LM317 As Electret Mic Amplifier - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 23rd May 2003, 10:23 AM   #1
diyAudio Member
 
mrfeedback's Avatar
 
Join Date: Feb 2002
Location: Perth, Australia.
Default LM317 As Electret Mic Amplifier

A useful little circuit maybe - kills two birds with one stone.

Eric.Electret Mic Preamp
Attached Images
File Type: jpg 50_circuit_combines_power_supply_and_amplifier_.jpg (74.8 KB, 508 views)
__________________
I believe not to believe in any fixed belief system.
  Reply With Quote
Old 23rd May 2003, 12:28 PM   #2
diyAudio Member
 
Join Date: Feb 2003
Location: GTA
rather clever design
those panasonic capsules are pretty amazing for the price
__________________
intentionally blank
  Reply With Quote
Old 23rd May 2003, 12:34 PM   #3
diyAudio Member
 
Circlotron's Avatar
 
Join Date: Jun 2002
Location: Melbourne, Australia
But you'd have to be a bit of a sausage to use a voltage reg as an amp...
Stop posting silly circuits, mrfeedback.
__________________
Best-ever T/S parameter spreadsheet.
http://www.diyaudio.com/forums/multi...tml#post353269
  Reply With Quote
Old 23rd May 2003, 12:37 PM   #4
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Default Sausages and 'roo's united...

It's amazing it works with C1 in circuit!

Cheers,
  Reply With Quote
Old 23rd May 2003, 12:42 PM   #5
diyAudio Member
 
Join Date: Feb 2002
Location: Germany
Ever seen an amp with 15 - 47 F on its output?
  Reply With Quote
Old 23rd May 2003, 12:44 PM   #6
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Perhaps if it's a Black-Gate, it'll be ok
  Reply With Quote
Old 23rd May 2003, 01:05 PM   #7
diyAudio Member
 
Join Date: Feb 2002
Location: Germany
Look at http://www.linkwitzlab.com/images/graphics/microph1.gif for the two standard ways to hook up an electret.

1) suggested by Panasonic uses the FET in common source mode, with a gain resistor in the drain connection:
+ gain
- distortion of the FET in common source mode

2) suggested by Sennheiser and Siegfried Linkwitz, uses the FET as a source follower with a 10 k load impedance:
+ lower distortion
- no gain

3) I have been thinking about replacing the 10 k with a constant current source:
+ even lower distortion
- higher parts count
- still no gain

The LM317-circuit gave me another idea:
4) Use the FET as it is, i.e. without disconnecting the membrane from the source. Connect the drain to a stable 2 V supply. Connect source to a virtual ground (negative input of op amp). The gain can be set through the feedback resistor. This hookup keeps the voltage across the FET constant and measures the current, just like the LM317. Haven't had time to look at typical FET curves. Would this by chance be more linear than 2) or 3)?
  Reply With Quote
Old 23rd May 2003, 01:29 PM   #8
cm961 is offline cm961  Canada
diyAudio Member
 
cm961's Avatar
 
Join Date: Jun 2001
Location: Peterborough, Ontario
Me and a buddy are working on an electret mic project for recording drums. We plan on hooking up one little capsule per drum/cymbol, and mixing it all down to two channels. We had to modify the electrets a la linkwitz because the loud sounds were saturating the FET stage inside the capsule.

Although we're still putting it all together, the one mic that I did make was decent. They are supposed to have pretty flat response, so I'm wondering why studios etc don't use them regularily. At like $0.50 a pop, you can't go wrong.

Pete
  Reply With Quote
Old 23rd May 2003, 01:51 PM   #9
diyAudio Member
 
Join Date: Feb 2002
Location: Germany
schematics 3 & 4:
Attached Images
File Type: gif mic_3_4_100dpi.gif (6.8 KB, 405 views)
  Reply With Quote
Old 23rd May 2003, 02:40 PM   #10
diyAudio Member
 
mrfeedback's Avatar
 
Join Date: Feb 2002
Location: Perth, Australia.
Quote:
Originally posted by Circlotron
But you'd have to be a bit of a sausage to use a voltage reg as an amp...
Stop posting silly circuits, mrfeedback.
LOL.
__________________
I believe not to believe in any fixed belief system.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY electret microphone capsule pre-amplifier EC8010 Analogue Source 4 26th October 2010 10:03 AM
4-pin mic converted to a 2-pin electret mic? silentblackhat Solid State 1 10th January 2008 06:50 PM
LM317 amplifier Russell Sit Solid State 3 5th June 2006 04:31 PM
Amplifier with LM317/337 voltage regs. DigitalJunkie Solid State 1 20th January 2005 11:36 AM
High Quality mic amplifier for Panasonic WM-60a electret? Toster Solid State 8 10th March 2004 06:29 PM


New To Site? Need Help?

All times are GMT. The time now is 11:29 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2