Microphonic effect

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richinva
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Post by richinva »

Recent umble pedal build, have a microphonic (I believe that is the correct term) effect with the cables and the enclosure. Tapping on them is audible through the amp. My limited reading on this indicates a capacitance issue, but I really don't know where to begin or if that is the reason. Fender 25R amp, no other pedals in the loop. I believe cables are good as this pedal is the only one that does this.

Any help would be appreciated.

Thanks.

Rich

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Hides-His-Eyes
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Post by Hides-His-Eyes »

What's the effect? Does it otherwise work well? Does it contain any ceramic DC blocking caps?
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DrNomis
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Post by DrNomis »

I've noticed that sometimes, if you're using a high-gain distortion pedal, and you tap your finger on the guitar lead plugged into the input, you can sometimes hear a tapping noise coming through the Amplifier.... :)

This is caused by a variance in the inherent capacitance-per-metre of the guitar lead as you tap on the lead with your finger, this causes a voltage-signal which is amplified by the distortion pedal, to a level that the Amplifier can work with....well my theory anyway, I think it's called "Triboelectric Noise"..... :)

Tube Amplifiers tend to suffer from Microphonic Effects when one of the Tubes develops loose electrodes, when this happens you can get effects ranging from a slight ponging-noise when you gently tap one of the Tubes with a pencil, to a very loud ringing or whistling sound..... :)
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richinva
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Post by richinva »

The effect: tapping on the enclosure and/or cables can be heard through the amp, regardless of whether the pedal is on or not.

Otherwise work well? : it seems a bit noisy, but since I have nothing to compare it to, it's hard to tell.

Yes, there are ceramic caps.

Solid state amp, no tubes.

Rich

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DrNomis
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Post by DrNomis »

richinva wrote:The effect: tapping on the enclosure and/or cables can be heard through the amp, regardless of whether the pedal is on or not.

Otherwise work well? : it seems a bit noisy, but since I have nothing to compare it to, it's hard to tell.

Yes, there are ceramic caps.

Solid state amp, no tubes.

Rich

Do you have your Amp set to give a clean sound?..... :)

Also, have you tried disconnecting the pedal from the amp and seeing if you get the noise if you tap with your finger on the instrument lead?..... :)

If you don't get the noise if you try that, then it suggests that one of the parts in your pedal may be Microphonic.... :)
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richinva
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Post by richinva »

OK, further dissection reveals...............POS I/O jacks. Output was probably OK, but swapped it out anyway. My input cable was near the daisy chain of my 1Spot, which was causing gosh awful noise. Rearranged all of that and now it's much, much better. Still has some hum that my other pedals don't, but now it sounds like it should (I think). Why do people ship these crap jacks in a kit? Sheesh...........

Anyway, I am wondering if this filter: http://www.beavisaudio.com/projects/Huminator/index.htm would help with the remaining noise? I still have some hum, but the hiss is pretty bad. No hiss with any of the other pedals, minimal hum. Microphonic effect is gone.

Thanks for the help.

Rich

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richinva
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Post by richinva »

The filter did nothing.

R

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DrNomis
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Post by DrNomis »

Try turning down the volume control of your guitar, if the hum goes away, then that would indicate that the hum is coming from your pickups, that's assuming that you have single-coil pickups fitted to your guitar..... :)


If that doesn't pinpoint the source of the hum, try putting batteries in your pedals, if the hum goes, then your power supply is causing the hum noise..... :)

If you go into the FSB Public Library, you can download a book on Grounding And Shielding:Circuits and Interference, make sure you also download 7Zip, and/or Zipgenius and install them because you'll need either of those to decompress the book file..... :)
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richinva
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Post by richinva »

I'm getting the most hiss from the OLC umble kit and just a bit from my modded BD-2. Hiss is present whether guitar is plugged in or not.

I really believe this is a power supply issue, may have to invest in something better or learn to live with it.

R

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Post by DrNomis »

richinva wrote:I'm getting the most hiss from the OLC umble kit and just a bit from my modded BD-2. Hiss is present whether guitar is plugged in or not.

I really believe this is a power supply issue, may have to invest in something better or learn to live with it.

R

What sort of power supply system are you using?, if it is based on Switchmode Power Supplies, these tend to produce an electronic whining kind of noise..... :)
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

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richinva
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Post by richinva »

I'm using a 1Spot, but I believe most of the noise is from the other crap plugged into the system. Lights, CD player, digital recorder, computer, etc., etc., etc............ Much better than it was, after I fixed the jack. They didn't give this kit away, looks like they could have sprung for the extra $.27 for a decent jack. Stuff like this is just baffling to me.............

I'm trying to isolate the circuit, may even put this loop on its own breaker and see if that helps.

One thing at a time, I guess.

R

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