build thread 5-String Aria Pro II SB1000/R150-ish bass

[Prostheta]

Now that's a hell of a title.

I think that's it's fairly well-known that I've somewhat of a fascination with Japanese instruments made from 1976-1986 in the Matsumoku factory under the Aria Pro II banner. For the last ten years or so I've been making replacement preamp modules for their classic SB-1000 basses, and doing a few complete restorations for clients.

The SB-1000 was an active single-pickup four-string bass made in two versions '76-'80 and '80-'86. It was made beyond this time in various forms, and is still made by the current incarnation of Aria Pro II, however the classic period for this bass was when they were made at Matsumoku. The 80s version introduced a slight geometry change, new headstock shape, finishes, switchable passive mode but fundamentally it was the same instrument.

 

70s SB-1000 (thumb rest not original)

80s SB-1000

 

During the 80s, APII also made a dual pickup flagship version of the SB-1000 called the SB-R150 with better appointments and flashier wood laminations.

 

Something I'd imagined a while back was to take the basis of the SB-1000, add in appointments from the SB-R150 and move it up into 5-string territory. In recent years, Aria Pro II have also made a 5-string SB-1000 however I have zero hands-on experience of those.

 

[Prostheta]

This is in fact a project started a few years back, however changes in employment and moving from city to city puts lots of things onto the back burner, in boxes and generally off the active list of to-dos. This is a strange time for me still, as the insani-demic is likely to leave me unemployed as the cruise ship industry is decimated. Documenting is always useful though, and I think most of the things have been done that need doing, and it might be achievable to finish without access to a shop....

This is where the design work stands.

 

Templates were laser cut a while back (thanks to Carlos at GW Guitars And Woods), the neck and wing blanks laminated and sat waiting.

A little about the specifics. The SB basses were generally neck-through, with the neck consisting of several lamination of Walnut and Maple. The wings on the SB-1000 were listed in catalogues as "Canadian Ash". The smell of the wood is flowery and somewhat incense-like (glorious, really) but not unlike the majority of Ash one encounters. The SB-R150 on the other hand had wings that were a laminated Chestnut core with Zebrano facings. The body of the SB is tapered  from around 40mm at the upper horn tip to 50mm at the rear behind the control cavity. This subtle weighting alters the stance of the bass nicely.

The neck lamination is a series of parallel 6mm Walnut stringers with Maple laminates bringing the overall blank size up to 74,5mm in width. Modification of this for a five-string for my required specifications results in a width of 101mm. The SB-1000 possessed a very strange neck taper and string spacing. That is, virtually no taper and a narrow 16mm spacing at the bridge! Whilst they certainly feel weird to the uninitiated, the consistency in profile from low registers to the upper ones is surprisingly fluid and useful. The narrow spacing makes fingerstyle pocket work a breeze with smaller motions required for playing and muting. The SB-R150 on the other hand had a more common string spacing and neck taper.

The pickups in both the SB-1000 and SB-R150 were large dual magnet ceramic humbuckers, with each bobbin having a two slug per string pattern similar to a Jazz bass bobbin. In the (active-only) 70s basses, this was fed straight into an 18v balanced preamp circuit with a (defeatable) active low pass filter built around a six-position rotary switch. The usual volume and passive tone controls provided a strong noise-free signal. The 80s basses introduced a backup passive mode, however not without additional complexity to the circuit.

70s SB-1000 internals

 

80s SB-1000 internals

 

....in essence, the 80s circuit obviated the varitone bypass switch in favour of one switch that directs the pickup signal and earthing either to the active floating balanced circuit, or a ground-referenced passive circuit. Believe me, these are an absolute pain in the arse to restore.

[Prostheta]

Veijo Rautia over at rautiaguitars.net spun me a custom pickup and vacuum formed a 5-string version of the MB-I/MB-1E pickup.

[Prostheta]

The specification I'll be using is more or less the same as that of the SB-R150. The fingerboard is Ebony, whereas the SB-1000 used Jacaranda in the 70s variant and Rosewood for the 80s. Jacaranda doesn't tell us much though as it's a name that covers timber from woods of dozens of different genera including Dalbergia. On that basis it is possible that both 70s and 80s used the same woods for the fingerboards, but hey. We're using an Ebony here.

I decided to move up to a 35" scale from the 860mm (33,86") original. As always, a zero fret is in play. I think that I've got some 57110 Evo fretwire somewhere.

The SB-1000 inlays were simple dot inlays whereas the SB-R150 used glitzy split ovals. I'm going to break here and use the very-Aria cats-eye inlays. These were found on other models in the SB and RSB range, such as the passive SB-R60 which provided the basis of the SB Black n' Gold, associated with Cliff Burton. Cliff never really played an SB-1000; from what I am aware, he was recommended and given one by Billy Gould, however Cliff preferred the passive sound and geometry of the more standard SBs. There's a lot of history here, so I won't go into that....mostly because I'm not the expert and also because it doesn't apply

An interesting thing to note is that Aria made the decision to drop the multiple laminations under paint for other SB basses at some point. This unfortunate example of a stripped SB BnG showing both the cat eye inlays and the simpler lamination.

 

I have laser-cut templates at 1:3 scale for the pantograph, so both the fingerboard and inlays will be cut that way. I have yet to get some gold MOP in for this purpose, but that's one of my next goals after slotting the board.

Tuners are Gotoh GB707 20:1 ratio with fat posts. The bridge will be a Hipshot A-style brass bridge in 18mm spacing, which I need to snag when I can. Brass bridges are less common this side of the pond, so I might have to hit up one of our US comrades for that.

The truss rod is a Gotoh aluminium extrusion bass rod. These are nice and simple to install and a nice snug fit unlike common cheaper welded types.

[Prostheta]

This work is a little bit after the fact, however I'd been chipping away at the project when the time and mental availability presented itself....

Tapering the wings was done in a series of processes. One length of white Oak was cut into the appropriate width and thickness, then cut into two shorter lengths, one rotated 180° as a slip match. These were then sent through a thickness sander on a tapering sled. This is simply a length of plywood the same length as the longest piece. A "stop" is glued and screwed to the back end to prevent the (squared) blank from moving backward and to provide square reference. Finally, a shim the thickness of the full taper difference and width of the rear stop is added to the leading edge. The sled rides on the corners of the stop and shim that are spaced apart a length equal to the taper needed in the workpiece. Sandpaper stuck to the surface of the sled provides additional grip. The numbers as written on the sled are always up to the next mm. That way, I can check the progress each pass and always be slightly over before dialling in the final passes manually.

[Prostheta]

I genuinely can't remember, however I recall that I used slightly thicker Zebrano laminates for the top than the back. Maybe something like 6mm and 8mm. Because of the tapering, I made a mental note to make the back the standard datum. That keeps things equal across both pieces and ensures (let's make up a new word for the day) squarity.

Talking of Zebrano, I came across some particularly (wife's description) "fucky" Zebrano at a guy's shop a few years back and kept it by for a project such as this. Unlike the usual ribbon stripe sort of patterning in Zebrano, this has a strange flaked wing structure due to some defect or other issue with the tree. The raw lumber had a light inclusion flaw, but is otherwise stable and good. It's a unique look though. I actually find Zebrano a little boring very easily, so this adds interest to what might otherwise be so-so.

[Prostheta]

Slotting for the truss rod was done whilst the blank was still square, allowing me to use an edge guide rather than sticking a slotting template for guide bushings. The edge guide's adjustment means I can use an 8mm cutter and wide the slot for the body of the rod. The lines with a chevron indicate the stop position for the rod. I could have used a physical stop such as a scrap of plywood clamped in place, but this works fine. The chevron allows you to see where you're sneaking up on a stop line as it "reveals", especially useful at the headstock end.

[Prostheta]

Speaking of guide bushings, the template for the pickup route was made using these as the basis. The pickup rout requires a specific corner radius, which may not necessarily correspond to a bearing-guided cutter size. In this instance it is 10mm, my closest being 11mm. I could have gone with that, however I'd be using a template made in the same way anyway, so why compromise?

Okay, so the way of calculating template sizes for guide bushes might not be obvious to most. It hurt my head for a while until it clicked, but now I can't imagine not being able to use them. The size of the pickup rout needs to be 111mm x 37,8mm (measured with calipers from the pickup itself). Take these measurements and add the difference between the cutter and bushing diameters. That is, the difference is (15,9mm - 10mm) = 5,9mm. (111 + 5,9) x (37,8 + 5,9) or 116,9mm x 43,7mm. Easy. The other way to look at it is that the outer surface of the bushing prevents the cutter reaching the template by about 2,95mm all around.

[Prostheta]

Glueing the stringers. These were sawn and planed to rough size, then placed to tack up with Titebond Original. I was considering hide glue for this, however it's not the best glue in fracture planes. One hit with a chisel along a hide glue seam can easily crack it, however I'm sure that is unlikely to take off an entire wing. Ultimately, this isn't a joint that should ever need to be repaired or opened so PVAc is a good choice here.

It's 22° outside and cool indoors. I'd estimate a good 10-15 minutes of time for Titebond to tack up enough that clamping pressure be introduced without significant hydraulic slippage. This is a cosmetic joint, so I want the highest clamping pressure I can apply to minimise the glue line. This piece is 325mm x (est. avg. 45mm) or about 22in². I'd like to aim for 200PSI (low end of ideal) which requires 4400lbs, or four big F-clamps.

[Prostheta]

Like that.

 

I retained the offcuts from the wings for this purpose. The slop in between the shapes from bandsawing and shaping is cushioned by a strip of leather. This also protects the workpiece. Since this was a tacked joint, less squeezeout is visible. I don't put excess glue into my joints, only what is needed with both surfaces physically wetted. Anything more than this is a liability from both slipping under pressure and squeezeout contamination, plus it's just wasteful and doesn't improve the joint. This is to a point though....any less than this and you're risking a dry joint. I've gotten this almost down to an artform now, especially after years of using glue rollers and calculating adhesive by weight and area!

[Prostheta]

In the last shot, you can also see the control layout. I've gone for a simpler array of four controls. The varitone is one of the defining features of the active SB sound, plus a volume and passive tone. A switch exists so that I can either add in a parallel/series configuration to the humbucker, or a coil cut. I always have the option of putting in two switches if I like both mode options. I need to see how I like the sound of the pickup in a 5-string configuration first....

The varitone is going to be built around a premium NSF GX rotary switch:

https://uk.rs-online.com/web/p/rotary-switches/0321379

The positions are marked on the body using 2mm ABS rod normally used for side dots. I think brass wouldn't contrast well enough against Zebrano, even though we're going for totally @RestorationAD-unfriendly gold hardware.

The dots were laid out using the 30° position specification of the switch, laid out in CAD, printed and then punched through using a sharp pointed carbide scribe/awl. Nothing more than a bit of Titebond is needed to mount these. Once dry, they're filed flat and smooth.

[Prostheta]

Whilst the second wing is being glued to its stringer....

The electronics are strange. At least, in the way that they're overly complex for the purpose but still very effective. Firstly, the supply is 18v over two 9v batteries, configured to -9v, 0v and +9v. This makes sense for a number of reasons, but requires a few boxes be ticked. The first is the switching. The input jack on single-ended supplies can operate by cutting the 0v line through use of the ring and sleeve of a stereo jack socket. This doesn't work here, as both batteries must be switched at the same time "at both ends". That is, a DPDT switched jack socket. Nobody really makes these, with the original Kobiconns being the item needed. I have a ton of these (people want them for restorations and repairs) so that's not an issue.

Rather than having the jack socket located on the front of the bass as per the SB-1000, I want to locate it on the side like the SB-R150. Not too difficult, however this means acquiring an Electrosocket Tele jack cup in gold with the same threading as the Kobiconn jack. I have to admit that I'm not au fait with this threading, so I might end up ordering and seeing what fits. The work will require a 3-4mm recess for the lip of the electrosocket, then either a full-depth (25mm? 28mm?) channel to the cavity, or a cavity enough for the jack and an extension through to the cavity. Thankfully there isn't a lot of distance to cover here, however the measurement still hasn't been taken. I'm 80% certain we're cool.

SB-1000 jack location

 

SB-R150 jack location

[ScottR]

4 hours ago, Prostheta said:

I genuinely can't remember, however I recall that I used slightly thicker Zebrano laminates for the top than the back. Maybe something like 6mm and 8mm. Because of the tapering, I made a mental note to make the back the standard datum. That keeps things equal across both pieces and ensures (let's make up a new word for the day) squarity.

Talking of Zebrano, I came across some particularly (wife's description) "fucky" Zebrano at a guy's shop a few years back and kept it by for a project such as this. Unlike the usual ribbon stripe sort of patterning in Zebrano, this has a strange flaked wing structure due to some defect or other issue with the tree. The raw lumber had a light inclusion flaw, but is otherwise stable and good. It's a unique look though. I actually find Zebrano a little boring very easily, so this adds interest to what might otherwise be so-so.

that looks like something you would expect to get from rotary cut veneer.

SR

[Prostheta]

I know, it's very strange. The orientation of the growth rings wasn't even weird with relation to the face. This deformity in the wood seems to be in one area, which - as you can see from the waste clamping caul material - was normal elsewhere. With a spritz of DNA, this has a light popcorn-y clouding about half an inch in diameter each. Very cool. I'd like to do more finish tests so I know what would look best. Tru-Oil doesn't darken the darkest stripes enough. DNA makes it look far deeper and adds higher contrast. It might simply be that I have to thin the oil down with naphthalene to get higher surface penetration on the flood coats, however I doubt it. The surface does need to be well wetted by any eventual finish.

[Prostheta]

Oh bums. It looks like I never re-adjusted the scale to 35" after all. Not to worry. 860mm is perfectly adequate! So, I prefer to use a simple Excel calculation for fret positioning:

 

Since I'm working with a Metric scale length, I entered "=860/25.4" in the scale length box resulting in:

 

I'm going to break out a steel rule and pencil. Bear with me.

[Bizman62]

These insider abbreviations drive me crazy! "DNA" - since it didn't add a reddish hue I thought about saliva until I figured out you must have meant DeNaturated Alcohol.

[Prostheta]

Not the Bill Clinton-y type of DNA either.

[JayT]

20 minutes ago, Bizman62 said:

These insider abbreviations drive me crazy! "DNA" - since it didn't add a reddish hue I thought about saliva until I figured out you must have meant DeNaturated Alcohol.

Same here, only not only abbreviations ... regional vernacular & terminology can often leave me scratching my head. What does @Prostheta mean by "appointments"?

[Prostheta]

This method is pretty lo-fi, however given a good approach it does an excellent job. Firstly, I make sure my values are accurate to two decimal places in mm on paper. We can't expect to translate that to the workpiece, however it's useful information when judging whether to be left or right or any one point. Since I use zero frets, I establish that position first and clamp my steel rule against the centre line with the end dividing the zero point line. Mechanical pencils are great for this job.

 

Essentially, the idea is to round up your number to one decimal place and use your judgement to either divide a half mm or whole mm mark accordingly. The marks I leave are intended to be cut dead centre, so if one is slightly too left, I widen it right. The centre mark is then scribed with either a craft scalpel, hobby knife or in this case a machinist's carbide scribe. The pencil mark is the rough guide to bring one's eye towards the mark, and the fine scratch from the blade/scribe increases the accuracy within that mark. So essentially we're starting out with about a quarter of a mm accuracy range, then bringing it in slightly with the scribe. Marks done in this manner (as long as you can align the blade over them) end up within about a quarter of a mm accuracy which is fine. It can be done more accurately, however the returns tend to be less than one might expect. For guitars, this might be more important on the very uppermost registers, on a bass....far less so. I'd take the taste challenge on this method versus slotting box templates any day

 

Mark for 377,34mm. As long as you're marking without introducing parallax errors (even the height of your steel ruler is important) this is fine. I'll scribe this one dead centre as I'm happy with the location.

 

Like that. Chalk will reveal the scratches during slotting.

 

The human eye is very good at dividing distances by two, discerning whether a point lays left or right of centre. A 0,5mm lead in a pencil can be further subdivided by eye. It just takes good light and patience. This took me less than five minutes.

[Prostheta]

25 minutes ago, JayT said:

Same here, only not only abbreviations ... regional vernacular & terminology can often leave me scratching my head. What does @Prostheta mean by "appointments"?

 

It is pretty archaic. If I recall, it's an old military term for uniform accessories and details that carried over to mean general decorative details and additions. Something along those lines. I like it because there it's one of those words that has no meaningful singular form, like scissors. That said, the verb form is singular even if it describes an activity plural by nature?

[Gogzs]

This is exactly the method I found on this forum and used on my build, works like a charm. You don't accumulate errors by using calipers from fret to fret. Great tutorial with nice pictures, I'm putting this one into my favourites so if someone asks me how I did the frets, I can link them this

[Prostheta]

Sweet. Always good to hear that my threads put something useful out into the world

[Prostheta]

Last job of the day was me testing the guide bushing pickup cavity template. The template was affixed using 3M double-sided tape. All dust was wiped off and the parts pressed firmly in place. These two steps are the reason so many people report failure with DST. I never use the superglue and masking tape "trick" as there are no guarantees. DST requires clean and well-fitting parts same as that "trick", but works every time with no risk because that's how it's engineered. Needless to say, anything described as a "hack" is generally pushed by one. That's not how the pro's roll, homes. *throws shape* 

 

Bazazz!

 

Hold up - has anybody seen my 10mm diameter cutter? This one appear to be 8mm! Bugger. Oh well, recut with the 11mm diameter cutter since, why not.

 

Yeah, that can be better. It'll work, however the tighter the actual rout will be, the better it will be. The pickup body has a draft angle, so when set into the body at the correct depth that gap will only be larger. Looks like I need to snag myself a 10mm cutter then.

[Prostheta]

Okay, more guide bushing stuff. Outside of using them to do things like make offset templates for finer control over cut depth and corner radii in pickup cavities, they're also good for creeping up on final dimensions when you don't have a bandsaw on tap.

This is an 8mm diameter cutter mounted in something like a 1/2" OD bushing. I cut my bushings shorter for use with 5mm acrylic templates.

 

In my opinion, this is the only reasonable time to be using acrylic templates for your actual routing. Even first contacting a spinning bearing to the template can cause friction melting. Separating out the guiding element (the bushing) from the cutter allows for any degree of cut depth and stepping. This should help protect the tips of the headstock wings, however I'm making sure that if they do decide to fuck off on me, I know where the bits will fly off to....

[Prostheta]

It's slow progress doing things this way, but very safe. My only complaint is that I would rather be using an offset router base for this kind of work. Plunge bases require awareness of how well the router is planted on small surfaces such as these, hence why I worked one side at a time, re-orienting my handling of the tool each time for best balance and control. An offset base increases this by a magnitude, however I haven't yet made one that is compatible with my bushing set. Certainly something to make though.

 

Things to take away from the photos: The long edge shows a step on the bottom, which is down to how I was holding the tool. The guide bushing wasn't centred using a spindle cone, so any slight offset can be seen through successive cuts if they're done with the tool oriented differently. Whilst not a problem for this type of operation, it can introduce both placement and sizing errors for critical cuts. In all likelihood, my router isn't engineered for this sort of accuracy, being a palm router or trimmer than a full-on router.

 

Halfway through the cutting, I sawed off the excess endgrain and split off the outer waste walls with a chisel. These are the marks you can see on the top surface, which appear like chipping. That was the saw establishing itself  We still have a 2,5mm thick facing to be fitted onto the headstock yet, which I'm starting to think might be good being thinned out even more. If I can figure out how to do that with what I have....routing is likely the only way.