greenmachine

How to build a Stereo Microphone and Battery Box

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The only thing you can't get there is the 10k ohm metal film resistors, unless you by them in a pack with a bunch of other values. All there single value resistors are carbon. But the metal film pack is only about $5, and by the time you pay for shipping from an online order, you'll pay about the same price.

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hey i like your altoid box thing...

anyone know where i can get a tiny tin box like that? canada doesnt sella altoid candies...

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you can buy them online for a couple of bucks, try ebay or just search google.

last time i needed some i bought high caffine penguin mints

http://www.peppermints.com/

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You could terminate that end with a 3.5mm stereo jack, and patch from the battery box to the minidisc with a male to male 3.5mm stereo cable, but you may have to do some creative stuffing to get it all in there.

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I've never done any electronics work but would nonetheless like to build one of these battery boxes, so forgive me if this is a stupid question: I can't figure out, from the circuit diagram and the actual project photos, how is the negative terminal of the battery tied into the circuit. It looks like it's soldered to one of the leads from the resistors. If that's incorrect I would appreciate someone setting me straight. Thanks.

Edited by War Throat

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No resistor on the negative side of the battery. It just ties between the negative of the input and output.

I didn't have any electronics background before this project, and have only been doing it a couple months now. This project has really got me going though. I have completed a direct box, a stereo mic preamp, a guitar preamp, a guitar boost pedal, and mods to a Boss DS-1 Distortion pedal. I also have a few more projects going on, and am in the planning process for a couple more. This can be addicting!!!

That being said, there are no stupid questions. I am still very much in the learning mode, and if it wasn't for people like greenmachine and others willing to answer my stupid questions, I wouldn't have known how to get started.

Edited by woulfer

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I've been looking into homemade mic-preamp but found the choices of opamps, etc a little overwhelming. What did you come up with for the preamp. I bought one anyway but these electronic projects are interesting and I'd like to try a homemade one anyway.

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i made this, and put up pics onto flikr at flikr. it was really quite easy and in total cost well under 10$ i have 3 electret mics from allelectronics.com that have mono 3/32 plugs, so i made the tin have 2 plugs for that, with a stereo 1/8 in output cord. i made that out of 3 braded strands of the wire inside cat5 cable. right now, my only issue is that i cant really record in stereo, as my computer only has line in as stereo, not mic, and ipodlinux hasnt come out with stereo recording yet. anyway, it sounds great, and is quite solid. feel free to tell me if u think i did something poorly, etc. oh, and the plugs are labeled r and l/m for right and left/mono, for if its going into a normal mono mic jack.

dan

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i made this, and put up pics onto flikr at flikr. it was really quite easy and in total cost well under 10$ i have 3 electret mics from allelectronics.com that have mono 3/32 plugs, so i made the tin have 2 plugs for that, with a stereo 1/8 in output cord. i made that out of 3 braded strands of the wire inside cat5 cable. right now, my only issue is that i cant really record in stereo, as my computer only has line in as stereo, not mic, and ipodlinux hasnt come out with stereo recording yet. anyway, it sounds great, and is quite solid. feel free to tell me if u think i did something poorly, etc. oh, and the plugs are labeled r and l/m for right and left/mono, for if its going into a normal mono mic jack.

dan

what opamp did you use and can you give me the other design particulars.

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i used exactly the circuit diagram from the origional project, then put on 3/32 inch jacks in place of wires directly to the mics to suit the mics that i had. what do you mean, what opamp did u use? this amplifies it up to mic line level, then i have a mixer with a mic input that i have run from the line out of that into the line in of my computer, if that's what you mean. it also orks to use the mic jack on the computer, just not quite as good quality.

dan g

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Finally found some time to solder caps to the wires yesterday. (had 4 panasonic mce2000 caps) I'm a noob when it comes to soldering, so I messed a bit with first 2 caps. Then thinking I had enough practice, I soldered the wires to the final 2 caps. I took me a few tries but I thought they were soldered ok.

I ran a test in front of my stereo. Levels in both channels were not the same, but I thought that was just because the caps weren't matched. Uploaded the sample to my laptop and equaled levels in soundforge. Listening through my stereo which was hooked up to my laptop, I was pleased with the result. But, when listening to it through headphones, despite the fact that I equaled both channels, the sound still came mostly from the right channel.

Link to the sample: attempt 1

So, this morning I resoldered the cap of left channel, which again took a few tries. Ran a test in the same setup as yesterday and uploaded the sample. Difference of both channels was 3 db now so I boosted the channel with lower volume till both channels were equal. Listening through headphones now gave a centered sound.

Link to sample:attempt 2

Only Thing that bothers me is that bass is much higher than it was before resoldering the cap. I did remove some bass with an eq which does make it sound better: link

Because of this bass thing and the fact that I needed a few attempts to solder the caps, I'm affraid soldering time was too long (maybe with both capsules, maybe with just the resoldered one). Maybe someone with more experience on making these kind of mics could give me some feedback on my story and the samples, and tell me if I did solder too long or if it all sounds ok.

Thanks in advance

ps. Test setup was mics>spsb1 (batt box @95hz)>sony mz-nh600. Also recorded a sample with sp-cmc-2>spsb1 (batt box @95hz)>sony mz-nh600 to compare with the self made mics, if anyone's interested.

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Over 150 views since my previous post.. No one who has some experience with these DIY mics with feedback on the samples?

Would love to know if the mics are ruined because of too long soldering or not.

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I asked before about effects of heat and no one seemed to know for sure. I know my 2nd try of over soldered Panasonic brand seem to be just fine, but they are not as sensitive as my 1st try.

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nobody comes here anymore, theyve moved on.

i dont have a loot of experience soldering electrets, but i soldere a great deal, and i always try to heat the thing im soldereing up the least possible, epecially if its an lectronic componant as opposed to wires, etc. my gues is that there is a good chance that, dpending on how long you had the iron on the contact, you partially melted part of the mic inside the casing, which is causing the distortion. i reccomend getting new electrets, and practicing soldering bits of wire together before doing the mics. try soldering 2 wires with only 2 mm or so stripped without melting any isulation. you have to do it fast, but it comes with practice, and if you can do that, you can quickly solder the mic, making sure not to damage it. my technique is to melt solder, then tin the wire with the melted solder so it heats up faster because there is more surface area contact, and only the part you want to solder is heated up. tin both sides like that, then melt them together quickly. letting them cool between solders is a good idea too, so the heat isnt tranferred inside the componant very much. allelectronics.com has 65 cent electret mics that are pretty good, but shipping is 7$ no matter how much you get, so i usually stock up when i shop there. as to you not getting a good contact, lightly sand the contacts, then tin them and there should be perfect conduction if its done right, whitch its relitivly easy to do. hope it helps.

dan g

Edited by patcheswfb

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Great info on diy mics and battery boxes.

Does anyone know where to get the omnidirectional electret condenser mics in the UK, 20Hz to 20Khz?

Mouser has them but postage to the UK is far too expensive.

I have checked Maplin but the best they have is "50hz to 13Khz".

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Anyway I can't find shielded cabling. Would the unshielded give me problems in a theatre setting where there shouldn't be much EM interference?

Beware of mobile phones!

I always ask my neighbours on concerts to turn off their phones COMPLETELY, not just the ringer :)

So, does anybody know for sure if mic cable shielding can help protect from mobiles?

If so, where do you connect the shield? Do you leave it unconnected to recorder and mics?

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Great info on diy mics and battery boxes.

Does anyone know where to get the omnidirectional electret condenser mics in the UK, 20Hz to 20Khz?

Mouser has them but postage to the UK is far too expensive.

I have checked Maplin but the best they have is "50hz to 13Khz".

I can send you capsules which are almost 20Hz-20kHz - they have some 6dB roll-off @ 18-20 kHz, which is easily corrected in software applying this graph:

[attachmentid=1585]

Here are some recordings made with these capsules:

http://www.stereo.org.ua/Events/Jazz/ednist-2006

(note: the 50 Hz hum you can notice on this festival recordings was really in the audio system of the venue)

Pricing: $2 apiece. $1.5 if you buy 10 or more, $5 shipping (from Ukraine)

Official name for the capsules: KPCM-6B

post-25114-1144750947_thumb.jpg

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I think I want to try to build this, but what is 1% film? Where do you use it?

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splumer

Definately worth having a go. I attempted the battery box the other night and I managed to build one. Not as neat as GreenMachine, as my shcematic reading skills are not great. However I was very pleased with my attempt, just going to look for a small tinned box of mints to house the creation :D

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I think I want to try to build this, but what is 1% film? Where do you use it?

I was referring to metal film resistors with 1% tolerance. If you don't have options, use whatever is available, the common 5% carbon resistors will also work.

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I'm in Australia, i was just wondering and have been unable to find anything appropriate here, searching for microphone capsule yeilds nothing at all the major electronics stores and the part number WM-61A doesn't help and doesn't even return a response on the Panasonic - ECG website.

any suggestions as far as where to buy and what i should search for

cheers

stephen

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