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I am using piezo speakers as pickup for my guitar. In one setup, for an amp, I have a 25 year old Philips powerhouse aw636 stereo, which has a mic in. The problem is that when I connect the piezo to the mic in on the stereo, there is a buzz, and it goes away if I touch the negative tip of the jack. A microphone from Philips works fine, without any hiss, but not the piezo by itself.

I was trying to remove the buzz/hiss from the setup using capacitors (trying to create grounding) but that never worked...

What can I do so that I don't have to connect my body to the jack -ve to remove the hiss?

The piezo pickups work fine without hiss when I connect them to the computer's mic in jack for amplification. The piezo in use a 35mm one.

EDIT:

One of the comments was an answer, that by Tony Stewart.

It says:

Use a large CM choke which balances the 2 wire impedance by raising CM Z while not raising differential Z.

cort ad810 with 35mm piezo speaker as pickup philips powerhouse aw636 stereo

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    \$\begingroup\$ Did you connect tip and ring of the jack together to the one terminal of piezo and sleeve to the another? \$\endgroup\$ – gabonator May 11 '18 at 6:34
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    \$\begingroup\$ does laptop buzz with charger on? If you dont have one the tower is earth grounded and thats the difference with your Philips Amp. Usually a 1nF or so cap from frame or (jack -ve) to earth ground is sufficient. The problem being unbalanced high Z mic and noisy supply.. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 11 '18 at 6:43
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    \$\begingroup\$ Do you have shielded mic wires>? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 12 '18 at 2:15
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    \$\begingroup\$ You might want to terminate the shield only at source and use a large CM choke which balances the 2 wire impedance by raising CM Z while not raising differential Z \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 12 '18 at 23:16
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    \$\begingroup\$ It's like a Humbucker coil except for conducted signals rather than string magnetic vibrations. If you dont know what Common Mode hum does to unbalanced signals, look it up on this site or others \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 13 '18 at 2:14
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To reduce the effects of ground loop try connecting ground loop isolator between the signal source and amplifier

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  • \$\begingroup\$ Okay Thanks for that, I didn't know readily made ones were available... I still will have to look at a DIY solution for now though \$\endgroup\$ – Vibhu May 11 '18 at 8:39

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