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Difference between a FET and a condenser.

Discussion in 'Microphones' started by Jer-vox, May 11, 2012.

  1. Jer-vox

    Jer-vox Active Member

    I was wondering if someone out there can answer what is the difference between a Fet condenser mic and a typical regular condenser. I have both tube and 48v powerd condensers and know about them but very little about FET's.

    What are some of the advantages of using one over another? What are the most common applications for using an FET? And what are the differences sonically and in tonality, or if there is any?

    I'm not sure if this question has been asked before, but I would really like to hear from some of you knowlegeble audiophiles out there.


  2. Boswell

    Boswell Moderator Distinguished Member

    I'm sorry to say you have been mis-informed. There is no such thing as a FET mic, in the sense that the transducing element from sound waves to an electrical potential is never done by a FET.

    The capsule in a condenser mic (the correct term for this type is a "capacitor" mic) needs to be connected to a very high impedance (several G Ohms), and this is usually be done using a FET or a valve (tube) internal to the mic. It's probably here that the mis-information has crept in.

    So microphones are categorised by transducer type (e.g. moving coil dynamic, ribbon dynamic, condenser). Within the condenser group, there are sub-categories for the type of internal buffer circuitry (valve, FET) and the type of polarizing charge used (electret etc).
  3. Jer-vox

    Jer-vox Active Member

    Thank you Boswell, aside from your technical explanation in your first two paragraghs, the third really kicked me in to understanding the first two. As far as use of an fet over another; are there any situations aside from preference, that one would use one over the other. For instance: Lawson sells an L 251 FET, and also a L251 tube for an additional $1000. I already own a Lawson L47 mp and love it!!
    I am seriosly looking to buy one of these mics but would like to know the sonic differences. Would they both sound the same even though one uses a power supply, and the other with electronics?(I hope that I asked that question kind of right as I'm a novice to understanding power supplies and electronics)

    You sound very knowlegeble and informed on this subject and I really appreciate your input.

    Thanks again

  4. Boswell

    Boswell Moderator Distinguished Member

    I've never knowingly used a Lawson mic, so can't comment on the sonic characteristics. If you compare the FET and tube families of other manufacturers (Neumann for example), there's less of a difference between the type of buffer circuity used (FET or tube) as there is between, say, whether they have transformer output or are transformerless. The point is that it's not just the FET/tube that makes the difference. Manufacturers have taken the advantage when designing with FET buffers (which can be powered by an internal battery or run off the phantom power supply) to change other factors in the microphone.

    What you should be doing is listening to is the sound of the mic into your choice of pre-amp on your choice of source material in your own studio, ignoring the engineering design and marketing behind the individual mics. Of course price pays a big part in whether you can get a sound that you like, but there are good reasons why a tube mic with its hefty power supplies costs more than a phantom-powered FET mic.

    I know there are others on the forum who have personal experience with the Lawsons, so I'll let them comment on the differences between the models in that series.
  5. Jer-vox

    Jer-vox Active Member

    Thanks much, your insight is very helpful and I will take your advice. Has anyone else out there had any experience with these mics?(Lawson 251 tube and Lawson FET)
  6. RemyRAD

    RemyRAD Guest

    The FET and the tube are there basically for impedance conversion. An FET virtually mimics what a tube does. The tube on the other hand can present a soft even order harmonic related soft overload. The FET just breaks up on overloads. While the tube can actually amplify the microphone, that's not its primary purpose. The distortion factors between tubes and transistors are quite different. To create second harmonic, even order distortion components. The transistor will create third harmonics and odd order distortion components. Even order distortion occurs in real life. Odd order distortion only occurs in the electronic realm. Both have their places. You can only know what to use by careful listening evaluations.Otherwise you are talking about a microphone with the same capsule so the actual tonal characteristics should be close. The 251 is actually patterned after a AKG. Whereas their other models are patterned after the darker Neumann characteristics. So the loss in 251 is designed to mimic an AKG C-12 à la the transistorized AKG 414. Lawson also manufacturers a 47 style microphone with either a transistor such as the U-47 FET Neumann or the one with the tube designed to mimic the original U-47. Which originally had a VF 14 metal tube, no longer made. So the later 47's utilized a nuvister, which was a tiny transistor like tube. After that came the U-67 which utilized a EF 86 pentode, run as a anode triode. Most modern day tube microphones utilize an actual dual triode, similar to the front end of a tube guitar amplifier. Either way, they all have their place which can only be determined through listening and experience. Tube microphones can sound magical while others just sound rather muddy. The transistorized FET microphones are the most common in use. Older transistorized microphones and their tube brethren, utilized some kind of output transformer. Newer transistorized & tube microphones have eliminated the output transformers. The transformers add to the coloration of the tonal characteristics of the microphones. Some folks don't want that. Others do. Some folks feel that they tube microphones have a softer and sweeter sound. The transistorized versions tend to be a little cleaner and more neutral sounding. Different tubes can cause a huge difference in sound being utilized on the same microphone. FET's, not so much so. So it really all depends on what you want and what you are going for. No one should tell you to use one over the other. That's for you to decide. Some condenser microphones such as numerous Neumann's already have their extreme low frequencies cut off so as not to cause " blocking ". Others just let it fly all the way down to 20 Hz. So Neumann's can have some components removed so as to prevent the low frequency cut but then blocking can occur. And that sounds nasty when that happens. AKG has also resurrected their C-12 in a more modern-day release. Those are quite popular and so are the imitations of that. There is no one microphone to own. However some of these nuance differences are hard for people to comprehend unless you can compare it to the other type of microphone. So this response was not made to indicate what you should use but the subtle differences between the different types.

    U-67/87 owner. Yup, I have both in pairs.
    Mx. Remy Ann David
  7. DrGonz

    DrGonz Active Member

    When I read the term "FET" it immediately occurred that it must be a Field Effect Transistor. Basically, it's like when you have a solid state guitar amp and you crank the crap out it and it breaks up nastily. Take a tube amp and start to crank it up and viola, it breaks up with much more impact to the sound. It colorizes the texture of the wave w/ all those distorted harmonics. Well that's my retarded way of explaining it... lol.
  8. Jer-vox

    Jer-vox Active Member

    Thanks everyone so much for a very informative thread. I now do have a basic understanding on this topic. The more that I read from reply to reply, the more I think I understand. Basicly what it comes down to is listen to your ears when doing an A B in mic comparisons and see whatever moves you in one direction or another. I already own a Austrian made 414 and like it a lot. It is nice on some vocals , ok on others, but a real dependable workhorse on almost anything else. My Lawson on the other hand is gorgeous on all vocals and I think from the way described from the above posts, has that subtle distortion that to it gives that warm magical sound that I crave. In short I will probably order the Lawson 251 Tube, try it out for a couple of days, and see how iot compares to my L47 mp. Lawson does give a 10 day trial period return policy, and I'll go from there.

    Anyways thanks again for all your valuable info and insight which I can alaways refer back to in the future if needed

  9. RemyRAD

    RemyRAD Guest

    There is one transistor used, in a sense, as a transducer. That transistor is called a thermistor which is a temperature sensing transistor and one of the most accurate ways to sense temperature. Now if we could only make those thermistors pick up sound? Then we might be able to have a true transistor microphone?

    Beam me up.
    Mx. Remy Ann David

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