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J-FET preamp/DI  vs tubes
J-FET preamp/DI  vs tubes
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Old 25th December 2004, 12:04 AM   #1
qveda is offline qveda  United States
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Default J-FET preamp/DI vs tubes

I'll start off by saying I'm not super techy. But thought you guys could help me understand how J-Fet preamps could offer advantages over tube preamps or other solid state preamps for use with elec.guitar and bass ( pre/DI application)

Some high quality pre/DI's boast the use of J-Fet to get a variety of warm harmonically rich tones by adjusting gain. (e.g. I think Neve consoles, and Universal Audio 2108 uses J-Fet, and maybe these less expensive products do too: Presonus Eureka, and Joe Meek products).

I have not had the opportunity to play though these. Can you offer comparison between J-Fet , other solid-state , and tube preamps?

Can J-Fet preamps offer a variety harmonically rich overtones by adjusting gain settings? like tubes can?

What are some advantages of J-Fet over tubes? warmth plus greater clarity?

When I read the blurbs for products, should I watch specifically for J-FET vs. FET ? is there a big difference ? or are these terms sometimes used interchangably?

thanks! and happy holidays
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Old 25th December 2004, 12:58 AM   #2
anatech is offline anatech  Canada
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J-FET preamp/DI  vs tubes
Hi Qua,
The best thing to do is go into a music store and play around with these. I am inclined to think the J fet is most often used. It's more robust in that enviroment. I know the older IG fets were noisier than J fets. Distortion quality depends on the design of the unit. Don't expect them to behave exactly like tubes.
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Old 30th December 2004, 05:05 AM   #3
Enzo is offline Enzo  United States
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Location: Lansing, Michigan
Keep in mind that mixers and mic pres are fundamentally different from guitar amps. The mixer tries to reproduce faithfully what comes into it. It wants to be completely neutral and lacking in coloration. Even when adding "warmth" the thing is just adding a subtle EQ change. But guitar amps are part of the instrument. They are meant to be anything BUT clear and faithful. You are now PRODUCING sound rather than reproducing it. SO what Neve does is unrelated to what Fender does.

If you are preamping an acoustic guitar, then you are not really using a guitar amp, "acoustic" amps are really small PA systems.

I know there are guitar amps using FETs, but I can't recall any specifically right now. JFETS do operate analogously to tubes, but as CHris said, they won't sound like them. Please do experiment though and share your findings.

One real advantage of JFETs over tubes is that you can run them off a 9v battery
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