Tube preamp vs FET preamp

CTC564 · #1 10-22-2011, 11:13 AM

I've heard many bassists regard tube preamps as "warmer...grittier...etc" than FET preamps and while I've used (and enjoyed the same) I'm starting to believe that FET preamps are more accurate in reproducing a "pure" sound...again, I'm guessing, based on my experience

So, my question is this....

Is it true and would it be best to get a pedal to give you that "tubey goodness" and leave the amp as clean and "pure" as can be?

RickenBoogie · #2 10-22-2011, 03:22 PM

All too subjective. An amps topology is only one factor, of many, in creating the end product- tone. Every amp should be judged on it's own, no matter the type.

CTC564 · #3 10-22-2011, 03:24 PM

Thanks...learning TONS of stuff

Thanks to all at TB :-)

Hellbastard · #4 10-22-2011, 03:31 PM

Usually tube pre-amps tend to have a bit more of character. Fet tends to be more neutral sounding, but there are also factors, like the EQ circuit, the center Frequencies also determine the voice of a preamp. However a tube preamp tends to produce overtones that some people find more pleasing than those of fet preamps

fdeck · #5 10-22-2011, 04:13 PM

It probably depends on what is meant by a FET preamp. If it's a preamp built from JFET-input op amps, then the FETs won't impart any character to the sound at all.

Or you can build it up from discrete JFETs and bipolar transistors:

seamonkey · #6 10-22-2011, 04:31 PM

Quote:

Originally Posted by CTC564

So, my question is this....

Is it true and would it be best to get a pedal to give you that "tubey goodness" and leave the amp as clean and "pure" as can be?

I would, so you can turn it off and on when you want it.

And to different degrees especially if you have presets.

And at any actual volume level.

craig.p · #7 10-22-2011, 04:51 PM

And on that "discrete" point, a discrete-FET circuit can be made to sound clean or grungy or anything in between, and a tube circuit can be made to sound... yep, clean or grungy or anything in between. It's more how the device is employed, than the actual device itself, that determines warmth or lack of it, grit or lack of it, and so on. Now, when we get into intentionally nonlinear operation, i.e. non-clean operation, that's when you're apt to find audible differences among device classes -- FET vs tube vs bipolar, etc. You could say they benignly misbehave in characteristic ways.

Don't forget there are other factors to consider as well, such as how an amp behaves when it's doing heavy lifting, i.e played loud. An amp's hard-driven power stage often plays a big role in the sound you get. One of the things I like about the MB200: Crank it up, and you get a little extra grit and you get a nice compression effect from the power module running wide open.

Jerrold Tiers · #8 10-22-2011, 08:23 PM

Some years back there was a guy at NAMM with a solid state device, a form of FET, but an older form, which I had seen described in texts, but never seen a real version.

Anyway, he had a 12AX7 using this SS device that WAS a 12AX7......... pretty much indistiguishable. No, NOT one of the things Mesa had years ago, this was different.

Worked like, sounded like, lookd the same on a curve tracer.... just like an NOS 12AX7

he also had some power devices, but they were not drop in parts like the 12AX7 replacement.

All in all, they were super parts, and we wanted to use them..... unfortunately, he could not get production financing, despite letters of intent to purchase from several companies.

chadds · #9 10-23-2011, 07:14 AM

Some folks want grit, some that lovely coating on each note, some that warm and clear that tubes give. Those can be disparate goals.

seamonkey · #10 10-23-2011, 01:18 PM

Maybe these are the SS tubes
Roberts RetroValve, Inc.

They are not shipping but it just could be too late

All you really need is an iPod as a pre-amp to due the same. Signal in to signal out is the same as original amps. Switch models with a touch.

Duke21 · #11 10-23-2011, 04:14 PM

Quote:

Originally Posted by seamonkey

Maybe these are the SS tubes
Roberts RetroValve, Inc.

They are not shipping but it just could be too late

All you really need is an iPod as a pre-amp to due the same. Signal in to signal out is the same as original amps. Switch models with a touch.

iPod is a bit too noisy compares to an iPad. It is iPad which is a great preamp, with Amplitube or Ampkit.