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Can piezo and mag pickups share an earth?
Old 17th June 2019
  #1
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grannis's Avatar
Can piezo and mag pickups share an earth?

I'm building a new guitar and want to experiment with a combination of 2 magnetic and one piezo pickup.

I'd like to simply use a stereo TRS cable and split the signal using an ABY box

1. any issues having them all share an earth?

2. I am not 100% sure which side of the pickups is the earth - when i installed the mag pickups, I just experimented until i got the wiring that sounded best. Any risk in doing the same with the piezo?

btw I don't have tone or volume pots at all - just going from pickup, via some DPDT switches, straight to an EQ pedal.

thanks
Old 17th June 2019
  #2
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Mikhael's Avatar
 

Quote:
Originally Posted by grannis View Post
I'm building a new guitar and want to experiment with a combination of 2 magnetic and one piezo pickup.

I'd like to simply use a stereo TRS cable and split the signal using an ABY box

1. any issues having them all share an earth?

2. I am not 100% sure which side of the pickups is the earth - when i installed the mag pickups, I just experimented until i got the wiring that sounded best. Any risk in doing the same with the piezo?

btw I don't have tone or volume pots at all - just going from pickup, via some DPDT switches, straight to an EQ pedal.

thanks
There should be no issue sharing earth (I'm guessing you're not in USA; we call it "ground"). I do that in a few of my guitars, and seem to have no issues with that, no matter what I've plugged into. I don't use a TRS cable, mostly because 90% of the time I use two wireless units, and they plug in individually.
Old 17th June 2019
  #3
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Quote:
Originally Posted by Mikhael View Post
I'm guessing you're not in USA; we call it "ground".
thank you! Yes I'm in the UK - where ground is for coffee
Old 17th June 2019
  #4
All piezos should be sent to NASA for quick transport to Mars, then they won't have to share Earth with anything.
Old 18th June 2019
  #5
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Quote:
Originally Posted by John Eppstein View Post
All piezos should be sent to NASA for quick transport to Mars, then they won't have to share Earth with anything.
Agreed. All piezos sound like the sound of a fart mixed with something vaguely resembling a cheap guitar of unknown provenance.
Old 4 weeks ago
  #6
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Don’t all things here share an Earth? Piezos ARE annoying, but we share an Earth with far more dangerous creatures.
Old 4 weeks ago
  #7
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Yuri Kogan's Avatar
 

Quote:
Originally Posted by John Eppstein View Post
All piezos should be sent to NASA for quick transport to Mars, then they won't have to share Earth with anything.
Are you discriminating against martians?!!!
Old 4 weeks ago
  #8
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As far as I can tell, Martians are very well represented on this forum. Check out the alien thread.
Old 4 weeks ago
  #9
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Bollocks, i normally speak pretty good Septic, but i really cocked this one up! I think I'll cheer myself up by going and smoking a fag.

toodlepip chaps.
Old 4 weeks ago
  #10
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Some piezos are better than others. The Graphtech offerings seem to "quack" a lot less than others. I find them useful, although I'll admit I'm still dialing them in (when I get a chance). But they sound okay run through an Aura pedal.
Old 4 weeks ago
  #11
I've played guitars with both and the biggest issue I noticed was the output mismatch between the pickups. The piezo was just much louder which meant it was a pain to balance if you wanted to blend pickups, and too easy to knock a knob and muck it up.
Old 4 weeks ago
  #12
Output mismatch is a major issue on my P-bass with Graphtech piezo saddles. The piezos are almost line level next to the PJ pickups. The bass is active with dual preamps and an active pan/blend pot. To equalize the level differences the preamp opamp gain shunt resistor is fed to the switch that selects the piezo pickup. Floating that gain set resistor from ground sets the gain unity. The gain resistor is connected to ground when the magnetic pickups are selected. It's a bit complicated in concept but easy in execution. Since the preamps each have gain trim pots I can equalize out the level differences. A 5 meg input impedance is perfect for the piezo or magnetic pickups = full bandwidth. Lower that input impedance and the magnetics loose top end, the piezos loose low end.
Old 4 weeks ago
  #13
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Quote:
Originally Posted by mdme_sadie View Post
I've played guitars with both and the biggest issue I noticed was the output mismatch between the pickups. The piezo was just much louder which meant it was a pain to balance if you wanted to blend pickups, and too easy to knock a knob and muck it up.
Output mismatch is never an issue for me. If you want the piezo output to sound like an acoustic guitar, you have to run it through full range amplification, not a typical guitar amp. So my piezo-equipped guitars run stereo out, piezos to the PA and magnetics to the guitar amp. I'v never used them together to a single amp; that's not what I'm looking for, so the output level of the piezo preamp has never been an issue for me.

You might look at the preamp on the guitar for the piezos, as it might be adjustable for lower output. Maybe.
Old 4 weeks ago
  #14
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grannis's Avatar
I play through a digital parametric EQ, into a valve preamp, then into IR loader direct to PA so I just need to bypass the preamp and load an acoustic IR. I can save the EQ and level settings I want for the piezo as a preset
Old 4 weeks ago
  #15
Quote:
Originally Posted by grannis View Post
Bollocks, i normally speak pretty good Septic, but i really cocked this one up! I think I'll cheer myself up by going and smoking a fag.

toodlepip chaps.
I had to look that one (septic) up. I get it that it's a rhyme slang thing (yank/tank) -- but I have to say that most American cities over a few thousand people are fairly proud of their sewage systems. And having used an actual outhouse (while renting a mountain cabin some years ago), I can see why.
Old 4 weeks ago
  #16
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Quote:
Originally Posted by theblue1 View Post
I had to look that one (septic) up. I get it that it's a rhyme slang thing (yank/tank) -- but I have to say that most American cities over a few thousand people are fairly proud of their sewage systems. And having used an actual outhouse (while renting a mountain cabin some years ago), I can see why.
Yes I do apologise to your nation- rhyming slang was never intended to be “appropriate” so much as humourous.
Old 4 weeks ago
  #17
Quote:
Originally Posted by grannis View Post
Yes I do apologise to your nation- rhyming slang was never intended to be “appropriate” so much as humourous.
Back in the 1970s, I had an Irish friend who was pretending to be Cockney (long story, that) who tried to clue me in on how rhyme slang worked. But we were drinking as he explained it and it all sort of spiraled into that jumble that results from long sessions of free-flowing booze and conversation.
Old 4 weeks ago
  #18
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Quote:
Originally Posted by theblue1 View Post
Back in the 1970s, I had an Irish friend who was pretending to be Cockney (long story, that) who tried to clue me in on how rhyme slang worked. But we were drinking as he explained it and it all sort of spiraled into that jumble that results from long sessions of free-flowing booze and conversation.
sounds like a great evening! In truth, I am from the wrong side of London, but in the 80's I played in an East London band. We were regulars in this pub..

https://en.wikipedia.org/wiki/List_o...ham_Roundhouse

..but not listed here!
Old 4 weeks ago
  #19
Quote:
Originally Posted by grannis View Post
sounds like a great evening! In truth, I am from the wrong side of London, but in the 80's I played in an East London band. We were regulars in this pub..

https://en.wikipedia.org/wiki/List_o...ham_Roundhouse

..but not listed here!
There's a slice of history!
Old 4 weeks ago
  #20
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Fay Smearing's Avatar
 

Quote:
Originally Posted by theblue1 View Post
Back in the 1970s, I had an Irish friend who was pretending to be Cockney (long story, that) who tried to clue me in on how rhyme slang worked. But we were drinking as he explained it and it all sort of spiraled into that jumble that results from long sessions of free-flowing booze and conversation.
Well at least he tried to give you the drum.
Old 4 weeks ago
  #21
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enorbet2's Avatar
Getting back to OP's original question... not only can they but they need to. Besides the terms "earth", "ground", and "sink" one other applicable term that should speak volumes to you is

COMMON.
Old 4 weeks ago
  #22
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Mikhael's Avatar
 

Quote:
Originally Posted by enorbet2 View Post
Getting back to OP's original question... not only can they but they need to. Besides the terms "earth", "ground", and "sink" one other applicable term that should speak volumes to you is

COMMON.
Earth, ground, common... I know all those. However, even having been in the electronics industry for over 3 decades, I can't recall running across "sink" before. Is that a construction term (as in sinking a copper rod into the ground)? I understand it can refer to bleeding off something (as in "heatsink"), but have never seen it in that usage.
Old 4 weeks ago
  #23
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Quote:
Originally Posted by Mikhael View Post
Earth, ground, common... I know all those. However, even having been in the electronics industry for over 3 decades, I can't recall running across "sink" before. Is that a construction term (as in sinking a copper rod into the ground)? I understand it can refer to bleeding off something (as in "heatsink"), but have never seen it in that usage.
I actually don't know the origin but I've seen it used on a few schematics over the years where a representation is made of the physical difference between signal ground and actual connection to chassis. Theoretically all commons should only ground, or sink, at one location on the chassis to eliminate ground loops

Vintage Fender amps for example used steel chassis which has less resistance per linear distance and employed many connections to chassis ground (or sink) often partly by use of what functions as a Ground Buss like the brass strip between the pots and the front panel.

Actually I have often wondered just how it is that Fender chose what to ground where since their topography is very effective and some alterations can result in rather large increase in noise floor.. Trial and error? Arcane knowledge? Interesting, eh?

FWIW Fender was not one of those firms that used "sink" as terminology but they did practice it.
Old 4 weeks ago
  #24
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Mikhael's Avatar
 

Quote:
Originally Posted by enorbet2 View Post
I actually don't know the origin but I've seen it used on a few schematics over the years where a representation is made of the physical difference between signal ground and actual connection to chassis. Theoretically all commons should only ground, or sink, at one location on the chassis to eliminate ground loops

Vintage Fender amps for example used steel chassis which has less resistance per linear distance and employed many connections to chassis ground (or sink) often partly by use of what functions as a Ground Buss like the brass strip between the pots and the front panel.

Actually I have often wondered just how it is that Fender chose what to ground where since their topography is very effective and some alterations can result in rather large increase in noise floor.. Trial and error? Arcane knowledge? Interesting, eh?

FWIW Fender was not one of those firms that used "sink" as terminology but they did practice it.
Well, ever since I can remember, people have liked to use a "star" grounding concept (all ground wires running to one central location, for those who don't know), and a big steel chassis will certainly sink more current than just about anything else in the amp...
Old 4 weeks ago
  #25
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grannis's Avatar
When it comes to pickups (mag and piezo) is there an actual difference between "hot" and ground? I get that reversing them in a multi-pickup scenario can make a difference, but if it was just one pickup, does it make a difference?
Old 4 weeks ago
  #26
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Mikhael's Avatar
 

Quote:
Originally Posted by grannis View Post
When it comes to pickups (mag and piezo) is there an actual difference between "hot" and ground? I get that reversing them in a multi-pickup scenario can make a difference, but if it was just one pickup, does it make a difference?
Well, there's not really a difference between either end of the coil (aside from phase with other pickups, that sort of thing). But "ground" can be a shield on the pickup, and it'll matter what that's hooked up to.
Old 4 weeks ago
  #27
Quote:
Originally Posted by grannis View Post
When it comes to pickups (mag and piezo) is there an actual difference between "hot" and ground? I get that reversing them in a multi-pickup scenario can make a difference, but if it was just one pickup, does it make a difference?
Theoretically the outer windings of the coil should be grounded and the inner windings hot. That way the coil is somewhat self-shielding.
Old 4 weeks ago
  #28
Connecting the inner coil towards the magnets will cause more buzz to enter and if you touch the pole pieces (an issue with the P-bass) it will buzz. Screen the pickup covers and then outside windings connected to hot will have less noise.
Old 4 weeks ago
  #29
Quote:
Originally Posted by Jim Williams View Post
Connecting the inner coil towards the magnets will cause more buzz to enter and if you touch the pole pieces (an issue with the P-bass) it will buzz. Screen the pickup covers and then outside windings connected to hot will have less noise.
If touching the pole pieces causes a buzz it means that the poles are not properly insulated from the coil and there's an insulation defect somewhere. This is a common problem with some Fender pickups. Ideally there should be a layer of masking tape around the poles to prevent contact. Sometimes there isn't.
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