DIY measurement mic

[Shaun]

I just found this via Google. Phase splitter transistor... not exactly an instrumentation amp but, hey... it is what it is...

BTW, it seems that there are a few different versions. I don't know which one this is.

[PB2]

Originally Posted by Shaun

I just found this via Google. Phase splitter transistor... not exactly an instrumentation amp but, hey... it is what it is...

BTW, it seems that there are a few different versions. I don't know which one this is.

Thanks for that!
Yeah, nothing fancy there. C6 looks to be drawn in the wrong place
it goes to ground rather than the other side of R6 at the phase splitter output.
Outputs are in a sense open emitter to the phantom power source resistors.

I'd like to up C2, C3, C6 to 10 uF to flatten the response down to below 20 Hz.

[PB2]

This subject is covered here, somebody measured the mic and there is no output on one pin, it is not actually balanced and the connection of the coupling cap is as shown in the schematic - as much as it makes no sense:
ECM8000 microphone measuring techniques and usage discussion - Page 5 - Home Theater Systems - Electronics and Forum - HomeTheaterShack

I comment further here the phase splitter resistors seem to be set up incorrectly also:
ECM8000 microphone measuring techniques and usage discussion - Page 5 - Home Theater Systems - Electronics and Forum - HomeTheaterShack

[jzagaja]

Maybe ultimate solution - MK301 capsule (widely used as reference) and DIY phase splitter preamp (below) plus CMOS voltage multiplier (200V) plus MicPortPro USB-AD converter.

[Alex from Oz]

Panasonic WM-60 and WM-61 microphones seem to have been discontinued.
Anybody know an equivalent replacement and a supplier in Oz?

Cheers,

Alex

[PLB]

Hi Alex,

Please see this link. Digikey have over 33000 in stock.

Digi-Key - P9925-ND (Manufacturer - WM-61A)

Regards

Peter

[Elbert]

What a great thread!

Been looking in to computer based measurement for DIY loudspeaker projects, it would be a great thing if I could plug a mic in to my mini-laptop and hook an amp to the audio-output and run some basic measurements on projects I do.

As I really don't do enough projects to justify putting too much money in to "proper" equipment, a cheap DIY solution is what I'm after.

Now, this is an interresting comparison I found! Microphone measurements and comparisons

After seeing this, I went and ordered a pair of WM-61 capsules off e-bay in order to build a the microphone described on the Linkwitz lab web-page.

From the price it is obvious that there will be limitations, but if the comparison in the link is anything to go by, this should still be very usefull for the happy amateur!

The greater uncertainty will probably be the performance of the buildt-in sound card of my Asus IEEE mini-laptop...

[Pano]

Your laptop sound card may be the stumbling block. But there should be ways of testing it and compensating for it. You'd need to build a little attenuator network.

[Elbert]

True!

Somehow, I didn't think about that! If I simply loop a test signal directly from the audio/ headphone output and back in to the mic input via some attenuation, well, then I'll soon enough se what the system performance is!

And whatever software I end up instaling is clever enough (haven't got a clue about which yet!) I might even be able to self calibrate / compensate accordingly. Wow, that would be neat!

Thanks for nudging me in the right direction!

[Alex from Oz]

Originally Posted by PLB

Hi Alex,

Please see this link. Digikey have over 33000 in stock.

Digi-Key - P9925-ND (Manufacturer - WM-61A)

Thanks Peter!

Cheers,

Alex