass....

Andyjr1515

There are actually very few jobs to finish off. So, will it be finished very soon? Well, not necessarily! The remaining ones are going to take considerable care and lots of fiddling about. Not least the pickups.

Here are the custom pickups supplied by Martin Herrick - do have a look at the great stuff on his website https://www.herrickpickups.com/ - there's some amazing stuff there 

They are wound individually with different resistances to balance the output of each of the strings. The pole pieces have been put in so that they can be adjusted from the back. 

And, by golly, this is a delicate, wibbly-wobbly, highly magnetic assembly! "Be careful with the blue wires - they are very delicate", Martin wisely advised...

So probably Martin has to look away at this point - because the first thing I needed to do was get the soldering iron out and desolder the one stable thing on the assembly - the stiff copper earth wire running across the four coils!

Why? Well, these coils have to go down into separate chambers so what I will do is solder 4 individual earth wires from the shields to hook up with the collective earth on the output cable.

Having removed the copper wire (but not yet added the individual earths) I did a very careful trial fit:

Looks good for a first go. I marked the position of the cable runs to rout some slots for them to slot into and the join up to the pre-routed cable channel that's sitting under that ebony strip:

Next job is to get the router out! 

Ravenous

I've said it before, but those pickups are seriously interesting.

If you had far too much time on your hands you could really go crazy with those - stereo wiring, MIDI outputs, individual effects channels, god knows what else...

Andyjr1515

Ravenous said:

I've said it before, but those pickups are seriously interesting.

If you had far too much time on your hands you could really go crazy with those - stereo wiring, MIDI outputs, individual effects channels, god knows what else...

Happily, I don't have far too much time on my hands

Routing was done, earth shield wiring wires added and everything fitted:


And here's the shocker - they work!

Next job is to fit the piezo and mixer unit

BigMonka

Those pickups are so brilliantly intriguing! Were they your idea or your customer's? 
Have you got any idea at what this bass will sound like with the funky pickups blended with a piezo?!

Andyjr1515

BigMonka said:

Those pickups are so brilliantly intriguing! Were they your idea or your customer's? 
Have you got any idea at what this bass will sound like with the funky pickups blended with a piezo?!

The idea was a bit of both. Originally, I was planning on a mini humbucker sunk into the back, but Mick was concerned that the thru' neck would be breached.  He put me onto Martin Herrick after I'd had a peep how the Wal pickups are arranged under the cover (basically coils like this). Martin let me know what the minimum sizes would need to be and I came up with the stagger that meant there would be a visual continuity of the neck.  We sorted the degree to which the outputs of the coils would differ in a telephone discussion.

I have no idea what the blend is going to be like....I'm hoping to find out this afternoon if I've read John East's mixer circuit correctly

BigMonka

Well get yourself off this forum and hurry up with your soldering - we want sound clips!!

Andyjr1515

Just in the nick of time - got to pack for an away day!

All wired up and all working Still got to tidy up the spaghetti, but this is basically all of it in place

On Sunday, I'll fiddle about with the gains and attenuation on the pre-amp and the balance of the magnetic pickups / string heights, etc.. But we have piezo, we have magnetic, we have blend, we have individual tone and volume

Sporky

Lovely work - that's neater than most of mine post-tidying!

Andyjr1515

Back to it this morning - the start of the tweaking and balancing of the magnetic coils and piezo process. Like the rest of the build, takes some thinking about...

So where I’m starting from:

• Martin Herrick custom coils, going through

• a John East MPM-02 preamp/mixer, mixing with

• an acoustic-bass undersaddle piezo

Starting point was a major (and not unexpected) volume difference between the piezo and the magnetic coils, with the piezo being much louder. This was even with pre-amp trim pots for gain on high for the magnetic and zero for the piezo.

So step 1 was to take out the optional pin shunt to attenuate the piezo signal.

The volume difference was much better but still there.

Next was a mains buzz (again not unexpected) from the coils. They are not fully humbucking and there is quite a bit of pre-amp gain on them. I checked against my own fretless and, sure enough, the magnetic only volume was significantly lower than on the new build. The piezo, on the other hand, is completely buzz free and VERY bright (think acoustic bass with bronze strings). Again, nice tone but very different. 

Still, before I turned the gain down to see if it cured the buzz, this was a good time to balance the individual coils themselves, with the high gain exaggerating the volume imbalance. This was pretty straightforward with these three essential components:

• Alternative length slugs, supplied by Martin

• Some various thickness foam pieces to place the individual coils at different heights inside their chambers

• Tape to hold the positioned coils in place while I fiddle about with the others

The slugs just screw into the back of the coils:

So the good news is that now the coils are balanced with a pretty even volume across all four strings. Nice tone, too, through my little electric guitar valve amp (I’m hoping that one of my local bass-playing colleagues will try it through his proper rig once I’ve done the main tweaks)

So next steps:

- Turn down the pre-amp gain on the magnetics to match a standard passive volume.

- if the buzzing is cured, move to the piezo

- if the buzzing isn't cured, pop a low value capacitor into the circuit to filter it out even when the tone is on treble

- then pop a trim pot into the piezo circuit to further attenuate the piezo signal to match the magnetic signal 

Well, that's the plan, anyway

DartmoorHedgehog

Looks like it's going well - good luck with taming the piezo volume later.  I've not used a piezo pickup before and was amazed how hot the output is from the piezo I'm using in my violin build.

Andyjr1515

DartmoorHedgehog said:

Looks like it's going well - good luck with taming the piezo volume later.  I've not used a piezo pickup before and was amazed how hot the output is from the piezo I'm using in my violin build.

Yes - they can be very hot, indeed!

TTony

Having just read the last 4 pages of this thread, I'm lost for words.

incredible?
amazing?
stupendous?
inspiring?

wow.

Thanks for sharing Andy.

Andyjr1515

TTony said:

Having just read the last 4 pages of this thread, I'm lost for words.

incredible?
amazing?
stupendous?
inspiring?

wow.

Thanks for sharing Andy.

Well, it is a bit of an opus magnus again, I'm afraid

Thanks for the feedback

Andyjr1515

ETA is the end of this week

It's been a long build, this one...

Just finished balancing the magnetic coils and also the magnetics versus the louder piezo.  The John East mixer has an attenuation shunt you can remove but it needed more.  I added a trim pot resistor to the piezo circuit (the blue one here):

After the 'road test' and tweaks of the various gain pots on a friend's proper bass rig tomorrow, I have still to do:

• the final tidying up of the finish - generally where the finish is a touch too thick on the ebony and so makes it lighter
• I'm on with the remake of the pickups cover - and the new one DOES line up
• I need to adjust the nut a touch
• re-polishing the frets where they've got a bit of finish on them
• sanding a small area of the main cover flush
• putting some brass ferules that Mick (the customer) wants at the bridge end. 

And then it's done!

Oh, by the way, this is how the controls area came out in the end:


This is the front view, now everything is working and in place - even the strap locks:


Talking of strap locks, the sit on the strap is as good as you could possibly wish, and over the knee it balances very well too! PHEW - there's a bit of luck!

Legionreturns

I've loved following this build. Will you be putting some sounds up once you're done? Bloody fantastic btw!