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Post by Ro_S on Oct 20, 2018 9:58:47 GMT -5
Hello Nutz. It's me 
[project now completed - 22nd Nov.]Please can I have help to check my wiring diagram attached/linked below. I'm particularly concerned about the ground wiring (purple lines). Is it all okay? Am I correct to ground the two output jacks to one another thereby combining the two circuits? Have I grounded the trapeze tailpiece okay? This is for a hybrid electric/piezo mod project on a hollow bodied archtop guitar. The modded guitar will have TWO outputs, as follows: - electric (magnetic pickups). passive. AND - piezo (piezo discs contact 'mics'). passive There will be two magnetic pickups. Each pickup will have its own dedicated volume and tone (treble cut) controls - i.e. Gibson style. A traditional 3-way toggle switch for pickup selection, in normal configuration. Plus, a master volume control. All pots 500k. The piezo circuit will be a PASSIVE circuit, intended to use with an external acoustic pre-amp. The on-board piezo circuit will have TWO piezo transducers in the DISC form (as often used on cigar box style guitars). These piezo discs will be affixed to the underside of the top of the guitar's body; one underneath the bridge area (the guitar has floating bridge). The on-board piezo circuit will also comprise two volume controls, one for EACH piezo disc. Both 500k pots. These two volume pots will then be wired direct to the second output jack - will that work okay? Thankyou MY DRAFT WIRING DIAGRAM: imgur.com/a/TZ2shoy |
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Post by JohnH on Oct 20, 2018 14:49:39 GMT -5
Hi Ro_S
The circuit looks basically fine to me. Just a few comments:
Im not personally a fan of master volume in addition to separate volume and tone for each pu, since it adds loading on your pickups, reducing max treble. But I think a number of archtops have them, and maybe the idea is a mellow sound for jazz etc.
Given its all passive its wise, as you have drawn, not to try to mix outputs of piezo and magnetic.
The two piezo volumes will interact and affect each other. Id reckon one piezo volume might just work better (or maybe none), and experiment with wring the piezos in parallel or in series to see which is better.
Good question about linking the grounds. I not sure but, given that they may go to different amps, there is probably no advantage in grounding them together, and possible risk of ground loops if they are linked. Ground the trapeze to the mag output ground.
I played with those piezos discs on a Strat, and its a totally different scenario to yours. But, the biggest suggestion I have is to try to rig up the piezos experimentally early, before committing to the internal build. eg, can you do a test wire up and then try placing them externally on the guitar to find the best places and check the output volume and tone?
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Post by Ro_S on Oct 20, 2018 18:45:15 GMT -5
Hello, Thanks for your reply. I'll make those two grounding changes you suggest. JohnH said: "The two piezo volumes will interact and affect each other."What will be the negative effect? I'd like to be able to adjust the volume and mix of the two piezos, you see. What about if instead, I had a single global volume for the piezos, and the secondary piezo has a pot configured as a blend control ? Thanks |
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Post by JohnH on Oct 20, 2018 19:55:17 GMT -5
Hello, Thanks for your reply. I'll make those two grounding changes you suggest. JohnH said: "The two piezo volumes will interact and affect each other."What will be the negative effect? I'd like to be able to adjust the volume and mix of the two piezos, you see. What about if instead, I had a single global volume for the piezos, and the secondary piezo has a pot configured as a blend control ? Thanks the issue with the two piezo volumes is similar (but different tonally) to the same in a humbucker guitar, when two pickups are selected. If you have one at full, and turn the other down, it starts to shunt the main pickup, eventually cutting out all signal. Along the way, the reduction of pickup 2 is loading pickup 1, which with piezos (being capacitive) will cut bass. Experiment is key to find what will work for you, I don't know enough to advise further. |
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Post by thetragichero on Oct 20, 2018 20:38:06 GMT -5
JohnH said: "The two piezo volumes will interact and affect each other."
what about one of those dual gang blend (sometimes called pan) pots? I have one in a two pickup bass and LOVE it instead of the standard jazz bass wiring
I had similar thoughts as John regarding master volume in addition to separate volumes for the magnetic pickups
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Post by Charlie Honkmeister on Oct 21, 2018 9:19:46 GMT -5
JohnH said: "The two piezo volumes will interact and affect each other."what about one of those dual gang blend (sometimes called pan) pots? I have one in a two pickup bass and LOVE it instead of the standard jazz bass wiring I had similar thoughts as John regarding master volume in addition to separate volumes for the magnetic pickups I would strongly suggest using at least 1 Megohm minimum, and 2-5 Megohm preferably, pots for the piezo discs.
500K , and especially two 500K's in parallel, will load the piezos down too much and mostly or completely kill the bass and lower midrange.
Buffering the piezos and mixing after the buffers would be a better solution. Another would be: going stereo output on the piezo jack, don't put any passive piezo volumes on the guitar at all, and buffer/mix with your external equipment.
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Post by Ro_S on Oct 21, 2018 10:34:22 GMT -5
Charlie Honkmeister Honkmeister - I'll go with your advice - and JohnH's - and NOT use any volume pots for the on-board piezo circuitry. So I'll eliminate them from my design. I'll just have some switching to select between the different piezo discs. I definitely do NOT want to get involved with any active on-board circuitry for the piezo. Thanks
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Post by Ro_S on Oct 21, 2018 18:44:01 GMT -5
I've elmininated the piezo volume pots out of my plan and substituted them with SPST 2-way on/off rocker switches. Have I wired these two new switches correctly? I've made the two grounding changes advised earlier in the thread. Thanks REVISED WIRING DIAGRAM BELOW:  |
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Post by newey on Oct 22, 2018 5:34:45 GMT -5
Your diagram looks fine if you were using SPST On-On switches (which have 3 lugs). Your diagram calls for SPST On-off switches, which only have 2 lugs.
But if it were me, I'd use DPDT switches to as to disconnect both ends of each piezo, just to be sure no noise issues arise. They probably won't, but better safe, etc.
Charlie's idea of a stereo output is I think a good one, do your mixing outboard. But I'll also reiterate JohnH's advice to experiment first with the piezos. When I have tried two of these piezo discs, it didn't seem to make much difference as compared to just one. But that was in a different context, so YMMV.
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Post by Ro_S on Oct 22, 2018 6:05:23 GMT -5
newey - You wrote. " Your diagram looks fine if you were using SPST On-On switches (which have 3 lugs). Your diagram calls for SPST On-off switches, which only have 2 lugs."Um, well, er, it's perfectly possible that I made a mistake in how I described and/or depicted the rocker switches that I intend to use. To help clarify what I am intending, below are the particular switches I have and want to use. So have I messed up with my proposed wiring? What do I need to do to fix it? Thanks.   
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Post by newey on Oct 22, 2018 21:28:15 GMT -5
Your wiring should be fine, although a quick check of the switches to be sure they operate as expected wouldn't hurt. As your diagram has it, these are On-On switches,and your diagram is correct for that type of switch.
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Post by Ro_S on Oct 24, 2018 4:59:36 GMT -5
Your wiring should be fine, although a quick check of the switches to be sure they operate as expected wouldn't hurt. As your diagram has it, these are On-On switches,and your diagram is correct for that type of switch. Okay, thanks. I'll adjust my nomenclature. |
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Post by Ro_S on Oct 24, 2018 5:04:43 GMT -5
I've revised my wiring diagram. Please see the latest version below.I noticed that my previous version omitted a ground wire between the 3-way switch and the pots; so I added that. I did right, yeah? I went with just a single piezo disc. I did the wiring yesterday and it seems to work fine but I haven't installed it in the guitar yet. (I need to add the grounding wire from the tailpiece.) How can I prevent or mitigate against the pop sound happening when the piezo circuit's switch is activated? Will adding a resistor or something somewhere sort it? Thanks  |
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Post by newey on Oct 24, 2018 13:31:30 GMT -5
Yes, that's fine.
Not sure on that, Ro, we'll need to await someone else's input. If it is due to a power surge with switching on the piezo, then there may be an electrical solution. But the piezo disc works based upon the vibrations of the surface to which it is attached. You may just be picking up the vibration caused by flipping the switch. If that's the case, then there isn't going to be any electronic solution. You might in that case be able to dampen out the switch with a small strip of rubber or something between the switch and the top of the guitar.
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Post by Ro_S on Oct 24, 2018 14:23:00 GMT -5
newey / all For what it matters, I was using a little battery powered amp for test purposes. It didn't matter how delicately I turned on the switch, it still created a pop sound. And, when doing so, I don't think the switch was physically connected via a hard surface to that of the piezo disc.
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Post by JohnH on Oct 24, 2018 14:40:39 GMT -5
Assuming that you want the piezo switch with just the one pickup, then those switching clicks might be solved by a resistor, either directly across the piezo, or directly across the jack output hot to ground. Depends whether it comes from charges building up in the piezo, or noise induced in the cable, or maybe both. These would be high value, maybe around 2M. Might need both.
But theres another simpler thing to try first. Instead of using the switch to disconnect the piezo, use it to short it out, hot to ground, with the piezo hard-wired to the jack. No spurious charges can build up then.
And hows the piezo tone sounding?. I know its just a test rig but are you getting a nice ranges of stringy highs down to full lows?
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Post by Ro_S on Oct 25, 2018 15:40:51 GMT -5
Assuming that you want the piezo switch with just the one pickup, then those switching clicks might be solved by a resistor, either directly across the piezo, or directly across the jack output hot to ground. Depends whether it comes from charges building up in the piezo, or noise induced in the cable, or maybe both. These would be high value, maybe around 2M. Might need both. But theres another simpler thing to try first. Instead of using the switch to disconnect the piezo, use it to short it out, hot to ground, with the piezo hard-wired to the jack. No spurious charges can build up then. And hows the piezo tone sounding?. I know its just a test rig but are you getting a nice ranges of stringy highs down to full lows? Hello, thanks. I haven't installed anything yet so I dunno how any of sounds with strings yet. I can tell stuff is working as it should, though. The single piezo disc gives a big output! Re: adding resistor/s - The biggest resistor values I have is 100k. Any good? Or, I have a 500k pots. If I added a pot as a volume control would that have the same effect? I don't understand your 2nd paragraph, sorry. Sorry to be dumb. How is that different to my diagram? |
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Post by thetragichero on Oct 25, 2018 21:05:32 GMT -5
I like the shorting the piezo is with the switch
to answer your question, you want a high value (for true bypass pedal switching noise it's in the range of 1-10M) resistor so that it just bleeds the excess charge to ground without actually affecting the signal being passed (that is my understanding, others may chime in with a more precise explanation)
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Post by newey on Oct 26, 2018 6:00:57 GMT -5
JohnH said:
RO_S said:
Your wiring shows the "hot" line from the piezo being disconnected by the switch,and then connected to ground in the other switch position. What JohnH is suggesting (and I concur) is to use the switch to short the hot to ground, without disconnecting it. IOW, the hot wire and the ground will both be permanently connected to the jack, and flipping the switch simply shorts the hot to ground.
The reason this may make a difference is this: Your switch is likely to be a "break before make" type (unlike, for example, a Strat-type lever switch which is "make before break"). A "break before make" switch means that, as you show it wired, the hot wire's connection to output is broken first when you flip the switch, before the connection to ground is made by the other throw of the switch.
The momentarily-open connection could potentially be causing the "pop", if John's surmise is correct. Grounding the second lug of the switch thus doesn't prevent the "pop" because that connection hasn't yet been made when the "pop" occurs.
If the switch were a "make before break" type, the opposite would be true, the hot would be grounded first, before the hot connection was broken. (Note that I am NOT suggesting you buy another switch, just to rewire the one you have!)
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Post by Ro_S on Oct 26, 2018 8:29:53 GMT -5
neweyOkay, but precisely how do need to alter the wiring to the switch (as shown in my Version 5 diagram) to achieve what you are proposing? Thanks
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Post by JohnH on Oct 26, 2018 18:18:49 GMT -5
newey Okay, but precisely how do need to alter the wiring to the switch (as shown in my Version 5 diagram) to achieve what you are proposing? Thanks Like this....  |
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Post by Ro_S on Oct 27, 2018 4:40:48 GMT -5
JohnH - Thanks! I shall try it and report back.
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Post by Ro_S on Nov 15, 2018 19:25:46 GMT -5
LATESTFix needed. I've completed the wiring and installation for this project but I need help with a specific problem, please... The switching and volume controls work okay, but neither of the TONE controls have any affect when adjusted. I have checked and I have wired it as per my latest wiring diagram. I sense that there is an error in the diagram; the wrong lug terminals probably.
Please can someone re-check my latest wiring diagram (the last one I posted above - version' 5'). Thanks. N.B. The pots in my diagram are depicted as if viewing their underside. The lug ref. numbers are annotated. Thanks P.s. the piezo disc appears to be working fine  Interesting sounds even without an acoustic pre-amp.
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Post by sumgai on Nov 15, 2018 21:04:45 GMT -5
R,
Your diagram is fine. Fortunately, there are some definite places to start our troubleshooting efforts:
* Bad solder joints. (Check the one point of possible failure, the ground wire that goes from the Neck Tone pot to the Neck Vol pot, both ends.):
* The pots themselves are bad. (Or possibly not the correct value);
* The capacitors might be the wrong value.
First and easiest thing to do is simply re-heat the two solder joints of the ground wire between the pots, and re-test. If that didn't work:
Unsolder the two caps and do a resistance check on each pot. They have been known arrive at your doorstep DOA. Or worse, mismarked in value. If that doesn't find the culprit:
Touch one of the cap's leads across the output jack terminals, then strum the strings. Did the sound get real dull? If yes, then the cap is good, and of the approximate correct value. If not, then the cap is too small a value.
Report back with your results, please.
sumgai
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Post by JohnH on Nov 15, 2018 21:14:06 GMT -5
hmmm...im not seeing any issue on the diagram...
Can you check with a meter that all pot backs are grounded to rhe jack ground? And are you confident in the value of tbe tone caps?
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Post by Ro_S on Nov 15, 2018 21:48:50 GMT -5
Thanks.
Noted that diagram is fine.
I will report back
Cap values are 0.047 uf. Pots are 500k, audio taper.
it's both tone controls that aren't working.
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Post by Ro_S on Nov 22, 2018 10:13:03 GMT -5
sumgai , JohnH -
I'm not sure what the problem was but I have fixed it. I re-soldered some connections and swapped a tone pot or two.
Thanks.
[project now completed - 22nd Nov.]
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Post by sumgai on Nov 22, 2018 11:47:53 GMT -5
sumgai , JohnH - I'm not sure what the problem was but I have fixed it. I re-soldered some connections and swapped a tone pot or two. Thanks. [project now completed - 22nd Nov.] Good to hear! Yer welcome, it was our pleasure.  sumgai |
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Post by Ro_S on Nov 23, 2018 17:40:58 GMT -5
Photo/s below of the completed project... New pickups and wiring. Plus passive piezo (separate output jack). New tuners and hardware. Soundport apertures added. The P90s covers are dummy covers only. Total costs: £68 ($95 ish?) Projects next up: new electronics for both my sitar-guitar project and my Disney Hannah Montana 3/4-scale complete overhaul project.   |
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Post by newey on Nov 29, 2018 23:29:14 GMT -5
She shore is purty . . .  What's underneath the stealth P90 covers? |
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Interesting sounds even without an acoustic pre-amp.
