What is a 'mosfet' and why do I want one?

[My name is Mudd]

In the past few days, I've seen ads in the classifieds here for (for example) Fulltone Bassdrives in both mosfet and non-mosfet versions, which gives me the perfect opportunity to display my almost-total lack of knowledge concerning circuit-like stuff and ask what a 'mosfet' is, and why is it important, and other stuff like that there...

 

[PilbaraBass]

Metal Oxide Semiconductor Field Effect Transistor

Field Effect Transistors have a transfer curve similar to a tube, hence when they're overdriven sound a bit more "musical" than the square clipping of say a Bipolar Junction Transistor.

MOSFETs can be driven to quite high gains and are therefore often used on the output stages of amplifiers (power MOSFETs)

I don't know anything about fulltone bassdrives and couldn't tell you how either version sounds, however.

 

[Alcyon]

Subscribed out of curiosity. I also know the Hartke 3500s with mosfets are considered a lot better than the non-mosfet ones.

 

[Chronicle]

My Mesa M6 is powered by Mosfets. It's the cleanest amp i've ever heard.

 

[Honk'n_down-low]

My Mesa M6 is powered by Mosfets. It's the cleanest amp i've ever heard.

MOSFET Really stands for Most Outrageous Sub Frequency -with- Excellent Tone

 

[KuruKuru]

I got a Fulltone Bass Drive Mosfet last week and all I can say is that its one of the best distortion pedals i've used on bass...you wont be disappointed!

 

[Chronicle]

MOSFET Really stands for Most Outrageous Sub Frequency -with- Excellent Tone

That's just Mesa's way of saying it....but it's true

 

[BeardedGnome]

I've also got the fulltone bass drive and love it, I've tried dozens of different drives, distortions, and fuzz pedals and the fulltone rules.

 

[afroman]

MOSFET Really stands for Most Outrageous Sub Frequency -with- Excellent Tone

Hahah YES.
My DB750 can attest to this.

 

[rcarraher]

Metal Oxide Semiconductor Field Effect Transistor

Field Effect Transistors have a transfer curve similar to a tube, hence when they're overdriven sound a bit more "musical" than the square clipping of say a Bipolar Junction Transistor.

MOSFETs can be driven to quite high gains and are therefore often used on the output stages of amplifiers (power MOSFETs)

I don't know anything about fulltone bassdrives and couldn't tell you how either version sounds, however.

This post covers it. They do have a "tube" like sound and quality with out the finickyness of tubes...in other words they don't go bad as often.

 

[rcubed]

Apparently they also compress the signal when saturated, similar to what tubes do.

 

[madmaskbass]

whatever MOSFET means it is good...i own Mesa Big Block 750 hybrid amp- tube pre. MOSFET power stage...it is still my favourite head ever..would still love to own a 400+ though...

redundant post i know.. i am also interested to know the answer to your question????

 

[My name is Mudd]

So they're used as another form of tube emulation, to be blunt about it?

 

[B.C.]

Mosfets, like said before are another way of clipping the signal. Different materials clip different ways, as we all know that silicon diodes clip much differently than germanium. Much like this, a MOSfet transistor will clip differently than a Bipolar Junction.

Cool stuff, I haven't played much with them, but I think I'll dig in a bit.