Vintage Gibson EB3 Wiring Question

[PolkaHero]

Going through the varitone control on my 1970 Gibson EB3 it seems like there's a problem in the third (both pickups on) position. In order for both pickups to work I have to have both volume controls all the way up. If I turn either down, it turns off both pickups. Shouldn't each volume control affect its own pickup rather than both acting as a master volume? The other settings all appear to work correctly. I can post a picture of the wiring inside if need be. Thanks!

[Fly Guitars]

No, that is actually correct, with the Gibson EB3 (and IIRC all Gibson v/v/t/t setups). When both pickups are selected you can not turn one right down. It is both stupid and annoying, but that is the way they were designed. You can turn one down some of the way, but not all the way. There is a simple mod that can change this, but most people like their EB3s stock and live with it. After all thats what the other varitone positions are for!

I have not done the mod, but I believe you can just switch some of the wires going to the volume pots...

[PolkaHero]

Thanks for the response, I posted this on another forum and found the modification which I've attached. Just switch the wires on both volume controls. However, if you do this it will affect the tone controls so that each will act as a master tone control regardless which pickup you're trying to change. It's a Catch-22 so I've decided to leave mine stock.

[nouroog]

Hello
I recently acquired a 1970 EB3 (cherry red, slotted headstock); this happened among other reasons because of hours spent on flyguitars website growing a passion for those basses.
I am thrilled with the bass, its feel and its tone. The bass is showing the expected amount of wear for a 40 years old instrument, but I was surprised to discover that :
1- the bridge pickup was a little off axis, placed too far toward the G string, leading to a lack of attack and volume on the E string, the string beeing too far from the pole.
2- the settings of the varitone are not routed like I expected i.e. pos 1 front PU w/ notch; pos 2 back PU; pos 3 both PU; pos 4 front PU. (1 & 4 interverted ?)

The bass is now at the luthier's to move the back PU.
I was wondering if those 2 problems were frequent on EB3s, have you encountered them on yours ? Is the varitone odd routing meaning the electronic 's been messed with ?
Thanks
JB

[PolkaHero]

Originally Posted by nouroog

Hello
I recently acquired a 1970 EB3 (cherry red, slotted headstock); this happened among other reasons because of hours spent on flyguitars website growing a passion for those basses.
I am thrilled with the bass, its feel and its tone. The bass is showing the expected amount of wear for a 40 years old instrument, but I was surprised to discover that :
1- the bridge pickup was a little off axis, placed too far toward the G string, leading to a lack of attack and volume on the E string, the string beeing too far from the pole.
2- the settings of the varitone are not routed like I expected i.e. pos 1 front PU w/ notch; pos 2 back PU; pos 3 both PU; pos 4 front PU. (1 & 4 interverted ?)

The bass is now at the luthier's to move the back PU.
I was wondering if those 2 problems were frequent on EB3s, have you encountered them on yours ? Is the varitone odd routing meaning the electronic 's been messed with ?
Thanks
JB

I'm just "rediscovering" my EB3 after about seven years of nonuse and never noticed that about the bridge pickup. Sure enough just took a closer look and discovered this:



I think Gibson's quality control started to suffer around this time period as they were bought out and under new ownership. I've never used the bridge pickup so this isn't really an issue for me.

Not sure about your varitone switch, does the neck pickup sound bassy in position 1 and midrangy in position 4 or the other way around? I'm thinking of bypassing the tone choke and/or resistor/cap inside to hear how the neck pickup sounds full range. Apparently it affects the sound in both varitone positions so you don't really hear what the neck sounds like full-range.

[line6man]

That sounds perfectly normal.

Traditionally when you have two volumes, the pickups are wired to the wiper terminals of the pots, so that rolling either pot all the way down shorts the pickup to ground. The problem with this is that the resistance of the pot varies against the pickup as you adjust the volume. It's preferable to wire the wiper terminal to the output so that the resistive load against the pickup remains constant, while the resistance parallel to the output varies, (It won't affect anything as long as you have a high impedance input on whatever you're plugging the bass into.) but the downside is that rolling the volume down all the way directly shorts the output to ground at 0 Ohms. This is why the wiper terminal can only be wired to the output when you either have a master volume only, or a pickup selector switch. With a master volume, obviously there is only one signal source to control, and with a pickup selector, all you have to do is solo a pickup with the switch if you don't want to use both pickups.

[SGD Lutherie]

Originally Posted by PolkaHero

I think Gibson's quality control started to suffer around this time period as they were bought out and under new ownership. I've never used the bridge pickup so this isn't really an issue for me.

That has nothing to do with quality control, since the pickup and bridge didn't change in width each time, so there was nothing to control. They were always like that from the very first bass they made. Gibson always did something goofy on every bass they ever designed.

The reason the bridge pickup is too narrow is it's based on a guitar mini humbucker. I had a '74 EB-2D and it was the same way.

It picks up the strings fine, but it's a fairly useless pickup, except for adding a little presence to the mudbucker.

[nouroog]

Originally Posted by PolkaHero

Not sure about your varitone switch, does the neck pickup sound bassy in position 1 and midrangy in position 4 or the other way around? I'm thinking of bypassing the tone choke and/or resistor/cap inside to hear how the neck pickup sounds full range. Apparently it affects the sound in both varitone positions so you don't really hear what the neck sounds like full-range.

The neck PU sounds like expected from a mudbucker in pos 1, and you have the mid notch on pos 4. It works well, it's just inverted compared to what you'd expect from a usual varitone. It's not a big deal but surprising, so I was wondering if the routing of the varitone was really as shown on the description of controls (http://www.flyguitars.com/gibson/bass/EB3_controls.php)
especially since mine is certainly a type 1 routing.

About the mini humbucker, it's indeed too narrow, but on my EB3 it was a little misplaced toward the G. That combined with the narrow PU, and the E pole was really far from the string.

I think the quality control has something to do with it, whether it was declining or not I couldn't tell.

[PolkaHero]

Originally Posted by SGD Lutherie

That has nothing to do with quality control, since the pickup and bridge didn't change in width each time, so there was nothing to control. They were always like that from the very first bass they made. Gibson always did something goofy on every bass they ever designed.

The reason the bridge pickup is too narrow is it's based on a guitar mini humbucker. I had a '74 EB-2D and it was the same way.

It picks up the strings fine, but it's a fairly useless pickup, except for adding a little presence to the mudbucker.

The pickup might not be wide enough, but it still isn't mounted correctly. I agree that Gibson made some strange decisions on their basses over the years.

[PolkaHero]

Originally Posted by nouroog

The neck PU sounds like expected from a mudbucker in pos 1, and you have the mid notch on pos 4. It works well, it's just inverted compared to what you'd expect from a usual varitone. It's not a big deal but surprising, so I was wondering if the routing of the varitone was really as shown on the description of controls (http://www.flyguitars.com/gibson/bass/EB3_controls.php)
especially since mine is certainly a type 1 routing.

About the mini humbucker, it's indeed too narrow, but on my EB3 it was a little misplaced toward the G. That combined with the narrow PU, and the E pole was really far from the string.

I think the quality control has something to do with it, whether it was declining or not I couldn't tell.

That link you posted is a series 2 setup from 1972 on, I'm not sure if those were different than series 1 which both of our EB3s are.

[SGD Lutherie]

You can get all the old schematics here:


http://www.gibson.com/en-us/Support/...ng%20Diagrams/

[nouroog]

Originally Posted by PolkaHero

That link you posted is a series 2 setup from 1972 on, I'm not sure if those were different than series 1 which both of our EB3s are.

You are right, that's a series 2 setup, my mistake.

SGD lutherie thanks for the link. I've seen that diagram before, but I can't understand it.

So on your EB3s which position is the front PU with the tone choke ?

None of you had noticed PU malpositions like on mine ? Maybe the end 69 - end 71 period (slotted headstocks) was a goofier period for Gibson ?

And SGD lutherie, I don't find the mini Humbucker that useless, to me it really adds some edge to the sound. I never use it alone, but I have it open most of the time, and play with each PU volume and tone to shape my sound.
Maybe it's a less useful addition to the tone of EB2s.

[PolkaHero]

Nouroog,
From my research on these models, the tone choke affects the neck pickup in both positions but differently. On position one it should cut the highs and high-mids whereas on position four it should cut the bass and low-mids. That's how I hear it anyway. There's also a resistor and capacitor in the circuit all of the time which must affect the frequency response of the neck pickup but I'm not sure how much. Once I get a new set of strings and output jack, I'm going to experiment with bypassing the tone choke and the components to hear what the neck pickup really sounds like.

[nouroog]

Originally Posted by PolkaHero

Nouroog,
From my research on these models, the tone choke affects the neck pickup in both positions but differently. On position one it should cut the highs and high-mids whereas on position four it should cut the bass and low-mids. That's how I hear it anyway. There's also a resistor and capacitor in the circuit all of the time which must affect the frequency response of the neck pickup but I'm not sure how much. Once I get a new set of strings and output jack, I'm going to experiment with bypassing the tone choke and the components to hear what the neck pickup really sounds like.

Wow that's interesting; I can't check that because my EB3 is presently at the luthier's. But when playing I usually felt there was a position of the varitone (pos 1 on mine) where the front PU was not affected by the tone choke, just by the usual tonality pot.
Please keep me informed of the results of bypassing the tone choke.

I'd also be interested by Fly Guitars' insight on those questions, since most of my knowledge about eb3s come from his website.

[PolkaHero]

Finally got to fiddling with the electronics today after replacing the output jack and putting new flatwounds on it. First I experimented with bypassing the resistor and cap in the neck pickup lead. This definitely opened up the sound more in both neck pickup positions (1 & 4). I then took the tone choke out of the circuit by removing the lead green wire that goes to the varitone switch. This gives positions 1 & 4 about the same sound (very full with more mids/highs than with the tone choke) with position 4 a little hotter (probably because the resistor only affects position 1?). It also makes position 3 (both pickups) more usable. I find that if I roll the volume of the bridge pickup off slightly in position 3 it makes for a nice full sound, much better than before with the tone choke. I think for now I'm going to leave the tone choke disconnected but leave the cap/resistor in the circuit. If you really want the sound of the neck pickup in position 1 with the tone choke engaged, all you have to do is roll the tone all the way down in either position 1 or 4 and it sounds about the same. Of interest to note is that bypassing the cap/resistor without the tone choke engaged doesn't make much difference tonewise. Hope this helps!

[nouroog]

Hey I had not seen your last post until now ! I thought you never did the bypassing tests.
Well, those are very interesting results. How did it come up with time ? Did you eventually leave the tone choke bypassed ?
Now I definitly want to try and do the same on my EB3, especially since I have recordings to come I wanted to use it on, using my new B15N.

[PolkaHero]

Originally Posted by nouroog

Hey I had not seen your last post until now ! I thought you never did the bypassing tests.
Well, those are very interesting results. How did it come up with time ? Did you eventually leave the tone choke bypassed ?
Now I definitly want to try and do the same on my EB3, especially since I have recordings to come I wanted to use it on, using my new B15N.

Haven't changed any of the mods I did although I haven't been playing it much since. I bet it would killer with your B-15N, I just got one of those in the meantime and have yet to play the Gibson through it. I've been using a heavy foam mute for my P-Bass lately to get an upright sound and that's been working pretty well.