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Author Topic: No piezo with stereo cable  (Read 296 times)

Offline Slo101

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No piezo with stereo cable
« on: June 16, 2017, 11:12:44 AM »
I've tried three different stereo cables and I get no signal from the piezo pickup. Using a mono cable the piezo comes through just fine. It appears that something in the output jack has come out of adjustment. I'm going to dig into it this weekend. Has anyone experienced this and found the solution? Anyone with pictures of what you did to fix it? Thanks.

Re: No piezo with stereo cable

Offline sybersitizen

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Re: No piezo with stereo cable
« Reply #1 on: June 16, 2017, 02:30:25 PM »
If it's an early model Fly, make sure the red button next to the jack is in the 'out' position when a stereo cable is connected.
'01 Fly Deluxe|'69 SG Standard|'69 EB-3|Pignose Strat|Savannah SGO-16CE|Fishman Aura Spectrum|Roland Amplifiers

Re: No piezo with stereo cable

Offline Slo101

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Re: No piezo with stereo cable
« Reply #2 on: June 16, 2017, 02:44:13 PM »
Thanks, but it's a 2008.

Re: No piezo with stereo cable

Offline sybersitizen

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Re: No piezo with stereo cable
« Reply #3 on: June 16, 2017, 03:15:44 PM »
Okay ... it seems the smart jack has lost its smarts somewhere along the way. I think the autosensing system for that is entirely in the electronic realm rather than something physical; but I could be wrong.
'01 Fly Deluxe|'69 SG Standard|'69 EB-3|Pignose Strat|Savannah SGO-16CE|Fishman Aura Spectrum|Roland Amplifiers

Re: No piezo with stereo cable

Offline mmmmgtr

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Re: No piezo with stereo cable
« Reply #4 on: June 16, 2017, 10:36:30 PM »
You are correct.  This had been reported before by a few others.  I'm not aware of any full proof solution,  but it seems related to the input impedance of whatever you are connecting to. This would include the cable being used as well as the input circuit of the amp or pedal or tuner,  etc... If you are going directly into an amp or board,  try putting a pedal or tuner in between to see if the different input impedance makes a difference.


It is still possible to be a jack problem. If the ring connection is loose or maybe the plug doesn't seat into the jack properly,  the ring connection might look like ground to the Powerchip, which would send it to mono operation.


Or, as you implied,  might need a new Powerchip...
 

Re: No piezo with stereo cable

Offline Slo101

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Re: No piezo with stereo cable
« Reply #5 on: June 17, 2017, 12:01:09 PM »
Turns out the problem exists only when plugging the stereo cable into the two inputs on my Vox AC15. It works fine plugged into two inputs on my vintage Supro and Silvertone amps, and it works fine going stereo with two Boss Katana amps. For some reason the Vox amp does not want the piezo signal. And it's not a problem with an input jack on the amp. If I switch the plugs and jacks I get the same result, mag signal but no piezo. Very strange.

Thanks for the help guys.

Re: No piezo with stereo cable

Offline mmmmgtr

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Re: No piezo with stereo cable
« Reply #6 on: June 17, 2017, 02:55:21 PM »
Try running only the piezo plug into a tuner (or any pedal) ,  then from the output of the tuner/pedal into the vox.  Continue to run the mags direct into the vox.  I'm betting it will work. It will isolate the guitar outputs,  each with their own different input impedance they will see.


I agree that if it is working with other amps, not a guitar jack problem. I wasn't implying an amp jack problem. The issue I tried to describe would occur on the guitar end,  not the amp end.
 

Re: No piezo with stereo cable

Offline Slo101

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Re: No piezo with stereo cable
« Reply #7 on: June 17, 2017, 04:01:21 PM »
Try running only the piezo plug into a tuner (or any pedal) ,  then from the output of the tuner/pedal into the vox.  Continue to run the mags direct into the vox.  I'm betting it will work. It will isolate the guitar outputs,  each with their own different input impedance they will see.


I agree that if it is working with other amps, not a guitar jack problem. I wasn't implying an amp jack problem. The issue I tried to describe would occur on the guitar end,  not the amp end.

Thank you very much, that works. If I plug the piezo into any pedal and turn the petal on it works. I don't understand it, but it works. I wonder why only the Vox does this.

Re: No piezo with stereo cable

Offline billy

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Re: No piezo with stereo cable
« Reply #8 on: June 17, 2017, 06:15:24 PM »
Iirc the box has a low and hi input?

The smart jack works based on impedance. So the pedal in front gives the power chip the impedance it needs to do the switching correctly.

If you have the two inputs I'm thinking on the vox, or maybe it's a switch somewhere, try the high one.
Billy

[always the beautiful answer who asks a more beautiful question.  e. e. cummings]

Re: No piezo with stereo cable

Offline Slo101

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Re: No piezo with stereo cable
« Reply #9 on: June 17, 2017, 06:46:26 PM »
Iirc the box has a low and hi input?

The smart jack works based on impedance. So the pedal in front gives the power chip the impedance it needs to do the switching correctly.

If you have the two inputs I'm thinking on the vox, or maybe it's a switch somewhere, try the high one.

It has a "Normal" channel and a "Top Boost" channel. It doesn't matter which one the piezo is plugged into, it doesn't work unless it goes through a turned on pedal. I usually run the piezo through reverb and chorus pedals but the other night I plugged in directly and found this issue. Anyway like I said I typically run through a couple of pedals so this isn't a problem. Thanks.

Re: No piezo with stereo cable

Offline billy

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Re: No piezo with stereo cable
« Reply #10 on: June 22, 2017, 03:24:32 PM »

If I plug the piezo into any pedal and turn the petal on it works. I don't understand it, but it works. I wonder why only the Vox does this.

I was responding to your "wonder why" comment- you might not be the only one with this issue and the details could help someone else. 

Like I mentioned, the smart jack works based on impedance.  Seems your Vox has a lower input impedance, and so the smart jack doesn't work right with it. 

Many pedals have the higher impedance the smart jack is looking for, so it's a nice workaround. 

I've never used a vox, and wasn't sure what the difference between the inputs was. 

However, in the old days, amps often had a "high" input and a "low" input.  These had different impedances, with the intention of minimizing how much tweaking you'd have to do to the knobs when switching between guitars with different pups, ie humbuckers vs single coils. That's why I suggested that a different input might work for you.

Not sure what your Vox inputs do but I guess that isn't it.
Billy

[always the beautiful answer who asks a more beautiful question.  e. e. cummings]

Re: No piezo with stereo cable

Offline mmmmgtr

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Re: No piezo with stereo cable
« Reply #11 on: June 22, 2017, 10:15:25 PM »
Here is an interesting test. Plug only the Piezo into the Vox and let the magnetics unplugged. Can you hear the piezo through the vox?


If there is still nothing then it is a basic input impedance issue with the Vox amp and compatibility with the Powerchip.


If it does work then its related to the circuit on the dual inputs creating a lower impedance somehow when the two inputs are both connected.


In either case it is the input impedance issue that I mentioned originally and was confirmed later by Billy.


The reason it doesn't work when you route the piezo through the pedal with the effect turned off is likely due to the pedal off position being true bypass.  That is equivalent to plugging the piezo direct into the amp.
 

Re: No piezo with stereo cable

Offline Slo101

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Re: No piezo with stereo cable
« Reply #12 on: June 26, 2017, 03:29:03 PM »
There's no sound with only the piezo plugged in. I'll just have to use at least one pedal with the piezo. Not a big problem.