Topic: Marantz/Superscope EC-5 cardioid mics

[ycoop]

Found a pair of these at my local salvage yard for $4 a pop. Decided to take them home and see if they still worked. While they have some shoddy re-wiring to convert them to RCA outputs (one goes RCA female and one goes RCA male  ), they surprisingly do indeed still functions as mics, both when run into my DR-40 set to "MIC" as well as an input into my small bass amp (though I think the level wasn't hot enough to come through aside from when I was speaking directly into the mic). Side note: how hard would it be to rewire these back to 1/4" for someone with no previous soldering/wiring background? Will snap a picture of the specific state of the wiring tomorrow, but it looks like the original wiring was cut close to the original 1/4" plug and simply rebound to the new RCA ones.

There’s almost nothing mentioned of these mics online, and only a single show using them that I could find on LMA. I have uncovered that they are electret condenser mics with a frequency response of 40 Hz-15000 kHz, which I know is quite limiting in terms of concert recordings.

Not expecting any worthwhile concert pulls to come out of them, but I'm interested in learning more about them. Anyone familiar with these, or have any idea about their history or intended use? Thinking they may be useful for home simple home recording.

https://i.ebayimg.com/images/g/3BgAAOSw5jpZh5c7/s-l1600.jpg

(not my image)

[rocksuitcase]

I think my Grateful Dead taping buddy used to own a pair of these he got with the purchase of his Superscope PMD420. He never used them all that much, patching out until he met me. I sent him an email to ask.
I would think anyone with soldering gear could help you put some 1/4 inch connectors back on.

[ycoop]

On a whim I decided to take apart one of these mics last night. It had a rattling sound when I shook it, so I figured there was an issue somewhere. After taking it apart I’ve identified two possible sources of the rattle: the capsule itself wasn’t well secured in its housing, and the wire connecting the capsule circuitry to the positive terminal of the battery was loose.

Anyway, the mic consists of the capsule housing and the body. My fledging electrical knowledge isn’t enough to really understand what’s going on, so I figure I’ll post some pictures and maybe one of you can help me figure things out.

The capsule/capsule housing unscrews from the mic body, and consists of 3 main sections. There’s the cap with wire mesh that holds everything, the capsule itself along with its inner housing and circuitry, and the piece that lies in between the capsule housing and the positive terminal of the battery.

The capsule itself only has a single (red) wire coming from it, which has a small clip that slides onto a pin coming up from the base of the inner housing circuitry. There appears to be three distinct wires in the circuitry. There’s the red connection that comes from the capsule and shares a connection via soldering to a black wire that runs down and makes a connection via a series of metal rings to a little metal “bowl” with a hole in it that touches the positive end of the AA battery held in the mic body. There’s also a green wire and a blue wire that appear to terminate on the circuit board.

Red wire and clip: https://drive.google.com/open?id=1ABzVylRvQbEhih9u5YvKptfmg8XDL8bp
Capsule connection to circuitry: https://drive.google.com/open?id=1nKb2qTxQgV--zQtP9SUPX5PIDtKlRuIk
Circuitry on bottom of capsule inner housing: https://drive.google.com/open?id=1WcufnJDvR4T4p-rPnAS-W01zLajLRSfm
Pieces that form connection between black wire and positive battery terminal: https://drive.google.com/open?id=1pJ49-8lmnwu68gyWGcolkzNv2xvmABnA
Mic body circuitry: https://drive.google.com/open?id=1JanKwOXK-dAP4gKl40E1-7wEzlwqcI5S

Anyone think they can explain what’s going on here?

[analogguru]

Noone ?

Ok, that's an easy task:
So what you've got is a microphone made by the japanese company "Primo" - at least the capsule.
This capsule was used in many brands including Nakamichi (CP-4), Akai, Jvc, Unisound, Universum, etc. and should look like this:



As you can see, the "capsule" from your first picture is normally spot-welded to the head assembly.  As can be seen in your third picture, the head-assembly got broken, therefore the "capsule" got off and caused the "rattling sound".  Since the capsule is spot-welded to the head-assembly there is not only the red wire, the ground connection is made via the case.

On the small (epoxy-)pcb which can be seen in the second picture are a FET and 2 resistors.  One 300M-resistor is connected to the gate of the FET, and a ~3,3k-resistor is between Source and Ground.  From this small pcb 3 wires go to the outer pcb, red is the drain, green is source, blue is gnd.

The red wire is connected to the black wire which goes to the "+"-terminal of the battery.  The "-"-terminal of the battery goes to the pcb which can be seen in the last picture, where on the invisible side a 680Ohm - 2,2kOhm resistor is mounted and connected between the "-"-terminal to ground.  The blue 10µF capacitor is for DC-decoupling.

If you have a multimeter you can verify the values by measuring between the green and the blue wire on the head assembly (3,2k - 3,7k) and between the "-"-terminal and ground (680Ohm - 2,2kOhm).




.

[ycoop]

Thanks for making an account to reply!

I’m just starting to learn about electricity and circuitry, and have a friend giving me some lessons. I’ll bring this to them, hopefully after enough lessons I’ll be able to follow more what’s going on.

Are these capsules worthwhile to potentially repurpose into a home brew mic? They sound alright, though I’ve only come across one recording using them, which doesn’t sound great. How much of the sound has to do with the capsule itself vs the circuitry?

[analogguru]

.....
Are these capsules worthwhile to potentially repurpose into a home brew mic?

Why do you want to do that ?  Don't you like the look of the microphones ?
I mean if you want another look you can search for:

Akai - ACM-50
Akai - ACM-100
audio-technica - ATM11
Unisound - EM-83
Universum - 45150
Universum - 381.561 0

They all use the the same capsule no matter that they look different and you should get them cheaper than DIY-ing anything would cost you.  Of course if you want to DIY something, I would say that this capsules are usable.

They sound alright, though I’ve only come across one recording using them, which doesn’t sound great. How much of the sound has to do with the capsule itself vs the circuitry?

Most of the sound comes from the capsule, the surrounding electronics are not so important as long as there are no design flaws.  Some people are convinced that even the design of the headbasket has a significant influence on the sound, but.....

[ycoop]

My interest in using the capsules in DIY projects is more about tinkering than anything else. Particularly interested in the possibility of running these using plug in power and shrinking their size considerably.

[heathen]

They sound alright, though I’ve only come across one recording using them, which doesn’t sound great. How much of the sound has to do with the capsule itself vs the circuitry?

Most of the sound comes from the capsule, the surrounding electronics are not so important as long as there are no design flaws. 

Can't a manufacture design the electronics so as to get a different "sound" from the capsule, though?  For example, one manufacturer may want to tailor its microphone for speech so it implements "hard-wired" bass rolloff?  In that scenario, different mics using the same capsule could produce drastically different recordings, right?

[analogguru]

They sound alright, though I’ve only come across one recording using them, which doesn’t sound great. How much of the sound has to do with the capsule itself vs the circuitry?

Most of the sound comes from the capsule, the surrounding electronics are not so important as long as there are no design flaws. 

Can't a manufacture design the electronics so as to get a different "sound" from the capsule, though?  For example, one manufacturer may want to tailor its microphone for speech so it implements "hard-wired" bass rolloff?  In that scenario, different mics using the same capsule could produce drastically different recordings, right?

Of course is this possible and it has been done, but I was talking about an linear approach.  I mentioned too "as long as there are no design flaws."  The Toshiba EM-120 is a typical example for this.  This microphone has a good capsule but an idiot-designer used a too small output coupling capacitor which would be sufficient with a high-impedance load.  But most of the mic inputs are low impedance, so if you connect this microphone to a "normal" mic-input there will be a significant bass rolloff and the mic will sound tiny and harsh.  By only changing the output capacitor with an appropriate value, you will not recognize this microphone anymore.