FETs - interesting devices

Frequently asked question on transistors: types, substitutions, how to test, use and misuse them.
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bajaman
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Post by bajaman »

Last edited by modman on 06 Jan 2009, 10:59, edited 3 times in total.
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Post by soulsonic »

Yeah, good stuff. Anything to help me understand these damned FETs better is a big help to me.

Is it just me, or is a tube a million times easier to bias than a FET? Ive never had any problems getting tubes to do what I want. Even when I was completely ignorant of what was actually happening in a tube, I still didnt have any problems getting them to work. But with FETs, they are such a mess its unbelievable. I feel completely hopeless when Im trying to get one to work right the first time. I have gotten MOSFETs to work well, but I am always thinking, "why do I need all these extra resistors?". It just doesnt seem practical to me.

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Post by bajaman »

Hi soulsonic
I love tubes too.
You can run them off all sorts of voltages and get completely different sounding music.
Fets take a little bit more getting used too - and they are inherently noisier than the good old 12AX7 or ECC83 for our European friends :wink:
My personal favourite jfet is the 2SK117 - Roland/Boss use them (and so do Tech 21, I am led to believe, in their Sans Amp Classic pedal - much better sounding pedal than the GT2, which does not use one :wink: )
I do hope you persevere though - practice makes perfect, as they say - hope you get some interesting new design ideas from these articles - I feel a BOOTEEK pedal design coming on :lol: :lol: :lol:
Cheers
Steve

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Post by soulsonic »

Funny you should mention the 2SK117.... so far that's the JFET I've had the most success with.
I'm sure I'll get it down to where I'm as quick with it as I am with tubes, but I really wish it didn't require all the additional biasing stuff. With tubes, if you have the bias way off it just sounds bad - with a JFET or MOSFET, you get no sound at all!

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Post by bajaman »

That is the problem with 9 volt stuff - not much margin of error :wink:
Now with a tube running off 240 - 380 volts :roll:
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Steve

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Post by modman »

Moved to the FAQ section, good excuse for a [smilie=bump.gif]
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Post by Fuzzer »

But now the PDFs are gone. :(
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Post by bajaman »

(check first post for link)
enjoy
:) bajaman
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Post by modman »

Fuzzer wrote:But now the PDFs are gone. :(
:scratch: :hmmm: :slap: :mrgreen: yeah, it was very late, I should have checked.
bajaman wrote:members/archive/FETS/
enjoy
:) bajaman
[smilie=a_goodjob.gif]

I hope this isn't a NZ based mag, will setup a central library folder or something later today.
thanks for saving
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Post by puppiesonacid »

I hope this isn't a NZ based mag, will setup a central library folder or something later today.
thanks for saving[/quote]


that would be a great idea. I was bummed when i realized it was so long ago haha, I was thinking " okay, maybe I should try to learn some more today and clicked excitedly, to no avail...

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Post by Fuzzer »

Thank you very much guys, now I'm gonna get reading.
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