Hello everyone,
Are you aware of this website? I have been following it for a while and I would like to make this microphone .
What are your opinions about this microphone??
Mr. Shin used SMD ED8 5P 600Ω：600Ω Audio isolation transformer and Mic capsule Panasonic WM-61A. I ordered 15 of them and I want to experiment with them. Since I can't find a topic about this DIY microphone in this group, I wanted to start a topic and ask for your opinion.

Many thanks, and I am waiting for your opinion.

The Panasonic WM-61A was good in its time... but there are now much better omni electret mic capsules, that will give you better sound with less noise.

Consider the PUI AOM5024L, or the Primo EM272 electret capsules. Electrically similar, but better. Also, on this group, read up on the simpleP48 circuit for using such electret capsules with +48v phantom-powered XLR mic inputs. Easier to build, and better performing than Mr Shin's transformer -equipped design.

Hi Kenn,
Yes, I absolutely agree with you, I have about 30 AOM-5024P-HD-MB-R and 200 Panasonic WM-61A (bought about 10 years ago, only used about 12).
What I want to focus on is whether it would be advantageous to use an Audio isolation transformer. I also use the SimpleP48 circuit (I used it for two theater events at our school). But although it depends on the type of Audio interface used, there is a 60Hz hum in the recorded sound. I wonder if we can eliminate this by using an isolation transformer?
My another question I would like to ask is what is the function of the 2.2uf capacitor in the SimpleP48 circuit?
Finally, how can I modify the SimpleP48 circuit to cut below 80Hz?
Many thanks for answers.

Hi Mauricio,
Yes, WM-61A is excellent and tiny, but I prefer AOM-5024P-HD-MB-R :)

Hello Adam,

Maybe the hum is related to your recorder/audio interface?
I built several mics with AOM5024 in different casings and experienced no issues. Even when I was, recently, recording trams really close to their power lines. With rather poorly shielded capsules. No hum at all.

A capsule (for Takstar CM-60) I was experimenting with, developped an exemplary 50Hz spike, with harmonics, after I slightly enlarged the vents but AOMs were dead quiet in the same environment.

[Quote]What I want to focus on is whether it would be advantageous to use an Audio isolation transformer. I also use the SimpleP48 circuit (I used it for two theater events at our school). But although it depends on the type of Audio interface used, there is a 60Hz hum in the recorded sound. I wonder if we can eliminate this by using an isolation transformer? [/Quote]
In most cases, hum is due to improper shielding of the capsule. Using a transformer? doesn't solve the issue.

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Hello Everyone,
Many thanks for feedback, I'll check everything again...

These are what I did:

1. A Heat Shrink Tubing was covered the capsule (AOM5024) and the copper tape wrapped on shrink tubing, copper tape soldered to shield pair on the cable and directly goes to XLR connector. The pressed and shaped as mic capsule metal grill mesh insulation piece was also put on the head of the capsule and it does not touch the capsule but connected to copper tape and cable shield. On the outside, a shrink tube was used to wrap it all. I used multi-turn potentiometer in XLR connection part for first time testing the best voltage for capsule.
2.? West Penn Wire 25291B was used as the cable (actually I also had Mogami W2697, but I didn't use Mogami for the first test, because I thought there was not much difference between them, maybe I'm wrong :) )
3. I also used the Neutrik NC3MXX-EMC Cable Connector as a XLR connector, but then the supply voltage of the microphone dropped to 3.1 volts, so I gave up using it...
As an Audio interface-mixer, I used Allen & Heath Qu-16C, Audient EVO 4, M-Audio AIR 192
The noise of recording with AOM5024 is really really low, I liked it.
Best,

Hi Adam,

Thanks for the updates.

I mainly use my mics outside, feeding a portable recorder with XLR inputs. I also currently have two PUI AOM5024, wired as simpleP48, "permanently"mounted outside, in our back yard, with about 40 ft (12 meters) of inexpensive shielded balanced wire (similar to your West Penn wire) running in our house to a USB audio interface that has phantom-powered balanced mic inputs. I haven't encountered any AC hum, or other interference in any of those situations.

This is what I suggest: make more tests with your simpleP48 mics, in different locations, to get a better idea of what circumstances lead to hum. Also try different devices if you can, like other recorders or interfaces, and borrow some commercial balanced mics, including ones with and without transformers, and try them in the same location, over the same wire, to see if they also have hum issues. Theaters can be difficult environments because of electronic noise from light dimmers.

And how long were your mic cables in the theater situation that gave you hum?? The simpleP48 arrangement is surprisingly good, but it's not perfectly, symmetrically balanced, so it might be more susceptible to interference in difficult situations, and/or runs of over 10 m.