DIY large-diaphragm condenser mic

[Michael Willis]

For a long time I have wanted to try a large diaphragm condenser mic, but the price of a nice one has always been more than I wanted to pay. Recently I found an Instructable called Modify a cheap LDC Condenser microphone; the idea is to buy a cheap microphone and replace the capsule and circuitry with better electronics. I wondered how much the parts would cost, so I told myself that I was just going to look it up (you know, out of idle curiosity). I went to digikey.com and found most of the components. After I had them all in the cart it was too easy to place the order. At that point, I just had to build it.

I tested the cheap microphone when it arrived, and sure enough it had a horrible high frequency hiss noise that was something like -30 or -40 dB relative to the signal. It was so bad that I initially thought it was picking up the sound of the AC, but I moved into a closet and blocked the entrance with a blanket, and still got the hiss.

I proceeded to gut it and set about replacing the internal parts. It took a few tries to get it right, which is a story of its own, but I finally got it working.

Here's a quick sound test:




Here are some pictures of the build:



This is a picture of the circuit installed in the microphone body, along with the new capsule in a mount that my brother made with his 3d printer:


This is the microphone with the cover replaced:

[Samulis]

Hey, that sounds really good for the price! Looks like an ambitious yet very rewarding electronics project.

It looks like the mic is a side-address capsule arrangement, though in your video it appears to be placed like an end-address microphone. In such an arrangement, lows will be rolled off and a ~3 dB signal to noise ratio penalty will occur around 1 kHz. Is that intended?

I've been thinking about trying one of these kits myself... they're more 'all-in-one' and hold ones' hand a bit more, but are much more expense as a result-
https://microphone-parts.com/collections...phone-kits

[Michael Willis]

(07-30-2020, 02:48 AM)Samulis Wrote: It looks like the mic is a side-address capsule arrangement, though in your video it appears to be placed like an end-address microphone. In such an arrangement, lows will be rolled off and a ~3 dB signal to noise ratio penalty will occur around 1 kHz. Is that intended?

Ha, I was trying to point the capsule toward the right-hand keys of the instrument, but instead it ended up pointed toward the floor. I was in a hurry and didn't fix it, but I should pay better attention to mic positioning in future recordings.

(07-30-2020, 02:48 AM)Samulis Wrote: I've been thinking about trying one of these kits myself... they're more 'all-in-one' and hold ones' hand a bit more, but are much more expense as a result-
https://microphone-parts.com/collections...phone-kits

I did look at that site, but I decided to do it the hard way. The S-25 Microphone Kit is very similar to what I built. It has the same capsule, and is based on the Alice Microphone. The S-25 has a lot more components than the one I built; from what I've learned about variants on the Alice design, a lot of those extra components provide additional surge protection in case something goes wrong on the wire, and maybe it includes some more sophisticated interference countermeasures. It also includes the -10dB pad switch, but I don't need that since my interface has a -10dB pad button.

The way I built this one, it is made from about $50 worth of parts. I ended up spending more than that since I bought most of the components in bulk and took a few tries to get it right. I have enough left over components to make three more, I would just need to buy additional capsules and mic bodies for them.