Which JFET Amp Sim?

[KerryF]

Im looking to build a nice JFET (Preferably J201) amp simulator to put through my new Valve Junior.  The amp sounds great, but I have a feeling that something like this would sound amazing!

I was thinking about the Thunderchief, but I dont know if Torchy's vero layout is verified and what the different leads off his layout go to: http://www.indyguitarist.com/torchy/amps_emulation/ROG%20Thunderchief/Thunderchief.gif

What are my other options for some good sims.

Theres also the other ROG sims, but I only want to use gain and volume pots for now because thats all I have until my Small Bear order gets here.  Thats why the Thunderchief would probably be perfect (I have those 2 exact pot values, and exactly 4 100k trimmers).  Can someone tell me if Torchy's layout is verified and what the pins go to.

Kerry

[markm]

I think my "fave" ROG build is probably the English Channel.
Although not a true emulator per se, it certaily has the personality of an old AC30. 

[rockgardenlove]

My amp sims sound much better through my ROG Ruby than through any of my tube amps.

I'd build a Fetzer valve boost.  Should sound cool on your VJ.

Though personally I'd open up the VJ and have a go at the amp!

[KerryF]

I have the Sparkle Boost which will sound great with the VJ.  I have used it, but not yet with the VJ.  I also have the Cream Pie on breadboard to test soon.I dont really want to do anything to the VJ or at least right now, because it sounds amazing how it is.

[rockgardenlove]

Here's something else to consider.  The tube OD sounds much nicer than the JFETs overdriving.
Maybe come up with something like ROG tone mender.  You can get an amp to sound drastically different with a different tonestack placed in front.  Try a Vox tonestack, a Marshall tonestack, a Fender, whatever.  Should sound cool.

[KerryF]

Yea thats actually a good idea to have a little passive tonestack.

I think a Vox tonestack will sound great with this thing!  With 250k pots.  Go into the Duncan ToneStack Calculator, go to the Vox setting, and change the pot values to 250k.  Does it look good to you? 

[KerryF]

Do you think its necissary to do a little JFET buffer pre Tone Stack?  Or should I just do the Tone Stack by itself?

Also, that Zsrc in it, I think thats the impedence?  Do the two lines on both sides of the symbol just connect?

[rockgardenlove]

Those passive tonestacks usually use cause a drop in volume.
Put a small boost before in after.  The input impedance will be too low otherwise.  A high Z input from your pre-boost and a low Z out would be best.  Then after the tonestack a recovery stage would probably help.
And remember, the amp has it's own tone too.  You may want to spend some time tweaking the thing.  The calculator shows the output without any equalization after it.  In your case the amp will add more equalization afterwards.

[KerryF]

What do I need to fix...

[Jay Doyle]

What do I need to fix...

First you need to either put a Drain resistor on the second J201 or take the signal from the source, otherwise you aren't going to get anything out of that circuit.

Second, I would put another 1M5 resistor from 9V to the gate of the first J201, this will ensure that the first J201 biases up better. You also may want to think about doing the same with two 1Meg resistors on the second J201, but in that case you will want a DC blocking cap from the wiper of rht 250k pot to the gate of the second J201.

The first is necessary, the second are just suggestions...

Jay Doyle

[rockgardenlove]

You might want to read this:
http://runoffgroove.com/fetzervalve.html
While you're at it I'd probably do the tube emu gain stages.

[Rafa]

Maybe you could build any ROG using fixed resistor values in the tone control, the matchless sound clips sound amazing.
Cheers
Rafa

[mojotron]

I did something like this on the Vibin Champ

http://www.diystompboxes.com/smfforum/index.php?topic=47371.0

I really like the tweak-ability of the fender EQ on this.

[KerryF]

I was actually thinking about the Vibin Champ yesterday.  I remember when that came out.  It sounds awsome.

[mojotron]

I was actually thinking about the Vibin Champ yesterday.  I remember when that came out.  It sounds awsome.

Thanks, it's a pretty subtle effect on clips, as the mp3 clips show; but in actual use it sort of turns what ever amp you're using into an older generation fender - sort of a fetzerizer thing and that allows me to cover a lot of sounds with one set of gear.

I built a peppermill-ed version that I have been playing with too - I should really put the original version back in an enclosure so I can compare the 2. But, I really like both versions... the JFET first stage - as posted - seems to have more dynamics/grit, but the MOSfet-first-stage version seems to be a fit more 'fendery' when playing clean.  I can post the MOSfet-first-stage version if anyone is interested.

Anyways, as an effect, this kind of circuit is much more of an 'enhancement' to the sound - but the direction you are taking this is right on, IMO, for something like a VJ - these kinds of circuits make great preamps and likely the perfect 'helper' for the VJ to make it a bit more versatile. Basically, I do this with my TubeWorks RT2100R amp - it's a great amp, but lacks authenticity when playing blues with a strat and several other sounds - this issue is completely dealt with by using JFET adaptations like Fetzer/peppermill-ish pedals, then using a Dr Boogey and a pedal that had evolved into what I posted as the Plexizer (a modded TC really). I have really liked where this sort of direction has taken me - I don't even use my SF Deluxe Reverb anymore, and my rig sounds better than the reissue JTMs I have played. The other thing that I really like is that the pedals have the passive tonestack integrated into them, so I can swap pedals and swap the pre/post gain<->tonestack sounds as I need.

[KerryF]

Cool Mojo...

Ok guys!  I have decided on the Thunderchief for my Gain Simulator.

Now I need a clean/mild amp simulator.  I have posted a poll.  Please vote in the poll to help me figure out which clean sim to build.

[KerryF]

Vote??? 

[MartyMart]

I voted for the Classic 35 , If you want great "clean to mild" OD it's perfect
Compared to my "real" '30 ( ignoring the amp emu "poo poo" thread ! ) it's pretty
damm close my friend !

MM.

[Rafa]

Where can I find them?:

Peavey Classic 35
Fender Bassman '59

Are they good adaptations?
Cheers
Rafa

[KerryF]

And your layout for the Classic is verified, correct?

I was leaning towards it and the Vibin Champ.