Is there an forum/area where microphones are discussed?
Has anyone tried doing an rf mic, like a Sennheiser MKH? I am aware of Uwe Beis' rf mic page at RF-Condenser Microphone Circuit
Has anyone tried doing an rf mic, like a Sennheiser MKH? I am aware of Uwe Beis' rf mic page at RF-Condenser Microphone Circuit
No the microphone capsule forms part of a FM circuit where the audio modulates the capacitance of the capsule in an oscillator and the FM is detected by a discriminator. There are no high impedances involved but the transformers are a difficult DIY. This is a rare DIY project.
Condenser mics. The "RF" bit means that the capsule is used to modulate an RF system comprising an oscillator (Sennheiser use about 8 MHz in their MKH-series mics) directly connected to an FM demodulator. This is not a wireless mic! Rather it uses a directly-connected FM system to read the motion of the condenser diaphragm.
Advantages: The circuit connected to the condenser capsule is low impedance; it does not require gigaohm-value resistors or high diaphragm voltages. Also, it is low noise and, because of the lack of high diaphragm voltage, inherently tolerant of humid environments. See Sennheiser's explanation at https://assets.sennheiser.com/global-downloads/file/11061/MKH-Story_WhitePaper_en.pdf and John Willett's description in Line Up, June/July 2003, available at Technology of RF Condenser Mics.
The Sennheiser MKH mics are some of the best mics money can buy; but you need quite a lot of it as they are /very/ expensive ($1,300-$2,600). The technology should be amenable to some DIY inventiveness, as Uwe Beis has shown (see link in my original post), but completing such a design is beyond my very limited electronic design skills.
I am hoping I might spark some interest here; perhaps, as many modern industrial instruments use similar technology for reading (often MEMS) sensors, some industrial instrument designer might rise to the challenge.
Advantages: The circuit connected to the condenser capsule is low impedance; it does not require gigaohm-value resistors or high diaphragm voltages. Also, it is low noise and, because of the lack of high diaphragm voltage, inherently tolerant of humid environments. See Sennheiser's explanation at https://assets.sennheiser.com/global-downloads/file/11061/MKH-Story_WhitePaper_en.pdf and John Willett's description in Line Up, June/July 2003, available at Technology of RF Condenser Mics.
The Sennheiser MKH mics are some of the best mics money can buy; but you need quite a lot of it as they are /very/ expensive ($1,300-$2,600). The technology should be amenable to some DIY inventiveness, as Uwe Beis has shown (see link in my original post), but completing such a design is beyond my very limited electronic design skills.
I am hoping I might spark some interest here; perhaps, as many modern industrial instruments use similar technology for reading (often MEMS) sensors, some industrial instrument designer might rise to the challenge.
You have the right idea, I think the transformers and the fine tuning of this circuit keeps folks away. I have only seen one or two DIY attempts over the years. The conventional approach is easier to understand for most folks I think, and after all there are not a lot of other commercial vendors either. Any patents have expired decades ago.
The capsule can be almost any distance from the head-amp.
I had a Stevens from the late 1950s. The electronics were bigger than a shoe-box. The capsule was hardly bigger than a tie-tack mike, coupled to the box with 20 feet of simple coax.
By the time I got it, it didn't work right, and diagnosis was non-obvious, keeps folks away. By this time JFET-Electret tie-tacks were so cheap the Stevens RF wan't worth fooling with.
I had a Stevens from the late 1950s. The electronics were bigger than a shoe-box. The capsule was hardly bigger than a tie-tack mike, coupled to the box with 20 feet of simple coax.
By the time I got it, it didn't work right, and diagnosis was non-obvious, keeps folks away. By this time JFET-Electret tie-tacks were so cheap the Stevens RF wan't worth fooling with.
Thread moved to PA Systems.As has been mentioned, this is not a very common DIY project, but I became interested in a similar request from the OP on the GroupDIY forum.
Over the last few months I have developed a workable example of this type of mic - with much useful input from the GroupDIY thread.
There are some project notes here:
DIY RF Condenser Microphone
Over the last few months I have developed a workable example of this type of mic - with much useful input from the GroupDIY thread.
There are some project notes here:
DIY RF Condenser Microphone
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