Dumble Preamp Mosfet Follower

[johngovan]

I know it's a bit dumb question. But i need your inputs on this project. I plan to build a clean dumble preamp, no overdrive so it is not so special at all. I want to build the clean channel of this amp and hook it up to any power amp (SS most of the time). But my problem is, it will surely cause impedance mismatch, with that in mind i think a mosfet buffer will do the job. But how can i hook the mosfet to act as buffer or source follower to lower the output impedance of the dumble preamp? Thank you. I hope i will be enlightened.

[xtian]

Here is some great reading on MOSFETs as cathode followers:

http://geofex.com/Article_Folders/mosfe ... tfolly.htm

[johngovan]

I tried to add that circuit at the end of my preamp but it makes a very loud sound with the gain off.

[pompeiisneaks]

Whats the mosfet you're using? I've heard on the el34world.com forums of multiple people trying this with no problems.

~Phil

[johngovan]

IRF830. I'll draw the schematic to trace my mistakes.

[10thTx]

I've done a few amps with mosfet CF design. I think they sound great.

So, maybe something like this?

With respect, 10thtx

[10thTx]

This is simply a photo of using a mosfet CF on a layout board for a D'Mars ODS build I did for someone who needed something for a "zero volume" stage situation.

With respect, 10thtx

[Mark]

Good topic, many of us should look into this sort of thing.

I myself have baulked at replacing the 12AX7 oscillator in my 18 watter with a FET. The motivation being more gain to allow more filtering to get rid of the dreaded thumping from the tremolo, but I digress...

[johngovan]

Will this work?

[johngovan]

I've done a few amps with mosfet CF design. I think they sound great.

So, maybe something like this?

With respect, 10thtx

Wow. Thank yoy 10thtx. This really answers my question. a really big help for me. i appreciate it.

[10thTx]

I don't know if your idea will work or not? I would be hesitant to have switching between the tube triode and the mosfet CF.

On one of the D'Mars ODS builds I did, I had a mosfet CF both on the clean channel and the OD channel. (circled in red) And these functioned as the "send" for an effects loop with the return being the tube triode circled in blue. It worked great!

IF you'd like to hear a soundclip of that amp: https://www.soundclick.com/html5/v4/pla ... D=11842172

With respect, 10thtx

[10thTx]

Thinking about your idea some more, maybe it would work OK? I can't give you a reason that it wouldn't work.

Here are a couple of more ideas for consideration. They may not be any improvement over your schematic idea?

With respect, 10thtx

[10thTx]

A last thought to consider ……………….

IF you are running into a SS power amp most of the time, why not have an active FX loop in your preamp?

with respect, 10thtx

[johngovan]

Thinking about your idea some more, maybe it would work OK? I can't give you a reason that it wouldn't work.

Here are a couple of more ideas for consideration. They may not be any improvement over your schematic idea?

With respect, 10thtx

This is super Awesome. A million thanks to you Sir. I will try to build this options. I will order turrets next week. I am realy excited about this. This is wonderful. Thank you so much for the ideas. I'd like to try the mosfet effects loop using lnd150. I' getting pumped up. Thank you.

[johngovan]

Further question. Are there any mosfet substitute for LND150?