I've now built and tried out several of these mics, using different capsules and circuit variations.
I've decided that the 2mA version I described above is probably the best option for most situations...
After all, this type of mic really comes into its own outdoors, and is therefore more likely to be used with portable recorders.
It's then that current drain can be important.
OK, the noise floor is slightly higher, but is still way below any outdoor ambient noise level I've managed to record so far ...
I've redone the schematic and parts list to allow for different capsule types, and have posted a combined document here:
http://www.jp137.com/lts/RF.AMX10.v.2.3.2mA.schematic.and.parts.list.08.20.pdf(There is a link to that document on the website Schematics page as well)
I'm not sure just how important this kind of mic is for indoor use? - but it has been interesting to listen to the same capsule, when used with both a 'standard' Hi-Z Schoeps type circuit and with this Lo-Z RF bias circuit.
It certainly sounds a little different - although it's difficult to qualify 'different'. ....Slightly less 'HF edge' seems to sum it up.
Understandable perhaps, when you change the bias on the capsule from c.60V DC, to around 2 or 3 volts of RF AC bias.....
March 04, 2006, 09:48:04 PM