Gibson EB-0 Lo Z Christmas project

[amptech]

Thanks for all the kind words, I am really satisfied with this one. I played fretless for many years, and after going completely short scale, it annoyed me not to have a fretless gibson. I only filled the fret slots with rosewood dust mixed with very thinned out white glue, in case I´d not be satisfied and wanted frets. One of my other ebay-0 projects came with
a set of ´pressurewound´GHS medium scales, and I put them on. Sounds OK. Going for Thomastik flats, wich I love on
EB´s. I bought 8 or 10 of the odd size nut blanks, took a while to find but i have enough to fool around with gauges.

As for the pickup; as said before this is a guitar pickup - and I had to rout so deep it almost went through the body. Not sure if a bass pickup would fit. Even a flat neck pitch might have given it trouble, but it worked. Simple electronics; tone and volume (1K CTS) with the tone through a 4,7 uF cap, might try different values. Amazing tone range, super bright at 10, honky midrange at 5 and plesantly mellow at 0. Will be fun to try what value that works best, but the range surprised me. Almost like an active circuit, it´s a wah-wah really! Mic to line trafo, xlr and jack. Both loud and noise free. A very plesant first time Lo-Z experience. I will have to learn how to post sound clips.

[amptech]

Thought I´d finish this thread by posting the schematics for the circuit, I noticed that someone might be interested.
As explained earlier, it´s a very simple circuit. It is based on the signature series LoZ basses/guitars, with the Lo out ac signal separated from the cable shield. I noted that I mentioned a 4,7 cap for the tone control, actually it is 3,3uF but I might try other values. It works really well, noise free and loud.

Here´s the schematics:


And a shot of the guts:

Thanks again for help and input throughout the project, turned out nice and landed well under $1000 including finishing products for many other projects, as well as a spare LoZ pickup. Cheers

[Granny Gremlin]

Thanks.  Gonna have to look at that later, because the way you have the XLR wired up looks weird to me at first glance.

[amptech]

I bet it does

No really, its just a regular hookup, I numbered the pins on the schematics to avoid confusion.
Ground/Shield to pin 1 and signal to pin 2 & 3. Might have a line or two crossed in the schematics, though -
that happens.. Build from sketches, then tidy it up for others to read.... I´ll have to check it myself!

Edit: these schematics should work, but note that the actual tone wiring have a NC lug 3, not 1.  Works anyway, just reverses the tone function.

Edit 2: ...and I see i forgot to 'hump' the wire from the vol. wiper to XLR pin 3 in the schematics but obviously it's not connected (shorted) to vol. lug 1. Sorry, will fix...

Edit 3: Humped!

[amptech]

Oh, and I a may also add that the voltage ratings for the caps doesn't have to be that high, I stock for tube amps and found i only had 3,3uF in high voltages. The .001 cap in the shock protection cct is recommended being 500V or higher, if I remember correctly. So that if you are struck by lightning, at least the cap will be fine

[Granny Gremlin]

Please bear with me here; trying to understand this (and maybe learn something).

I am still a little confused about why you have the brown lead from the pup connected to XLR pin 2 both pre and post the transformer in parallel.  First of all, shouldn't pin 2 be connected to vol pot wiper (just like TRS tip - you wired it as pin 3 hot which is 60s XLR standard; no real biggie, just a polarity inversion when plugging in to modern gear).  I also do not understand how you got the COLD (reverse polarity) signal out this thing.... unless it's not proper balanced output but just Z balanced, in which case miswiring pin 2 is a problem (unless you're only plugging in to old unmodified Ampex, Altec and RCA tube preamps), but that  would explain my confusion from the first sentence (usually I've seen that done with a simple resistor between cold/pin 3 and ground/pin1 with R = output Z of the previous stage)?

Why use a TRS jack (ring and sleeve will be connected when you plug in a standard TS guitar patch)?  Though it doesn't technically matter, usually ground is sleeve (vs ring).

[amptech]

Please bear with me here; trying to understand this (and maybe learn something).

I am still a little confused about why you have the brown lead from the pup connected to XLR pin 2 both pre and post the transformer in parallel. 

I doubt there is much to learn here, as I have mentioned this cct is just pulled out of gibson LoZ schematics. The only thing   
I´ve done here, is to remove parts in the tone cct, and use XLR instead of a TRS jack. As for red and brown, or hot/cold if you like, I have not given a thought which is start and end of the pickup coil so I decided to let the colour coding (red/brown) on the transformer lead the way here. (The transformer was wired this way in the mic pre console it took it from, which is also why I put brown to XLR pin 2) The brown wire is connected to both sides of the transformer because thats the way it is hooked up in the gibson schematics (and most other I´ve seen) and it works properly that way.

Why use a TRS jack (ring and sleeve will be connected when you plug in a standard TS guitar patch)?  Though it doesn't technically matter, usually ground is sleeve (vs ring).

Because the shield wiring of the XLR would have been connected to pin 2 if i used a TS jack. It´s just a logic mechanical solution.

[Granny Gremlin]

But the original Gibson schem has no balanced output and that's what's confusing me - I am trying to understand where you get the COLD (-ve / out of phase) signal from (I understand this can be done with a tranny, but it would need a 1:1 not 4:1, and it doesn't look like you wired it for that anyway).  Further, in the original schem, the output  is only connected both pre and post tranny with a switch so that only one connection (either pre or post; lo or hi Z) is active at any one time (lo and hi Z output is on same jack vs separate jacks on yours) -  your schem has them permanently in parallel which is very different. 

Also my point about pup polarity is not which lead is +ve (not really important unless dual pup instrument and you don't want them out of phase), but that you have the the 1/4" and XLR connectors wired backwards to each other (i.e. XLR pin 2 should = TRS tip, but it doesn't) - if you plan to mix the two outputs this may cause problems.  Further, if the XLR is not actually outputting a proper balanced signal (including being just Z balanced) pin 2 needs to be hot not pin 3 (again, unless you will be exclusively plugging in to vintage gear made before the standard changed that hasn't been rewired accordingly yet).

All of these things could be wired right in the bass itself just noted wrong on the schem, I suppose.  Can't quite tell from the gut shot you posted.

Sorry, not trying to be annoying just trying to understand and, if I am reading the schem right, help. 

[amptech]

Sorry, not trying to be annoying just trying to understand and, if I am reading the schem right, help.

To be honest, I only looked at the schematics after you pointed out something was wrong, but as far as I can tell the schematics are correct for the actual hookup, which works.

To start with, for the LoZ  out I use an XLR because the gear I might plug into will have an XLR connector. I could have used a jack plug, I know. Where do I the cold from? I never shot for a  balanced out, I just connect with an XLR and have a separate shield, it´s one pickup straight out of pin 2 & 3 and shield 1 and I see no point in complicating things at all. If I have said in earlier posts that I was going to balance the LoZ out, sorry, but that is not the point in this application. I am well aware that gibson only used a switch across the matching transformer, but you questioned the brown wire hookup to the transformer, which is believe is hooked up like gibson did. I think the signature series was connected something like this, with a TS for HiZ and a TRS for LoZ. I might be wrong, but again... as long as it works.
I´m sure you can google that if it is of any interest.

And of course the XLR and jack out cannot be used together, I hope I haven´t said that either. I have the choice of using either, using a TRS for the Hi out so I don´t need a switch to lift ground (or cold if you like that better) from shield. You obviously understand electronics, so there is no need explaining further why this cct wold not work properly
if I had used a regular mono jack for the HiZ in this application.

Vintage gear, well that´s anything older than five years (according to ebay ) so I guess that includes my two Yamaha mixers, but my three years old digirack protools setup was also noise free and sounded fine (with a regular 10m XLR cable) so if there is something wrong with the schematics, I honestly can´t find it! I´d have to open the cave and check, maybe I have looked my self blind on this schematic.

Please forgive me if it still is confusing, electronics in foreign languages is not my strong side.
You´d have to build one yourself

[Granny Gremlin]

I just looked at the LP Sig (bass and guitar) - I see that they do use a TRS for the Lo Z out.  Never noticed before (or forgot).  I was confused because usually for unbalanced XLR  one simply connects +ve to Pin 2, -ve/ground to pin 1, and jumpers pin 3 to pin 1.

You should still switch pins 2 and 3 on the XLR though.   TRS Tip = Pin 2. You have tip = pin 3.  This is wrong.

Also I do not see the LoZ +ve connected both pre and post transformer in either LPSig schems.  Look again; that's just the ground (sleeve/pin 1) not ring/pin3 or tip/pin2. 

Anyway, we are having a language barrier here  as you say (I did not realise you were not a native English speaker, sorry) so this is what I am recommending and I will bother you no more:



Note: I added the ground lift as an option because I don't think it's worth it, but the LPSig you're basing your wiring off of *appears* to have pup -ve (brown in your case) not connected to ground.  In practise, when you plug a TS jack into the loZ TRS output it will short ring to sleeve, thereby connecting pup -ve to ground.  In the case that a TRS cable was used (unlikely at the time of the instrument's release, as they weren't popular at the time outside of patchbay applications and headphones, but possible) this would not be the case, hence the optional ground lift idea,  but I do not know what effect that would have; probably fine depending on what you're plugging in to. 

Also, I do not think it's a good idea to use a TRS cable for your Hi Z out (assuming it's also plugged into a TRS input) as the pup won't be grounded.  TS would be safer here - but if you never sell or lend it to anyone without explaining this it's a trivial matter as you understand this.  You could also put in a ground lift switch between TRS ring and sleeve (or use a dual gang/DPDT in place of the optional XLR ground lift so as to lift both at the same time and not have too many switches on the damn thing).  That way you can have separate ground and pup -ve as you said you desire (I personally see no real useful purpose for this, but suit yourself), but still be safe. The way you have it wired now (ground to ring) it will hum like a bastard if TRS is used (as said before - at both ends, into gear with TRS input ... which I suppose isn't likely as most, if not all,  HiZ gear is TS/unbalanced, but as we say in IT: if it's possible to do, some idiot will try it eventually - not an issue, as stated, if you never sell or lend) because the bridge/strings won't be grounded.

[amptech]

Thanks, input on a project is always positive wether it is balanced or not

Note: I added the ground lift as an option because I don't think it's worth it, but the LPSig you're basing your wiring off of it *appears* to have pup -ve (brown in your case) not connected to ground.  In practise, when you plug a TS jack into the loZ TRS output it will short ring to sleeve, thereby connecting pup -ve to ground.

I´m aware of XLR to TRS jack coupling, but it is not relevant to this application. I did not intend to use HI and LO together, and the HI jack out is meant to use with a regular mono jack plug. I just used the TRS chassis plug so that no switch was needed, and it works as intended. I don´t  need switching when the hardware does the job.

I guess i should have mentioned that i meant to use the Hi Z with a normal mono guitar cable.

[Granny Gremlin]

Even if TRS and XLR not used at the same time, XLR should be wired properly because all modern XLR inputs look for the signal on Pin 2 not 3.  If you misswire a balanced XLR connection you just get an out of phase signal (no real biggie), but misswiring an unbalanced XLR can lead to actual problems.

The only reason this might appear to work is that you don't tie either red or brown to ground (unless there's a TS jack plugged in to the HiZ out).  You got lucky on that one, but I still think the pre and post tranny connection you have would at the very least cause a level mismatch; I've never tried that but think you may have just developed MidZ 

[amptech]

I've never tried that but think you may have just developed MidZ 

That was jus what I was aiming for

[SGD Lutherie]

It's not exactly Jamerson nailed to a T, but gets you in the neighborhood - if anything, a more modern/hihfi version of that tone:  Triumph with flats, tone position 3 into any 60s era Ampex tube preamp.  This is how most Motown bass was recorded; even when micing JJs B15 an Ampex preamp was always in the chain, and they definately add a certain character. JJ did also went through DI - the Ampex and a P with deadish flats were the only constants to his (recorded) tone in terms of gear.

Actually Jamerson's bass was usually recorded direct. He had an Ampeg B-12 as a studio monitor, but the bass you hear on the recordings was DI. And likely through a tube compressor. The Ampeg B-15 as part of his tone is a myth, but he did use one for live gigs.

Much of the Motown bass is brighter than most people expect too, when you hear it soloed. Jamerson clearly either had more foam rubber under the strings to deaden them, or his action was kind of high, making the stock mute's foam press down on the strings more.

Here's Jamerson's soloed DI track on What's Going On



Heard it through the Grapevine



Reach Out



Here's a mix I did of soloed Motown bass lines. (no Jamerson)



I Want You Back (Wilton Felder), Brick House (Ron LaPread), Let's Get It On (Wilton Felder)

[amptech]

I smell a heated debate back on track.... on the other hand, I get calls and mails all the time from people who wants to buy
James Jameson's fretless Gibson

Nice to see you post, David - I read through many of your postings on MI forum when I sarted making sidewinders some years back,
and if I remember correctly you have written a couple of interesting pieces on Gibson LoZ pickups too?