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FAS Class A - Parameter Adjustment

200man

Veteran
Trying to develop a logical approach to parameter adjustment...

First, which parameters would you folks check/adjust, to ensure the amp is clean, accurate and fast?
 

dsimms

Inspired
Not sure accuracy comes in here... the FAS models are Cliff and team's virtual examples of how they would have built an amp to cover a particular sound or amp architecture.
 

200man

Veteran
Thanks, fellas...appreciate it!
Okay, put another way:
When you look at the parameters, which ones do you make dam sure are set up a certain way?
I know enough to set up the normal amp settings...it's the "under the hood" guys.
It's peculiar in that most folks ask how do I get it spongy...or get it to bloom...or what's the magic sauce?
I wish to be more adept at these finer adjustments and become proficient in their application for all amp models.
...but slowly...and methodically... :)
 

simeon

Axe-Master
i think you've picked an odd one to start with - the FAS models are cliff's creations and are his educated opinion about what an ideal amplifier of a particular type should sound like, so in theory they shouldn't need any under the hood tweaking.
in fact, the amps are so close to the originals now, that you could argue that no advanced tweaking is necessary. you wouldn't buy an amp from a shop and then immediately take it apart and start changing capacitors and fiddling with different values...you'd just play it.
having said that though, there are some parameters that are worth learning about - input trim, sag, negative feedback, transformer match etc - are ones that are commonly adjusted to fine tune the "feel" of an amp.
you may find this helpful - http://olongjohnson.xp3.biz/_assets/Amp_&_Cab_Quick_Reference.pdf
 

unix-guy

Legend!
i think you've picked an odd one to start with - the FAS models are cliff's creations and are his educated opinion about what an ideal amplifier of a particular type should sound like, so in theory they shouldn't need any under the hood tweaking.
I don't think that is the case with all of them. In particular, the FAS Class-A was the result of an "accident" if my memory is correct. Cliff used the wrong power section or something when reworking one of the models but liked the results... So he gifted it to us :)
 

simeon

Axe-Master
i know, i was just trying to make a general point

it's worth having a look at the "tech notes" subforum, because cliff has posted a lot of good stuff in there.

i would always say, as a general rule, that getting the master volume level right (on non-mv amps) is more important than anything you can do in the advanced pages
 

simeon

Axe-Master
well it's not really an answer is it...more of a general "figure it out yourself". i guess everyone is different...the only two advanced parameters i ever touch are input trim and sag. i do adjust speaker low frequency resonance to match the IR i'm using and i often change the preamp valves, but nothing beyond that. some people fiddle about with all sorts of stuff...it just depends on what you're trying to achieve i guess. definitely have a look at cliff's tech notes...it's a goldmine of good info in there.

i'm sure some other people will chime in with some good tips
 

200man

Veteran
Understoood, and again thank you for responding.

With respect to "what you're trying to achieve", I thought I was clear, transparent and well maybe not so fast. :)

I like this fas amp and I understand how to bugger with the basics...and the tech notes are interesting reads but from a practical perspective you have kind of laid out my argument. In effect you leave things at default and you focus on a subset to achieve what you are looking for. I'm not trying to bite the whole apple, just wanting to know if I am wanting audiophile clean but willing to push the preset a little off course to get more attack[re: fast], etc...how do others approach the problem?
 

unix-guy

Legend!
Understoood, and again thank you for responding.

With respect to "what you're trying to achieve", I thought I was clear, transparent and well maybe not so fast. :)

I like this fas amp and I understand how to bugger with the basics...and the tech notes are interesting reads but from a practical perspective you have kind of laid out my argument. In effect you leave things at default and you focus on a subset to achieve what you are looking for. I'm not trying to bite the whole apple, just wanting to know if I am wanting audiophile clean but willing to push the preset a little off course to get more attack[re: fast], etc...how do others approach the problem?
By "audiophile clean" are you talking about having no distortion? The Class-A is probably not the best amp for that. Try the JC-120, or USA Clean or Tube Pre models.

Maybe post an audio or video clip of what you have got and what you are trying to go after?
 

200man

Veteran
Really? I am in the process of building a patch and it appears VERY clean. ...and it sounds good.:)
At the end of the day, once I like the tone...I am thinking this amp might be a good choice to get it to sing as opposed to distort when driven ever so slightly.

Oh, the first amp I played with was the usa clean...then the tube pre...i wanna stay in the tube modelled realm.
 

∞Fractals

Forum Addict
Yup; really. ;)

FAS Class A amps are very much in the vein of the various VOX brand amps.


If you have a specific tone you are shooting for, post a clip and this place will help you get it. A ton of helpful, and experienced talent here.
 

unix-guy

Legend!
Really? I am in the process of building a patch and it appears VERY clean. ...and it sounds good.:)
At the end of the day, once I like the tone...I am thinking this amp might be a good choice to get it to sing as opposed to distort when driven ever so slightly.
Well... Maybe my memory since I haven't played with that one in a while, and I tend to dial in a lot of breakup but that is based off of an AC30 (I think) which is not the cleanest amp. Of course that can depend quite a lot based on how it's adjusted.
 

unix-guy

Legend!
Well... Maybe my memory since I haven't played with that one in a while, and I tend to dial in a lot of breakup but that is based off of an AC30 (I think) which is not the cleanest amp. Of course that can depend quite a lot based on how it's adjusted.
Well... I just loaded it up and it is actually pretty clean for me at default settings :)
 

200man

Veteran
I will say I just figured out the difference between the null versus none mic type.
By default, the axe selects none for the mic type, but the null sounded much better to my ears.
I think this is because selecting null enables the proximity knobs.
...decreasing the proximity knob simulates the mic being pulled away from the speaker.
...it sounds better! :) ...and now i know.... :)
 

200man

Veteran
from yek....
FAS CLASS-A
: added in firmware 12. Another amp model that was born by accident.

“A “Blackface” preamp into a cathode-biased 6L6 power amp with no negative feedback. This was a happy accident when originally modeling the Carr Rambler in the beta version of this release. Several mistakes were made in the model prior to MIMIC’ing the amp but the model was so well liked that we decided to make it into its own custom amp model."
 

lqdsnddist

Axe-Master
The amp defaults are already where it should sound "best", or most accurate, etc

Cliff doesn't just randomly assign all those parameters after all. One can certainly make adjustments to his or her own taste, but there is no one method where you go and change 5 parameters and suddenly it sounds better. If anything, usually adjusting that stuff makes things sound worse, at least to my ears

Its like saying "I just bought a new Ford GT40, what should I change to make it fast?", even though some of the best brains in the business spent years on R&D making it already fast....
 

∞Fractals

Forum Addict
Its like saying "I just bought a new Ford GT40, what should I change to make it fast?", even though some of the best brains in the business spent years on R&D making it already fast....
Hey careful there, I resemble that remark…I modified the crap out of a 2004 996 X50 Cabriolet

Nothing like "more boost" :)
 
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