passive mods inspired by G&L circuits

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passive mods inspired by G&L circuits

Postby BassOn » Fri Jan 20, 2017 3:01 pm

I wanted to post a word of thanks to Ken and this site/forum for helping me revive a bass that wasn't quite my thing anymore. I'm very fond of my SBMM SUB Ray4 in terms of looks and feel, but I've grown less fond of the tone over time. (I'm more into warm, classic tones.)

The Kiloton recently got me thinking about the possibility of a passive bass with a pickup in the Stingray sweet spot. I had tried this before, but I found the lowest notes a bit lacking without a preamp. But the Kiloton got me thinking... So after quite a bit of research (lots of it on this site), I cooked up a wiring scheme that draws inspiration from the the Kiloton and the L1000 circuits. I have to say, it's really cool how G&L advanced the passive tone possibilities beyond ye olde standard Volume-Tone circuit.

Like the Kiloton, I wired up the standard 250K pot Volume-Tone harness, and since I had an extra switch on my control plate from a previous mod, I made that into a capacitor switch: .022 and .047 uF. So far so good, but since my pickup is an alnico MM-style humbucker, and not a mighty MFD, I needed to resolve the low end issue. Enter the L1000. I didn't see a point to a bass cut control with only a bridge pickup, but I liked the idea of the .001 uF loading capacitor to drop the resonant frequency of the pickup--making it a bit less bright/more bassy. (It's connected between the pickup and the volume pot.) I was also very curious about the OMG setting.

I first experimented with series, parallel, and single coil wiring (like the Kiloton), but to my ear, series wiring offers the best sound for a passive MM pickup; parallel and single coil have a big volume drop from series, and the tone isn't as rich (running passive). So my three-way toggle differs from the Kiloton and the L1000--it's three different variations on series wiring: normal series wiring (no OMG capacitor) and two OMG settings (north coil or south coil with a .1 uF capacitor). All three settings sound really good (they're more like variations on a theme than totally distinct sounds, but the harmonic content does shift between settings, so they're not redundant, either).

I'm enjoying the tight, punchy, growly, burpy-but-bassy sound. There are plenty of lows and mids, and the passive tone control allows me to roll off the high end more broadly and warm up the sound more than the stock preamp did. (And it's fun having the smaller and larger tone caps--they both roll of the high end, but they affect the mids differently.) All in all, a great success, and a nice 'refresh' for a bass I wanted to like but didn't quite. In fact, it's now the top pick for one of my projects!
Last edited by BassOn on Wed Feb 01, 2017 1:30 pm, edited 1 time in total.
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Re: passive mods inspired by G&L circuits

Postby Ken Baker » Sun Jan 29, 2017 4:02 pm

BassOn wrote:I'm enjoying the tight, punchy, growly, burpy-but-bassy sound. There are plenty of lows and mids, and the passive tone control allows me to roll off the high end more broadly and warm up the sound more than the stock preamp did. (And it's fun having the smaller and larger tone caps--they both roll of the high end, but they affect the mids differently.) All in all, a great success, and a nice 'refresh' for a bass I wanted to like but didn't quite. In fact, it's now the top pick for one of my projects!


Glad you're liking it and I'm happy that we had a hand in modding a modern SUB4.

Congrats!

Ken...
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Re: passive mods inspired by G&L circuits

Postby Eastcoasteddie » Fri Sep 08, 2017 6:17 pm

I did this same exact mod to a Squier Jazz V. I installed an Alnico MM humbucker in the bridge and wired it for Series/South coil/North Coil. I had the same exact concerns as you did wth the sound of Parallel and non-OMG single coils.

Image

The pickup is about 1" closer to the bridge than a Stingray, but still kind of gets into that similar tone realm in a series. It is definitely an interesting combo. Adding the neck pickup adds a lot of low end to the sound as well without taking away from that MM pickup.
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Re: passive mods inspired by G&L circuits

Postby GeorgeB » Sat Sep 09, 2017 1:39 am

This might be of interest wrt passive mods for single pup basses : viewtopic.php?f=9&t=1519
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Re: passive mods inspired by G&L circuits

Postby bigtone23 » Mon Oct 09, 2017 9:35 am

It's fun to repurpose a bass for changing/evolving tone requirements.
I have a 1983 Ibanez RB920, which is much like the Kiloton-a passive bass with volume, tone and a 3 way switch for parallel/single/series modes. The pickup is in the MM sweet spot, but is an Ibanez Super J6, which is a dual Jazz layup. Each coil is spec'd like a Jazz pickup, about 7-8K, which have plenty of punch and output in single and parallel mode and are monsters in series. The Kiloton MFD is also super loud and punchy. As you found out, MM pickups are much lower output and designed to use the preamp to get solid output, especially in single or parallel modes. Ibanez did their homework on this one, the stock tone cap is a .068uF, which is great for getting a darker tone out of that pickup placed in a brighter spot.

I also have a 1984 Ibanez RB630, which was their bread and butter P bass of the time. This one has been through all kinds of mods over the years. The last iteration was an EMG P with the BTS bass/treble system. This was my active/EMG nod to the SB1. Currently, it sports a Peavey T45 electronics package with the addition of the metal P knobs and triangle string tree found on that era of Peavey bass. The T45 is similar to the L1000: a humbucker in the P sweet spot with a passive treble roll off and coil splitting. The difference was instead of a passive bass roll off, it has a coil/inductor LCR circuit that rolls off low mids (as also found in the Gibson Ripper). I considered doing the L1000 electronics, but went with the T45 for two reasons. First was cosmetic: the Peavey pickup, knobs and string tree just look way more funky than G&L's more subdued look. Second was the electronics. I like the PTB controls and intended to install them with the 3-way switch, but the Peavey pickup would have to be taken apart to get it wired appropriately for parallel and OMG mode. Not wanting to perform surgery, I found an appropriate coil and did the Peavey LCR system. The LCR is a low mid roll off, which is more useful (for me) vs bass roll off. I tuned the circuit to center around 400Hz, which takes the bass to a cleaner, active kind of sound to a big, dubby tone with fully rolled out. This mid cut could be a cool mod to do to a L1000 if one finds that they don't use the bass roll off.
July 1983 El Toro. Rosewood, black, alder? body. 10 pounds.
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