How to build a Stereo Microphone and Battery Box

[greenmachine]

... is the battery box as detailed in this thread suitable for powering a 'source follower' modified microphone? I have seen web pages which seem to suggest that a more elaborate pre-amp is necessary.

It will work just fine with the battery box design as described in this thread as well as with plug-in power from the mic-in. There is a way carry out the sf-mod in a way so that the casing doesn't get positive, but the mics would require a reverse voltage (not plug-in power compatible). With the mod, the mics will lose about 5-6 dB of sensitivity, the S/N will remain the same or improve slightly.

[Bingo1979]

Hi greenmachine!

first i want to say thanks for your DIY thing.

this look really great and i would really really like to try.

i'm totally new to this (selfmade thing), so could you please give me

some more details want i exactly have to buy and were i can get it (i live in germany)...

i have no plan what capacitors and resistors i have to get...

i'm taping band for some years now and i like to built

some mic's and battery boxes for 2 of my friends...they just started taping this year

[dontbugme]

so does this make audio come different from both sides of stereo?

is it "binaural"

if so then i use instead have to wish for $100 dollar one i never possible buy.

so in theory can it be use to make recordings like virtual haircut

http://www.i-am-bored.com/bored_link.cfm?link_id=22913 <

exscue me english.

if so i commend you.

[greenmachine]

so does this make audio come different from both sides of stereo?

is it "binaural"

if so then i use instead have to wish for $100 dollar one i never possible buy.

so in theory can it be use to make recordings like virtual haircut

http://www.i-am-bored.com/bored_link.cfm?link_id=22913

exscue me english.

if so i commend you.

The mics are quite flexible if built this way. Put them close to your ears, just above them for a semi-binaural (hrtf) recording without the nasty colorations of putting them into your pinna. Your head (or any other physical barrier between the mics) will give them a natural directionality, which is perceived as if you were there when listened to the recording via headphones, just like in the example link you provided.

The influence of microphone position on the resulting sound should not be underestimated.

Edited August 13, 2007 by greenmachine

[giar]

Hi there! I built my battery box and mics about a year ago but I didn't have the chance to thank you Greenmachine, so thank you!!

My battery box has been made without spending any money lol I have taken pieces from old radios and CD players I was about to throw away.

The component are installed into an old lozenges casing that was lying in my garage for years. Well, I'm pretty amazed by the results. As a matter of facts, I used it since I have built it and it has stuck with me through at least 30-40 shows.

I don't have my digital camera with me right now, so I "scanned" the battery box. It is blurry, but it gives you a good idea of my design.

For the mics, I used the radioshack caps that I have mounted into a cheap set of earbuds.

I bought new mics recently, to try them out, and I'm facing a little problem beacause the mics are independant (apart from each other : they both have their own 3.5mm connector)

Since I want to use them in stereo recordings, how can I build a "two input, single stereo output" battery module? Do I have to use two 9V batteries? The mics have stereo mini-jacks output connectors so which type of female mini-jack inputs will I need?

If someone could help me out, I would really appreciate it, thanks!

[Malcolm Stewart]

At last, some time after making my battery box, I've used it "in anger" for the first time, and it didn't disappoint. I went to the NDF in south Birmingham (UK) last weekend, and recorded some of the percussion demos from a seat about 20-30 feet away from the stage. I used a pair of Yoga omnis, with the output of the battery box feeding directly in to the Line input of my RH1.

I was in luck. When I checked what I thought was the best track for peak level, I found that it peaked just 0.6dB below max level. I'm very pleased with how the resulting CD sounds on my HiFi system, and am surprised at how clean it is compared to many of my CDs.

[Dagger_pca]

hello everybody

hello greenmachine, loock, i've got some electronic stuff out

of my old kassette walkman and an old "powerbox" of pc

so please tell me the best combination for the batterybox,

i want it to use for an elektret condensator mic (binaural) with a md

and tell me one more time, is it true, doesn't the battery box preamp the mic?

i thought so, because electret mics don't need power from outside, don't they?

thank you

a

b

c

d

Edited November 23, 2007 by Dagger_pca

[greenmachine]

hello everybody

hello greenmachine, loock, i've got some electronic stuff out

of my old kassette walkman and an old "powerbox" of pc

so please tell me the best combination for the batterybox,

i want it to use for an elektret condensator mic (binaural) with a md

and tell me one more time, is it true, doesn't the battery box preamp the mic?

i thought so, because electret mics don't need power from outside, don't they?

thank you

I'd use the 2.2uF and 4.7k's, but the other parts should work as well. Electret mics need a small voltage between 1.5 and 10V typically for the FET. The battery box just supplies power and does not preamplify. Use the line-in for recording loud sounds or the mic-in (preamplified) for quiet sounds.

[Dagger_pca]

I'd use the 2.2uF and 4.7k's, but the other parts should work as well. Electret mics need a small voltage between 1.5 and 10V typically for the FET. The battery box just supplies power and does not preamplify. Use the line-in for recording loud sounds or the mic-in (preamplified) for quiet sounds.

thank you:)

[Dagger_pca]

so, i did it!

it's may be ugly, well it is ugly, but it's my & it works

Edited December 16, 2007 by Dagger_pca

[jamedo]

hey guys, im a new guy and just read this.

nice work greenmachine from what ive seen in these tutorials

i came to this site as im an ameteur filmmaker looking for a cheapish way to get good quality sound recordings.

so i bout an MZ-R500 and clumsily forgot to check for a mic jack

so i checked here and this sounds perfect for what i'll be doing

just one question tho (not sure if this has been covered or not) but...

would this work with a "standard" stereo (i think) mini lapel microphone? or will i need more/less/another piece of equipment? as i have next to no audio experience

(dunno why im here then lol) and im uncertain as to what type of microphone that is.

Edited December 22, 2007 by jamedo

[Malcolm Stewart]

would this work with a "standard" stereo (i think) mini lapel microphone? or will i need more/less/another piece of equipment?

You should be OK. The microphones I used in reply #286 (above) were bought as mono lapel mikes, with an omni response. The stereo aspect shouldn't make much difference. I bring my two leads together into a stereo plug where it goes into the battery box.

HTH

[A440]

Many lapel mics are only mono. You can tell the difference between mono and stereo by looking at the plug: a stereo plug has two rings around it (just like your headphone jack) and mono just has one. The one ring will just give you a signal in the left channel if you plug it directly into the mic jack. I don't know what it will do if you plug it into a battery box. But you can easily find a mono-to-stereo adapter with a mono jack connected to both channels of a stereo plug.

There's really no such thing as a "standard" stereo mic. Every mic varies.

Mic-->battery box-->Line-in depends on how loud your source is and on the sensitivity of the mic. More sensitivity means more signal. A low-sensitivity mic and a quiet source, like speech, will produce a very low signal into the Line-in jack.

The difference between Mic-in and Line-in is that Mic-in has a preamp behind it to amplify the mic signal. Line-in just takes what it gets. With loud music (a strong signal) plus a battery box (providing enough power for the mic to work), Line-in is fine. With speech, possibly (works fine with close conversation with my Sound Professional BMC-2 mics and a 9V battery box). With quieter sounds, probably not. But it will depend entirely on the sensitivity of your mic.

With a lower-sensitivity mic, you may need to get a preamp--which would probably be nearly as expensive as just getting a used NetMD with a mic jack, like the MZ-N707.

Edited December 23, 2007 by A440

[Sonic_Stuff]

Finally I've built a stereo Electret Microphone using this great Greenmachine tutorial. I ended up not using the WM-61A instead I used a no-name brand that sounds pretty good.

I don't own a mini-disc, I use a Boss Micro BR 4-track recorder by BOSS/Roland and it works excellent. You can check my results in Micro BR review with sound samples and on Wich Microphones for Micro BR Line IN.

Greenmachine: Thanks for the tutorial. The recorder (Micro BR) is very good and works great with the Stereo electret microphones. (You asked me this about one year ago... )

[greenmachine]

Hey, thanks for letting me know - excellent review. Good things take time I guess.

[jamedo]

Many lapel mics are only mono. You can tell the difference between mono and stereo by looking at the plug: a stereo plug has two rings around it (just like your headphone jack) and mono just has one.

ive checked my mic's and they have 2 rings on them

one just behind the tapered"tip" bit and one bout 4mm from that,

i compared it to my pc's speaker plug and they look identical

or is that a different plug type altogether?

soz bout all the Q's but i warned that i had basically no experience in this field

[Strungup]

@440 , not all mics with TRS are stereo

Actually quite a lot are wired for a seperate power supply so the the ring carries the power but tip carries signal , I just sold a Pro mic the The guy that does Yoga , that was TRS but wired for dual Mono and Plugin Power .

@Jamedo if your Lapel mics have TRS plugs (Tip , Ring , Sleeve) go ahead and plug one into you MD and test record something , see if it comes out Left channel , or you get a Dual Mono .

You will know if the mics are Stereo , because they will be labeled as such ( With L/R markings on the head) if they arent marked stereo they probably are not .

[A440]

@440 , not all mics with TRS are stereo

Actually quite a lot are wired for a seperate power supply so the the ring carries the power but tip carries signal , I just sold a Pro mic the The guy that does Yoga , that was TRS but wired for dual Mono and Plugin Power .

That's good to know, thanks. But Jamedo does seem to be describing a basic a stereo miniplug. Testing with the R500 won't work because it has only a line-in jack. No power to the mic.

Jamedo, if you're handy, build a battery box and then try recording mic-->battery box-->line-in. It will depend on the mic. If for some reason the mic isn't sensitive enough, you'll already have the battery box to use with a different mic.

[jamedo]

That's good to know, thanks. But Jamedo does seem to be describing a basic a stereo miniplug. Testing with the R500 won't work because it has only a line-in jack. No power to the mic.

thats the plug if u need to see it, but when i can find the right jack (waiting to determine between stereo and mono lol) i will give the battery box a try

[Strungup]

yep that was built for a power supply, please post a pic of the mic head as well just to be sure

[denes44]

Hy!

I can only get 3 types of microphone capsules:

- KPCM-G15E (CZN15E,EM-9767)

- KPCM27B

- MCE100

Which one is the better?

[jamedo]

yep that was built for a power supply, please post a pic of the mic head as well just to be sure

thats the head(DUH!!)

and that writing is "EPE"

not an f-ing clue what that means but hopefully that will shed some light on this

BTW is there any UK guys with experience in making B-Boxes that could make and send me 2? for a fee ofc

as i fear this may be a bit fiddly for my hands and will probs sound better if an experienced guy handled it lol

i need 2 cus im operating as audio manager for my film group and we intend on an interview with a decent recording.

thanks to any info

if anyone from UK(or anywhere if shipping aint much) pm me and we'll discuss it

Edited January 29, 2008 by jamedo

[Strungup]

yeah dude , the mic is a mono mic , just as I thought , two wires go to the element ,third wire is sheilding

it needs power

[jamedo]

cool, following that any takers that could make me 2 battery boxes and ship to the UK

providing the shipping/handling is low but will pay good enough money for parts + labour on making them

lol

[adessio]

It probably has been asked, but if my mic says it's supposed to use with 1,5-2V, the 9V provided from the battery module could damage the mic?

[Dagger_pca]

It probably has been asked, but if my mic says it's supposed to use with 1,5-2V, the 9V provided from the battery module could damage the mic?

well, I think so, but the system of resistors and capacitors prevents it

so, when you want you can put your special voltage on the output,

you have just to reckon, but following workshop, you get right voltage...

Edited February 1, 2008 by Dagger_pca

[AkK]

Do you suggest this mic for pro recording? For just voice recording.

And what is the difference between these mic capsules and the capsules which we could get from any headphone? They look smililar outside. =P (There is a secret question lies under this non-funny sentence, how could we use headphone capsules for making mic? )

And i respect a lot to greenmachine because this topic is 2 years old and he is still online while i'm reading this.

Edited February 1, 2008 by AkK

[CHURCH-AUDIO]

Hi,

I'm totally new to live recording and even more to all the technical details here. Since I have a minidisc I thought to give this DIY a go. I think it's clear enough for even a total beginner like me. So thanks for this DIY.

I just have one question about matching the microphone capsules.

How do I do this? Do you mean by matching that they should have sequential numbers?

Thanks

Um that's not the way to match a capsule.. Actually doing it that way will introduce phase issues that will fool you into thinking a capsule is matched.. The best way for a person who does not have a lot of knowledge to match capsules is with a 1k tone.. You make up some kind of jig that allows the capsule to be held in the exact same spot. Then you measure the output voltage in AC from the capsule after a coupling cap. Then with out turning the 1k tone off you place the second capsule in the same exact spot and do the test again you want to match the ac voltage at the capsule output. This method is used for matching sensitivity of the microphones and is very accurate. This test is the industry standard test for sensitivity. I use an acoustic coupler that has been custom designed for my capsules and a very expensive software and hardware. BUT the DIY guys can do it the way I mentioned above and get very good results.

Chris Church

Church Audio

[Strungup]

He Chris , the boards here are kinda glitchy lately , when you klik the "Post Reply " button , dont reklik it because it is loading slow , just scroll up and klik Get New Posts" it will already be there .

[mark18]

ok, i'm finally going to attempt this. before i do, i read someone you need to match the capsules. i searched this thread a couple of times, so i must have read it elsewhere. how do i go about matching he components? do i just measure the resistance with my multimeter?

[greenmachine]

Scroll up two posts.

[mark18]

Um that's not the way to match a capsule.. Actually doing it that way will introduce phase issues that will fool you into thinking a capsule is matched.. The best way for a person who does not have a lot of knowledge to match capsules is with a 1k tone.. You make up some kind of jig that allows the capsule to be held in the exact same spot. Then you measure the output voltage in AC from the capsule after a coupling cap. Then with out turning the 1k tone off you place the second capsule in the same exact spot and do the test again you want to match the ac voltage at the capsule output. This method is used for matching sensitivity of the microphones and is very accurate. This test is the industry standard test for sensitivity. I use an acoustic coupler that has been custom designed for my capsules and a very expensive software and hardware. BUT the DIY guys can do it the way I mentioned above and get very good results.

ok, i'm going to repeat this to be sure i understand it. generate a 1k tone, hook up the element to a multimeter with a capacitor and measure the voltage. find two capsules that deliver similar ac output and i should be good to go.

what size capacitor would i use as a coupling cap?

would this work for testing: wire up the capsule and battery box. plug them into a recorder (ihp-120 in my case) keeping the mics as close together as possible, record a sample, compare the frequency response of the two channels. if the differences are minimal, you have a match.

last question - if all else fails, where can you find a pair of matched capsules?

Edited March 6, 2008 by mark18

[jojo314519]

I went to radio shack to get my supplies for the battery box, but had trouble finding the right capacitor.

I could not find a 1 micro farad capacitor that is cylinder shaped like in the photos. I did find a 1 micro farad Tantalum capacitor. It is smaller than the pictured one and is egg shaped on top with the two leads coming out the same direction.

Is this an acceptable alternative? I did some quick research on tantalum capacitors and it seems the are more efficient for some reasons i dont understand. It also seemed because they are more efficient the farad rating is different.

If anyone can help my understand this that would be great. Thanks in advance.

[greenmachine]

Here's a new idea: battery box built into the lead of the microphone. Uses diodes to forward the plug-in power from the recorder's mic-in jack. Can be used with or without battery. The battery clip should not be touched if used without battery.

[beefstew]

dbl post

Edited March 23, 2008 by beefstew

[beefstew]

triple post

Edited March 23, 2008 by beefstew

[A440]

The battery clip should not be touched if used without battery.

Very cool idea. What do you mean "should not be touched"--static on the recording? Is there a way to put something on the battery clip--maybe even a dead battery--to prevent that?

[greenmachine]

Yeah, problems with static. You could connect a dummy battery clip with no outgoing cables to prevent touching. A dead battery wouldn't be such a good idea (low inner resistance).

[moddhayward]

Here's a new idea: battery box built into the lead of the microphone. Uses diodes to forward the plug-in power from the recorder's mic-in jack. Can be used with or without battery. The battery clip should not be touched if used without battery.

Dear Greenmachine. This is very cool. Do you have the wiring diagram, and the spec for the diodes you used? And does the spec of any of the components change depending on which exact capsules you get? Mike

[greenmachine]

Dear Greenmachine. This is very cool. Do you have the wiring diagram, and the spec for the diodes you used? And does the spec of any of the components change depending on which exact capsules you get? Mike

I'm not sure about the specs of the diode, but it should not be a z-diode. Mic capsules with a higher current consumption will need resistors with a lower value. The higher the value, the better the channel separation. The mini mics I use consume less than 1mA a pair, 6.8 or 10k resistors work nicely.