Grateful Dead Music Forum

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 #71702  by Rusty the Scoob
 Wed Jan 13, 2010 2:00 pm
I have the pickups chosen for my super-secret EB3 project:

But I don't know much about passive wiring. From the factory I believe this bass was wired just like an SG except with an added "Tone Shaper" which was esentially a rotary switch that added various capacitors to the circuit to behave roughly like a master tone control. A lot of people swap this out for a pickup selector swich like a Les Paul.

There's no way that Phil had the stock wiring, of course. So what do you think he had? It's been suggested that he had buffers near the pickups, similar to Alembic Blasters. There's also at least one extra knob of unknown function, occupying the hole where the output jack was originally. The added output looks like an XLR cable or something like it... Any ideas? Or just ideas of cool ways to wire this up? I'm really partial to pickup blend knobs rather than Volume/Volume setups....

 #71712  by SarnoMusicSolutions
 Wed Jan 13, 2010 4:46 pm
I talked to Ron Wickersham about this because we modded a friends EB3 with the Hammon Dark Star pickup. We never did the active electronics, but I did learn a bit about it from him. The buffers were definitely NOT like the Blaster. The Blaster, technically speaking, really isn't a buffer. It's more of a booster, preamp since it's set up as a gain stage with a high-z output.

A true buffer suggest that it's unity gain and has a low Z output. On Phil's bass, Ron had hooked up each pickup with its own buffer. He used a (now ancient and archaic) RCA transistor device that internally was set up as a "Darlington Pair". This made it a great buffer, with gobs of ability to drive all kinds of cable length and "crap" without suffering tone loss. But those old devices are noisy and unstable compared to more modern parts. If you want a much higher performance transistor to do this identical job, look for the more modern and readily available MPS-A18 transistor. This is a very high gain, low-noise, Darlington pair type transistor. When used as an "emitter follower" buffer, all that gain translates into unity gain with all kinds of current drive ability. Just look up "emitter followers" and it should be cake to accomplish. All you'll need is a couple of cap's, the MPS-A18, and a resistor and 9 volts. That's per pickup.

As far as tone controls and filtering, I can't help you there, but maybe Fred Hammon could.

 #71715  by hogan
 Wed Jan 13, 2010 5:11 pm
Then I would make a power supply box that will feed each pick-up. That's where that big barrel connector you see comes in. You'll need a +/- for each pickup. you could probably gather all the grounds to one rail and you could also run your signal in the same cable. So you'll need 7, 8,9,10 0r 11 pin connector and jack depending on how many p/u. I've seen a couple alembic basses that have this kind of set up. THe guy in my band plays one, i'll take a closer look and report back. Then it would be as simple as isolating the actual bass signal to a 1/4" jack and out to your amp rig.
 #71718  by SarnoMusicSolutions
 Wed Jan 13, 2010 5:47 pm
The two pickup buffers could share the same power supply. Just one clean 9v supply should be fine. Even a 9v battery on board would do it. Plenty of clean headroom for any kind of signal voltage those pickups would make.

 #71722  by waldo041
 Wed Jan 13, 2010 9:15 pm
so, 1 clean 9v power supply for both pickups preamps and each pickup gets it's own tone and volume control with 3 way pickup switch. that means 1-9v, ground, treble pickup, and bass pickup signals down the barrel connector to a 9v power supply and junction box. from the junction box the treble pickup goes to it's own channel or preamp and amplifier and dialed in accordingly, and the same for the bass pickup. so each pickup essentially has it's own rig. an f2b would work perfectly or 2 dual showman heads OR 2 sms classics. iirc, later he goes to each string having it's own buffer, preamp and amp.

oh and i believe it's actually an EB-0?

 #71747  by Rusty the Scoob
 Thu Jan 14, 2010 9:49 am
My wallet is terrified of how Waldo thinks! :lol: I'm in no position financially to give each pickup a rig, and I don't think I'd want to carry them around even if I did! For now it's going to have to share the same amp as my current bass.

I'd also like to stick with commercially-available cables... I was planning to leave it as 1/4" or maybe XLR. A combo jack would be ideal, the best of both worlds. I do have a BlueTube mic preamp that could phantom power it through an XLR, provide some warmth and a little grit, and then send 1/4" to my amp. But of course the phantom power is 48V... not sure how big of a problem that is. I know a lot of guys run the active electronics in their basses at 18V for more headroom just by hooking up two 9V batteries in either series or parallel (I forget which). I've tried it myself with some of my basses and it does sound a little fatter and cleaner. But 48v is a lot more than 18v.

A combo jack like this would be extra sweet: ... etail.aspx The XLR even if not phantom powered, could have DI circuitry. Then I could go straight to either a mixing board or to my mic preamp, and I'd still be able to use a regular 1/4" cord into an amp as well.

Back to the buffers. I did some searching for Emitter Followers and my head is spinning! I see the transistor that you spec'd easily available for .21 cents... can't beat that price! I can solder but I'm no circuit designer... I only vaguely understand what this circuit is meant to accomplish, much less what to do with the resistor or caps. How similar to this buffer is Waldo's tiger-clone buffer?

To answer Waldo's question - An EB3 is identical to an EB0 except with the added bridge pickup. My bass is currently an EB0 but will be an EB3 before I'm done, so I've been calling it that for the sake of brevity. Phil called his an EB1 in an interview for the Grateful Dead Gear book but it clearly wasn't that, those are very different.
 #71750  by Rusty the Scoob
 Thu Jan 14, 2010 10:58 am
A picture is worth 1000 words. This is the wiring diagram that is in my head. Let me know what parts are feasable and where I've completely screwed it up.
Complex Wiring Diagram.jpg
EB3 wiring diagram that's in my head.
Complex Wiring Diagram.jpg (86.95 KiB) Viewed 4347 times

The Noll Mixpot is a pickup blend or pan knob that also uses 9v to correct some sort of problem where the volume drops a little when both pickups are on full. There are also passive blend knobs that I'd consider using if it's better.

I'm not sure if the pickup selector switch will work the way I want. I could use a rotary switch if that's better... it'd be a little more accurate to the look of the original bass.
 #71752  by waldo041
 Thu Jan 14, 2010 11:01 am
the tiger clones are opamp based the emitter follower he suggest is a transistor based circuit.

as for the seperate pickup rigs, that was only inline to what phil was doing with that EB-0. if you were to use batteries onboard, then either a stereo 1/4 inch jack or xlr would be needed to run the pickup lines to a junction box. but again, that would be if your were going to run it like phil did. that said if you are not going to run it like phil, then a single buffer is probably your best bet right off the 3 way. i actually use a homemade blaster in my bass and it works great.

 #71754  by strumminsix
 Thu Jan 14, 2010 11:13 am
Rusty, here is my simple poor-mans idea:

Run each pickup unique (separate vol & tone) going to 2 Sansamps then to a then to a stereo poweramp then to a pair of cabs.

My guess is that you likely have a stereo poweramp and a pair of cabs and a bass sansamp. It would only require some wiring and a jackplate and another sansamp.

A bassist I spoke to years ago said he tried, as he put it, the "Phil thing" with a similar setup but used an F2B and said "it was more trouble than it was worth.

The issue was he was required to balance volumes between the cabs when going from neck to bridge to both.

My suggestion above was just a "feasibility" test.
 #71827  by Rusty the Scoob
 Fri Jan 15, 2010 9:22 am
I didn't realize he had each pickup going to a separate output, but now that I know... I'm still not going to do that. :lol: Like you said, S6, that sounds like way more trouble than it's worth, especially in small bars.

So back to the buffer... I thought that opamp was a broad term describing lots of different circuits, most of them using transistors. Hmmm... off to search Amazon hoping that they have Emitter Followers for Dummies.
 #71830  by waldo041
 Fri Jan 15, 2010 9:47 am
Rusty the Scoob wrote:I didn't realize he had each pickup going to a separate output, but now that I know... I'm still not going to do that. :lol: Like you said, S6, that sounds like way more trouble than it's worth, especially in small bars.

So back to the buffer... I thought that opamp was a broad term describing lots of different circuits, most of them using transistors. Hmmm... off to search Amazon hoping that they have Emitter Followers for Dummies.

simple bar setup would require an f2b sized preamp and stereo power amp of choice, then you have the combo needed to run seperate rigs with a 4 or 5 space rack unit. the other missing thing i forgot to mention is that the lowside would go to the 15 or 18" speaker and the high side would go to 10 or 12" speakers. so 2 cabs or 1 with something like that would be best for that setup.

as for the emitter followers, brad is being humble and has not mentioned his freeloader device, which can be removed from it's box and placed inside the bass as it only requires 9volts. check it out.

 #71832  by Rusty the Scoob
 Fri Jan 15, 2010 10:41 am
Someday I want exactly that setup... a 15" in a cab, two 12"s in a cab, a good power amp, and preamps for each era - an SMS for 68-72 and John Kahn, an F2b for 73-86ish, an SWR Grand Prix (out of production) for 87ish-95. With the two-output setup you describe I could run the neck pickup through something cleaner like the F2B and the bridge through the SMS with a little more dirt.

Sigh... ok, back to earth. :cry:

That Free-Loader looks sweet! Hmmmm, how about one of those per pickup, then to a blend knob (could I use a passive one in this case, like the 8th or 9th one from the top here?: Then to a master volume and single output. Yes, I'm sorry I'm lame... one output for me, please! For now, anway. :twisted: So that would give me the controls of Volume, Blend, Load Controller, Load Controller, then the switch which can do... what? I don't know. Maybe switch one pickup to out-of-phase? Just for special effects during Space?

I don't find passive tones to be all that helpful so I don't mind not having them... but I could put one in the current out-put jack hole and move the ouput to the body edge the way Phil did.

Hey, Brad... how much for one or two Free-Loaders, voiced for bass and with no cases? If this is a good idea, that is...
 #71836  by waldo041
 Fri Jan 15, 2010 10:58 am
sure one output will work, but i don't think you'll need 2 preamps unless your going to seperate the outputs of the pickups. i would think locating the freeloader right after the blender would be suffice. i could be wrong though, and brad will have a little better knowledgeable insight to it, since it is his product.