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From previous experience I know you are a source for good advices. Here is the thing.

I have a cheap Fender guitar that use to play at Church. Since they changed the cable "asigned" for guitars it doesnt amplify at all. When asked the audio guy he plugged a different (and cheaper) guitar and it did work, thus telling me to fix mine. I dont really have a chance to test it anywhere else. Here are a couple of things I would like your ideas on:

The cable we used to work with was a TS (guitar) -XLR (console), now they are using a TRS (guitar) - XLR (console). I noticed that because today a different guitarrist brought his Epi that used to work as well and spent 1 hour trying several things until he slightly pulled the plug and achieved sound. The question is: do I need in general a TS-TS cable or it shouldnt matter if I have a TRS-TS for example?

Long before all the onboard tuner of the Fishman Presys started acting out, and stopped working. It is the main reason why I do not think is totally a cable/plug thing, I think there is something really wrong in the whole electronics.

Today I pulled the strings and pulled out the undersaddle pickup to take a look, it is in very bad shape. I guess I could get bad sound from it but not no sound at all.So, if I get a replacement, Ive seen three different types, mine is like a braided thick cord, Ive seen a flat, thin, usually red coloured type and the third are like made of metal. Is it ok any of the three or do I need an specific one?

Now for the win, the thing I asume I need to do first is to test connectivity between all parts of the electronic since from the symptoms it would appear that either the pickup is not getting the signal to the preamp or that the circuit in the preamp is fried. My guess is to test connectivity between the undersaddle pickup ant the output jack and then start to narrow it down, is that right?

Sorry for the barbaric language, it must be painful to read but I really need help.

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    You have to have a place to test your guitar against known good equipment and with someone who knows how things work. If your sound guy gives you a TRS cable to plug into your guitar, there’s something wrong. I’m afraid neither you nor the sound guy know what you’re doing. :) Try a DI box, plug your guitar in the instrument input and a mic cable from the DI box’s XLR output to the mixer. Check phantom power or battery power requirements. – piiperi Reinstate Monica Dec 30 '19 at 5:10
  • Yes, I know, but I have to work with what I have at hand. I do have a DI box but the only cable I can connect it to the guitar is TS-TRS (I know, its a hack) I would appreciate and advice about the connectivity test with a multimeter, the type of piezo pickup if I neeed a replacement and if the onboard tuner stopping working is a credible sign that something is wrong in the electronics. I mean apart from all the cable chaos. – Earendil Dec 30 '19 at 5:22
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Your sound engy is hacking the guitar's connection to the mixer. To what end, I can't say, but I can say that the change in cable is significant and is the primary reason for your woes.

Acoustic-electric guitars have a battery-powered preamp. To avoid that battery being constantly connected to the preamp, draining the battey when you're not using the guitar, the ground side of the power supply circuit is usually run into the jack using the "ring" contact of a tip-ring-sleeve or TRS jack in the instrument. Insert a standard two-conductor "tip-sleeve" 1/4 plug, and the ring and sleeve contacts are shorted together through the plug's sleeve, completing the battery circuit and powering up the preamp. This is why you're told not to leave your guitar plugged in overnight or when you're not using it.

The old tip-sleeve plug you were using worked for this purpose, and it gave the mixer a usable if probably noisy and rather mid-heavy signal. But, when the engy changed it out to a TRS-to-XLR cable, two things happened.

  1. Your guitar's preamp can no longer complete the power circuit to ground, because the "ring" and "sleeve" contacts only have continuity through the long cable run back to the mixer, where there's likely a 600-ohm resistor between those two conductors that provides an "impedance-balanced" circuit for microphones and other low-impedance audio sources. That reduces the current flow through the preamp below the minimum power requirements.

  2. Your signal ground is likely wired to the sleeve conductor, which is expected for an unbalanced audio signal. However the mixer, given a three-conductor input, is expecting signal through the "hot" (tip) and "cold" (ring) conductors of the input, meanwhile the ground (sleeve) is considered pure noise and never enters the mixer's signal path.

The Epiphone player's guitar eventually worked because pulling out the plug slightly either used the sleeve contact as a jumper between the ring and sleeve to complete the preamp circuit, or if it was a traditional electric guitar with no preamp, the sleeve connector simply made contact between the ring of the plug and the ground contact of the jack without disconnecting or shorting the tip, to produce a valid audio circuit for the mixer.

The cheaper A/E probably worked because its jack design was slightly different, either connecting power through two contacts for the same conductor of the plug, or using a separate switch for power that isn't electrically continuous with the plug (this avoids the annoying "pop" you get when you plug in a preamp-powered instrument). Just because the guitar's cheaper doesn't necessarily mean corners were cut in the electrical design; there's a lot of other corners to cut in the construction of an acoustic instrument to hit a pricepoint.

Anyway, it's the "audio guy" who is screwing up here. The mistake wasn't swapping the cable, the mistake this whole time has been not using a DI box on-stage to produce the low-impedance balanced signal circuit the mixer expects from the high-impedance unbalanced signal circuit of the guitar. Your guitar should be using a typical two-conductor instrument cable, fed into a direct input box which uses a transformer to "isolate" the high-impedance circuit of your guitar from the low-impedance circuit output to the mixer, thus giving both devices the electrical circuit they were designed to use while transmitting the signal between the two circuits. Plug in a DI, or a tone-shaping preamp stage like a SansAmp or an L.R. Baggs PADI, and not only will you get your signal path back, the sound quality will likely be dramatically improved from what you'd been getting with just the TS-XLR cable.

The fact that other guitars "work" with the new setup is only weak evidence that something's wrong with yours, and in any case, the audio guy is there to make his system work with your guitar, so by telling you your guitar is the problem, when it's clear his change caused other problems for other people, the audio guy is just trying to dodge his responsibility to you as a fellow member of the worship team.


As for the status of your pickup and preamp, what's going to work depends on the sound you want, what parts of the existing system you want to keep, and how much you want to spend. I'll tell you that a replacement preamp and pickup, plus a knowledgeable luthier's labor time to swap out, can easily cost you more than the guitar's worth when you're done, and may exceed the cost of a new comparable replacement off the rack.

Replacing like-for-like, that Fishman Presys+ will set you back about $200, and that's if you're confident in your ability to swap out the old and new components so you can save the labor costs of installation. It's not rocket surgery, and it's a big help that the guitar's already got a system installed so you're not drilling/cutting holes, but it can still take you quite some time to fish wires and tighten down connections and fittings. If you're serious about what you do on Sundays, this might be an opportunity to upgrade the entire instrument, say to a Yamaha FGX series or possibly even one of the lower-end Taylors. The Fender will still work acoustically, so you can keep it around as a "beater", or you can trade it in to lower the cost of the replacement.

Either way, if you honestly suspect your electronics are going the way of "Total Incapability To Sustain Usual Performance", it's best to get ahead of that ASAP, before the guitar ends up crapping out on you in the middle of service.

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  • Thanks a lot mister, I think Im gonna keep this for reference besides this case. Im gonna make a general answer because yesterday I could finally test it and narrowed down the problems. – Earendil Jan 3 at 14:22
  • Btw, Ive seen in amazon these fishman presys both for 199$ and 25$, are the cheap ones fakes or it depends on the dealer. I mean, the whole thing doesnt seem to me worth 200$ – Earendil Jan 3 at 15:11
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    @Earendil "Fake" is a relative term these days. The $25 ones were probably made to be actual Fishman systems, but Fishman rejected them for one reason or another, probably QC. The Chinese have a noted history of passing off the product to the highest bidder in these cases, and Amazon, much like YouTube, FB etc, just doesn't have the manpower to keep up with millions of Chinese entrepreneurs passing these rejects off as the first-line brand-name product. – KeithS Jan 3 at 15:57
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    I mean, if you wanna take a chance, they're only $25, but you won't get any guarantees, especially not from Fishman. – KeithS Jan 3 at 15:59
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On a cheaper Fender guitar, it's incredibly unlikely that you have a TRS connection from the Fishman pickup. You're just going to have a standard 1/4" mono cable (TS - but rarely called that).

Buy a 10ft 1/4" Mono instrument cable. Connect it to the DI box you have, and let the sound engineer earn his money by using a standard XLR cable to connect your DI box to the stage box or mixing console. Investment, about $15 for the cable. Payback - priceless. Because you've just shown the sound engineer how it's really done. You have a 10ft unbalanced instrument level connection, which now goes into a balanced mic level connection via the DI; your guitar will actually sound better, because the impedance level will be correct.

When you're buying the instrument cable, don't do it online - go to a local music store. There, you'll be able to discuss the issue with them, and try it out to ensure that it's not a simple issue like a battery in your guitar (the case of your associate's Epiphone indicates that it is a cabling issue, however.)

For info; a TRS->XLR cable does have its uses. But normally, it's for connecting outboard equipment rather than instruments. It has the advantage of providing a balanced signal to disparate end connectors - but that's not a use-case that you're interested in. Plugging a TRS into a mono connection just turns it into a mono cable (with the potential for not working at all, depending on how it's wired...)

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  • Thanks a lot, could you share some advice about how to use a multimeter to check connectivity in the whole electronics?? Ive seen so many tutorials online but just for electric guitars. – Earendil Dec 30 '19 at 16:18
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    @Earendil - there is no point. As Pete said, you need to use a normal guitar cable, not a TRS cable. If you really do need a tutorial, the electric guitar ones are just as valid - as your guitar is semi-acoustic: the elctric elements are just the same as any electric guitar. – Doktor Mayhem Dec 30 '19 at 17:16
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    @Earendil Your guitar probably has a piezo pickup underneath the bridge (so not a magnetic pickup like most electric guitars.) Have a look at senscomp.com/pdfs/using-piezo-sensors.pdf. Your brain will then explode, and you'll get that the best way to test your pickup is to plug it into an amp using a guitar cable and see if it works. – PeteCon Jan 2 at 13:50
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note: I've had to change my answer, thanks to a comment pointing out what's happening.

TRS-XLR cables often don't work for connecting a guitar to a balanced circuit. The TS connector in the guitar does not have a ring contact, which means pin 3 on the XLR floats. The preamp on the mixer input works by measuring the difference between pin 2 and 3. If pin 3 floats, you can't do this so the input does not see a signal.

If pin 3 is grounded, the mixer input works correctly.

If a guitar works when you pull the plug slightly, that indicates the above situation is going on: when you pull the plug, the ground contact also contacts the ring, grounding pin 3.

Less likely problems: the cable might be wired incorrectly, or the connector is out of spec and the tip doesn't make contact when the connector is inserted fully.

Use a cable tester or a multimeter to confirm all 3 leads are connected. This is the correct pinout: enter image description here

You can use a TS->TRS cable to get your guitar to work. As the other answer indicates, a DI is the best method of connecting a guitar to a balanced circuit.

To test your guitar: is there a music shop nearby where you can plug your guitar into an amp?

A TS-TRS cable should be wired like this:
tip->tip
sleeve->sleeve and ring

You can't do resistance tests directly between pickup and output: there will be active elements (transistors etc) in the preamp which lead to weird results on a resistance test.

You could remove the preamp from the guitar to inspect the wiring to the output jack and the pickup.

Also check the batteries: low battery voltage or contact corrosion can lead to all sorts of trouble.

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  • this is great, thanks. And what would be the correct way to male a TS-TRS connection? does the ring on the TRS needs to be bridged to the sleeve or can it just stay like that? How about the multimeter test? Should there be connectivity between the piezo and the output jack? – Earendil Dec 30 '19 at 12:53
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Yesterday I could finally take it not to a music shop, because living in Cuba, the closest thing to a music shop available is the bazar where they sell conga drums, lol, but to a friend of mine whohas a little repair shop for electronics in general. We spent the whole day taking apart the preamp and measuring conectivity and looking for probable faulty components or shorts. There were none. He resoddered everything just in case and we put all together back. Then we tested the guitar with an 1950 vacuum valve 10 W amplifier, the thing is an antiquity but the sound quality is still awesome. We could get sound but it was barely audible. Then we did two things, he checked my TS-TRS cable and besides shoddy soddering the tip was kinda loose (ill have to replace it anyways eventually) While he was at it I pressed hard on the saddle since I already told the piezo is looking kinda worn out. First thing was that the onboard tuner started working again (with inconsistencies but well... And then when checked again we got a decent amount of sound and no noise. I dont think is still at full capacity but Im inclined to think that the piezo is actually faulty because I dont think I should have to press that hard the saddle to get a better (even if still insuficient) sound.

Thanks for all your answers. I will be starting a new question just to adress the piezo replacement.

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