I built up a 3-band preamp for the Sirena Modelo Uno bass. I voiced it to work specifically for the Funktronic Bass Sidewinder pickup placed in the bridge position. It bumps a little low end up around 35Hz. A friend recommended swapping the TL072 out with an LT1352 and it sounds great. I’ve been gigging with this rig for a while now and it definitely does the job.
I got a little snippet of the some of my work out in the wild. It’s an iPhone vid the li’l Lady shot at a House Arrest gig in Santa Barbara the other night. She missed the intro, but it sounds OK. Anyway, I’m playing the orange Uno I built earlier this year and it’s loaded with the Funktronic Sidewinder and my 3-band preamp. The backline was a Fender Bassman 1200 Pro and an SVT cab with an indeterminate number of blown speakers. The Fender Bassman controls were confusing at best, but I think I managed to get a fairly representative tone out of it. I’d bust out the big speakers; the bass is pretty sub-sonic. Hope you enjoy.
Research and development – my desk has been a real mess! I’m finalizing my bass sidewinder revamp. I built 6 new versions along with a whole new preamp design. I should have the new version of the pickup singled out and built early this week. I got the new circuit boards in a few days ago.
Stay tuned for more updates! I can’t wait to clean off my desk!
Today I’d like to introduce the Sirena Modelo Uno bass guitar.
When I drew the original sketches for this bass, my intent was to design an instrument that combined the unpretentious elegance and sound of a funky Japanese or or Italian department store bass with the playability of a Fender and the advantages of modern electronics and construction. After gigging with it a, I feel that for the most part, I have unwittingly succeeded at accomplishing what I’d set out to do.
The heart of the Sirena Modelo Uno is the uniquely-constructed Funktronic Bass Sidewinder pickup. Using a modular design, the two epoxy-encased coils are sandwiched between three stainless steel blade poles. The result is a stylish, but balanced-sounding pickup that drives a 18v Tillman 2-band JFET preamp. While the tone is deep and bassy like a neck-loaded bass, it has the snap and clarity and the response of an instrument that runs off of a bridge pickup.
The body is constructed with a chambered mahogany core and maple cap, while the bolt-on neck constructed of maple and Indian rosewood.
Body: Chambered Mahogany and Maple Top
Neck: Hard Maple
Fretboard: Indian Rosewood
Pickup: Funktronic Bass Sidewinder
Preamp: 18v / 2-band
Bridge: Gotoh Vintage
OK I’m just going to post a weekly update – no pix today.
I’ve been working on the pickup and preamp. Using my new cardboard bobbins I wound a couple of coils with 44awg wire and increased the wind count. I after casting them I mocked up a pickup with the new ceramic 8 cores. From there, I rebuilt my preamp using a James tone stack instead of the Big Muff/Tilt tone stack.
1) On one of the cast bobbins, I somehow didn’t add enough hardener to the epoxy resin. I think that’s a pitfall that comes with mixing tiny 10ml quantities – if you’re off by just a tiny bit, that turns out to be a lot. Anyway, the piece didn’t cure and came out kind of rubbery. It’s good enough for testing, but not for a finished pickup. In the process of experimenting with various ways to build and cast my modular coils, I used all the pre-cut cardboard flatwork (I only ordered 14 pc to start). I ordered some more – it should be on its way soon.
2) I changed the preamp to a James/Baxandall tone stack because while the one-knob preamp was kinda cute, there just wasn’t any real control over the tone. Once you added any treble, you started to cut bass and vice-versa. With the James/Baxandall I’m able to fine tune the amount of highs and lows. I was even able to fine-tune the circuit itself by bumping 400Hz up by about 2dB. I also upped it to 18v much more headroom.
I know I’ve said this before, but this new pickup and preamp combo is a huge improvement. Keep in mind, pickup design is kind of a long process of experimentation that isn’t all that straightforward. In any case, the C8/44awg sidewinder rendered a much more controlled-sounding pickup. No more crazy high mids from the neos and with the ceramics wrapped in all that stainless steel, the biting highs are in the right place – nicely placed on top of a big cushion of clear lows and warm mids. With the neo versions, I felt like I was always struggling to contain this beastly pickup with these upper mids that just didn’t want to behave. Now I can really dig in to the strings without having to worry about it topping out.
I think it’s possible to design a really good-sounding neodymium pickup. I don’t know that the sidewinder design is the best application. I think maybe a more conventional humbucker with a steel core and the magnets placed on the bottom of the pickup might be a better approach with the neos. That keep the super strong neos away from the strings would make the magnets have to permeate all the way through the steel core. I dunno, just theorizing.
Mwa-ha-ha, my plan worked! The slot came out A-OK. The polypropylene plug tapped out pretty easily with a mallet and screwdriver.
After I clean it up, I should be able to pop the magnet in.
My only concern is that when I’m casting, the bobbins are held in place with friction and pressure against the sides of the mold. If for some reason, the bobbin slid down just a teeny bit, it would ruin the whole piece. When I was using cylindrical magnets, I used the holes in my master to create these little nubs in the sides of the mold. The nubs fit into the holes in the bobbin and held it in place. Since I haven’t cut the slot in my master, I don’t have that option here. I’ll just have to make extra sure the bobbin is in place before I pour the epoxy.
After all the different pickup-making techniques I’ve experimented with along this particular journey, I’m back to making cardboard bobbins.
Why, you ask? Well, first of all the bobbin flanges need to be very thin. Like .02”. I was using Garolite and FR4 before, but I was using cylindrical pole pieces; drilling 1/4” holes into the flatwork is relatively easy. The ceramics are bar magnets – cutting nice slots into the Garolite or FR4 by hand is no fun. No fun at all! I figured I’d get those pieces laser-cut ‘cuz it’s pretty cheap. However, there was a monkey wrench in my plan! Most of the stiffer industrial plastics they have available at the hobby-grade laser cutting places are things like Delrin or polypropylene and they are resistant to glues and such. Other plastics they had aren’t chemical resistant. I called around, and none of them seem to want to cut FR4 and stuff like that.
So, cardboard. And that’s fine. It’s easy to glue and the bobbins are really easy to make. I just cut a 3/16” strip of stiff architectural paper, wrap it around a magnet that I use as a form, and tack it on to the pre-cut bobbin. Plus, the pre-cut cardboard flatwork is cheap – like 20¢ each.
The only downside is that it’s not very strong and the bobbins are prone to flaring. I may have to do a slightly looser wind with 44awg instead of 43 – which I think will be OK. I don’t think it’ll change the sound enough so that it will be a deal-breaker. I dunno – I’ll experiment with that.
Bruce showed me these things he’d made to sandwich his bobbins onto his winder. I’ll have to make something similar to keep the bobbins from flaring. I’ll coat the sandwich thingies with wax and leave the wound bobbins in there while I apply the Penetrating Epoxy Sealer. Once that hardens for a day or two, I can take them out. Theoretically, the copper wire and cardboard bobbins will be just one hard happy lump of epoxy-coated goodness.
After that, I gotta make a new master for casting. The old one, pictured below was made for cylindrical magnets. I need to cut one with a slot. Using the limited tools I have at my disposal will make this an interesting project to say the least!
Yay! My custom fabricated ceramic 8 magnets came in! Just waiting for some laser-cut flatwork to come in and I’ll be making pickups. #funktronicpickups
Instagram filter used: Clarendon
I installed the electronics last night and gave it a whirl. It sounds pretty good, but I’m still waiting for the ceramic magnets to come in before I call it a wrap.
The li’l Lady sent me this pic this morning. She likes to put my guitars on this shelf for some reason.
I still have some more work to do on it. I have a rogue fret up by the 12th fret, and I need to get some new strings and do a proper set up. I might bring it to rehearsal tonight just for kicks.
Overall, I’d say it was a success. Most of the fellas didn’t know at first that I had actually made the whole thing myself and had assumed it was a new bass. I got compliments on the colors, while our drummer said he loved the Jetsons look.
It plays and handles really nicely and for a semi-hollow it feels really stable and solid. It’s about the right weight and is well balanced. I still have to address the fret noise, but it wasn’t so bad that I couldn’t play around it. I’ll take a look at that over the weekend. It may be as simple as adding some more relief to the neck.
Now, granted are these two things: the bass amp at rehearsal is this old 100w Yamaha 115 combo that basically sounds like crumpled paper and the neodymium pickup is a placeholder. That being said, I got a lot of compliments on the tone. The neodymium version of this pickup sounds kind of plain and nondescript to me, but where it excels is in playing dynamics. It really responds really to touch, and I really liked that I didn’t have to really pull on the strings to get a lot of tone out of it. However, the amp wasn’t really able to render those dynamics as well as my Markbass.
The one-knob preamp is a cool feature. When it’s turned all the way to “treble” the bass is cut way down and the highs are boosted. Turned to bass, the treble is cut and the bass is boosted. I had it somewhere in the middle, give or take a few clicks. While it’s not a very sophisticated preamp, it gives you a really quick way to dial in your tone. The pickup and electronics are dead silent when you are not playing.
We had a great rehearsal, and without getting into specifics, there a few pretty good jokes passed around about me being the white guy from Oakland. Our drummer went as far as saying he wants to commission one of my basses for his studio, but he was probably just being nice.
I went home that night and A/B’d it with the ceramic pickup in the test bass. The step boy was there and he plays guitar in a local band as well. We both agreed that while the neodymium version sounds good, the ceramic version is better. The ceramics bring a faster low end response and the ceramic version is generally fatter, warmer and punchier sounding. The neo is much brighter without sounding harsh, but that’s not to say the ceramic is not bright. Using a set of well-broken flatwounds, the ceramic pickup is definitely bright sounding. Brightness and bassiness aside, what really sets it apart is its well-defined upper-midrange. I think that while the neodymium version puts out wider more even tone, that is ultimately its undoing – it has no emphasis on anything in particular.
The good news is, I think my ceramic magnets will be here soon. I just got a shipping invoice from Magnetic Hold this morning.