Grundig GCCM-320

The Grundig GCCM 320 is your standard amateur field recording electret microphone from the late 70s, but with a twist: where other electret microphones might offer the choice between on and off, it offers the possibility to switch directional patterns between omnidirectional and cardioid! Don’t do this while the mic is connected and you’re wearing headphones or amplifyng it in any way, though, switching patterns will blow out your ears with a single pure and flawless POP noise.

The mic, which feels quite solid with its metal body – nothing like the plastic electret condensers we have come to expect during the 1980s and 1990s – was sold for capturing sound in acoustically problematic environments and was available in a stereo configuration, known as Grundig GCMS-333. Accessories included a foam pop killer and, of course, a table stand. It uses a rather uncommon 5-pole DIN connector with an extra voltage pin in the middle, which makes it 6 pins total and which is – quite frankly – a harrowing aberration of DIN standard 41 524, known as DIN 45 326 and probably only enforced by the German Institute for Standardization after Max Grundig himself had dumped a large pile of electret microphones wrapped in brand new 1000 DM bills on their desks.

Highly recommended for picking up electrostatic noise on your carpet: The Grundig GCCM 320

Highly recommended for picking up electrostatic noise on your carpet: The Grundig GCCM 320

As for feeding the beast: There is no space inside the nice metal microphone for a battery, the voltage (not P48 phantom voltage, but more like P24 or something like that) was provided by the Grundig tape machine to the GCCM 320 – a case for cutting off the phony DIN connector and getting to work on some serious DIY. Or, if you have a female 6-pole-DIN panel jack at hand, you might just build a box with two 9v batteries inside and equip it with an XLR male out. We were lucky enough to have said box from another mic and used it with good results!

As for the sound: it is not very typical for an electret mic of the late 70s, as it lacks most of the jarringly hyped high-end. It sounds quite straightforward, bold and blunt and might not provide the detail most people are looking for when they use an electret condenser – but then again, this lack of detail also makes the sound quite charming, a little blurry and rather warm. You basically get the sound of a quite good old dynamic mic with a sprinkle of electret magic on top.

Not really detailed enough for acoustic guitar, but neat for fat compressed overheads or even room mics. The capsules also seem to have aged rather well (or at least uniformly), our two mics from different sources are indistinguishable in terms of sound and almost identic in terms of gain.

In case you need to open it, I’ve found some instructions online, written by Klaus Ortwein. I’ve taken the liberty and translated them:

The plastic head unscrews quite easily with a slight counter-clockwise rotation (bajonet system).The capsule is click-fastened to the plastic frame at two points. The cables are long enough to desolder the capsule without problems. In case you need to replace the cable, you’ll have to remove either the glued-on Grundig logo and then open the two philips head screws. Now gently twist and push the strain-relief to produce the circuit board and the switch without even removing the frame. The only thing that can go wrong is that you scratch the plastic Grundig logo.

On newer models like the one on the picture, this is significantly easier – simply screw off the head, remove the switch and open it.

  • Frequency response: 40 – 20.000 Hz
  • Sensitivity at 1 kHz: >= 0,7 mV/µbar
  • Impedance: 850 Ohm (omni); 1000 Ohm (cardioid)
  • Supply voltage: 4,5 V – 20 V
Style:3 Stars (3 / 5)
Sound:3 Stars (3 / 5)
Uniqueness:3 Stars (3 / 5)
Usefulness:3 Stars (3 / 5)

Trash:Gold ratio – 2:3

Grundig GCCM-320 frequency graph

Wiring diagram for the weird connector, provided by Steve from Hawaii. Thanks a lot!

Wiring diagram for the weird connector, provided by Steve from Hawaii. Thanks a lot!

11 Comments
  1. Thanks for great investigative work!! I have a GCMS 333 stereo pair, they have no switches and are described as having “kidney characteristic” pickup pattern. The schematic for the stereo din plug wiring is included in the 4-language brochure — I can send a picture if it would be helpful.

    • Thanks for commenting! A picture or a scan would be fantastic, I could put it up here for others to download. “Kidney characteristic” is actually the German name for the cardioid pattern, literally translated, haha. Too bad that Grundig obviously cut down on the omni option for the stereo pair.

  2. Thanks for this! Since information about these Mics is rare – I can provide a scan of the original 320-brochure. I have tried to make my 320 work with an XLR-connector and 9V-batterypower, but failed. The mic works connected to the tape recorder, though. If anyone KNOWS how to do the electronics to make these 6-pin-DIN microphones work with nowadays setups – please leave hints here. All I know so far is:

    Pin 8 (the one in the middle) is for the supply voltage
    Pin 2 is ground
    Pin 1 and 4 take the signal

    Converted 48V phantom power will not work easily since the microphone’s connection is not symmetrical. Though this would be the preferable solution.

    • Thanks for your comment, and I’d definitely appreciate a scan of the 320 brochure and put it up here! Maybe this can become the #1 Grundig electret microphone information hub on the net, hehe.

      Personally, I haven’t tried converting any of the GCCM or GCMS mics, but I know that Steve (who commented above) made the GCMS-333 stereo pair work with a battery power supply in a small altoids tin – maybe you can provide some more input on that, Steve?

    • On my 333 set, the 6-pin DINS were cut off and XLRs installed. Red wire to XLR 3; White wire to XLR 2; and shield to XLR 1.

      I powered it up with an AT8531 power module this morning, it worked fine but seemed somewhat bass-y and low signal output. Probably the low voltage (1.5v) from the AT8531 is inadequate.

      Hope this is helpful to your quest!

    • Tested further using two 6-volt batteries in the AT8531 power module (rather than 1.5v AA). I don’t know if running 12v through the power module is good for its long term health, but the mic definitely sounds better!

      So, with red wire to XLR3, white to XR2, and shield to XLR1, these mics work fine with 10 to 12 vdc power. Hope that helps.

  3. Yes, I’ll be happy to send it. I may also have powered them from an AT “Unipoint” power module but am not sure. I will investigate and report back shortly!

  4. Great info. I am considering buying one of these mics soon to try out with my Uher Report Monitor 4000 tape deck. How much are these mics worth now days ? The one I am looking at is kind of expensive.

    • Hi Chris, they actually go for almost nothing in auctions on eBay Germany (often with the shipping being more expensive than the actual mic). I guess that’s because they are somewhat hard to use with current recording gear, and I am not even sure if they will work with your Report Monitor 4000 out of the box. You might also have to build a little battery box.

  5. Ok, thanks for the info.
    I will not be buying the one I was watching then, too expensive, even with the matching power supply unit.
    My Report Monitor does supply 5v on the mic connector, but is not really adequate enough to power this mic well, it will have low output level.
    I have bought a nice AKG D130 instead !
    And a Sennheiser C1000S

  6. Hi,thanks for sharing your knowledge! I happen to have one of these grundigs, it similar to the one on the picture above, its plastic and slight golden in color. to my despair the cable is cut of :(( im hoping to get it working again(with my poor soldering skills) i see there is differert aproaches to this, Please help if you guys know how. Thanks a bunch..

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