Mod an El Toro? Most definitely!

Seeing as how we are fortunate to count Paul Gagon as a member here, it seemed like a good time to give him a home to stretch out in and relax a little. Maybe exercise the grey matter and present a little history of the guitar and bass (amps too!) from his perspective as one of the eminent designers of our time.

Got questions? Great! Good questions might be, "What kind of windings are on the S500 pickup and why?" Or, "What was the thought process behind the MJ-4?" Troubleshooting questions should remain in the regular forums (he reads those too). Finally, please be mindful of how I feel about tech questions via PM or email.

Moderator: Paul Gagon

Mod an El Toro? Most definitely!

Postby Ken Baker » Sun Dec 03, 2017 6:35 pm

This whole thing started off here. Then member bigtone23 comes along with the same idea - taming the El Toro.

If you recall, Paul had only had hands on a Bull once and didn't get to really dig in other than draw out a wiring diagram and schematic.

I was having some work done that would preclude me from playing bass for a few weeks so I took the El Toro to Paul so he could give it a thorough inspection and figure out why it was essentially unplayable in active mode. Turns out that it probably was a pretty experimental beast. All sorts of stuff in there that give it big gain and a huge treble boost. Loading cap at an odd value, 500K treble pot (makes it even brighter) with a non-standard cap, and a preamp that generally screamed treble. Sounded great passive but active was pretty unusable.

So he changed it.

Before I go any further, I am extraordinarily fortunate to count Paul and his lovely wife as friends. He does this stuff because he just loves doing it. We should all be so lucky.

What I ended up with is a prototype preamp and a couple other things changed (like the 500K pot for the 250K it should be). The preamp is really simple and not at all designed for the El Toro pickups. It does add a weensie bit of gain (which is adjustable via a small trimmer on the board), but it just sounds SO CLEAN. Warm & punchy. And dead silent; not even a hint of hiss, even wide open. And it sounds great and is very controllable and responsive with everything dimed. I'm still learning how to EQ this thing at the amp, but it's really straightforward. One thing that has kind of surprised me is that I have less desire to run it through a Sonic Maximizer, but this is still kind of preliminary. I do love me some Sonic Maximizer.

One thing I need to do is learn how it interfaces with the rest of the bass, but I should be able to get that eyeballed eventually. Here's Paul's comment when I asked if it was tailored to the pickups:

Paul Gagon wrote:It’s not specifically tailored to El Toro pickups but the input impedance of the preamp is set to simulate a tube preamp and the current adjustment resistor on pin 8 is much lower than normal to drop the chip noise level and give a better transient response. What you're hearing is just the killer tone of those pickups.


Pics! Got a few for you to gape at, as well as the preamp schematic. Not an overall wiring diagram (yet).

I'm going to do the pics a little differently than I normally do. You'll see a thumbnail pic. Under each one will be links to larger versions of the images: 1024x768 JPG, 3648x2736 JPG, and 3648x2736 TIFF. The TIFFs are there for those of you with a pile of bandwidth and a desire to zoom in tight and still get a clean image. You may have to download the TIFF files, as some browsers can't handle them inline.

They are not in any special order, just different angles.

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And, finally, the preamp schematic. Sorry, no TIFF here.

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And because of the bass' provenance, this is totally reversible. Not that I intend to reverse anything - but I do have the parts safely stashed away.

As per the usual, this post will likely be a work in progress. If you have any questions for either Paul or myself, ask away!

Thanks, Paul!

Ken...
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Re: Mod an El Toro? Most definitely!

Postby Paul Gagon » Mon Dec 04, 2017 8:57 pm

You’re very welcome Ken. I enjoyed working on your El Toro. That baby just sounds so amazing. Sharon and I also count you amongst our greatest friends. Always a pleasure when you swing by and visit. I love this website. It’s got so many helpful and knowledgeable people that are passionate about their basses and are always ready to lend a hand.

Thanks,
Paul
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Re: Mod an El Toro? Most definitely!

Postby bigtone23 » Tue Dec 05, 2017 11:59 am

So cool!
I was waiting to see the results of your EL Toro issue. What a great fix--a custom pre!
July 1983 El Toro. Rosewood, black, alder? body. 10 pounds.
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