DIY electret microphone capsule pre-amplifier - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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
Thread Tools Search this Thread
Old 17th May 2009, 09:18 PM   #1
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
EC8010's Avatar
Join Date: Jan 2003
Location: Near London. UK
Default DIY electret microphone capsule pre-amplifier

Electret microphone capsules are cheap and ideal for measuring your latest loudspeakers, but you need a pre-amplifier to take it into your sound card. Traditionally, people have fitted a resistive load to the capsule's FET as per the manufacturer's recommendation, but this isn't the only way it can be done. I've successfully turned the FET into the lower element of a cascode, with the advantage that the low load resistance means that cable capacitance from the capsule to the pre-amplifier is lesss of a problem. I power the whole shebang from a pair of 9V batteries in series. It all fitted in a 4" x 2" x 1" cast aluminium box...
Attached Images
File Type: gif wm60 microphone amplifier.gif (7.9 KB, 708 views)
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 8th March 2010, 07:07 PM   #2
jeepee is offline jeepee  Netherlands
diyAudio Member
Join Date: Apr 2009
Default Yet Another Mic Amp

Here is a variation on the theme. The transimpedance amplifier stage also provides a low impedance input, similar to the cascode transistor, reducing the cable capacitance problem. The 2nd opamp forms a offset correction amp (DC-servo) with a 3Hz roll-off. Hence the total amp as a 3Hz high-pass characteristic. 220R at the output to keep the Opamp stable. When using 220kOhm for both input of the 2nd opamp, the DC offset at the output <5mV. Whole circuit is supplied with two 9V batteries. If more gain is required the 2k2 resistor can be increased. Should fit in the same box.
Attached Images
File Type: jpg mic_preamp_jeepee.jpg (49.8 KB, 504 views)

Last edited by jeepee; 8th March 2010 at 07:15 PM.
  Reply With Quote
Old 17th March 2010, 12:00 PM   #3
diyAudio Member
giralfino's Avatar
Join Date: Feb 2009
your preamp looks simple enough that I can build one. The main problem is that the NE5533AN is hard to find or very expensive, while I can have a couple of NE5534AP at the rs-components warehouse which is only a little walk from home for small money. It is possible to use 2 x NE5534AP instead of the NE5533AN?
If the answer is yes, I have other questions about the connection/build - can I contact you about that?
TIA, Ralf
  Reply With Quote
Old 24th October 2010, 10:13 AM   #4
diyAudio Member
Join Date: Nov 2004
Location: UK
Send a message via AIM to HuntTheShunt Send a message via MSN to HuntTheShunt Send a message via Yahoo to HuntTheShunt
Did you get the NE5534AP version working?
  Reply With Quote
Old 26th October 2010, 10:03 AM   #5
diyAudio Member
giralfino's Avatar
Join Date: Feb 2009
In a word, no. I hadn't any answer for my doubts. I quickly built the TL071 version (first circuit on this thread), using a different opamp that I had lying around (a 4560DD). It worked and was pretty easy to build, but eventually I built the Wallin preamp for the clipping circuit. It was a lot more work, because of the greater number of components (and me not having a PCB).

  Reply With Quote


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
Condenser microphone capsule for AKG-NEUMANN stevenHK Vendor's Bazaar 3 20th August 2010 09:06 PM
Max spl of electret capsule Circlotron Analog Line Level 24 20th February 2008 08:32 AM
Anyone have an extra electret capsule? Kilentra Swap Meet 2 3rd March 2004 05:57 AM
Help with circuit for condenser microphone capsule ? mwmitchell Solid State 6 28th July 2003 03:46 PM
best way to generate Gate-Drain or Gate-Source short in electret capsule JFET? capslock Parts 2 27th September 2002 08:07 AM

New To Site? Need Help?

All times are GMT. The time now is 12:22 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2