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Preamp Tube Types

Poparad

Experienced
Try as I might, I just cannot hear a difference between the different tube types in the amp block. I've got pretty good ears, and I can hear the differences in most other subtle things, such as the new mic preamps in the cab block. I own a Deluxe Reverb and know first hand how different it sounds with new/old/different brands of tubes in it. I've also had a JCM800 combo in the past, too. So after a decade of playing on real tube amps, I've got a sense of how a few of the different tube types sound. However, I just can't hear any discernible difference in the Axe. Now, I have complete faith in FAS's programming and attention to nuance, so I'm sure this has to be a case of PEBCAK (Problem exists between chair and keyboard - or Axe). What am I doing wrong?
 

musicdr

Inspired
The differences to me are pretty subtle but noticeable. The el34 is a little more aggressive, the el84 has a little more spank in the mids, the 6l6 has a little more headroom-clarity, and the 6v6 is a little smoother. I realize these are just my impressions
and everyone has different ways of describing these things. Maybe the different types give me a different feel or playing sensation also. I have mostly explored these with mid to high gain amps. So many tools, so little time!
 

Randy4Guitars

Power User
I think changing tube types in the axe is a little different than in a real amp, as the axe automatically changes the output transformer to match the new tube type. You can simulate it by adjusting the transformer match parameter, and I think also the speaker lo and hi resonance values may play a part, but that may be old fw info. I never investigated it, but here is one thread:

http://forum.fractalaudio.com/axe-fx-ii-discussion/85673-changing-tubes-transformer-match.html
 

dbun

Experienced
The differences to me are pretty subtle but noticeable.
I agree.
I don't usually bother with this though as I have little interest in putting 6L6s or EL34s in my Vox for example.
I like the amps just the way they are :)

I can see how some people could tinker away with these settings though.
 

musicdr

Inspired
I usually check these things out when they come out so I know what they do. The amps sound pretty stellar without touching a thing these days.
 

Rex

Legend!
A little insight...

Changing the power tube between pentode and tetrode doesn't change the sound in the same way actually changing tubes would because it only changes the distortion curves. It does not change the transconductance so the transformer matching is constant. When you put different power tubes in an amp the difference in tone isn't due to some inherent difference in the "sound" of the tubes. It's mainly due to the different transconductances. An EL34 has more than twice the transconductance of a 6L6. This means that the plate current will be twice as great for a given grid voltage. This makes EL34s sound "more midrangey" and 6L6s sound "tighter" or "fuller". The truth is that if you bias them correctly and compensate for the difference in transconductance you will hear very little difference. Unfortunately you can't compensate for the transconductance easily in a real amp without changing the gain of the phase inverter and/or putting in a different output transformer.

I don't know what happens in a Mark V when you select EL34s as the tube type. I'm assuming it changes the bias but it might change other things. Fortunately you don't really need to worry about all that. Tone Matching will take care of that stuff. People underestimate what Tone Matching does. Yes, it is "just" EQ but that is 99% of what you hear in an amp like that. All of the distortion comes from the preamp so changing power tubes is just altering the output frequency response. I'd be surprised if the curve deviated that much from flat.
 

VegaBaby

Fractal Fanatic
I think changing tube types in the axe is a little different than in a real amp, as the axe automatically changes the output transformer to match the new tube type. You can simulate it by adjusting the transformer match parameter, and I think also the speaker lo and hi resonance values may play a part, but that may be old fw info. I never investigated it, but here is one thread:

http://forum.fractalaudio.com/axe-fx-ii-discussion/85673-changing-tubes-transformer-match.html
^ this exactly. following the mentioned links should give you a pretty good idea about what's going on...
 

Poparad

Experienced
A little insight...
Thank you! Thank makes a lot of sense and explains why I'm not hearing what I'm expecting to hear. I figured there was some element in the real world that was changing as an consequence of the tubes that wasn't directly linked to the tube type selector.
 

RONJONES2020

Inspired
There was a slight mistake in my original post. The transconductance of an EL34 isn't more than twice a 6L6. It's about 30-40% more.
Great Scotts! That changes everything now! Must smash all my gear and start all over!

I kid I kid. Happy New Year Fractal! I shall blow the roof off my jam room in your honour on the 31st!
 

api4u

Experienced
A couple of thoughts here:

* If you can't hear it, it may not matter.

* It could be an issue of your speakers or head phones; you can notice things more with better monitors, that you may not have noticed if you're using a bit more budget ranged driver.

* It's "somewhat" more of a "feel" thing. Direct, bright quick tones (6L6) vs spongier, rubbery-er (EL34) or maybe a bit of a clean to slight breakup (6V6). These are somewhat sweeping generalizations, but may give a sense of what you're probably looking for, here.

EDIT: I just noted you said "Preamp" and not "Power" tubes - my comments for the tube types may not be applicable, but the concept still applies.
 

pdup

Experienced
Try switching from a Russian EF86 to a Telefunken E806F in a VOX or Matchless.
This is not a question of sheer transconductance...
 
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