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Wish Interchangeable preamp tube “slots”

York Audio

Power User
I spent the entire day today trying different preamp tubes in different slots on my 5150 and Dual Rec to see what effect it would have on the tone. I had TAD, Gold Lion, and Tung Sol 12AX7 tubes and was shocked by how much swapping a single tube changed the tone and feel of the amp.

The most noticeable changes were in the V1 and PI slots, but I read about guys changing the V2 or V3 tubes as well to alter distortion characteristics. In my 5150, using all Gold Lion preamp tubes made it extra gainy and fizzy. I tried all Tung Sol tubes and it was looser in the low end and grainy in the top end. So I went back to the Gold Lions and tried a single Tung Sol in each slot. Putting the Tung Sol in V3 made the amp come alive by taking away some fizz and adding a little body. It was amazing to hear and feel the difference that single tube made in the overall tone and feel of the amp. I went through the same process with the Dual Rec and had similar results.

So my wish is to have the ability to change individual virtual tubes in the Axe. I don’t know if the preamp tube algorithm would change things as much as it did in the real world, but I noticed a huge difference here and thought it would be a cool way to bring more versatility to the amp models.


Even just swapping between multiple tubes of the same brand/spec can produce different results... I did that on my Budda just rotating the 3 JJ ECC83S tubes that were in it.

I suspect with the modeling that's implemented, that would not happen on the Axe Fx.

But definitely +1 to have different tube types for each "socket".


Power User
+1. Even in the PI slot on my ODS build, the tube used makes a difference, especially how it’s balanced. Would be really cool!


Fractal Fanatic
Cliff has already made his point about swapping tubes in several occasions. In a shellnut: just tweak the Axe-FX advanced parameters around the tube


Cliff has already made his point about swapping tubes in several occasions. In a shellnut: just tweak the Axe-FX advanced parameters around the tube
You are missing the point. A tube amp usually has more than 1 preamp tube.

The wish is to select the tube type for each tube in the circuit.

Right now we can choose the type for ALL preamp tubes but not the individual ones.

Omri Bazelet

Could be also great to do the same with Power Amp Tubes and also could be awesome for Mix of 6L6 and KT88 along with Solid State "Power Tube" for Randall amps and JC120

Joe Bfstplk

Fractal Fanatic
I think that's a very different thing. Power tubes usually operate in pairs or quads (as far as I know), so I suspect a mix and match approach there wouldn't be the best.
Some Boogies have mix-n-match outputs that allow 6L6 and EL34 or all 6L6 in the Simul-Class output section....
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