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Preamp tube type

edo

Power User
just curious if the different characteristics of the different preamp tubes have ever been discussed - say x is warmer, y is tighter, z is cleaner etc. I can hear the difference, but it's so subtle it's hard to tell what the actual difference is!
 

unix-guy

Legend!
I'd be interested to see it. I can also tell subtle differences. I do seem to recall from actual tubes that a 12ax7B is supposedly a bit more gain than a 12ax7A... I've also read recently that the EF86 is a higher gain tube. Could be internet BS, but a comparison or "characteristic" chart would be cool.

I've found that for edge of breakup tones, I tend to like the JJ better than the Sylvania type...
 

StickMan

Experienced
Watch the preamp hardness change as you swap the tube types. From what i can tell, this tends to minimize the differences between the tube types. For instance, the JJ sets to a lower hardness than the Sylvania (I think 7.0 for the JJ and 8.4 for the Sylv). So if you adjust the hardness you can see more difference between the tube types.

For instance compare the JJ with a hardness of 8.4 to the Sylvania at the same hardness. There's a big difference.
 

Toopy14

Fractal Fanatic
Watch the preamp hardness change as you swap the tube types. From what i can tell, this tends to minimize the differences between the tube types. For instance, the JJ sets to a lower hardness than the Sylvania (I think 7.0 for the JJ and 8.4 for the Sylv). So if you adjust the hardness you can see more difference between the tube types.

For instance compare the JJ with a hardness of 8.4 to the Sylvania at the same hardness. There's a big difference.
According to the settings @edo posted a few versions back, he sets the Preamp Hardness to 0. If that's still the case, he may be wondering what the differences are with that value set to 0.
 

edo

Power User
According to the settings @edo posted a few versions back, he sets the Preamp Hardness to 0. If that's still the case, he may be wondering what the differences are with that value set to 0.
Did I?? I can't remember if/when I did that, but have mostly been sticking with default values for at least a couple fw's! 0 sounds awkward though..
 

edo

Power User
Ah, I totally forgot about that.. but I think that was back when we only had 2 or 3 preamp tube types.. anyways, I've been using default values since fw 3
 

edo

Power User
Does using a hardness of 0 imply any kind of bypassing of something?
If i remember correctly, the preamp hardness sets the simmetry of the preamp saturation - lower values = softer distortion, higher values = harder distortion
 

Toopy14

Fractal Fanatic
Ah, I totally forgot about that.. but I think that was back when we only had 2 or 3 preamp tube types.. anyways, I've been using default values since fw 3
Do you use the SDD preamp in front for songs like AIWIY, ISHFWILF, Streets, etc.?
 

Toopy14

Fractal Fanatic
I use it for ishf, gloria, electric co, bad and pride
What I like about the SDD block, is that you can increase the drive and lower the level. I have the SDD pedal and it sounds great with my amp, but I have no way of setting the level if I increase the drive, even though it's called Input Level on the pedal.
 
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StickMan

Experienced
If i remember correctly, the preamp hardness sets the simmetry of the preamp saturation - lower values = softer distortion, higher values = harder distortion
I checked the wiki. Preamp hardness does affect the symmetry, which results in more even harmonics. So 0.00 is totally symmetrical, which is the softest distortion. Cliff's comments indicate that real preamp tubes are very asymmetrical, though.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
I checked the wiki. Preamp hardness does affect the symmetry, which results in more even harmonics. So 0.00 is totally symmetrical, which is the softest distortion. Cliff's comments indicate that real preamp tubes are very asymmetrical, though.
0.00 is not symmetrical. In fact there is no value that is symmetrical.
 
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kisslorand

Experienced
I think hardness can be compared somehow to the "knee" parameter of a compressor.
Bias is the one that affects symmetry, not the hardness of the distortion.

just curious if the different characteristics of the different preamp tubes have ever been discussed - say x is warmer, y is tighter, z is cleaner etc. I can hear the difference, but it's so subtle it's hard to tell what the actual difference is!
From my observations:
JJ - cleaner/tight, less distortion
SYL - spongy/looser, heavier distortion
12AX7A - tight
21AX7B - tight, brighter/edgier than 12AX7
ECC83 - kind of JJ with more distortion and a bit more upper mid; open, tight
 
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StickMan

Experienced
0.00 is not symmetrical. In fact there is no value that is symmetrical.
Do we need to update the Wiki then? Because it links to this post from 2013:

There is no correspondence that I can offer as the modeling algorithm is different. What the parameter does now is control the asymmetry of the triode model. The higher the value, the more asymmetrical the clipping. A value of zero would be completely symmetrical which will decrease the even harmonics and increase the odd harmonics. Triodes are very asymmetrical. The default values are rounded to the nearest 0.5 based on the MIMIC measurement for that amp.
 
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