Jump to content
Electronics-Lab.com Community

"L6" - what kind of transistor?


Recommended Posts


You forgot to tell us what the pickup is used for. A guitar? A piano? A drum? The horrible circuit will work with an N-channel Jfet or NPN transistor if the piezo pickup is in a drum. 

 

The circuit will not be a linear amplifier with a high input impedance if a Jfet is used. The circuit is designed to use an NPN transistor but will work poorly when a piezo pickup or magnetic guitar is used because its input impedance is too low.

If an N-channel Jfet is used then its gate must have a 2.7M resistor to 0V, not to its output. Use a 2N5457 or 2N5484.

Link to comment
Share on other sites

Hi audioguru,

thanks for the fast reply!

The pickup is a simple piezo-disc (buzzer) used in a very cheap throat microphone. Since it wasn´t doing its job - sound was heard from all directions, not only from the throat - I have meliorated the throat-mic by acoustic means using silicon gel as sound conductor and expanded rubber as isolator. Now it works just lovely!

As a matter of fact, it works that well, that I wanted to make some more on my own account, but I can´t figure out which transistor to use. The "horrible circuit" works actually very well.

Searching the internet I now found as possible candidate the 2SC1623-L6, which has "L6" printed on the SOT23 housing, and which is a NPN. Do you think this transistor is possible?

 

Thanks again,

Michael

 

Link to comment
Share on other sites

The circuit you found will not work with a Jfet but will work with an NPN transistor and a low impedance signal source (not a piezo).

A piezo throat mic is a contact mic. Go to http://makezine.com/2011/12/20/collins-lab-diy-contact-mic/ to see the different circuit used for a Jfet preamp for a piezo mic.

There is a similar circuit at http://www.homemade-circuits.com/2014/07/diy-contact-mic-circuit.html but it has the drain and source pins of the Jfet connected backwards.

Link to comment
Share on other sites

Thank you very much, audioguru, for your advise and detailed information.

These two schematics posted by audioguru, work both with 9V. Could they work with 3.3V?

What I need is a circuit to work with the 3.3V you can get out of a PC-mic input, where the tip of the phone jack caries the audio signal, the ring is connected via a resistor of 2.2k to 3.3V, and the sleeve goes to GND. Since the preamps in the PCs do always have a decoupling cap, ring and tip can safely be shorted to supply the 3.3V as phantom power.

Thanks again!

Link to comment
Share on other sites

  • 1 year later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
  • Create New...