Author Topic: Guitar preamp op amp tl072 input noise  (Read 16109 times)

0 Members and 1 Guest are viewing this topic.

Offline Richard Crowley

  • Super Contributor
  • ***
  • Posts: 4310
  • Country: us
  • KE7GKP
Re: Guitar preamp op amp tl072 input noise
« Reply #125 on: December 12, 2017, 10:54:14 pm »
I meant like audioguru's circuit, but with the JFET, R1 and R2 separated from the rest of the circuit with a cable, consisting of two cores.
Note you can do that with 1-core shielded cable.  In fact that is how virtually all electret condenser microphone circuits are designed.  Your common, 82-cent jelly-bean electret condenser mic capsule is just a FET that has its gate connected to the electret mic element.  The power required by the FET is fed through the same conductor as the signal comes back through.  And that powering convention is called "plug-in power" by most consumer gadgets that have external mic connectors. Phones, recorders, camcorders, etc. etc.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 14157
  • Country: gb
  • 0999
Re: Guitar preamp op amp tl072 input noise
« Reply #126 on: December 14, 2017, 11:41:25 am »
I meant like audioguru's circuit, but with the JFET, R1 and R2 separated from the rest of the circuit with a cable, consisting of two cores.
Note you can do that with 1-core shielded cable.  In fact that is how virtually all electret condenser microphone circuits are designed.  Your common, 82-cent jelly-bean electret condenser mic capsule is just a FET that has its gate connected to the electret mic element.  The power required by the FET is fed through the same conductor as the signal comes back through.  And that powering convention is called "plug-in power" by most consumer gadgets that have external mic connectors. Phones, recorders, camcorders, etc. etc.
Yes, that's true. With that sort of signal level, it's possible you might be able to get away without screened cable. I've recently used a common emitter amplifier to boost the signal level of a dynamic mic and it worked fine with an unscreened cable, even in a fairly high noise environment: the cable was over 10m long and ran past several switched mode power supplies. The impedance of the amplifier was lower at a 510R, rather than 6k8, though the signal level was slightly lower too.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf