Triode Hardness Measurments

Gamedojo

Gamedojo

Power User
I was wondering what type of 6l6 tubes where measured for the Fender amps? I noticed the Super is set at 8.5 and the Vibro is 7.5.... did the amps have old NOS 6l6 tubes or current production?

I ask because I have been recently dropping the triode hardness to about 6 on the fenders and the low end perks back up without too much loss of note separation and making the amps sound closer to my old '67 super with NOS 6l6s.

I also like to increase the Dynamics Damping a tad in conjunction to this tweak.
 
FractalAudio said:
Triode Hardness sets the "hardness" of the preamp tubes. The type of power tube is irrelevant.
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OMG! I feel like a fool. I've been reading "triode" as "Tetrode" for some reason.

Though I guess my question still stands. Did you have modern production preamp tubes in place?
 
Triode hardness sets how hard the triode goes into saturation. Some "NOS" 12AX7s go into saturation a little more gracefully than newer tubes. I have no idea why.
 
FractalAudio said:
...Some "NOS" 12AX7s go into saturation a little more gracefully than newer tubes. I have no idea why.
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If you would have figured this out... You would have sold Fractal Audio, started a vacuum tube manufacturer and make billions. Its a mystery to everyone from what i can tell.

This new information is going to open up a bunch more experimentation. I remember when I first discovered NOS tubes when building/modifying amps, I found the right "soft" preamp tube would allow me to coax better treble response from the preamp. Since I was assuming this setting was the power tubes, I kept it high because I've always wanted harder sounding output tubes to keep it all tight to the speakers.

:)
 
mmcm4 said:
So turning the Triode Hardness down can help simulate "NOS" tubes?
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I suppose. It can simulate "softer" preamp tubes. If the "NOS" tubes happen to be softer, then yes.

Hidden in the Axe-Fx II is a statistical analysis module. This module lets me analyze clipping characteristics. I have noticed that certain NOS tubes exhibit a softer clipping behavior than modern tubes. Why? I have no idea.

However I have found that softer clipping is not necessarily desirable. For higher gain tones softer clipping reduces string definition because one tends to increase the gain. The harder the clipping the more overtones are created and, hence, more harmonic distortion. Softer clipping yields an overtone series that tapers off faster and thus less harmonic distortion. To compensate people turn up the gain but this makes the low end mushy and undefined.

It's all a delicate balancing act. The clipping needs to have the right hardness, asymmetry and dynamics for the best sounds. Tube amps just get it right without really trying. I've analyzed a lot of modelers and they always seem to miss one or more of those characteristics.
 
FractalAudio said:
I have no idea why.
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The 12AX7 tube was introduced in the 40s from RCA. It had much longer plates than many of the current production. Earlier 12AX7 were more microphonic sensitive cause of the longer plate design, but they had a different saturation point than newer short plate tubes

Cheers
Paco
 
FractalAudio said:
,,,However I have found that softer clipping is not necessarily desirable. For higher gain tones softer clipping reduces string definition because one tends to increase the gain. The harder the clipping the more overtones are created and, hence, more harmonic distortion. Softer clipping yields an overtone series that tapers off faster and thus less harmonic distortion. To compensate people turn up the gain but this makes the low end mushy and undefined....
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Ah, but for us low-gain vintage nuts, the softer clipping is key to what we like to hear.

I still remember when I got my first "high gain" amp.. a Marshall Jubilee. I thought, putting in my treasured NOS GE tubes I was using in my Fenders, it sound so much sweeter, but after installing, it was a mess of mush.

...but in non-master, simple circuit vintage amps, there is no comparison.

Also, in long conversations with folks, its been discussed that modern tubes actually sound best in new boutique amps as well. This is because that harder sound was designed around, just like the vintage amps where designed with the tubes of their era.

either way, I'm going to have a blast experimenting with this parameter.
 
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Is this the idea behind tube ratings from, for example, Groove Tubes where a lower rating has softer, earlier clipping than the higher rating, which is used for more headroom?
 
jyflorida said:
Is this the idea behind tube ratings from, for example, Groove Tubes where a lower rating has softer, earlier clipping than the higher rating, which is used for more headroom?
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I don't think so. I think that's a rough measurement of transconductance but I could be wrong.
 
Have you played with the bias setting? I know that's specially a power tube adjustment, but I tended to prefer running the power tubes a bit on the hotter side (in Marshall type amps, not in Fenders though). I know that when I screw around on the Axe using the KT66 tube type in the plexi 100, I change the bias to the .4 area (as thats what I did in real life on my Marshall type amps). I don't alter anything else (output transformer modelling). Should I?
 
Interesting topic.

I quickly dialed up a pushed Princeton Reverb last night before practice and it ended up being a go-to amp for a song that needed some chunky rhythm work. There was a really nice sweetness in the high end with single coils but to get some chunk in the low end I had to use a brighter pickup setting. I was planning on cutting lows before the amp to tighten things up but triode hardness might be worth messing around with. Then again, I suppose that could take some sweetness away from the high end.

Terry.
 
After working with this parameter, just backing off a bit from 8.5 (8.0 - 8.4) really does act exactly like using some NOS preamp tubes that break softer harmonically into clipping. I really don't know what to say about where Cliff has brought the AXE-FX2. Like many here, I've been playing for too long to mention. This innovation has to be a marvel in the pro industry. Its like owning these amps mic'd correctly in a pro studio.

It only takes a quick reminder of the progression of the "other" modelers - One dimensional, sterile, flat tone (no nuance) that makes your guitar sound misplaced in the mix. This problem has always been a number one issue with the "others". When using them in a mix, they sound artificial and misplaced. The AXE sounds like a real amp mic'd, with open air 3D tone. Since v12.3 , the AXE just sounds so damn good- of course it was good before ;)

Also, I should also mention Cliff, as he has stated, has the triode hardness parameter set correctly for it mimicked amp, Use this parameter if your looking to soften the edges.
 
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