Made a mic

PhilGood

Juice box hero
mshilarious said:
OK then, we completely understand each other! :)

I ordered enough parts today to make 10 of my phantom version :) Hope they sound good :o

Can I have a copy of your skeematic when you're done?
 

SuperGeek

New member
mshilarious said:
Aluminum is electrolytic. Does it look like the one in rory's pic?

Mylar is metallized poly film, the smallest one I can find in 10uF is just a little smaller than a 9V battery. In an external power supply, like the mic you built, that fits fine. Electros will absolutely work too, it's just that polys are commonly thought to have better audio response.

Anyway, I was referring to the schemo I linked, which is driven by phantom power. That cap is too big to fit in a small omni mic body, especially if using an XLR connector for the body! So I think electro is the only possible choice there.

I just might try to bang together a phantom powered model . . .

Was thinking about a phantom powered version as well. just got to work out some sorta voltage divider so I wont cook the mic element. :eek:
 

mshilarious

Banned
Yeah, phantom I think is better, not only to avoid the external PSU, but the Tape Op mic will get cooked pretty bad if you accidentially turn phantom on.

Here is what I am going to build. I did a test run with some parts yesterday, just to see if the parts would fit. I can get 3 10uF Nichicon PW series caps (C1-3) in an XLR connector and there's enough lead to fold over so I don't have to use axials. So at least I can use good electros :)

C4-6 are poly film type, optional (if they fit). C4 should fit no problem, C5 and C6 bypass the electros at around 10kHz, depending on preamp input impedance. For these mics, higher input impedance (3K) is better.

The use of the zener regulates the voltage nicely, it will allow for phantom voltages anywhere from 12 to 48V. I used less of a filter cap than the schematic I linked--although a 22uF cap would fit there, I decided to go with simplicity and use the same 10uF cap. The phantom supply should be well regulated anyway, and the zener helps too. I believe that should supply the capsule with a little over 2V.

All resistors should be metal film type, 1% tolerance, and then matched as best you are able with your multimeter.

The mic capsule I ordered was the Panasonic WM-61A, which has better specs than the now discontinued capsule of the Tape Op article (higher sensitivity, better S/N ratio).

Finally Neutrik has a new style of connector, much sleeker looking and smoother, check it out here:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=092-308
 

Reggie

PutsTheLotionOnItsSkin
Wicked awesome. I might have to put this on my "to do" list. I have an LA2A waiting to be built....but this looks like a fun piece of cake--and cheap. You guys should try building the Gyraf tube microphone. G7 I think? I guess it sounds real good.
 

Minion

Blow Me !!!
Have you Guys heard of this...I heard of instead of useing a Big 10uf Poly you can use a 10uf Electro or Tantalum and then put a Small Poly (of any Value less than 10uF) after the Electro which is supposed to Clean the Signal...

Do you guys know if that will work??

Because I don"t understand how the Electret Condensers that you Buy that are Battery Powered are so small ?? They can"t have a 10uF poly in them as they wouldn"t fit in the Body of those small Electrets.....

I also Don"t see why the Cap has to be Such a Large Value when it is Dealing with such low Voltages and Amps, It is only a 9v Battery and the Element only needs 1 Milli-Amp at 3v so I don"t see why such a Large Cap has to be used......

Does anyone with some electronix knowlege know the answer to these questions???

ThanXX
 

mshilarious

Banned
Minion said:
Have you Guys heard of this...I heard of instead of useing a Big 10uf Poly you can use a 10uf Electro or Tantalum and then put a Small Poly (of any Value less than 10uF) after the Electro which is supposed to Clean the Signal...

Rather than cleaning the signal, it distorts high frequencies less. See my schematic above for an application.

Because I don"t understand how the Electret Condensers that you Buy that are Battery Powered are so small ?? They can"t have a 10uF poly in them as they wouldn"t fit in the Body of those small Electrets.....

They don't; they use electros. Or they use another transistor stage to buffer the capsule from the preamp input impedance, which allows them to use smaller caps.

I also Don"t see why the Cap has to be Such a Large Value when it is Dealing with such low Voltages and Amps, It is only a 9v Battery and the Element only needs 1 Milli-Amp at 3v so I don"t see why such a Large Cap has to be used......

The size of the cap is not a voltage rating, that is separate. So the Tape Op mic cap is 10uF/10V. However, poly caps usually come in minimum 50V rating, that is just their nature, so that would be 10uF/50V.

The capacitance rating (microfarads, or uF) is selected based upon the signal requirements. A cap in series with an audio signal acts as a high-pass filter. If you use a smaller cap, it will lose more lows. The 10uF cap was selected to pass everything above roughly 10Hz. If you used say a 1uF cap, for which you can get a smallish poly, that would cut below 100Hz, which is obviously not desirable.
 

mshilarious

Banned
Phantom Powered Tape Op Mic

OK, I built the prototype tonight. I couldn't quite stuff in all the components, if I left out the bypass polys I would have been OK, but I think with a bit more effort, I can fit it all. In this prototype I left out the RF filter cap since I was already over my space budget :o If you try this, definitely get the new style Neutrik XLR connector I linked before, you'll need the extra space. Looks cooler too!

Works fine! I didn't test it with much more than a soundcheck, since it still has no body :o I did do a frequency response curve vs. an Apex 220 reference omni, using white noise through my monitors (calibrated to 85dBSPL at mix position). My bodyless mic has less bass response than the Apex, and somewhat hotter high end response. My mic was 3dB hotter than the Apex, which is 94dBSPL = -43dBV, although I wouldn't bank on that since I was just hand holding the mics.

The voltage drop across the capsule was a bit less than I anticipated; only 1.2V. I attribute that to phantom power a little below spec (45.8V) and a bad guess on my part as to the capsule's DC resistance--it was 680 ohms, for some reason I thought it would be closer to 1K ohms. I don't know what effect that voltage has on mic response, but I would change the dropping resistors to 15K, maybe a little lower.

Here's a picture of the prototype:
 

Reggie

PutsTheLotionOnItsSkin
Haha that is really ghetto. You should just wrap it in layers of electrical tape and duct tape and call it good. That would be sweet; and it would be fun to see the worried look on people's faces as you put the mic in front of their amps or whatever.
That response looks pretty decent!
 

mshilarious

Banned
Reggie said:
Haha that is really ghetto. You should just wrap it in layers of electrical tape and duct tape and call it good. That would be sweet; and it would be fun to see the worried look on people's faces as you put the mic in front of their amps or whatever.
That response looks pretty decent!

Well it fell apart shortly after the photo :eek: but here is v2, looks much nicer I think:

I changed the resistor values on this one, all I had in metal film 1% laying around was 7.5K and 1K, so that is what I used. That yielded 2.3V across the capsule. Not sure what the net effect on sensitivity will be, I think it should be up 2dB :confused:

I did fit all the components in the schematic in the connector :)

Tomorrow I'll run the response test and hopefully post an audio sample too :)
 

jaykeMURD

I sit on you.
mshilarious said:
Well it fell apart shortly after the photo :eek: but here is v2, looks much nicer I think:

I changed the resistor values on this one, all I had in metal film 1% laying around was 7.5K and 1K, so that is what I used. That yielded 2.3V across the capsule. Not sure what the net effect on sensitivity will be, I think it should be up 2dB :confused:

I did fit all the components in the schematic in the connector :)

Tomorrow I'll run the response test and hopefully post an audio sample too :)

What did you ise to make that body? It doesn't look half bad! Looks better than my flashlight body design!
 

mshilarious

Banned
OK, tonight's test of the fully assembled mic:

Sensitivity is about -3dB less than the Apex 220, which would make the mic about -45dB/Pa :confused: Last night's ghetto mic was 3dB more, and I used the same capsule, just with different resistor values. I need to assemble a mic with the original resistor values and compare, because I thought the gain in capsule voltage would more than offset the signal loss to the smaller resistors :confused:

Anyway, here's a frequency response graph vs. the Apex 220. So it seems my mic is a little brighter.

I'm working on audio samples of the mic vs. the Apex and a Shure KSM141. Stay tuned!
 

mshilarious

Banned
While I'm posting fun DIY pics, here's a Jecklin disc I've been working on:

OK enough playing, off to work on audio samples :o
 

PhilGood

Juice box hero
mshilarious said:
While I'm posting fun DIY pics, here's a Jecklin disc I've been working on:

OK enough playing, off to work on audio samples :o

You need to work on your embroidery too. I can't read any of the stitching! :D

"Studio, sweet studio" would be nice.
 

mshilarious

Banned
PhilGood said:
You need to work on your embroidery too. I can't read any of the stitching! :D

"Studio, sweet studio" would be nice.

Don't laugh . . . my mom has an embroidery machine, she can just type the letters and it does the rest . . . I could do it! :p
 
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