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.
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!
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.
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.
My circuit boards finally came in from the fabricators a few days ago. They’d been delayed and sent to the wrong address. Also, I’ve since made some slight changes to the circuit, but I was able to easily hack the board with a jumper wire to make it work.
Last night, I populated the board and wired up the pots, the switch and the jack. At this point it looks kind of like a mess of wires; this is my first circuit board design and I wasn’t too sure what was going on while I was doing it. Really all that matters is that I can fit the electronics into the cavity with no problems, and it does fit no prob. The next iteration will be much better, and for now, with 3 circuit boards running me about $7, I’m not sweating the costs or anything.
Next, I’m going to install a pickup I built a while back. I have some ceramic magnets on order from the fabricator, but they won’t ship until mid-October. Coupled with the fact that my original design used 16 small cylindrical magnets instead of 2 larger bar magnets, I’m going to have to make a few changes in my manufacturing process. In the end, I’m faced with a choice between installing the older neodymium magnet design today or waiting until mid-November for the newer ceramic design. The neodymium pickup sounds fine, but I prefer the character of the ceramic magnet design. I can just swap out the pickup when I finish with the improved design.
The last few I’ve been tinkering around with a preamp design to go into the new bass. Here are some reflections on my little preamp project…
I set up my breadboard in an old stomp box enclosure I had laying around and populated the board with a opamp booster circuit I pulled off of Jack Orman’s site. It’s feeding a modded Big Muff Pi tone stack I took from the Kreuzer preamp.
I was really hoping that I would lose interest in this – I don’t know jack about circuits and electronics and I really have no business trying to design an onboard preamp. The only problem is, so far it sounds really good! I actually like it more than I like the MM pre I’ve been using. I gotta bring the gain down a little bit, pick the right sized input cap and get the LPF part of the tone stack to attenuate more highs, but that’s it, really. I should probably stick a buffer in there somewhere as well.
After rocking out with the opamp version of the boost section for a few days, I built a JFET version. Here’s my thoughts. Both preamps are really simple boosts directly feeding a BigMuff tone stack.
The opamp version sounded great. It had a really muscular sound that knocked my socks off. On top of that, it really opened up the highs and upper mids that really brought the bass to life in a really cool way. Not harsh, but bright and really present sounding. Overall, it gave my little pickup a really forceful vibe that would have no problem supporting a band and a rhythm section. The downside is that the gain is really intense – there’s a really fine line between driving the amp to the point of clipping and driving it to the point of sounding bumpin’. That’s just a matter of fine tuning one resistor.
The JFET version also sounds great, but it’s a different beast altogether. The JFET has a fatter and warmer sound. It’s still bright, but the highs are more pleasantly rounded and has less “bite” than the opamp version. The JFET is not a tight in the low end, but that’s not a bad thing. It also doesn’t clip like the opamp version, but it drives in it’s own way. I hate using the word “vintage” but for the sake of coming up with contrasting descriptions, I’ll say it’s kind of akin to “vintage” vs “modern”.
I may be imagining these differences, so I will test the JFET version for a few days and switch back to the opamp.
Since both of these boosts consist of maybe 5-6 parts tops, I am putting forth the idea of installing a switch between the two and installing both in the bass. It would be a really simple wiring job – it would literally be choosing between one short signal path and another. I don’t know if that’s a crazy idea or not.
The EQ section is really cool and functional. It’s kind of like a “tilt” EQ that really places the emphasis on either the lows or the highs, and it’s easy to just twist in a sound with just the turn of one knob. That, combined with ability to really fine tune the amount of mids coming out of the preamp via use of the Duncan Tone Stack Calculator it would also be conceivable to put a little “mid-switch” that either swapped out caps or placed an extra cap in parallel. Because of the placement, the pickup puts out a ton of mids, I could back the off mids drastically and have a lot tonal options coming out of one pickup.
I’m also contemplating building in a buffer circuit, although I don’t know enough to know if it’s even necessary. According to the notes on the AMZ site, there’s an implication that R1 sets the impedance at 1M – which, from what I kind of understand, is the job that the buffer is supposed to do. So, does it make sense to set the impedance twice?