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.
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
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Trash:Gold ratio – 2:3