How to build a Stereo Microphone and Battery Box

[greenmachine]

Nice thread this! I made up some mics recently and they perform well. They're hidden inside some headphones to be descreet. I actually us foam on them too, not pictured, but you get the idea.

Nice, but shouldn't the mics point outwards?

[Jamesy]

Nice, but shouldn't the mics point outwards?

lol, valid point. I don't put them in my ears, I just let them hang round my neck and point them outwards a bit, sounds fantastic.

[subatomic]

will this design work for recording quieter sounds? i.e. wind instruments, crickets, talking voices...

nice article, looks cool.

i have a neuros (20gb hard drive) with line in, looking for a portable mic for foley work, and strange sounds for music samples

on a shoestring budget of course

Edited April 23, 2007 by subatomic

[subatomic]

will this design work for recording quieter sounds? i.e. wind instruments, crickets, talking voices...

nice article, looks cool.

i have a neuros (20gb hard drive) with line in, looking for a portable mic for foley work, and strange sounds for music samples

on a shoestring budget of course

nevermind, I found the answer:

Or you may get no signal at all - electret mics require "plug in power", which is usually not available at the line-in. A battery box would supply the mics with the necessary voltage, but there would be still no pre-amplification, which usually leads to a (very) low signal unless you record from a really loud source.

anyone have a link to a DIY 'shoestring budget' preamp to go along with this greenmachine project? (which is very cool by the way)

[A440]

Try Google for diy mic preamp.

This showed up:

http://sound.westhost.com/project66.htm

[subatomic]

Try Google for diy mic preamp.

This showed up:

http://sound.westhost.com/project66.htm

found this stereo preamp, looks good, meant for electrets and line-in, and looks like it will fit in an altoids tin... looks simple too, has 2 gain settings: 1 for loud concerts, and 1 for quieter sounds.

It also powers the mics...

http://www.geocities.com/ferocious_1999/md/micpreamp2.html

[Seekerr]

Hey all - a few questions related to this project:

1) Has anyone had any luck sourcing quality electret capsules in Australia? I really don't want to pay $60 AUD to get a pack of 10 from the UK.

2) Does anyone have any idea as to the usefulness of the electrets in the Sony DS-70P? I know the mike is considered fairly poor (although I have heard some fair recordings from one), but they can be had secondhand extremely cheaply, and I'd had the thought of disassembling one, and using the electrets for this project. Thoughts?

Thanks

[boojum]

Hey all - a few questions related to this project:

1) Has anyone had any luck sourcing quality electret capsules in Australia? I really don't want to pay $60 AUD to get a pack of 10 from the UK.

2) Does anyone have any idea as to the usefulness of the electrets in the Sony DS-70P? I know the mike is considered fairly poor (although I have heard some fair recordings from one), but they can be had secondhand extremely cheaply, and I'd had the thought of disassembling one, and using the electrets for this project. Thoughts?

Thanks

Buying ten from the UK would be smart. You have a couple to ruin with your first attempts, one pair to keep and three pair to sell making back your money and maybe some more. Could be the beginning of a huge new mic business. Many start small.

[Seekerr]

Buying ten from the UK would be smart. You have a couple to ruin with your first attempts, one pair to keep and three pair to sell making back your money and maybe some more. Could be the beginning of a huge new mic business. Many start small.

Indeed, but it doesn't make sense to me that it costs so much. I realise that the preferred electrets are no longer produced, but to pay over twice what they were worth, plus shipping, is quite a substantial whack, and for me (I'm still in school), that's a very large sum. If I could buy 6 for $35 AUD (About $30 USD, for anyone reading and thinking "hey, I've got some surplus I could sell that kid") plus shipping, I'd go for it, because I can afford that kind of expense.

[goldenbreast]

i have just found some panasonic wm-61a capsules on ebay: the guy has 1 set of 10 for sale left at just under £19

i have a question which might seem stupid...whats the difference between wm-61a and wm-61b?. do i need one of each to make it stereo (like a=left and b=right?). im starting to worry as ive already bought a lot of 5 wm-61a's...

is it simply a case of them being two different versions?

would appreciate some advice

thanks

Alex

p.s. ebay link:

http://cgi.ebay.co.uk/10-Panasonic-WM-61A-...1QQcmdZViewItem

Edited May 6, 2007 by goldenbreast

[greenmachine]

The B model is the pin type, see here.

[goldenbreast]

The B model is the pin type, see here.

thanks for the info. thats sorted things out nicely!. im heading to my nearest electrical shop, maplin tomorrow afternoon to see if i can get what i need.

thanks again

Alex

p.s. greenmachine, can you pm information about your mics and battery boxs in english? - no rush, would appreciate it when you get the chance. i'd like to know specifications, delivery costs to UK etc...are they only binaural or do you have cardioids?.

Edited May 9, 2007 by goldenbreast

[goldenbreast]

i recieved my panasonic WM-61A capsules this morning. i didn't realise they were so small!. i went into maplin the other day but was completely overwhelmed by all the bits and bobs - ive also searched on their website but im still unsure what im after as there appears to be different types of one thing thats needed - perhaps its just me being thick...

for anyone that can be bothered, can they check http://www.maplin.co.uk and point me in the right direction for whats needed for the mic and battery box? - i would really appreciated it

cheers

Alex

Edited May 9, 2007 by goldenbreast

[tiburns]

Can anyone tell me where to get good cable to make the microphones from. I have not seen anything in the posts. Or I missed it. I know some cut up headsets but I would like to have good shielded cable if possible.

[goldenbreast]

Can anyone tell me where to get good cable to make the microphones from. I have not seen anything in the posts. Or I missed it. I know some cut up headsets but I would like to have good shielded cable if possible.

if your in the UK, maplin appears to be your answer - i have found on their website, the following cable - i think thats what is needed?

http://www.maplin.co.uk/module.aspx?Module...y=13m5#overview - Twin Individually Screened Microphone Cable. A very flexible, high quality twin screened microphone cable. Stranded cores 14/018mm copper conductors with red and white PVC insulation, individually lap-screened and sheathed overall in grey PVC. Overall diameter: 62mm

[goldenbreast]

http://www.maplin.co.uk/Basket.aspx?source=20&doy=13m5

the above link includes what ive added to the basket. i have everything apart from the 3.5mm stereo connector with cable and the circuit board. i can't seem to find the stereo connector with cable but would it be possible to use the cable that is used for the mics and solder some of that cable to the stereo connector?.

also, im not sure which type of circuit board im looking for - help?

it seems nobody has stepped up with some advice but i would really appreciate some help - does that basket look like it contains the right things?

many thanks

Alex

[Karl P]

http://www.maplin.co.uk/Basket.aspx?source=20&doy=13m5

the above link includes what ive added to the basket. i have everything apart from the 3.5mm stereo connector with cable and the circuit board. i can't seem to find the stereo connector with cable but would it be possible to use the cable that is used for the mics and solder some of that cable to the stereo connector?.

also, im not sure which type of circuit board im looking for - help?

it seems nobody has stepped up with some advice but i would really appreciate some help - does that basket look like it contains the right things?

many thanks

Alex

The shopping cart is specific to your machine, so that link you provided shows empty for me.

[goldenbreast]

The shopping cart is specific to your machine, so that link you provided shows empty for me.

oops...

seems i messed up - im going to my local maplin today to see if i manage to get some help from their staff...if not i will post back

cheers

Alex

[Malcolm Stewart]

if your in the UK, maplin appears to be your answer - i have found on their website, the following cable - i think thats what is needed?

http://www.maplin.co.uk/module.aspx?Module...y=13m5#overview - Twin Individually Screened Microphone Cable. A very flexible, high quality twin screened microphone cable. Stranded cores 14/018mm copper conductors with red and white PVC insulation, individually lap-screened and sheathed overall in grey PVC. Overall diameter: 62mm

When I was making my battery box and binaural stereo microphone set-up, I bought cheap stereo earphones (from Maplins) and cannibalised them so that I could get gold plated stereo plugs and lightweight cable at a sensible price. With the voltage supplied to the mike capsules, the low noise gold plated connection made a big difference in handling noise. The screening may not be good enough for use in a building where mains fields exist, but in the countryside it's fine, and environmental noise from distant motorway traffic, aeroplanes, and helicopters is my main problem.

[goldenbreast]

i went to maplin today and bought the following:

mic components:

Stereo Double Shielded Microphone Cable - 1 metre :

http://www.maplin.co.uk/Module.aspx?Module...amp;doy=14m5%5b

Right-Angled 3.5mm Stereo Plug

<a href="http://www.maplin.co.uk/Module.aspx?ModuleNo=1184&criteria=stereo%20jack&doy=14m5"" target="_blank">http://www.maplin.co.uk/Module.aspx?Module...;doy=14m5

heat tubing: (7mm as capsules diameter is 6mm)

http://www.maplin.co.uk/Search.aspx?criter...0X&DOY=14m5

capsules - i already have the panasonic wm-61a capsules

battery box:

2.2uF capsules (63v) X6

10kohm resistors X6

3.5mm stereo jack:

http://www.maplin.co.uk/module.aspx?Module...82&doy=14m5

3.5mm stereo socket (not sure if this is correct):

http://www.maplin.co.uk/module.aspx?Module...91&doy=14m5

cable for stereo jack:

http://www.maplin.co.uk/module.aspx?Module...27&doy=14m5

plain circuit board X1

for the battery, do i simply solder the cable to the stereo jack?

as i say, i may have purchased the wrong stuff but i was advised in the shop that this was what i needed.im a little confused as the instructions say 1 cable with stereo connector - the guy in the shop said that meant i needed to get the cable and attach it to the stereo jack - right?

UPDATE:

i think i may have got the wrong cable for the mic as the picture shows two cables - one for each mic right?. but then those two cables are connected to one 3.5mm stereo jack - how does that work? - what cable should i be looking for then...this is becoming more frustrating as its just so bloody complicated! . apart from buying a set of headphones and chopping the headphones off, can i not buy a cable which is the same - 2 cables that join up at the end so that it can be soldered to a 3.5mm stereo jack (like the one i bought)

Edited May 14, 2007 by goldenbreast

[Karl P]

UPDATE:

i think i may have got the wrong cable for the mic as the picture shows two cables - one for each mic right?. but then those two cables are connected to one 3.5mm stereo jack - how does that work? - what cable should i be looking for then...this is becoming more frustrating as its just so bloody complicated! . apart from buying a set of headphones and chopping the headphones off, can i not buy a cable which is the same - 2 cables that join up at the end so that it can be soldered to a 3.5mm stereo jack (like the one i bought)

I'm interested as well in any sources of this cable. I have not found anything like the wires you can cannibalize from ready made headphones. Having some longer wires would be nice.

[Seekerr]

I have found that one of the best sources for such cable is ready made RCA -> Stereo leads...as the stereo signal must be split between the two RCA plugs, the wire is made in two parts that can be split apart. Just chop the RCA connectors off the end, and you should have a lead ready to go...only possibly problem is weird insulative coatings on the wires that prevent soldering. A good strong flux or "soldering fluid" with make working with such wires much easier.

I'm interested as well in any sources of this cable. I have not found anything like the wires you can cannibalize from ready made headphones. Having some longer wires would be nice.

[goldenbreast]

I have found that one of the best sources for such cable is ready made RCA -> Stereo leads...as the stereo signal must be split between the two RCA plugs, the wire is made in two parts that can be split apart. Just chop the RCA connectors off the end, and you should have a lead ready to go...only possibly problem is weird insulative coatings on the wires that prevent soldering. A good strong flux or "soldering fluid" with make working with such wires much easier.

i ended up buying a stereo 3.5mm jack to twin phono lead:

http://www.maplin.co.uk/Module.aspx?Module...IN&doy=17m5

cost £3.99. i chopped off the red and white phono connections to and each of those has two strands of wire - one of which is encased in a red/white plastic cover. as far as im aware, this should do the job. not a very technical explanation but i hope you get my drift. would also appreciate some info as to whether this can be used for the mic lead

cheers

Alex

[Seekerr]

Just strip off the plastic insulation. Should be fine...if you're not familiar with soldering, I suggest you read up and learn how to tin wire and how to create a good bond. Beyond that, you should be fun. However, if the other wire (the one without its own insulation) does not appear to be a silvery or copper color, and is instead a red, green, or blue, or seems to have a plastic rather than metallic sheen, it may have a thin insulating coating that is very hard to solder. As I said before, a good flux or soldering fluid, along with a hot soldering iron (when tinning the leads, NOT when soldering to the capsules) will help with that.

Good luck, I'll still be lurking around this thread if you have more questions.

i ended up buying a stereo 3.5mm jack to twin phono lead:

http://www.maplin.co.uk/Module.aspx?Module...IN&doy=17m5

cost £3.99. i chopped off the red and white phono connections to and each of those has two strands of wire - one of which is encased in a red/white plastic cover. as far as im aware, this should do the job. not a very technical explanation but i hope you get my drift. would also appreciate some info as to whether this can be used for the mic lead

cheers

Alex

[goldenbreast]

Just strip off the plastic insulation. Should be fine...if you're not familiar with soldering, I suggest you read up and learn how to tin wire and how to create a good bond. Beyond that, you should be fun. However, if the other wire (the one without its own insulation) does not appear to be a silvery or copper color, and is instead a red, green, or blue, or seems to have a plastic rather than metallic sheen, it may have a thin insulating coating that is very hard to solder. As I said before, a good flux or soldering fluid, along with a hot soldering iron (when tinning the leads, NOT when soldering to the capsules) will help with that.

Good luck, I'll still be lurking around this thread if you have more questions.

i have taken of the insulation on the 'inner wire' - each cable now has two wires showing, both are copper. i might have a problem getting enough distance between the mics when i finally get round to making them as i you can only split the two cables untill it reaches a blocker (a circular plastic thing) - as far as i can tell, its not possible to take that bit off in order to split the cables more so to get enough distance to mount on spectacles...any ideas? - does this make sense? lol

UPDATE:

i managed to hack off the plastic bit mentioned, im now able to seperate the wires as much as i want - ive seperated each one approx 15cm. i will test it out with my glasses to get the optimum seperation which fits comfortably and then perhaps use some tape to stop the cable splitting anymore - unless there's a better way of doing it.

p.s. i tried to upload some pics of the cable (that ive modified) but for some reason wasnt able to (?)

Edited May 18, 2007 by goldenbreast

[pepsi_max2k]

does anyone see where i may have gone wrong with my battery box attempt? no matter what i do i don't seem to be able to get any sound out of the right hand channel, even touching the right hand wire i don't here any feedback like i do on the left). i've tried replacing almost every component on the thing, and also tried multiple stereo cables for the 3.5mm plug.

i was thinking it might be the stereo cable but i've just tried with another cable and just placed the neg bit on the neg battery wire, then held the left wire on to the correct solder spot, and i get sound recorded on the left channel, but if i stick the right wire on the right solder spot i get no sound (though i know the cable's ok, just touching it with my fingers i get sound on the right channel). so i don't know if it's the cable or something else, but like i say i've tried a few times resouldering stuff and always get the same problem, so maybe it's my layout.

anyone see anything wrong in the following pics (the circles bits are all soldered together)? thanks.

[Strungup]

does anyone see where i may have gone wrong with my battery box attempt? no matter what i do i don't seem to be able to get any sound out of the right hand channel, even touching the right hand wire i don't here any feedback like i do on the left). i've tried replacing almost every component on the thing, and also tried multiple stereo cables for the 3.5mm plug.

Is the plug a 4or6 pin switching type plug , you might have the wrong tab soldered

[pepsi_max2k]

Is the plug a 4or6 pin switching type plug , you might have the wrong tab soldered

errr... no idea. but there's a pic of the 3.5mm socket here. there's only 3 tabs and it's pretty obvious what each is for.

[pepsi_max2k]

okaayy... had another look at what might be wrong by feeding a speaker's mic out into the battery box circuit's mic in, then held the end of some headphones on the battery negative spot and poked the rest about and came up with the following...

which makes me think one of the capacitors may be bad, as it's the only thing between the high sound level on one side and low sound level on the other side, so low i can barely hear it and probably why it looks like i'm getting no output from the right channel of a mic when i try to record stuff. could a bad capacitor cause the sound level to drop?

Edited May 30, 2007 by pepsi_max2k

[Strungup]

okaayy... had another look at what might be wrong by feeding a speaker's mic out into the battery box circuit's mic in, then held the end of some headphones on the battery negative spot and poked the rest about and came up with the following...

which makes me think one of the capacitors may be bad, as it's the only thing between the high sound level on one side and low sound level on the other side, so low i can barely hear it and probably why it looks like i'm getting no output from the right channel of a mic when i try to record stuff. could a bad capacitor cause the sound level to drop?

Yes , two things

A resistor when it faults it usually Opens ( no signal ) if it is only partially faulted , its resistance level will go way up. (which is the symptom you describe)

a Capacitor will short or open depends on how it goes , Over heating either by to long on the soldering iron can cause that .

Good soldering technique is a must when working with electronics . using a Low Temp Flux solder is also a good idea. Keeping the soldering tips VERY clean and well shaped is another point to think of.

As well , when you bend the ends ( wire off the resistor ) use a small pair of pliers to hold the part closest to the resistor body so that you dont break the connection inside the resistor, same for the caps

Edited May 31, 2007 by Guitarfxr

[Jamesy]

Also, those caps are polarised, have you definitely got them the right way around? I must admit I haven't read everything thoroughly so you may already have checked this, but try swapping the mics over - I find these mic capsules very easy to damage by overheating when soldering.

[pepsi_max2k]

woohoo i have a working battery box not entirely sure what it was cos i changed the capacitor before checking the output wire. needless to say the capacitor had no affect on the missing left channel to start with, so i figured the only thing left was the 3.5mm output wire / plug, so replaced that with another one and it works great now i recon the right channel wire on the output wire must have been shorting out somewhere or something like that... anyway, it works now bring on the gigs...

[Malcolm Stewart]

woohoo i have a working battery box

Congratulations - these things happen!

I remember making up a simple microphone extension lead, and checking at every stage; so how did I get left and right reversed!

Let's hope your recordings go well.

[pepsi_max2k]

here's some samples of the recording i made with greenmachine's battery box, an archos gmini400 mp3 player/line in recorder (records to 44 KHz 16bit wavs) and a cheapo stereo mic (think this thing from maplin).

it was recorded at a moderately loud indie rock gig, a smallish stage with not the biggest of speaker setups there but it did dull my hearing for a while afterwards. all came out pretty good with the exception of quite a bit of noise during the quiet stuff, though i dare say some decent components, better soldering skills and an all round better recording setup would get rid of most of that.

http://www.inaudible.co.uk/temp2/sheffieldtests/

pretty self explanatory - orig is the original recording, amp is the original increased by 18db in audacity, and ampnoise is the amp'd stuff with audacity's built in default noise reduction. orig_dx_lesshighend is a friend's go at using winamp filters on the original to see if he can come up with anything better. i prefer my attempt though any comments / reccomendations on it?

the whole recording (after amping and noise reduction) is at http://www.inaudible.co.uk/crimea/mp3s/Sheffield07/ should you care for more

Edited June 13, 2007 by pepsi_max2k

[greenmachine]

here's some samples of the recording i made with greenmachine's battery box, an archos gmini400 mp3 player/line in recorder (records to 44 KHz 16bit wavs) and a cheapo stereo mic (think this thing from maplin).

it was recorded at a moderately loud indie rock gig, a smallish stage with not the biggest of speaker setups there but it did dull my hearing for a while afterwards. all came out pretty good with the exception of quite a bit of noise during the quiet stuff, though i dare say some decent components, better soldering skills and an all round better recording setup would get rid of most of that.

http://www.inaudible.co.uk/temp2/sheffieldtests/

pretty self explanatory - orig is the original recording, amp is the original increased by 18db in audacity, and ampnoise is the amp'd stuff with audacity's built in default noise reduction. orig_dx_lesshighend is a friend's go at using winamp filters on the original to see if he can come up with anything better. i prefer my attempt though any comments / reccomendations on it?

the whole recording (after amping and noise reduction) is at http://www.inaudible.co.uk/crimea/mp3s/Sheffield07/ should you care for more

Try to set the levels higher the next time when recording to get less noise after post-amplification.

The less you need to amplify afterwards, the less noise will be amplified along with the signal.

[pepsi_max2k]

Try to set the levels higher the next time when recording to get less noise after post-amplification.

The less you need to amplify afterwards, the less noise will be amplified along with the signal.

I would have done that, though I was testing the stuff out with a support band before the main one went on and I seemed to get a bit of distortion at higher levels. Not sure how much though, they were a little louder than the main band and I had to take up residence in the venue toilets to actually hear anything through my headphones, then deleted all the stuff to make room for the main band. I'll see what happenes at the next gig i go to though

[mark18]

n00b here. using these mics and battery box, do i still need a preamp?

[greenmachine]

n00b here. using these mics and battery box, do i still need a preamp?

A battery box does not pre-amplify, it just supplies power to the mics. If you record relatively quiet sounds like conversation, unamped instruments,... , you will need a preamp to get sufficiently high levels. If you record rock-concert-like levels, battery box to line-in will be sufficient, no preamp necessary.

[mikearmstrong]

Hi greenmachine.

Firstly, thanks for your inspiration. This DIY electronics thing is really addictive!

My questions...

I have a few WM-61A capsules and I'm going to have a go at doing the source follower mod. I have seen the diagrams and can see that I have to cut the trace from the ground pad to the capsule casing and then treat that as the positive side. I also have to make a connection from the former positive pad over to the square contact right at the edge. This solder also must make contact with the capsule case for grounding.

My soldering technique when making up something small and heat sensitive like this is to firstly tin the wire then let it harden. I then press my iron onto the tinned wire-end (pressing into a surface as support) to melt the solder and then move the wire adn the iron together with the iron still touching the solder pad. Because the wire-end is still molten, the contact is made immediately and I can withdraw the iron immediately also. The only drawback to this method is that I have to be very precise and get the wire into the correct position without making a mistake.

So the new + side is easy, just scrape out the trace and make the connection to the + wire.

It seems to me that the ground side should be quite easy too. using my technique it seems that I should just place the wire so that the tip is just touching the case at the point where the square contact bit is. Sufficient solder should ensure that contact is also made here with the square contact. The wire then runs to the -ve solder pad and bends up from there. As long as I don't make accidental contact with the positive pad then I can't go wrong.

Can you make any comment based on your experience of carrying out this mod?

In addition, 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.

Finally, Do you have any idea where I can get the lapel clips from in EU/UK. I only want something cheap, similar to that which comes on a mobile phone hands free kit, ie the clip holds the wire, not the actual mic. The only clips I can find on the internet are based in the US and are minimum $6 each + $30 shipping to the UK I can't believe the clips are more expensive than the mic capsules!

Thanks again.

Mike

[Malcolm Stewart]

...

Finally, Do you have any idea where I can get the lapel clips from in EU/UK. I only want something cheap, similar to that which comes on a mobile phone hands free kit, ie the clip holds the wire, not the actual mic. The only clips I can find on the internet are based in the US and are minimum $6 each + $30 shipping to the UK I can't believe the clips are more expensive than the mic capsules!

Thanks again.

Mike

Hi Mike,

Maplin do a range of affordable microphones, and if you can visit one of their stores, I think you'll find one of them has the lapel clips that you are looking for - albeit in a kit with a microphone.

HTH

Malcolm

Milton Keynes