<My apologies Marik, it was this one. Still supplies about 12V without the use of a zener and that's all the volts those capsule types are rated for... Don't get me wrong about the PZMs, they still sound like crap, and even though I also replaced the capsules with the Panasonics mentioned in TapeOp (soon to be discontinued I hear!).>
Hoof,
No apologies neccessary.
Actually, properly modified Realistic PZMs can sound very good. But, since there are some confusions let's start from the beginning...
<
http://prosoundweb.com/recording/tapeop/buildmic/buildmic_16 _1.shtml ) very big claims are made on this DIY mike. Now at what goes into the mike its worth its money even if it does a crappy imitation of radio-shack mike, and itll keep me warm this summer if i make a couple, im still curious whether anybody made one and what they thought of it>
Anton,
The biggest problem is that in this configuration internal FET of the capsule is in its stock connection and works as a common source amplifier in self-biasing mode. In this connection it has a very limited dynamic range and highest input capacitance possible for a given FET, which loads input signal (think of this as a cap used in a -10 pad in condenser mics). Another disadvantage is that output impedance is high (around 2-3K depending on a capsule), so you cannot run long cables and there is a serious mismatch with input impedance of mic preamplifier. In order to overcome all these, the very first thing is to make a Linkwitz mod. Basically, you disconnect source of the FET from capsule's ground and reconnect the FET as a source follower. It greatly increases overload capabilities of the capsule and makes its sound less muddy. Then, in order to bring the output impedance to more 'conventional' 200 Ohm, you have to make an output buffer. Realistic does it by means of transformer. Since it is a poor quality one, here it would be a much better idea to make a transformerless output.
As Chikenbop has already mentioned, I had a big thread on HR forum about ECM8000 mods, which would be relevant to PZMs, as well, and the thread has a lot of discussion in depth on all these things. Have a look:
http://homerecording.com/bbs/showthread.php?t=111051&pag e=1&pp=25
Also, although it is not in the thread, I cut a resonator from the Panasonic capsule, and the capsule sounds much more natural.
<Some experimenters have spent a lot of effort trying to figure out a way to neutralize the internal FET in an electret capsule and use an external FET. It's no small feat to do so. I don't know of any electrets available without internal FET, but I'm nothing even close to an expert. The most common "good" Panasonic capsules have internal FETs.>
Josh,
Although it is quite tricky, I took apart Panasonics and rebuilt it using external 2SK170. It doesn't work. Since capacitance of the capsule is very low, any stray capacitance (wiring, or input capacitance of bigger FET) will load the capsule and its low output becomes unusable. That's the reason why with capsules THAT small, there ought to be an internal surface mount sized FET.