Guitar with 2 independent signal paths - no output

[ozrictentacle82]

Hello.

I have some ideas as to why this is happening, but I'd like to run it across the forum for insights:

I made a 12-string guitar with 2 independent signal paths, each with 1 3-way, 1 vol, 1 tone to 1 output jack. 

***I made a wire for string ground that connects to each tone pot.***

The issue is that when I go to play, there is no sound unless I touch the volume knob (which is metal), suggesting to my limited electrical exp that I am grounding the whole circuit, or that both circuits are putting a load on each other, something to that effect that makes it an issue.  (Do I need to separate that wire that couples them to the same string ground or what?)

Please help me fix this so it works like it should.

Thanks!

[sumgai]

ozzy,


I changed the title of your thread to more accurately state your problem - "1 Vol 1 Tone no volume" doesn't quite describe the problem, does it?

First off the bat, we'll need to see a diagram of what you've actually installed into your instrument. Photos will also help, but they're secondary, that wiring diagram, or schematic, will be critical to troubleshooting this thing.

BTW, if you built it, do you feel like posting photos to The Gallery?




sumgai

[ozrictentacle82]

[unreg]

1.) My inquiry to other Nuts: Do the 2 independent signal paths create a ground loop since the string ground is connected to both jack grounds? Like if 2 cables are plugged in at the same time. It’s quite unique.

2.) Why use a linear potentiometer for volume? The human ear responds to sound in a logarithmic manner. So, if you turn a log vol pot knob down half way, the volume level will sound to your human ears like it’s at around 50%. Linear taper causes sound levels to reach your ears in an alternate manner.

Though, perhaps the “Lin” label, on each pot case in your wiring diagram, just showed up by default?

[sumgai]

ozzy,



OK, assuming that the Vol pot ground wires are going to the output jack sleeve terminal in some fashion, your diagrams looks good on the face of it, but I now have a different question - are there truly 4 pickups, or did you install only two pickups, and you're running wires them over to each of the two 3-way switches?

Reason I ask is that if there are 4 pickups, then your diagram should work as intended, but if there are only two pups, then there's a much greater chance that one channel could interfere with whether or not the other channel works correctly.

As for grounding, I think you've done it correctly, but there can be a hidden 'gotcha' if you're not careful. Consider that you have two separate signals going to two separate amplifiers. If you are playing in a venue that has only two-conductor power outlets (no ground), then a lot of things can (and will!) go wrong. The least of them would be a loud hum, the next undesirable thing might be a fire, as competing power sources find a bridge across that ground wire from Tone pot to Tone pot. The last and worst thing would be you getting shocked in some manner. Probably not life-threatening, but shocks of this nature do hurt, and you're not gonna feel like playing for a few minutes afterwards. Trust me on this one.   If you find yourself faced with 2-conductor outlets quite often, consider removing any 'shared' wire between the two signal paths.  This includes the bridge ground, just connect that to only one channel, and use that one for those times when "mono" is the name of the game.

However, if both amps are plugged into 3-conductor power outlets, then there should be no problems... providing that the electricians who did the wiring weren't high at the time. That's why I always carry an outlet tester, to tell me if the wiring is up to code or not. Available for less than 6 bucks at Amazon:



Similar items can be found locally, but at a bit higher of a price.

HTH





sumgai

[perfboardpatcher]

Hello Mr. O,

Outputs A and B should be grounded. Are they?

[ozrictentacle82]

Hi unreg! Yeah, the linear pot was just default label, I usually use audio taper.

[ozrictentacle82]

Hey sumgai! Good points, thank you! 

There are 4 pickups, 2 for each 3 way switch and vol/tone to output. I opted for that over having 4 pickups wired together in series as this retains parallel without a much more elaborate diagram that I would not be able to draw up myself (I'm more skilled at the actual soldering than making wiring schematics).

[ozrictentacle82]

Hello perf, they're wired like the diagram, so maybe that's what I missed. The output jack just has a wire coming from the tone pot that also shares a solder point for the bridge ground wire.

[sumgai]

ozzy,


Forgive me if I sound like I'm lecturing you, that's not the tone I wish to impart here.

Essentially, in the world of hobbyist electronics, we often have two schools of thought when it comes to drawings: one is to use shortcuts, because "everybody understands", or two, we try to be overly complete, which sometimes turns a drawing into a rat's nest. We see both kinds here in The NutzHouse®, and we get it, either way is OK because we're all made up a little differently, and where one person might not understand, others here will be able to step in and "save the day".

What I'm seeing is a shortcut for the Volume pots - the wire from terminal #3 is going to a ground symbol, and that's correct, but as a matter of being a pictorial (versus an actual schematic), one might be tempted to do just that - find the nearest "ground point" without following it through for continuity.

What am I talking about? Easy - it's the method of soldering actual wires from pot-back to pot-back, because if you rely on the shielding under the pot's mounting washer, you may not be getting a good connection all the way through to the output jack. Your drawing implies them, so that's a shortcut, but if you did exactly what's shown, it's possible that the circuit is not complete, or at best, it's being impeded by a high resistance somewhere in the ground side of the equation. That's a mechanical issue, and usually it's a result of either a bad solder joint, or a bad mechanical connection (as discussed a moment ago).

That lack of solid ground connections all the way around is a likely cause of 'no output'. I suggest that you re-flow all of your solder joints (yes, all of them, not just the ground side of things), the entire kit and kaboodle. Then double-check everything with a multi-meter afterwards, to ensure continuity where expected, and no shorts where not expected.

Oh, and troubleshoot each channel by itself, don't try to plug both channels into amps at the same time until you've made sure that each channel works like it should, all by itself. Dividing up your troubleshooting process into smaller bite-size pieces tends to make things easier than trying to make sense of what's essentially two guitars crammed into one body.

HTH





sumgai

[ozrictentacle82]

Hello sumgai!

I did remove the shared string ground, put string ground to its own screw. I put each circuit into its own ground terminal to be set by a screw into the body, not yet set. I did not re-solder all the points yet. 

When I did check each output jack alone (which is how I've done it), it was worse than before and only hums when you touch both the vol and tone knobs instead of the original problem of only having output when you touch the volume.

I set it aside as it is an experiment at this point and I have to regain the gumption to keep spending time on it and it not work.

Thanks again for your help!

[unreg]

Oct 7, 2024 11:19:23 GMT -5 sumgai said:

Then double-check everything with a multi-meter afterwards, to ensure continuity where expected, and no shorts where not expected.

ozrictentacle82, do you have experience using a multimeter to check a wire for continuity?

[ozrictentacle82]

General multimeter experience but not point to point in circuit. Mods I've done never needed it, or the way I knew it worked was by tapping pickups with a screwdriver when plugged into a pignose amp.

[unreg]

Hmmm… since it doesn’t work now, checking continuity would be super helpful… and it’s quick to do. 0 resistance == best continuity, so it also helps magnify your focus by testing resistance. If you check spots far from each other… say a volume pot case and the ground lug of its jack and you receive continuity; then you will know that each solder spot connecting ground from volume pot case to that jack’s lug is soldered well. However, if you don’t receive continuity, then test a smaller section of that path… start by testing directly on each side of that jack’s ground lug’s solder spot (i.e. the jack’s ground lug and the exposed wire piece soldered there); if that has continuity, GREAT, next test on ether side of the next solder spot in this long path that lacks continuity. Find a spot lacking continuity OR that has resistance above 0, remelt that solder spot.

This continuity testing was SUPER HELPFUL for me during my guitar editing and pedal building! It doesn’t take long, if done correctly; and then you will KNOW everything is working as it should.

EDIT: When everything has continuity report that success and they’ll be better equipped to help you. Right now, it seems like at least one solder spot lacks continuity, so proving you have an entire continuity on your guitar solidifies your foundation in GN2 minds and the troubleshooting can become more specific; at least that’s how it worked for me.

[ozrictentacle82]

Hi unreg! Thank you! Will do!

[unreg]

I really THINK newey has stated, in the past, that he’s ok with a few ohms of resistance. IMO, my guitar functions better with 0 resistance for each solder spot; but, it’s more important to check your entire guitar for continuity, than spend ALL your time attempting to “fix” 2ohms of resistance to 0ohms resistance.

Note: THINK is entirely in caps since I don’t want to be beheaded again for actually falsely stating what others have said. My memory isn’t perfect; sry.

[newey]

Not sure that I ever said that, unreg. We were speaking of real-world measurements, the probes, wires and clips of the meter can add a bit, minimal to be sure but nonzero. And meters aren't perfect, there is a tolerance of plus/minus some little bit. I only meant that a real-world reading of a few ohms, in a circuit like our guitars, would not lead me to believe the connection was bad.

[ozrictentacle82]

Good news:  guitar works now! 

I re-soldered a few points, but I also re-soldered the 3 - way switches and double-checked wires!

I have done more complex wirings successfully which is why I was perplexed for a while about this.

I think there were a few minor errors done since everything was done in duplicate. I may have crossed a wire somewhere, lol, and also not had proper ground wires between vol and tone like usual. I also separated the grounds from the string and the volume of each circuit.

Anyway, thanks for the advice!  Here's a picture of this experiment!