Condenser Mic element question./OT

[petemoore]

I bought a 270-090 from Radio Shack, a condenser Mic element.
 At 2.49 I figure it's worth a try.
 However the little daigram on the back is rather incomplete, anyone know of a well drwn schematic and or explanation as to how to wire this thing?
 It came with these specs:
 Supply voltage 1-10vdc
 Nominal supply 4.5vdc
 Current drain .3ma
 Signal/noise 60db min
 output impedance 1k
  Seems liket he output impedace could/should be improved...with a buffer or booster.
 It looks like a simple enough diagram [has a triangle with three lines going to it and a box witha line coming in one side and going out the other]
 Any suggestions as to any ckts that would help the little thing work/work better?

[Rob Strand]

Standard deal,

http://www.epanorama.net/documents/audio/electret.html

There's not much to improve. You might not be aware they actually have a JFET preamp inside (and if it isn't JFET it's an IC).  The output impedance is already pretty low on those.  

It's possible to to tinker with the resistor to change the gain to some extent too.

There's are some mods for specific applications which involves cutting tracks on specific brand microphones - may or may not work on other brands.  The mods are only useful if the problems they fix are problems to you.  See the Linkwitz labs site.

[petemoore]

Must be an IC in this package, I was looking at the Mic Schem [on the included diagram] they have on the left but separate separate from what's on the link you provided.
 we used to Condenser Mic the guitar with...WOW [till the battery dies} then woah...A high quality condenser, Now I Need to find one [maybe more] of those and try it out.
 Although the one I got boasts wide range, for 249$ I'm not expecting that much.
 I have no idea what a 'good' one is..anyone know of a good to 'better' one to try?

[Rob Strand]

> anyone know of a good to 'better' one to try?

The panasonic WM60, 61, 62 types are extremely good and quite cheap like < $3 US (I think one of those large mouser-like companies sell them).  Being omnidirectional condensors, by good I mean they have very flat and extended responses - and therefore faithfully reproduce the sound at the recording position.  Mic's for recording guitar is more of a recipe.

[petemoore]

Of amp nimbing proportions came out of it.
  I hope not too much damage was incurred...it made a funny whizzouf
sound then seemed  fairly normal...I think DC was getting in the amp...
  Gonna try it with the puterset [amp/speaker] instead of the Dynakit [dohh].
  Cant see what could be wrong though...cap, R, and one side of the mic connected ... the other side of the cap being output and the other side of the mic going to groung. Battery connected to +/-respectively...

[Mark Hammer]

For a number of years I taught evening sections of university courses to people who could not always make it to class, so I would tape lectures for people to catch up.  Initially I used a simple Radio Shack cassette recorder with the on-board condensor mic but this proved to be unsatisfactory for a few reasons.  First, you get the motor noise.  Second, the tonal balance did not favour voice and the room resonances would often make it hard to discern what was said.  Third, I paced around a lot to maintain interest, and the on-board mic simply couldn't catch me if I was anywhere other than in front of the thing.

So, I made an outboard mic unit with a cheap electret cartridge a bit above the level of the chassis and pointing up, a simple op-amp preamp and bare-bones frequency-shaping circuit and plugged that into the external mic jack.  Worked amazingly well.  Loud, clear, crisp.  Rolling off the lows and boosting the sibilants a bit made for a nicely balanced tone that let all the right stuff print to tape.  Having it be a hotter signal also made the on-board ALC/AGC/Limiter behave better too.  People were coming in with $200 units that simply could not compare to a $29 tape deck and a $5 homebrew mic unit.

Those little $2-3 cartridges have a lot more potential than folks give them credit for.

[petemoore]

YES must have been the bad cap, [I had a 22uf] when I was getting the amp numbing blasts, I put a tenuf instead there...pretty good sounding mic.
 Ill be trying it to record with as the second mic [first mic being EV 757],
 the way to do it im thinking is to put the mic, mic ckt and booster ckt oon the same board, 'pad' mount that in a box that allows sound waves to travel through a hole [giving some directionality] with booster vol., and one battery clip.
 Not real 'hot of 'gainy by itself, but respectable highs content.
 NTE guys got some Condensers coming in [some guy came in last weekend and bought the available 5$ units] at that cost I might as well try at least another... or two.
 The EV is the only one I have left that hasn't 'evaporated'.

[aron]

As usual, use your meter to tell if DC is present on the output.

I've used these and they work well. I just made a standard voltage divider for the 4.5V and put a big cap on the end. Now that I think about it, I didn't need the voltage divider. I should have used a voltage regulator or something else.

[petemoore]

And quite well using just a battery, a 1k, and a 10 uf.
 Plug the battery in first, then the input plug for reduced amp numbing pops.
 Im running it thrgouh a Micro Amp, and it has push enough to get the 70w Power amp pretty loud w/4x12's...
 Should I be using a voltage divider, or regulated supply?

[Rob Strand]

What you need to do is add a 47k to 100k or so resistor from the output (amp) side of the cap to ground - the same thing that is done at the output of effects pedals.

This will stop the big pops/bangs when you plug it it.

[Quackzed]

http://www.epanorama.net/circuits/microphone_powering.html

[Nasse]

I have been satisfied with the sound quality of these cheap electrets when testing. The next challenge is how to make a wind shield and stop mechanical/handling noise and they are not the most low noise mics anyway